Paediatric, the reference

During apnoea, the only oxygen store is the gas left in the lungs at end-expiration, which is the FRC. Infants have less FRC per kilogram than adults. Their weight-adjusted metabolic rate is higher, so they use more oxygen. Minute ventilation and oxygen uptake are therefore large compared with this small store. Induction shrinks the FRC further through the supine position, paralysis and the anaesthetic drugs themselves. The small reserve runs out within moments, and saturation falls much faster than in older children or adults.

Vital capacity explains the desaturation. Vital capacity measures the largest breath, not the gas remaining at end-expiration. During apnoea, oxygen is drawn from the FRC. A small FRC, not vital capacity, explains the child's rapid desaturation.

Infants tolerate apnoea poorly, desaturating sooner because their FRC per kilogram is lower and their metabolic rate, hence oxygen consumption, is higher. Their oxygen reserve is small relative to ventilation and consumption, and induction reduces FRC further.

Sources: Barash 9eFaustMiller 10e

The FRC acts as a reservoir that dilutes each fresh breath of agent. In the infant, alveolar ventilation is about 5:1 relative to FRC, against 1.5:1 in the adult. Lung gas is replaced quickly, so alveolar partial pressure rises fast towards inspired, and brain partial pressure follows. A high cardiac output would normally slow that rise by carrying agent away. In infants it speeds equilibration instead, because a large share of the flow goes to the vessel-rich organs.

High cardiac output per kilogram. Greater cardiac output per kilogram is tempting because textbooks list it among infant factors. On its own, though, a higher cardiac output removes more agent from the alveoli and slows the rise in alveolar concentration. It helps only because so much of the flow goes to the vessel-rich group.

Textbooks attribute faster uptake in infants to high alveolar ventilation relative to FRC: about 5:1 against 1.5:1 in adults. More ventilation speeds equilibration between inspired and alveolar gas. Perfusion of the vessel-rich group outweighs the slowing effect of a high cardiac output.

Sources: Stoelting 8eBarash 9e

Blood crossing a left-to-right defect has already passed through the lungs, so it carries agent back into the pulmonary circulation for another pass. This slightly reduces alveolar uptake and could in theory dilute an intravenous bolus through recirculation. In practice, cardiac output rises to compensate and cerebral perfusion is kept up, so the brain receives agent at the usual rate. Induction slows at first only when the shunt lowers systemic perfusion. Right-to-left shunting is different: venous blood that never met the agent goes around the lungs, which slows inhalational induction.

Slowed gas induction with any shunt. Slow gas induction is the best-known effect of a shunt, so it feels right. But that effect belongs to right-to-left lesions, where unexposed venous blood dilutes arterial agent. A left-to-right shunt only recirculates blood that already carries agent, and the extra cardiac output keeps delivery to the brain normal.

Pharmacology and paediatric texts agree that a pure left-to-right shunt does not change the rate of inhalational induction. Even with marked pulmonary overcirculation, intravenous onset shows little or no clinically relevant change. Induction slows only if the shunt reduces systemic tissue perfusion.

Sources: FaustStoelting 8e

Most newborns who are slow to breathe respond to touch. Rubbing the baby dry with a towel gives that stimulation and also cuts evaporative heat loss. If stimulation fails, the problem is inadequate spontaneous breathing, so assisted ventilation becomes the key step. Stimulation should be brief and should never hold up ventilation. Airway instrumentation comes only after these steps.

Immediate intubation. A blue, floppy baby looks critically ill, so a definitive airway seems right. But most such infants start breathing with drying and stimulation alone. When they do not, the next step is positive-pressure ventilation. Going straight to intubation skips the sequence and delays simple measures that usually work.

Drying, with suction where needed, is usually enough stimulation to start breathing; flicking the soles or rubbing the back can add to it. If after a minute the baby is apnoeic, gasping or below 100 beats/min, positive-pressure ventilation follows, and stimulation must not delay it.

Sources: FaustMayo reviewOutside our books: Singapore Neonatal Resuscitation Guidelines 2026 (2026)

A newborn's lungs must fill with air before gas exchange can begin. A slow heart rate at birth usually means the baby is not breathing well enough, not that the heart has failed. Helping the baby breathe is therefore the key intervention. Escalate step by step, using the heart rate as the guide. If the rate stays low, correct the ventilation technique first. Intubate if the chest does not rise. Add compressions only when the rate drops below the lower threshold despite ventilation.

Chest compressions at a rate of 80. A cyanosed, bradycardic baby looks like an arrest, so compressions feel urgent. But a rate of 80 is above the compression threshold of 60. At this stage the problem is inadequate breathing. Compressions come later, only if the rate falls below 60 despite good ventilation.

Initial drying, stimulation and assessment take 30 to 60 seconds. If apnoea, gasping or a heart rate below 100 persists, start bag-mask ventilation at 40 to 60 breaths per minute. Supporting breathing is the central step, and compressions begin only below 60.

Sources: Barash 9eFaustOutside our books: 2025 American and European Guidelines on Neonatal Resuscitation: Concordance and Differences (2026)

A newborn's heart slows mainly because the lungs have not been inflated and the baby is hypoxic. If the rate stays low during positive-pressure ventilation, the usual cause is ventilation that is not working: a mask leak, poor head position, a blocked airway or too little inflation pressure. Fix these first. If the chest still does not move, a tracheal tube secures the airway. Compressions and adrenaline only help once the lungs are inflated, so keep them for a rate below 60 that persists despite effective ventilation.

Start chest compressions at a rate of 60 to 100. Compressions feel like the right escalation for a baby who is not improving. But at a rate between 60 and 100 the heart is not the problem. The lungs are not being ventilated, and compressing the chest without effective inflation only pumps unoxygenated blood around.

In the newborn resuscitation algorithm, a heart rate below 100 during positive-pressure ventilation calls for corrective ventilation steps, then intubation if the chest does not rise. Coordinated compressions start only below 60. Adrenaline is considered if the rate stays below 60 despite compressions and ventilation.

Sources: FaustMayo review

Clearing meconium from the airway was once thought to prevent aspiration. Barash still advises suctioning the mouth and pharynx at delivery, with selective tracheal suction. Later evidence showed that routine suctioning gave no benefit. Mayo and Faust now limit a vigorous baby to gentle clearing with a bulb syringe. The Singapore guideline advises suctioning the mouth and nose only if they are visibly blocked. The baby's vigour, not the thickness of the meconium, decides the plan. Intubation and tracheal suction are kept for depressed babies.

Intubate for tracheal suction. Intubation looks like the careful, thorough choice because meconium used to be suctioned routinely from below the vocal cords. It is wrong because a vigorous baby gets no benefit from it. Tracheal suction is only for non-vigorous babies, and the thickness of the meconium no longer changes that.

Mayo advises only gentle bulb clearing of the mouth and nose for vigorous babies. Intubation is reserved for non-vigorous babies, whatever the meconium's appearance. Faust keeps such babies with their mothers for first care. Singapore advises against routine suctioning unless the airway is blocked.

Sources: Mayo reviewFaustOutside our books: Singapore Neonatal Resuscitation Guidelines 2026 (2026)

Both too much and too little oxygen harm preterm babies. Excess oxygen narrows immature retinal arterioles and damages their lining; when oxygen levels normalise, vessels regrow abnormally, causing retinopathy of prematurity. Too little is also dangerous: babies missing the 5-minute saturation target have more deaths and more severe intraventricular haemorrhage. Starting oxygen differs by guideline: AHA/AAP allow 30–100%, whereas the ERC starts at 30%. Both start with blended oxygen, then adjust to saturation. Starting at 30% and increasing as needed satisfies both.

Intubating to push saturation above target. A saturation of 85% in a 27-weeker looks worryingly low, so mask support can seem too little and wrong. But 85% is acceptable during transition, and mask ventilation is standard first-line support. The real error is intubating to push saturation above the upper target, which risks hyperoxic retinal injury.

The preterm table uses an oxygen blender, with saturation goals rising each minute to 85–95% at 10 minutes. For infants under 32 weeks, ERC starts at 30% oxygen; AHA/AAP allow 30–100%. Missing the 5-minute target raises risk of death and severe intraventricular haemorrhage.

Sources: Miller 10eOutside our books: Singapore Neonatal Resuscitation Guidelines 2026 (2026)Mayo review

A newborn whose heart rate stays low despite good ventilation is likely hypoxic and acidotic, with poor coronary perfusion. Compressions restore coronary flow, but ventilation must not be sacrificed. So compressions and breaths alternate. Each 2-second cycle holds three compressions and then one breath. That gives 120 events a minute: 90 compressions and 30 breaths. Keep them coordinated rather than continuous, even after the airway is secured.

90 compressions with 60 breaths per minute. It has the right ratio and the right number of compressions, so it looks correct. But the arithmetic fails. At 3:1, 90 compressions give only 30 breaths a minute. Sixty breaths would need a different ratio and would break the 2-second cycle.

Several textbooks and the Singapore neonatal guideline agree. If the heart rate stays under 60 after adequate ventilation, compress at a 3:1 ratio: 90 compressions and 30 breaths per minute, or 120 events. Compressions and breaths stay coordinated even with an advanced airway in place.

Sources: Barash 9eFaustOutside our books: Singapore Neonatal Resuscitation Guidelines 2026 (2026)

Bradycardia in a newborn is usually caused by hypoxia, so ventilation comes first. Adrenaline is added when the heart rate stays below 60/min despite effective ventilation and chest compressions. A vein or bone gives a predictable dose straight into the circulation, so the small dose is enough and this route is preferred. Absorption from the airway is erratic and plasma levels are unpredictable, so a much larger tracheal dose is needed. That route is a stopgap until access is secured.

Same IV dose via tracheal tube. It is tempting to think the tube is just another route into the blood, so the dose can carry over unchanged. But uptake from the airway is unreliable. Giving the small IV dose down the tube would underdose the baby, which is why the tracheal dose is several times higher.

