Obesity hypoventilation for emergency laparotomy48-year-old man, 168 kg, BMI 58, for emergency laparotomy for small bowel obstruction

The patient

The examiner asks

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1. Consider

   What are the key issues in this man?

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   • A 48-year-old with obesity hypoventilation, BMI 58, for emergency laparotomy on an obstructed bowel. Patient
   • His PaCO2 of 54 and bicarbonate of 33 show daytime hypoventilation, not sleep apnoea alone. Disease
   • Obstruction with vomiting is a full stomach: rapid sequence induction, with the nasogastric tube aspirated first. Surgery
   • Obesity shortens his time to desaturation once he stops breathing, so oxygen reserve is my first problem. Airway
   • OHS patients go to ICU and need ventilation after surgery more often than obese patients without it. After surgery
   • His obesity alone raises his DVT and fatal PE risk: enoxaparin prophylaxis and early mobilisation.

2. Prepare

   Which preoperative checks matter for him?

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   • Arterial gas now: his PaCO2 of 54 meets the OHS threshold of 45; bicarbonate 33 is well over 27. Disease
   • SpO2 91% on air with that bicarbonate puts him in the high-risk OHS group.
   • ECG and bedside echo for his right ventricle; repeated night-time hypoxaemia leads to cor pulmonale.
   • I measure his neck: 40 cm or more predicts difficult mask ventilation and intubation. Airway
   • I mark his cricothyroid membrane with ultrasound, neck extended, before induction.
   • Glucose kept between 140 and 180 mg/dL while he is nil by mouth. Disease

3. Plan

   How will you induce, intubate and ventilate him?

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   • Ramped until his ear canal is level with the sternal notch, then tilted 25–30 degrees head-up. Airway
   • Pre-oxygenate head-up with positive pressure, and keep high-flow nasal oxygen running through laryngoscopy.
   • Videolaryngoscope first with a bougie; front-of-neck kit ready, vertical incision as my default.
   • RSI: propofol dosed on lean body weight, suxamethonium 1.5 mg/kg on total body weight. Stem trigger
   • With rocuronium, 1.2 mg/kg; dosing on his total weight roughly doubles its duration.
   • Once intubated, a recruitment manoeuvre then PEEP, watching his BP as venous return falls. Airway
   • Opioid-sparing analgesia: a regional technique plus paracetamol 1 g IV every 6 hours. After surgery

4. Crisis

   Ten minutes after intubation, SpO2 falls to 84% on FiO2 0.5. Peak pressure 34 cmH2O, BP 128/76, HR 98. What do you do?

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   • FiO2 to 1.0, and I confirm the tube: a sustained capnography trace and the tube seen through the cords. (Crisis)
   • I listen to both sides; one-sided air entry with high pressure means a bronchial tube.
   • Equal sounds and a good trace in a supine super-obese man: this is atelectasis.
   • Recruit at 30–40 cmH2O for 30–40 seconds, stopping if his BP drops.
   • Then higher PEEP and reverse Trendelenburg, which holds his FRC.
   • I recheck BP after each step, because PEEP reduces his venous return and cardiac output.

5. Crisis

   In recovery, extubated, he snores then goes quiet. SpO2 82%, RR 6, drowsy, BP 170/100, HR 110. What do you do?

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   • OHS obstruction and hypoventilation: help, jaw thrust, then oxygen titrated to SpO2 88–92% once the airway is open. Crisis
   • Sit him up to 45 degrees; it opens his airway and restores his FRC.
   • Check his train-of-four: a ratio under 0.9 is residual block; sugammadex 2 mg/kg if T2 is back.
   • Naloxone 40 mcg IV every 2 minutes, at most 200 mcg; enough to restore his drive, not his pain.
   • CPAP or NIV now; his own NIV machine should come with him.
   • Blood gas for his CO2; if he stays too drowsy for NIV, I reintubate.
   • He goes to HDU on continuous oximetry, not to the ward. After surgery