Three anaesthesia texts agree. The IV or intraosseous dose is 0.01–0.03 mg/kg, repeated every 3 to 5 minutes if needed. The 0.05–0.1 mg/kg tracheal dose is kept for the intubated newborn without access, because blood levels after tracheal instillation are unpredictable.

Sources: Barash 9eMayo reviewMiller 10e

Vomiting removes extracellular water and salt, so restoring circulating volume comes first; correcting the total deficit and electrolytes comes later. Only a glucose-free fluid with near-plasma sodium (131–154 mmol/litre) expands the vascular space well. Stoelting and the Mayo review give 20 mL/kg; NICE allows 10–20 ml/kg in under 10 minutes. Give the full 20 mL/kg for frank hypovolaemia, reassessing after each bolus. Once stable, switch to dextrose in half-saline. Do not add potassium until urine output returns.

Dextrose in half-saline as the bolus. The volume is correct for 12 kg, and the fluid looks like a complete replacement. But dextrose in half-saline is hypotonic, so it is the fluid for after resuscitation, not a bolus. Potassium given before the kidneys are making urine is unsafe.

Stoelting and the Mayo review both start severely dehydrated infants on a 20 mL/kg isotonic saline bolus, then switch to dextrose 5% in saline 0.45%. NICE allows 10–20 ml/kg of crystalloid with sodium 131–154 mmol/litre. Potassium is added once urine output rises.

Sources: Stoelting 8eOutside our books: Intravenous fluid therapy in children and young people in hospital (NICE guideline NG29), recommendations page (2020)Mayo review

Bleeding removes blood and extracellular fluid, so the replacement fluid needs electrolyte content close to plasma. An isotonic crystalloid spreads across the whole extracellular space in proportion to the size of each compartment. Only 250 mL of every litre stays in the circulation, so about three volumes are given for each volume lost. Dextrose–saline mixtures are hypotonic. Given in replacement volumes, they dilute plasma sodium and add a glucose load. Any glucose the infant needs comes from a separate maintenance infusion run at a steady rate.

Dextrose in dilute saline for replacement. Dextrose in dilute saline is the usual infant maintenance bag, and worry about hypoglycaemia makes added sugar feel protective. But the fluid is hypotonic. Run in fast enough to replace blood loss, it lowers plasma sodium and raises blood glucose, so it is the wrong fluid for replacing lost volume.

In children, blood loss is usually replaced at 3:1 with isotonic crystalloid. Surgical losses should be matched with a near-isotonic fluid such as lactated Ringer, not a hypotonic one. Hypotonic dextrose-containing fluids cause hyperglycaemia and hyponatraemia, so they are not recommended for replacement.

Sources: Stoelting 8eBarash 9eMayo review

Fluid need per kilogram drops as weight rises, so the hourly rate is tiered by weight band. A fasting child keeps losing water at roughly the maintenance rate, so the deficit builds up hour by hour. The traditional scheme pays back half the deficit in the first hour on top of maintenance, then a quarter in the second hour. Barash says this calculated-deficit approach has largely been replaced by smaller volumes in healthy day-surgery children with short fasts. After a long fast, the deficit calculation still applies.

Whole fasting deficit plus one hour's maintenance. You get this figure if you add the whole fasting deficit to one hour of maintenance and give it all at once. The traditional scheme gives only half the deficit in the first hour. The rest is spread over the next two hours, so this overestimates the first-hour volume.

Review text sets maintenance at 4, 2 and 1 mL/kg/h across weight bands. Fasting deficit equals hourly maintenance times hours without intake; half is given in the first hour, plus maintenance. Barash notes healthy day-case children with short fasts now usually receive smaller volumes.

Sources: Mayo reviewBarash 9e

Blood volume per kilogram is greatest at birth and declines through infancy, reaching a plateau in childhood. Barash gives a term neonate 90 mL/kg, dropping to 75 mL/kg between 6 months and 5 years, then 70 mL/kg from age 5. Miller reaches the 70 mL/kg plateau sooner, after 1 year. The books differ only on when the plateau starts; by school age both use 70. Review tables quoting 70–75 mL/kg for children begin at that same figure. Total volume is weight multiplied by the per-kilogram value.

Infant multiplier of 75 to 80 mL/kg. This answer feels safe because it comes from a plausible multiplier of about 75–80 mL/kg. That is the infant range. By school age, blood volume per kilogram has fallen to 70, so the higher figure overestimates this child's volume by several hundred millilitres.

Barash and Miller both give 70 mL/kg for older children, with higher values for neonates and infants. Another table gives 70–75 mL/kg for children. A worked review example multiplies a child's weight by 70 mL/kg to get blood volume.

Sources: Barash 9eMiller 10eMayo review

A wheeze in a child with a cold is an adventitious sound that marks lower-tract infection. Stoelting names it as a reason to cancel elective cases. A long delay was once favoured because virus-triggered bronchial hyperreactivity can last 6 weeks or more, beyond the visible illness. Miller now reports consensus that a 6-week wait is unnecessary: about 2 weeks after symptoms resolve is enough. The wait extends to four weeks after severe illness, such as high fever, in a child with significant asthma.

Give salbutamol and proceed. A beta-agonist feels right because it relieves wheeze and premedication lowers airway events. But wheeze with a cold signals lower-tract infection, and a bronchodilator does not treat that. Only a well-controlled asthmatic with mild wheeze and no infection gets an inhaled bronchodilator and goes ahead.

Stoelting advises postponing elective surgery when a child shows signs of lower-tract infection, including abnormal breath sounds. Miller cites consensus for a gap of roughly 2 weeks after symptoms clear. It advises four weeks after resolution when severe symptoms coexist with significant asthma.

Sources: Miller 10eStoelting 8e

Delay is a tool for elective surgery only, giving an inflamed, hyperreactive airway time to settle. Even there, Stoelting judges the traditional waits of 1 to 2 weeks for mild and 4 to 6 weeks for active or severe infection possibly too cautious and often impractical. An emergency cannot wait, so it goes ahead whatever the severity of the infection. The airway stays irritable, so the task becomes preventing bronchospasm: recent guidance advises salbutamol before induction, intravenous propofol to dampen airway reflexes and avoiding desflurane.

Defer surgery for 4 to 6 weeks. The 4 to 6 week wait is the classic teaching for an active infection, so it feels like the safe choice. But that wait applies only to elective lists. An incarcerated hernia cannot be deferred, and emergencies go ahead however severe the infection is.

Stoelting states emergency surgery must go ahead whatever the severity of the respiratory infection, and calls the traditional elective delays possibly too cautious. Recent guidance recommends pre-operative salbutamol. A laryngeal mask trial excluded active infection and emergency cases, citing aspiration risk.

Sources: Stoelting 8eOutside our books: Is General Anesthesia Safe for a Child with Acute Upper Respiratory Tract Infection? A Narrative Review (2025)Outside our books: Hyomental distance measured ultrasonography versus weight-based criteria for laryngeal mask size selection in children: a randomized controlled trial (2025)

The deficit is estimated as hourly maintenance multiplied by hours fasted; Mayo's traditional scheme gives half of it plus maintenance in the first hour of anaesthesia, then a quarter plus maintenance in the second hour. Barash notes smaller fixed volumes have largely replaced 4-2-1 deficit calculations, but only for healthy day-surgery children with short fasts. A child unfed all day has a genuine deficit, so the traditional scheme applies, given intravenously during the case. Incarceration can obstruct bowel, so the stomach is untrustworthy despite fasting.

Delay surgery for preoperative rehydration. Hydrating the child for hours before theatre feels like correcting dehydration first. The sources replace the deficit during the anaesthetic itself, with most of it given in the first hour, so holding surgery for pre-hydration only adds delay.

Mayo works out the fasting deficit as hourly maintenance times hours fasted and gives half of it plus maintenance in the first hour of anaesthesia. Barash limits the newer smaller-volume approach to healthy day-surgery children whose fast is not prolonged.

Sources: Mayo reviewBarash 9e

Persistent vomiting strips gastric acid, chloride and potassium, leaving the infant dry with hypochloraemic, hypokalaemic alkalosis, so surgery waits for correction. Volume comes first as a balanced isotonic salt solution; potassium is added only after the infant starts passing urine, and chloride should exceed 85 and be rising. The obstructed stomach holds a large volume, so it is aspirated before induction. Infants are extubated yet prone to later respiratory depression, so need hours of cardiorespiratory monitoring. Stoelting avoids opioids for that apnoea risk: one book's stance, not settled.

Half-normal saline as the opening bolus. Half-normal saline sounds gentle for a small infant, and it does appear in the regimen, but only as the later dextrose-containing maintenance fluid. It is hypotonic and a poor volume expander. The opening bolus must be isotonic.

Texts call it a medical, never surgical, emergency with hypochloraemic, hypokalaemic alkalosis; resuscitate with balanced salt solution, add potassium after urination, aim for potassium at least 3 and chloride above 85 rising, aspirate the stomach, extubate, and monitor cardiorespiratory function postoperatively.

Sources: Miller 10eBarash 9eStoelting 8e

Vomiting strips hydrogen, chloride and potassium; the volume-depleted kidney then holds sodium at the cost of potassium and hydrogen, so alkalosis persists until chloride and volume are restored. Urine chloride climbing above 20 shows volume is back. Barash accepts plasma chloride above 85 if it is trending up; Faust sets the stricter 105. A level between the two passes Barash but not Faust, so aim higher. Uncorrected alkalosis risks postoperative apnoea, and CSF pH lags plasma, so a normal pH beside high bicarbonate is compensated, not corrected.

Normal pH taken as proof of correction. A normal-looking pH seems to prove correction. With bicarbonate still high, though, it shows a compensated alkalosis that is still present. No textbook sets a pH target, and CSF pH trails plasma, so the risk of apnoea after surgery remains.

Barash wants sodium above 130 before pyloromyotomy and, for obstructed infants, urine output between 1 and 2 mL/kg/h. Faust treats urine chloride above 20 as volume restored, then expects plasma chloride above 105. Miller warns persistent alkalosis raises postoperative apnoea and CSF pH lags.

Sources: Barash 9eFaustMiller 10e

Congenital heart lesions are common in Down syndrome, mostly atrial and ventricular septal defects. They can be missed by a fetal scan or a normal clinical examination. So the American Academy of Paediatrics wants every child scanned and the scan read by a paediatric cardiologist. If no scan is available, surgery should wait for cardiology review. The neck is a separate question. Barash lists cervical spine films only for patients over 3 years, where instability is judged by the atlanto-dens gap. A neonate or infant therefore gets no neck film.

Routine cervical spine films in infants. Atlanto-axial instability is the best-known airway concern in Down syndrome, so a neck film feels like the expected test. But films are listed only for children over 3 years, so a newborn or infant gains nothing from one. A missed septal defect, on the other hand, changes the anaesthetic plan.

Faust reports that the American Academy of Paediatrics advises a paediatric cardiologist-read echocardiogram for every child with trisomy 21, even after a fetal study; if unavailable, delay surgery. Barash lists cervical spine films only for patients older than 3 years.

Sources: FaustBarash 9e

The fistula is often one sign of a wider developmental defect. Vertebral, anal, renal, limb and cardiac anomalies tend to occur together with it. Most of these can wait. A structural heart lesion cannot. These infants die more often from the heart defect than from the operation on the fistula. Echocardiography defines that lesion before induction. It also shows whether the aortic arch is right-sided. So the cardiac scan is essential before the baby goes to theatre.

Vertebral defect as key anomaly. Vertebral defects come first in the acronym and really are part of the association, so they are what clinicians think of first. But a vertebral anomaly does not change the immediate anaesthetic plan. The heart lesion is the one that drives mortality, so it must be found and defined first.

The texts place the fistula within the VATER and VACTERL cluster. They name the cardiovascular lesion as the most serious associated anomaly and say deaths from it exceed deaths from the fistula repair. They advise echocardiography before anaesthesia, including a check for a right-sided arch.

Sources: Barash 9eMiller 10e

Omphalocele often comes with prematurity and other congenital anomalies, and heart defects are among the most important. A cardiac lesion nobody has found changes how the anaesthetic is planned. Closing the defect raises intra-abdominal pressure, and pressure on the liver or the vena cava can cause hypotension. A heart with a structural defect may not cope with that. So the cardiac anatomy has to be known before surgery, even though repair should not be delayed for long because of the risk of infection and bowel damage.

Liver imaging for hepatic sac contents. Tempting because the liver often lies in the sac and pressure on it during closure can cause hypotension. But surgery shows the abdominal contents directly, and liver imaging does not change anaesthetic risk. The hidden danger is an associated heart defect, which only echocardiography detects.

These neonates are often premature and often have other congenital defects, especially heart disease. The preoperative workup should include an echocardiogram. Repair should not be delayed, but the baby needs fluid resuscitation and correction of electrolytes first.

Sources: Miller 10e

Preoperative anxiety is the most consistent predictor of emergence delirium, so the best premedication calms the child before induction and also protects them on waking. Dexmedetomidine is an alpha-2 agonist and does both. Alpha-2 agonists reduce delirium whether given by mouth, intravenously or caudally, and intranasal dexmedetomidine works better than midazolam as a premedication. Desflurane or sevoflurane maintenance makes delirium more likely, while propofol TIVA rarely causes it.

Midazolam as default premedication. Midazolam is the familiar default anxiolytic for children, so it feels like the safe choice. But the parents want two things: anxiolysis and a smooth emergence. Dexmedetomidine covers both, and studies show it outperforms midazolam as a premedication in children.

Heightened anxiety is the one consistent predictor of emergence delirium, and dexmedetomidine shows promise against it. A meta-analysis found that oral, intravenous or caudal alpha-2 agonists reduce delirium. Intranasal dexmedetomidine beats midazolam as a premedication. Delirium is more frequent after sevoflurane or desflurane maintenance.

Sources: Barash 9eMiller 10e

Many paediatric centres once treated parental presence at induction as standard care. Barash still says it can help at mask induction when a child is anxious and has had no premedication. Miller cites recent studies that do not support it as a routine way to reduce anxiety. It is therefore no longer routine and is kept for chosen cases: behavioural problems, developmental delay or repeated procedures. Its value depends on separation distress, and infants up to 9 months show less of that, so they gain little.

Parent present for crying infant. A crying baby held by mum looks like the obvious case for comfort. But infants up to 9 months are less prone to separation anxiety, so a parent in theatre adds little. The tearful, unpremedicated preschooler is the child this measure is meant for.

Miller says recent studies do not back routine parental presence, but it may matter for behavioural problems, developmental delay or repeated procedures. Infants up to 9 months are less prone to separation anxiety. Barash says it may help the anxious unpremedicated child at mask induction.

Sources: Barash 9eMiller 10e

Anxiety before surgery and preschool age both make agitation on emergence more likely, and so does ENT surgery under sevoflurane. Prevention starts on the ward. Calm the child, distract him, and tell him what to expect in terms that fit his stage of development. Even children who were told beforehand can be frightened by unfamiliar sensations afterwards. Keep the explanation truthful, give it with empathy, and add to it after surgery when needed.

Detailed technical explanation of the procedure. This feels honest and thorough. But technical details of cutting and needles do not suit a five-year-old's stage of development, and they can raise the anxiety that preparing him is meant to lower. Tell him what he will notice and feel, not how the operation is done.

Preventing emergence delirium should begin before surgery. Treat the child's anxiety, distract him, and prepare him with age-appropriate teaching about what to expect. Clear explanations are given before surgery about what will happen afterwards. Empathy and further explanation help reduce anxiety after surgery.

Sources: Barash 9eMiller 10e

When a child has no intravenous line, the oral route is best accepted. Midazolam suits premedication: it acts quickly, has a short elimination half-life, causes anterograde amnesia and has few side effects. The dose is weight-based, with an absolute ceiling of 15 mg (Miller), so heavier children stop receiving more once they reach it. Miller gives onset of calm and sedation as about 20 minutes. Barash gives the same weight-based dose 30 minutes before surgery and finds emergence is not delayed.

20 mg maximum ceiling. The 0.5 mg/kg dose is right, so the ceiling attached to it is the part that is easy to misremember. Miller caps oral midazolam at 15 mg. A 20 mg ceiling would let a heavier child receive more than that maximum.

Miller recommends oral midazolam at 0.5 mg/kg, not exceeding 15 mg, with sedation and anxiolysis in about 20 minutes. Barash gives the same 0.5 mg/kg by mouth 30 minutes before surgery and reports dependable calming without slow emergence. Barash gives no ceiling.

Sources: Miller 10eBarash 9e

Chloral hydrate is an oral sedative with unpredictable onset that cannot be titrated, so it suits short, painless studies tolerating slight movement. MRI is long and needs the child completely still; a single dose often wears off or never reaches sufficient depth. Failure is more likely with longer procedures, heavier or older children, inpatients and children with syndromes. Textbooks give no figure, stating only that sedation alone fails more often than general anaesthesia. The percentages come from two outside retrospective series, each describing its own population.

About 20% failure for MRI. Twenty looks right because the large series report about one in five failures. But that figure covers all procedures together, or developmentally delayed children only. MRI on a single dose failed in about two in five, and neurologically normal children failed far less often.

Textbooks say only that sedation alone fails more often than general anaesthesia. One outside series found 21.8% failure across all procedures on a first 50 mg/kg dose, 39.7% for MRI. Another found brain MRI failure of 22% in delayed versus 6% in normal children.

Sources: Outside our books: Risk factors for chloral hydrate sedation failure in pediatric patients: a retrospective analysis (2024)Outside our books: Effectiveness of Chloral Hydrate on Brain MRI in Children with Developmental Delay/Intellectual Disability Comparing with Normal Intelligence: Single Tertiary Center Experience (2021)Barash 9e

Children find it hard to say how much something hurts. Cartoon faces that show more and more distress let a child point to how they feel, without needing words or abstract measures. Babies who cannot talk yet and children with developmental delay cannot use any self-report scale. For them, an observer scores five behaviours: face, legs, activity, crying and how easily they are comforted. No one tool works for every age or developmental stage. Single-score scales give a quick, practical measure that suits children.

Detailed multidimensional McGill questionnaire. A week of pain sounds long-lasting and complex, so a detailed tool that looks at many sides of pain seems right. But it is slow and awkward to complete. It is also not one of the scales the books list for children, who need a simple picture-based self-report tool.

For children who can report their own pain, Barash lists the visual analogue, numeric and Wong-Baker faces scales. For those who cannot, it uses the FLACC behavioural scale. Barash also says faces scales suit children, and calls detailed tools like McGill more cumbersome.

Sources: Barash 9e

General paediatric texts accept either intramuscular ketamine or a sevoflurane gas induction when no cannula exists. For shunt surgery specifically, the neuroanaesthesia chapter favours sevoflurane: despite theoretical concerns, volatile inductions prove well tolerated in practice, even once fontanelles have closed. Ventilation is taken over by mask as early as possible, giving a controlled airway while a vein is found; relaxant and intubation then follow through the new line. The exception is the already stuporous child, in whom gas induction is avoided.

Intramuscular ketamine induction. IM ketamine is tempting because general paediatric sources list it for absent access, and it helps cannulation in uncooperative children. For a shunt revision, though, the neuroanaesthesia source describes sevoflurane with early mask-controlled ventilation, then a cannula, relaxant and intubation. It does not describe IM ketamine for this setting.

A neuroanaesthesia text describes gas induction with sevoflurane plus prompt bag-mask controlled ventilation when a vein cannot readily be found in shunt patients, then a cannula, relaxant and intubation; it avoids gas induction in stuporous children. A general paediatric text accepts IM ketamine or sevoflurane.

Sources: Miller 10e

In ex-preterm infants, systemic opioids and sedatives make postoperative apnoea more likely. A regional technique used without them lowers that risk and still gives good groin analgesia. Caudal volume decides how high the block spreads. 1 mL/kg reaches the lumbar dermatomes, which covers a hernia repair. A larger volume, such as 1.25 mL/kg, spreads towards the thoracic levels and is not needed. The block lowers the apnoea risk but does not remove it. So a young ex-preterm infant is admitted and monitored on the ward, not sent home.

Oral analgesia with same-day discharge. This looks right because hernia repair is often day surgery and oral analgesia also avoids opioids. It is wrong because this infant is still young enough in post-conceptual age to need admission for apnoea monitoring. It also gives weaker analgesia than a caudal block.

A board review case describes an ex-preterm infant at 41 weeks post-conceptual age. It says he must be admitted and prefers caudal 0.25% bupivacaine 1 mL/kg with overnight ward observation. Another textbook adds that avoiding opioids and sedatives during regional anaesthesia may reduce apnoea.

Sources: Mayo reviewStoelting 8eBarash 9e

Neonates on CPAP have little respiratory reserve, and most intrahospital transfer mishaps are respiratory, so CPAP may fail during the move and scan. Textbooks say only that, in general MRI practice, anaesthesia usually starts away from the scanner; they do not say where to intubate these babies. Sources outside the textbooks add that, when non-invasive support cannot be reliably maintained during transfer, intubating first in intensive care is the reasoned preference, though not a fixed rule.

Induce in room beside scanner. It is tempting because textbooks describe starting anaesthesia in a separate room next to the scanner. That works for stable patients. A CPAP-dependent neonate first has to survive the transfer on fragile support, and respiratory events cause most transfer incidents, so securing the airway before leaving is preferred.

A transport review suggests intubating in intensive care may be better if non-invasive ventilation cannot be maintained during transfer. One report intubated children in paediatric intensive care, if needed, before MRI transfer. Induction often occurs away from the scanner.

Sources: Outside our books: Error Traps in the Intrahospital Transport of Critically Ill and Anesthetized Children (2025)Outside our books: “Feed-and-wrap” technique versus deep sedation for neonatal magnetic resonance imaging: a retrospective comparative study (2024)Faust

Spontaneous breathing acts as a built-in brake: as the child deepens, breathing falls and less agent is taken up. If you take over ventilation while the vaporiser is still high, such as 8% sevoflurane, the brake is gone, so depth rises quickly and the heart is depressed. Nitrous oxide was once added routinely because its second gas effect speeds induction. The same textbook now lists it, with volatiles and opioids, as a cause of vomiting to minimise. Strabismus surgery carries high vomiting risk, so nitrous oxide is now omitted.

Adding nitrous oxide for faster induction. Adding nitrous oxide is tempting because it was the standard partner for a gas induction and its second gas effect speeds loss of consciousness. Here that gain is outweighed: strabismus surgery is a high-risk operation for postoperative vomiting, and nitrous oxide is one of the drugs that cause vomiting.

Sources give no strabismus-specific guidance, so general principles apply. Spontaneous breathing is favoured during gas induction, as controlled breaths at a high vaporiser setting deepen anaesthesia rapidly and depress the heart. Nitrous oxide, once routine for speed, is now minimised in high-PONV strabismus surgery.

Sources: Barash 9e

A cuff adds bulk outside the tube and, once inflated, seals the airway, so the tube need not be oversized to prevent a leak. A tube of uncuffed size would press the cuff against the narrow subglottic mucosa and risk injury. A cuffed tube is therefore taken 0.5 to 1.0 mm below the uncuffed Cole size. Barash's table and Motoyama both give age/4 + 3.5, the usual default. Khine's age/4 + 3 is not an error: it is the lower edge of the same reduction.

Using the uncuffed age/4 + 4 size. At six years, 6 is tempting because it matches the age, but the uncuffed Cole size is only slightly smaller, so 6 is bigger than even an uncuffed tube. The cuffed choice is half a size smaller than the uncuffed one, and a further half size smaller is acceptable.

Cuffed tubes should be 0.5 mm to a millimetre smaller than uncuffed. Commonest formulas: Khine, age/4 + 3, and Motoyama, age/4 + 3.5. Beyond 2 years, Barash lists age/4 + 3.5 for cuffed and age/4 + 4 for uncuffed.

Sources: Outside our books: Pediatric cuffed endotracheal tubes (2013)Barash 9e

The anaesthesia textbooks use a single cut-off at 1,500 g. Barash and Miller give 2.5 mm below it and 3.0 above, and Mayo simplifies this to 2.5 for every premature newborn. Neonatal resuscitation weight tables, such as Faust's, split preterms into gestation and weight bands and move up to 3.0 at 1100–1400 g. Every one of these figures is for an uncuffed tube. So for a preterm between those cut-offs, both sizes can be defended, and the textbook answer is 2.5. For the tiniest babies, every source agrees on 2.5.

3.0 mm from resuscitation weight table. This is tempting because the resuscitation weight tables move up to 3.0 at 1100–1400 g, so it is the table answer in that band. It fails for the smallest preterms, where every source gives 2.5, and the anaesthesia textbooks keep 2.5 right up to 1,500 g.

Barash gives 2.5 mm for preterms, especially those under 1,500 g. Miller gives 2.5 below 1.5 kg and 3.0 above it. Mayo gives an uncuffed 2.5 to every premature newborn. Faust's weight table gives 2.5 for the lightest bands and 3.0 from 1100–1400 g.

Sources: Barash 9eMiller 10eFaustMayo review

Hypoplastic lungs are easily damaged, so ventilation uses peak pressures below 25 cm H2O and accepts a raised PaCO2 of 45 to 55 mmHg provided pH stays above 7.25. CO2 should not be driven down. Mask inflation forces gas into the stomach lying in the chest and compresses the lung, so intubate first. Titrate oxygen to a range: Barash sets a preductal floor above 85%, and Faust gives an intraoperative band of 90%–95%. Give enough to reach it, no more. Nitrous oxide is contraindicated.

Maximal inspired oxygen for pulmonary hypertension. Maximal oxygen feels right for a cyanosed neonate with pulmonary hypertension, but no text fixes inspired oxygen at full strength. Oxygen is titrated to a preductal saturation target and hyperoxia is avoided. Once the target is reached, inspired oxygen is weaned down.

Texts advise immediate intubation without mask ventilation, peak pressures below 25 cm H2O with PEEP 2 to 5, permissive hypercapnia with PaCO2 45 to 55 mmHg and pH above 7.25, preductal saturation above 85%, intraoperatively 90%–95% without hyperoxia, and no nitrous oxide.

Sources: FaustBarash 9e

The fistula connects the airway to the stomach. Until the tube lies beyond the fistula, or the fistula is tied, positive-pressure breaths can pass through it and distend the stomach. A muscle relaxant stops spontaneous breathing, forcing positive-pressure ventilation, so paralysing rapid sequence induction is avoided. Stoelting accepts intravenous induction too, provided spontaneous breathing is maintained and inflation pressures are minimal. Awake intubation is reserved for when no alternative exists. Once the fistula is tied, controlled ventilation is safe.

Rapid sequence induction with relaxant. Fear of aspiration makes rapid sequence induction seem the safe reflex for any stomach risk. But the relaxant abolishes spontaneous breathing, so the infant needs positive-pressure ventilation before the fistula is controlled. That gas passes down the fistula and distends the stomach, the very harm the technique should avoid.

Miller prefers inhalational induction, preserving breathing until ligation; Faust adds controlled ventilation afterwards. Stoelting allows inhalational or intravenous induction if breathing is preserved, reserving awake intubation for when there is no alternative. Mayo names sevoflurane and rejects paralysis and mask positive pressure.

Sources: Miller 10eFaustStoelting 8eMayo review

Once the covering membrane is removed, exposed bowel loses extracellular fluid heavily. Replace these losses liberally with balanced salt solution, and use an arterial line to track blood pressure and serial gases for acid–base status. Putting viscera back into a small, underdeveloped abdominal cavity needs a fully relaxed wall. A tight closure can compromise breathing and impair bowel, renal and limb circulation. That respiratory compromise often needs 24 to 48 hours of ventilation before extubation.

Restrict fluids to reduce bowel oedema. Restricting fluid looks sensible because less bowel oedema might make the viscera easier to reduce. But exposed viscera lose large volumes of extracellular fluid, and under-replacement leaves a hypovolaemic, acidotic neonate. Closure is made possible by muscle relaxation or a staged silo, not by drying the patient out.

Exposed viscera lose large extracellular volumes, replaced with balanced salt solution; an arterial line tracks pressure and blood gases; relaxation is essential for closure; and 24 to 48 hours of postoperative ventilation is often needed unless the defect is very small.

Sources: Barash 9eMayo review

Vomiting gastric hydrochloric acid removes hydrogen and chloride, leaving bicarbonate unopposed. The plasma becomes alkalotic and chloride falls. The kidneys defend pH by trading potassium for hydrogen, which causes hypokalaemia. On readiness for surgery, Barash accepts chloride above 85 mEq/L if it is still trending up. Faust asks for above 105 mEq/L once urinary chloride over 20 mEq/L shows volume is restored. Treat Barash's figure as the minimum floor and Faust's as the fuller endpoint: never operate below the floor, and aim for Faust's level.

Metabolic acidosis from dehydration. It tempts because a dehydrated infant suggests poor perfusion, and late in the illness the urine turns acidic as the kidney conserves sodium. But losing gastric acid makes the plasma alkalotic. The acidic urine is a paradoxical renal response, not a systemic acidosis.

The texts attribute the alkalosis and low chloride to loss of gastric acid, and the hypokalaemia to renal potassium–hydrogen exchange. Bicarbonate and chloride gauge dehydration. Barash's threshold is chloride above 85 mEq/L and rising. Faust's is above 105 mEq/L after urinary chloride exceeds 20.

Sources: Mayo reviewFaustBarash 9e

Platinum drugs such as cisplatin top the list of chemotherapy agents that damage the kidney. When a heavily treated child's regimen is not named, it is reasonable to infer that one was given. The kidney injury cisplatin causes typically shows as worsening renal function plus magnesium loss. Cisplatin is also a known drug cause of renal potassium loss. Both electrolytes can fall, each on its own, so potassium loss should not be explained as a result of low magnesium. The hallmark is low magnesium.

Hypokalaemia rather than hypomagnesaemia. Low potassium is tempting because cisplatin is a recognised drug cause of potassium wasting. But hypokalaemia has many causes. Low magnesium with declining renal function is the typical presentation of cisplatin kidney injury, so it is the more specific finding.

The cancer chapter names platinum agents such as cisplatin first among nephrotoxic chemotherapy drugs. It describes renal impairment with low magnesium as the usual first signs of that injury. An electrolyte table also lists cisplatin among drug causes of low potassium.

Sources: Stoelting 8eMiller 10e

After birth, oxygen tension rises sharply, so the newborn no longer needs its high haemoglobin mass. At the same time, fetal haemoglobin is gradually replaced by adult haemoglobin. As a result, the concentration falls to its lowest point at 8–12 weeks. After 3 months it rises steadily and reaches adult levels by 6–9 months. Preterm infants fall lower, earlier and for longer. The quoted nadir varies slightly between texts, but every version places a value of about 10 g/dL within the normal range.

Iron deficiency anaemia needing iron treatment. Iron deficiency is the commonest cause of childhood anaemia, so it feels the safe choice, but this healthy infant is at the expected physiological nadir. Falling oxygen demand and the switch to adult haemoglobin after birth cause the dip, which corrects itself without treatment.

The texts describe term haemoglobin falling to a low point of about 10 g/dL at 8–12 weeks as adult haemoglobin replaces fetal haemoglobin. It then recovers after 3 months. In preterm infants the fall is deeper (7–9 g/dL), comes earlier (3–6 weeks) and lasts longer.

Sources: Mayo review

In children, hypotension is defined by systolic pressure measured against an age-specific cut-off. For a term neonate up to 28 days old, a systolic of 60 mmHg is roughly the 10th centile. A systolic of 65 is above that and sits within the normal resting range for babies under three months. The heart rate is also within the normal 100–150 band. A low-looking diastolic does not make the baby hypotensive on its own, so you do not need fluid or a vasopressor. Keep watching the trend after induction.

Fluid bolus for a normal neonatal pressure. A fluid bolus is tempting because, when a child really is hypotensive with a normal or fast heart rate, low circulating volume is the usual cause and fluid is the preferred treatment. Here the systolic is above the neonatal cut-off, so there is no hypotension to treat.

The review defines paediatric hypotension by systolic pressure. The resuscitation guideline puts the 10th-centile systolic for term neonates up to 28 days at 60 mmHg. The normal-values table for babies under three months gives a systolic of 65–85 and a heart rate of 100–150.

Sources: Mayo reviewOutside our books: Singapore Paediatric Life Support Guidelines 2026 (2026)Barash 9e

In omphalocele, the developing gut fails to move back from the yolk sac into the abdominal cavity. The bowel, and sometimes the liver, stays inside the cord, covered by a membrane. Because the failure happens early in development, it often comes with other defects: trisomies, heart disease (ventricular septal defect is the commonest) and Beckwith-Wiedemann syndrome. Textbooks quote different rates of associated anomalies (50% to 80% in one review, 75% in another). All agree they are common, which sets omphalocele apart from gastroschisis.

Paraumbilical defect, no sac. Both lesions sit right next to the umbilicus and their names are easily swapped, so 'paraumbilical' sounds right. But a defect beside a normal cord, with no sac, is gastroschisis. Occlusion of the omphalomesenteric artery is also a gastroschisis mechanism. An omphalocele lies within the cord itself.

Omphalocele lies within the cord with a sac; gastroschisis lies beside the cord without one. Omphalocele results from failed return of gut from the yolk sac. Associated defects occur in 50–80% (or 75%), including heart disease in 20%, mostly ventricular septal defect.

Sources: Stoelting 8eMayo reviewFaust

The upper oesophagus ends blindly, so swallowed saliva and milk pool in the pouch and spill into the larynx, causing drooling, coughing and cyanosis; nothing reaches the stomach to be ejected. Through the lower fistula, air enters the stomach, so a plain film shows a coiled tube above a gastric bubble. The fetus cannot swallow, so polyhydramnios raises suspicion and around 40% to 50% are found before birth. Barash gives about 85%, Faust 90%, the Mayo review 85%-90%; all call it the commonest type.

Projectile vomiting at first feed. Vomiting feels like the natural sign of a blocked feeding tract. But with a blind upper pouch, nothing reaches the stomach to be forcefully expelled. Saliva and feed overflow into the airway instead, giving drooling, choking and cyanosis. Projectile vomiting belongs to pyloric stenosis.

Barash and Faust put the distal-fistula, blind-pouch form at 85% and 90%, so most atresias have a fistula. Faust flags antenatal polyhydramnios and drooling or coughing at birth. Mayo reports 40–50% are diagnosed prenatally. Keep the upper pouch on continuous suction preoperatively to prevent aspiration.

Sources: Barash 9eFaustMayo review

Vomiting removes hydrochloric acid from the stomach. Chloride falls and bicarbonate rises, so the blood becomes alkalotic, not acidotic. The lungs compensate for a metabolic alkalosis by breathing less and letting carbon dioxide build up. Alkaline cerebrospinal fluid also depresses the drive to breathe, and overventilating the lungs during anaesthesia makes this worse. As a result, these infants often breathe inadequately after surgery. Males are affected about 4 times as often as females, especially first-borns.

Postoperative hyperventilation as compensation. It is tempting because these infants have a major acid–base disturbance, and hyperventilation is the familiar response to acidosis. But the disturbance is an alkalosis. The body compensates by breathing less, and alkaline cerebrospinal fluid suppresses breathing further, so the postoperative risk is ventilatory depression.

Ultrasound confirms the diagnosis. Gastric acid loss causes hypochloraemic metabolic alkalosis, compensated by hypoventilation. Alkaline CSF, aggravated by intraoperative overventilation, often depresses breathing after surgery. Males are affected 4 times more, especially first-borns, presenting at 3 to 5 weeks.

Sources: Mayo reviewFaustBarash 9e

In gastroschisis the umbilical cord is normally sited and bowel emerges through a separate abdominal wall defect beside it. No peritoneum or hernia sac covers the bowel, so the exposed gut becomes inflamed, swollen, dilated and shortened, a chemical peritonitis. The defect is usually isolated, so other congenital anomalies are uncommon, although prematurity is frequent. In omphalocele, bowel herniates into the cord within a covering sac; this is the condition associated with cardiac disease, bladder exstrophy and Beckwith–Wiedemann syndrome.

Cardiac anomalies expected with gastroschisis. It is tempting because reviews of abdominal wall defects stress screening for associated heart disease and discuss both lesions together. But that cardiac link belongs to omphalocele. Gastroschisis rarely has other anomalies. Its typical problem is damaged, inflamed bowel.

Gastroschisis is a defect beside the umbilicus with viscera uncovered by peritoneum. Its typical problem is inflamed, swollen, dilated, shortened bowel. It is rarely linked to other anomalies but often to prematurity. Cardiac disease, bladder exstrophy and Beckwith–Wiedemann syndrome are listed under omphalocele.

Sources: Miller 10eFaust

The right hand receives aortic blood upstream of the duct; the legs, and sometimes the left hand, lie downstream. Desaturated blood entering the descending aorta through the duct lowers only downstream readings. In PPHN, triggered by sepsis, asphyxia or meconium, raised pulmonary vascular resistance pushes right-sided blood across the duct, so hypoxaemia resists oxygen while pulses and limb pressures stay equal. In a duct-dependent coarctation the right ventricle perfuses the lower body via the duct, giving the same split plus weak femoral pulses and higher arm pressure; the echocardiogram decides.

Duct-dependent coarctation despite a normal echocardiogram. Coarctation is tempting because a duct-dependent coarctation really does make post-ductal readings lower. It fails once the echocardiogram is normal, which excludes it; clinically it also brings weak femoral pulses and higher arm pressures, not oxygen-resistant hypoxaemia with equal pulses in a septic baby.

Barash: left-hand or leg probes may read below the right hand with high pulmonary or low systemic pressure; sepsis can trigger PPHN. Miller: in critical left-sided obstruction, desaturated right-ventricular blood perfuses the body via the duct. Stoelting: hypertensive arms, weak delayed femoral pulses.

Sources: Barash 9eMiller 10eStoelting 8e

After birth, pulmonary vascular resistance keeps falling. As it falls, more blood crosses a ventricular septal defect from left to right and floods the lungs. This overcirculation causes pulmonary oedema and congestive heart failure. In an infant, heart failure shows as poor feeding, sweating, tachycardia and fast breathing. There is no cyanosis because the shunted blood is already oxygenated and simply passes through the lungs again. Tetralogy of Fallot and transposition send deoxygenated blood to the body, so they are classed as cyanotic lesions.

Atrial-level left-to-right shunt. An atrial septal defect is also an acyanotic left-to-right shunt, so it seems to fit an infant who is not blue. But small atrial defects usually cause no symptoms for many years and are often first found in adults. Heart failure in infancy points to a ventricular-level shunt.

Miller lists ventricular septal defect among newborn lesions that present as congestive heart failure, and lists tetralogy and transposition as cyanotic. Infant heart failure includes poor feeding and sweating. With a left-to-right shunt, falling pulmonary resistance increases lung blood flow and can cause pulmonary oedema.

Sources: Miller 10eMayo review

In laryngomalacia the larynx is not stiff enough to stay open. The cause may be immature neural control of the laryngeal muscles, or pressure on the laryngeal cartilage. When the infant breathes with normal effort, the soft structures fall inward and partly block the airway. The turbulent airflow through that narrowing is what makes the stridor. Because the problem comes from the larynx's own development, it is common, and it outnumbers cysts, masses and lower-airway collapse.

Tracheomalacia as an equally common cause. Tracheomalacia is also a floppy-airway disease of infants, so it sounds like an equally good answer. But laryngomalacia alone accounts for most persistent infant stridor, so no other cause can be the commonest. Collapse of weakened lower airways is more typical of ex-intensive-care infants with specific risk factors.

Stoelting says laryngomalacia comes from a larynx that lacks rigidity and collapses during normal breathing. It causes over 70% of persistent stridor in newborns and young infants. Weakening of the lower airway cartilage is described separately, mainly in infants after long neonatal intensive care.

Sources: Stoelting 8e

The reflex only continues while the eye is being stimulated. Triggers include traction on an extraocular muscle, pressure on the globe, orbital haematoma, eye injury or eye pain. Once the stimulus stops, the reflex loses its drive and heart rate recovers quickly. If the same manoeuvre is repeated, the response is usually weaker, so the operation can normally continue after the rate settles. A drug given while the traction goes on treats the slow heart rate but leaves the cause in place.

Giving atropine before stopping traction. Atropine tempts as the familiar drug for vagal bradycardia, with a child-appropriate dose and a decisive feel. But the source says first treatment is removing the stimulus. The reflex settles quickly once traction stops; giving a drug while pulling continues leaves the cause in place.

The reflex is common in squint surgery and can cause a range of arrhythmias, from sinus or nodal bradycardia to, rarely, asystole. First treatment is to stop the surgical stimulus. The reflex settles quickly, and repeating the stimulus usually provokes a weaker response.

Sources: Mayo review

Children with Down syndrome are unusually prone to severe bradycardia during inhalation induction, reported in up to 57%. The usual cause is too much agent. An 8% sevoflurane setting is roughly 4× MAC. If breathing is controlled while the dial is still high, depth rises quickly and depresses the heart, which is a recognised route to paediatric cardiac arrest. Cutting the inspired concentration removes the cause straight away and needs no cannula. Deepening makes it worse. Venous access is often difficult in these children, so drugs come second.

Giving atropine before lightening anaesthesia. Atropine is tempting because bradycardia in these children is well known and anticholinergics do treat it. But it leaves the excessive sevoflurane depth in place, the hypotension reflects myocardial depression, and venous access may be slow. Drugs are for severe bradycardia, alongside lightening.

One textbook reports severe bradycardia in up to 57% of Down syndrome children during inhalation induction, treated with an anticholinergic or adrenaline when severe, and warns venous access may be difficult. Another links high vaporiser settings under controlled ventilation to rapid deepening and cardiac depression.

Sources: Barash 9eFaust

Succinylcholine is shaped like two acetylcholine molecules joined together, so it stimulates muscarinic receptors on the sinus node. Infants have high vagal tone, so even a first dose can slow the heart. A second dose within 10 minutes adds to this. Its breakdown products, mainly succinylmonocholine and choline, have built up and act on the node, causing sinus bradycardia or a junctional rhythm. Atropine given beforehand blocks this muscarinic effect.

Propofol induction dose as the cause. Propofol is a known cause of bradycardia, and a large induction dose makes it look plausible. But here the heart slowed after a repeat dose of succinylcholine in a vagotonic neonate. That is the classic setting for muscarinic bradycardia from built-up succinylcholine metabolites.

Succinylcholine acts like acetylcholine, and its vagotonic effects are strongest in infants. Repeat doses within 10 min can cause sinus bradycardia or junctional rhythm because metabolites build up. Atropine 10 to 20 mcg/kg prevents bradyarrhythmias at all ages, including infants.

Sources: Faust

Pulseless VT is an arrest rhythm with no cardiac output, so it is treated exactly like VF: an unsynchronised defibrillating shock, not cardioversion. Classic textbook teaching fixed the first dose at 2 J/kg. A later meta-analysis found that low dose no better than higher ones, so current guidance accepts 2–4 J/kg to start; 2 J/kg is therefore safe under both. Later shocks rise to 4 J/kg. For a 20 kg child that means 40 to 80 J; a small infant needs roughly twice its weight in joules.

Synchronised cardioversion for pulseless VT. Synchronising feels right because VT has organised complexes, and synchronised cardioversion is the familiar VT treatment. Without a pulse, though, this is cardiac arrest. It is managed like VF with unsynchronised defibrillation, so the mode is wrong whatever the energy.

Textbook teaching gives 2 J/kg first, rising to 4 J/kg for a second shock. One guideline recommends 2 J/kg first for VF or pVT. Another, citing equivocal meta-analytic data, accepts 2–4 J/kg. A review applies this as 40 to 80 J at 20 kg.

Sources: Miller 10eOutside our books: Singapore Paediatric Life Support Guidelines 2026 (2026)Outside our books: 2025 Korean Guidelines for Cardiopulmonary Resuscitation: Part 8. Pediatric advanced life support (2026)Mayo review

Unstable re-entrant SVT means the circuit must be broken now. Vagal manoeuvres and drugs are for the stable child, who has time for them. A synchronised shock interrupts the re-entry loop. Because the rhythm is organised, a low weight-based energy is enough to start with. You double to 2 J/kg only if the first attempt fails. Shock straight away when the child is unstable, when there is no IV or IO access, or when adenosine has failed. If the child is conscious, sedate first.

High adult-level defibrillation energy. A bigger shock can seem more certain to work, and adult or defibrillation energies come to mind first. In a small infant, this energy is above even the 2 J/kg escalation dose. Organised SVT responds to a low weight-based starting dose, so start low and increase only if it fails.

Miller's and the Korean PALS guideline agree: treat unstable re-entrant SVT with synchronised cardioversion. Start at 0.5–1 J/kg and increase to 2 J/kg if it fails. Sedate conscious children first. Vagal manoeuvres and adenosine are for stable patients.

Sources: Miller 10eOutside our books: 2025 Korean Guidelines for Cardiopulmonary Resuscitation: Part 8. Pediatric advanced life support (2026)

The best place to feel for a pulse depends on the age group. In infants it is the brachial artery. Once the patient counts as a child, the carotid and femoral arteries are equally acceptable. Only trained providers should check for a pulse. Lay rescuers are told not to try in infants or children because they often report a pulse that is not actually there.

Brachial pulse in a child over 1. The brachial is the right site for an infant, so it feels like the natural choice for any small patient. The source moves to the carotid or femoral once the patient is a child, so the brachial is wrong for a child older than one year.

Providers who feel for a pulse should use the brachial artery in infants and the carotid or femoral artery in children. Lay rescuers should not check for a pulse in infants or children because they often wrongly feel one.

Sources: Mayo review

The cyanosis in a spell comes from a sudden tightening of the right ventricular outflow tract. That sends deoxygenated blood right-to-left across the ventricular septal defect instead of into the lungs. Beta-blockade relaxes the hypertrophied infundibulum and slows the heart, which lengthens filling time. Sedation with morphine breaks the cycle of agitation and catecholamine release that drives the spasm. Ongoing beta-blockade makes spells less frequent and less severe. If spells keep returning despite this, surgery that secures pulmonary blood flow (a shunt or full repair) is the answer.

Isoprenaline rescue during a tet spell. Isoprenaline is tempting because a desaturating, hypercarbic child seems to need a rescue inotrope. But beta-stimulation makes the infundibulum contract harder and speeds the heart. That tightens the outflow obstruction and increases the right-to-left shunt, which is exactly the opposite of what beta-blockade and sedation achieve.

One text lists a short-acting beta-blocker, or a sedative such as morphine, as further steps to ease spastic outflow tract obstruction during a spell. Another notes that beta-blocking drugs reduce how often cyanotic spells occur and how severe they are.

Sources: Stoelting 8eFaust

In diaphragmatic hernia both lungs are underdeveloped, and the lung opposite the defect does most of the gas exchange. Forceful inflation, especially when trying to open up the collapsed lung on the hernia side, can rupture that opposite lung. Air under tension then collapses the working lung and presses on the heart and great veins. Oxygenation, compliance, venous return and cardiac output all fall together. Draining the opposite pleural space fixes the cause. Drugs only buy time.

Endobronchial tube migration. In a tiny neonate the trachea is short, so a tube in a bronchus feels like the obvious cause of desaturation and hard ventilation. But a misplaced tube causes hypoxia without abrupt cardiovascular collapse. Vigorous lung expansion followed by bradycardia and hypotension points to a ruptured opposite lung under tension.

During repair, an abrupt fall in heart rate, blood pressure, oxygen saturation or lung compliance points to a pneumothorax on the side opposite the hernia. Treat it promptly with a chest drain.

Sources: Faust

Reactive pulmonary vasoconstriction raises pulmonary vascular resistance. This drives right-to-left shunting, hypoxaemia and acidosis. Inhaled nitric oxide relaxes the pulmonary vessels and lowers that resistance. Haemoglobin inactivates it before it reaches the systemic circulation, so systemic pressure is spared. Miller credits it with better survival in reactive neonatal pulmonary hypertension. Barash adds that in diaphragmatic hernia it has not reduced the need for ECMO. The two fit together as a sequence: give inhaled nitric oxide with gentle or oscillatory ventilation first, and consider ECMO if the hypertension persists.

Intravenous nitroprusside. Nitroprusside is tempting because it also works by releasing nitric oxide and lowers vascular resistance. Given intravenously, though, it dilates the systemic circulation too. Systemic pressure falls and right-to-left shunting gets worse. Only the inhaled route acts selectively on the lungs.

Stoelting advises trying inhaled nitric oxide and oscillatory ventilation when pulmonary hypertension persists or recurs, with ECMO also considered. Miller says it lowers pulmonary resistance, improves neonatal survival and is inactivated by haemoglobin. Barash notes it has not reduced ECMO need in hernia.

Sources: Stoelting 8eMiller 10eBarash 9e

The neonatal abdominal cavity is too small for the returned viscera, so a tight fascial closure pushes intra-abdominal pressure up. The diaphragm is forced cephalad, functional residual capacity and compliance fall, so peak airway pressure climbs; the inferior vena cava is squeezed, so preload and blood pressure fall. Sustained, this is abdominal compartment syndrome, the recognised complication of one-stage closure under tension. Primary closure is advised against when inspiratory pressure exceeds 25 to 30 cm H2O or bladder or gastric pressure exceeds 20 cm H2O.

More neuromuscular relaxant to ease ventilation. Large defects do need deep neuromuscular block for closure, so more relaxant looks like the fix for stiff ventilation. But the high pressure comes from a crowded abdomen pressing on the diaphragm, not from muscle tone; relaxant cannot make the cavity bigger, and the vena cava stays compressed.

Tight closure compresses the vena cava and limits diaphragmatic movement. Avoid primary closure above inspiratory pressures of 25 to 30 cm H2O or bladder/gastric pressures of 20 cm H2O; excessive pressure means removing fascial sutures, closing skin only, or a silo.

Sources: Stoelting 8e

Gas from a positive-pressure breath takes the easiest path. With a fistula, that path often runs from the trachea into the stomach, especially when the fistula is wide or the lungs are stiff. The swollen stomach pushes the diaphragm up and reduces functional residual capacity. Each further breath then reaches the lungs less and the stomach more, and this spiral ends in hypoxaemia and arrest. Venting the stomach through the abdominal wall, or clamping the lower oesophagus, breaks the spiral. Harder bagging does not.

Paralyse and intubate immediately. Intubation is the usual answer to failed mask ventilation, but paralysis removes spontaneous breathing, leaving the baby dependent on positive pressure, which forces more gas into the stomach. A tube not beyond the fistula cannot bypass it, and the distended stomach still splints the diaphragm.

Mask positive pressure can inflate the stomach through the fistula and reduce functional residual capacity, and this is worse with a large fistula or poor compliance. Sudden gastric distension with desaturation may need urgent decompression through the abdominal wall. Paralysing before intubation risks more distension.

Sources: Miller 10eBarash 9e

The tumour compresses the renal artery and activates the renin-angiotensin-aldosterone system. Textbooks describe this only at presentation. A recent cohort outside the textbooks found 9 of 16 hypertensive children still needed treatment after resection, so the renin drive often outlasts surgery. Residual or metastatic tumour can also sustain it, so residual disease is the preferred explanation. A recent review lists pain, urinary retention and fluid overload without ranking them, and an undersized cuff overreads. Check for these too: they are possible, but they are not the expected cause.

Postoperative pain as the leading cause. Pain is the reflex explanation for high blood pressure in recovery, and the review lists it, but no source ranks it first. In a child hypertensive before an uneventful resection, tumour-driven renin hypertension already explains the reading. Look for pain and treat it; never assume it.

Cohort study links Wilms tumour hypertension to renal artery compression and renin activation; 9 of 16 hypertensive children needed treatment beyond resection. A review lists postoperative pain, urinary retention, fluid overload, excess renin, incomplete excision and metastases. Small cuffs read falsely high.

Sources: Outside our books: Predictors and course of hypertension in Wilms tumour patients: a retrospective observational cohort study (2025)Outside our books: Perioperative Management of Paediatric Hypertension (2025)Barash 9e

Isolated premature beats usually come from ectopic automaticity and are harmless, so most need no treatment. A newly placed central venous catheter is the exception: a tip lying against the heart can provoke extra beats, and the fix is to pull it back. The paediatric text describes this for ventricular beats. An atrial tip touching atrial tissue is the same mechanism. A chest radiograph shows where the tip lies, so it finds this correctable cause before anyone settles for watching and waiting.

Reassure and observe the ectopy. It is tempting because premature atrial beats are usually benign and need no therapy. That reassurance only holds when there is no removable cause. A freshly inserted line whose tip may be touching the heart is exactly such a cause, so check its position first.

Premature atrial beats in children are usually benign. A central catheter touching the heart can increase ventricular ectopics and should be pulled back. Catheter position can be confirmed by chest radiograph, among other methods.

Sources: Miller 10eFaust

Before birth the placenta clears waste. Arterial pressure is low, renal vessels resist flow, glomerular capillaries let little through, and glomeruli are few and small. These are the reasons filtration starts low. After delivery, arterial pressure rises and filtration climbs quickly. The newborn also cannot hold on to sodium or concentrate urine as an adult does. This wasting is greatest in the first days and in preterm infants, and term babies soon conserve sodium better. Poor glomerular permeability and sodium wasting are both real differences from the adult.

Newborn GFR is high. Filtration climbs steeply over the first weeks, so it is easy to picture a newborn's GFR as high. In fact it rises fast from a very low start. Compared with the adult, newborn filtration is reduced, and it reaches adult values only in early childhood.

One text lists four causes of low filtration: low arterial pressure, high renal vascular resistance, poorly permeable glomerular capillaries, and few small glomeruli. Another says term newborn GFR is greatly reduced but rises about fourfold within weeks. Newborns obligately lose sodium and need perioperative supplementation.

Sources: Barash 9eStoelting 8e

Once breathing starts, pulmonary blood flow rises and left atrial pressure climbs above right, holding the foramen shut by pressure alone. Rising arterial oxygen constricts the ductus, which then seals permanently within weeks. The foramen only seals permanently when its tissue fuses: Stoelting places this between 3 months and 1 year, Millers says months to years if at all, and many adults keep a probe-patent channel. One year is the far end of that range, so fusion cannot be assumed.

Foramen ovale reliably sealed by one year. It sounds right because textbooks say the foramen ovale closes anatomically by about one year. But one year is the end of the quoted range, closure may take years or never happen, and a probe-patent foramen persists in many adults, so it cannot be called reliably sealed.

Foramen ovale: functional closure within the first hour; anatomical between 3 months and 1 year, possibly years or never, with 20% to 30% of adults probe-patent. Ductus: functional closure 10 to 15 hours after birth, anatomical by 4 to 6 weeks.

Sources: Barash 9eStoelting 8eMiller 10e

At birth the duct and foramen ovale shut only functionally, not anatomically. The newborn pulmonary bed stays reactive. Hypoxaemia, hypercarbia and acidosis constrict it and push pulmonary vascular resistance up. Right-sided pressure then exceeds left, so desaturated blood crosses right-to-left through both fetal channels. This reverts the circulation to a fetal pattern and cuts lung blood flow. That deepens the hypoxaemia and acidosis, a self-perpetuating cycle sometimes called persistent fetal circulation.

Blaming oxygen for the persisting shunt. An intubated, ventilated baby makes oxygen feel like the variable at play. But a rising oxygen tension reverses the hypoxaemic, high-resistance state that holds fetal channels open. It is the cure, not the cause.

Stoelting notes the newborn duct and oval foramen close only functionally, so raised pulmonary resistance, high carbon dioxide or low oxygen can reopen them. Miller adds that acidosis or hypoxia holds pulmonary vessels constricted, increasing right-to-left shunting across both.

Sources: Stoelting 8eMiller 10e

When cold opens a gradient of about 2 °C between core and skin, noradrenaline enters the bloodstream. This adrenergic signal raises metabolism in brown fat, which is rich in mitochondria, and can double heat output in neonates and infants. Shivering gives newborns little heat. Stoelting and Barash say they do not shiver at all. Miller says shivering stays limited for the first 3 months. Both views lead to the same point: brown fat is the infant's main heat source, while non-shivering thermogenesis adds very little in adults.

Parasympathetic drive of brown fat. It sounds right because it names brown fat and nerve control. But the trigger is noradrenaline, which is a sympathetic, adrenergic transmitter. Parasympathetic activity does not drive heat production in brown fat.

Cold releases noradrenaline into the blood, which raises metabolism in brown fat. In neonates and infants this can double heat production, but the effect is minimal in adults. Newborns shiver poorly or not at all, so brown fat thermogenesis is their main source of heat.

Sources: Barash 9eFaustStoelting 8eMiller 10e

The Mayo review attributes the newborn's low MAC to an immature central nervous system, high progesterone acquired transplacentally from the mother, and raised beta-endorphins. Requirement then rises after birth: Barash states 50% by 6 months; Miller states 30%, peaking between 1 and 6 months. The books agree on direction and differ only in size. Preterm babies are 20% to 30% lower than term, per Barash. Sevoflurane is an exception: Barash notes its peak may be the full-term neonate.

MAC highest in the newborn. This is tempting because MAC falls steadily through adult life, so people extend that line back to birth. It fails for most volatiles: the newborn sits below the infant peak, and preterm babies are lower still. Only sevoflurane may peak in the term neonate, so the claim cannot be generalised.

Barash reports MAC rising 50% by 6 months and falling 20% to 30% in premature infants, with sevoflurane possibly peaking at term birth. Miller places the peak between 1 to 6 months. Mayo links the newborn's low MAC to CNS immaturity, progesterone and endorphins.

Sources: Barash 9eMayo reviewMiller 10e

The cord and dural sac end at different levels. In the newborn, the cord tip lies in the mid-lumbar region and the sac reaches deep into the sacrum. Both reach adult levels (conus L1, sac S2) only by the end of the first year. Classic teaching puts the newborn conus at L3 or L4. Newer ultrasound data put it at L2. Either way, the cord ends above L4-L5, so a needle at L4-L5 or L5-S1 passes below the cord and still enters the sac.

Using the adult S1 sac level. S1 is tempting because it is close to where the dural sac ends in an adult. People carry adult anatomy over to the infant. In a newborn the sac reaches lower, to S3-S4, so S1 is wrong. Also, never give the sac the cord's lumbar level.

At birth the conus sits at L3 or L4 and the dura at S3 or S4. Adult levels are reached by the end of the first year, and in adults the sac ends at S1-S2. Paediatric spinals are placed at L4-L5 or L5-S1.

Sources: Miller 10eMayo review

Prematurity means organs and stores are immature. Without enough surfactant the lungs collapse and respiratory distress follows. The fragile vessels of the immature brain bleed easily. Glycogen and calcium stores normally build up late in pregnancy, so early birth leaves too little and blood levels fall. The immature liver conjugates bilirubin poorly, so unconjugated bilirubin rises. Every problem comes from too little or too immature, so the metabolic answers point low (glucose, calcium). The only one that runs high is bilirubin, because the baby cannot clear it.

Hyperglycaemia as the typical preterm derangement. Hyperglycaemia is tempting because it is a real metabolic disturbance and sick neonates on dextrose can run high. But the typical derangement of prematurity is the opposite: blood sugar falls because stores are poor. Choose the low states, low glucose and low calcium, plus high bilirubin.

Birth before 37 completed weeks counts as preterm. The serious complications listed for these infants are respiratory distress syndrome, bleeding inside the skull, low blood glucose, low blood calcium and raised bilirubin. Excess glucose or calcium does not appear.

Sources: Barash 9e

Post-term and growth-restricted babies share one cause: a failing placenta that under-supplies oxygen and nutrients. Chronic mild hypoxia pushes the fetus to make more red cells, so the newborn is polycythaemic rather than anaemic. Starved of substrate, it lays down little glycogen, so glucose falls in the first hours and days. Hypoxic stress around delivery brings asphyxia and meconium aspiration, and a blunted immune system raises later sepsis risk. Because the cause is shared, the two problem lists largely overlap.

Anaemia in the undernourished baby. Anaemia sounds right for a small, sick, undernourished baby, and it does appear on preterm problem lists. But growth restriction and post-maturity mean chronic hypoxia before birth, which pushes the haematocrit up. The expected finding is polycythaemia, the opposite.

The anaesthesia textbooks say only that small- or large-for-dates babies carry metabolic, developmental, infectious or structural problems. Detail comes from elsewhere: the Merck Manual lists asphyxia, hypoglycaemia and meconium aspiration after term, and polycythaemia from placental hypoxia; Sharma's growth-restriction review adds hypothermia and late-onset sepsis.

Sources: Outside our books: Postterm Infants (Balest AL), Merck Manual Professional Edition; full review Feb 2025 (2025)Outside our books: Small-for-Gestational-Age (SGA) Infant (Balest AL), Merck Manual Professional Edition; full review Feb 2025 (2025)Outside our books: Intrauterine Growth Restriction: Antenatal and Postnatal Aspects (2016)Miller 10e

The risk of apnoea after anaesthesia falls as gestational age at birth rises and as postconceptual age rises (postconceptual age is gestation plus age since birth). The risk continues up to 60 weeks. Most episodes happen before 45 weeks, but ex-premature infants stay at risk for longer. So the day-case guideline gives two limits: 44 weeks for well term-born neonates having minor procedures, and at least 60 weeks for infants born preterm.

45 weeks as the safe threshold. Most apnoeas happen before 45 weeks, and well term-born neonates can have day surgery from 44 weeks. That makes five weeks past 45 look a safe margin. It is not: ex-premature infants can still have apnoea after anaesthesia up to 60 weeks.

A review text says infants younger than 60 weeks are at risk, with most cases below 45 weeks. A day-case guideline allows day surgery from 44 weeks for well neonates, but from at least 60 weeks for infants born before 37 weeks.

Sources: Mayo reviewOutside our books: Day-case surgery guideline 2022 (2022)

The index counts obstructive events hourly; Stoelting treats one an hour as diagnostic, so an abnormal index is the defining finding, outranking an isolated desaturation or a waking saturation, which are not diagnostic criteria. The alternative criterion is carbon dioxide above 50 mmHg for more than 25% of sleep. For severity, Miller requires a high index and a deep desaturation together, whereas Barash grades on the index alone; the US guideline resolves this for disposition by admitting on either finding, so a dip to 80% marks significant disease.

Raised resting carbon dioxide as diagnostic. A raised carbon dioxide sounds like hypoventilation, which is a diagnostic criterion. But that criterion needs carbon dioxide sustained above 50 mmHg through a large part of sleep on the study, not a marginally raised resting value; the recognised marker here is desaturation to 80%.

Stoelting diagnoses childhood obstructive sleep apnoea on one or more obstructive events per hour, or sustained hypercapnia above 50 mmHg. Miller calls it severe when the index exceeds 10 and the nadir falls below 80%. The US guideline admits children with either finding.

Sources: Stoelting 8eMiller 10eOutside our books: Outpatient Safety for Pediatric Patients With Severe Obstructive Sleep Apnea Undergoing Adenotonsillectomy (2026)

Children with OSA respond abnormally to carbon dioxide, so airway obstruction during postoperative sleep can cause respiratory adverse events. Very young age and severe OSA carry the most risk. Barash calls an index above 10 severe. Miller also requires a nadir below 80%. The otolaryngology guideline admits on either finding, from an index of 10 upwards, so following it satisfies both books. Barash also requires that every child with OSA is shown to keep adequate saturation while asleep on room air before going home. A same-day discharge cannot show that.

Same-day discharge because it was booked day surgery. Many children go home the same day after tonsillectomy, and this list was booked as day surgery. But with known OSA and no sleep study placing the child below the admission thresholds, nobody has shown adequate saturation asleep on room air. Overnight monitoring is required.

The US otolaryngology guideline advises inpatient monitoring for children under 3, or with an index of 10 or more, a nadir below 80%, or both. Barash lists young age and severe OSA as admission risk factors and requires observation until saturating asleep on room air.

Sources: Barash 9eOutside our books: Outpatient Safety for Pediatric Patients With Severe Obstructive Sleep Apnea Undergoing Adenotonsillectomy (2026)Miller 10e

Repeated night-time hypoxaemia is thought to alter µ-opioid receptors, so a standard opioid dose acts more strongly in these children. The ASA task force advises roughly half the dose; Barash, a reduction of up to half. The same airway risk decides where the child recovers. The otolaryngology guideline admits on age, index or nadir criteria. A single-centre retrospective study tests a higher index cut-off for discharge but has not replaced it. Grading differs: Barash uses the index alone, while Miller also requires a low saturation nadir.

Day-case discharge because she is over three. At four, she is past the under-three age cut-off, so day-case discharge looks reasonable. But age is only one of three separate admission triggers. An index far above the guideline threshold is enough on its own to require overnight monitored admission.

Barash and the ASA cut opioid doses in OSA by up to half; the ASA blames hypoxaemia-altered µ-receptors. The otolaryngology guideline admits children under three, or with index 10 or more, or nadir below 80%; Miller calls severe index above 10 plus nadir below 80%.

Sources: Barash 9eOutside our books: Practice Guidelines for the Perioperative Management of Patients with Obstructive Sleep Apnea: An Updated Report (2014)Outside our books: Outpatient Safety for Pediatric Patients With Severe Obstructive Sleep Apnea Undergoing Adenotonsillectomy (2026)Miller 10e

A squint may be one local sign of a wider skeletal muscle disorder. People prone to malignant hyperthermia often have patches of muscle weakness or other musculoskeletal defects, so eye-muscle disease was thought to mark higher susceptibility. Barash describes how this link was long assumed and how recent studies have questioned it. The risk is still possible in theory, so the anaesthetist should keep the diagnosis in mind. The oculocardiac reflex is different: it is the familiar, frequent response to traction on the eye muscles.

Oculocardiac reflex as main danger. The reflex is what you actually see during squint surgery. Pulling on a muscle can make the heart rate fall suddenly, so it takes up the anaesthetist's attention. But it is common and expected. The rare hypermetabolic crisis is the condition that becomes deadly if nobody recognises it.

Barash lists the oculocardiac and oculogastric reflexes, forced duction testing and malignant hyperthermia as concerns in strabismus repair. It calls the reflex a well-known trigger. It links squint to a higher malignant hyperthermia incidence, which recent work disputes but which still calls for awareness.

Sources: Barash 9e

An anterior mass sits right against the trachea, main bronchi, heart and great vessels. Lymphoma is a common anterior tumour and grows quickly. Signs of SVC obstruction, or imaging showing major vessels squashed or pushed aside, mean the mass is already compressing neighbouring structures. A pericardial or pleural effusion suggests the tumour has spread to the serous linings. Any one of these makes it more likely that the airway or circulation will collapse when anaesthesia removes muscle tone and spontaneous breathing.

Posterior mediastinal mass as the dangerous site. Location clearly matters, and a large posterior mass looks threatening on a chest film, but the dangerous compartment is the anterior one, where a mass lies over the trachea and great vessels. Posterior masses mostly press on the spine and oesophagus.

Predictors are anterior site, lymphoma on histology, SVC syndrome, radiological compression or displacement of major vessels, and pericardial or pleural effusion. Take tissue first from an effusion or extrathoracic lymph node, usually avoiding general anaesthesia.

Sources: Miller 10e

Children who need a new liver have a different mix of underlying disease from adults, so adult reasoning does not apply. Biliary atresia accounts for about 44% of paediatric grafts and inborn errors of metabolism for about 34%; together they make up most cases. Biliary atresia also matters before induction. It can occur with cardiac defects and situs inversus, so assess the heart and anatomy before the procedure. Portopulmonary hypertension, which is a concern in adults, is rare in children.

Inborn errors of metabolism as the commonest indication. This is tempting because metabolic disease is a major and well-known reason for transplanting a young child, and it really is the second most common indication. It is still less common than biliary atresia, roughly a third of cases against nearly half, so it is not the commonest.

Paediatric transplant indications differ markedly from adult ones. Biliary atresia is the leading cause at 44% and inherited metabolic disorders follow at 34%. Biliary atresia can occur with heart defects and situs inversus, while portopulmonary hypertension is uncommon in children.

Sources: Barash 9e