Medical and endocrine disease08 / 30
Severe untreated hypothyroidism for hip fracture fixation81-year-old woman, 52 kg, for fixation of a fractured femoral neck
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Know this first
- TSH above 20 with low free T4 is overt hypothyroidism.
- Myxoedema coma: altered mentation, hypothermia, bradycardia, hypotension, hypoventilation, low sodium and glucose; mortality 30–50%.
- IV T4 200–500 mcg load then 50–100 mcg/day, reduced in ischaemic heart disease; hydrocortisone too, in case the adrenals are also failing.
- Sedatives and opioids hit hypothyroid patients hard, and they cool quickly.
The patient
81-year-old woman, 52 kg, for fixation of a fractured femoral neck; theatre tomorrow morning.
Months of lethargy, cold intolerance, constipation and a hoarse voice; puffy face; slow to answer; never diagnosed.
Labs: TSH 68 mU/L, free T4 low, Na 126 mmol/L, glucose 72 mg/dL. ECG: sinus bradycardia, low voltages.
Vitals: BP 104/70, HR 48, SpO2 94% on air, RR 12, temp 35.4 °C.
The examiner asks
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Consider
What are your considerations?
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- An 81-year-old with undiagnosed severe hypothyroidism, for urgent hip fracture fixation. Patient
- At 81, frail and slowed, she's at high delirium risk; every dose is reduced and titrated.
- Lethargy, cold intolerance, hoarseness, a puffy face and TSH 68 mean overt hypothyroidism. Disease
- She's edging towards myxoedema: slow pulse, low temperature, low sodium and slowed thinking.
- Severe disease would usually delay surgery, but her hip should be fixed within 36–48 hours. Surgery
Prepare
How do you prepare her in the time available?
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- Cortisol sent, then hydrocortisone 100 mg IV and 25 mg 6-hourly; adrenal insufficiency may coexist. Disease
- With endocrinology, IV T4: 200–500 mcg load, then 50–100 mcg daily, lower if her heart is ischaemic.
- T4 takes days to work, so her hip doesn't wait for it. Surgery
- Sodium 126: dextrose in normal saline, nothing hypotonic, and correction under 8 mmol/L a day. Disease
- Her glucose is watched; she's prone to hypoglycaemia.
Plan
How will you anaesthetise her?
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- Regional suits her if her volume is kept up: a spinal with a small dose. Surgery
- No sedative premedication; narcotics and sedatives hit her hard. Disease
- If she needs GA: small titrated doses and controlled ventilation, as she hypoventilates on her own.
- Hypotension: ephedrine or adrenaline, not phenylephrine alone; hydrocortisone if it won't respond.
- Warm theatre, forced air and warmed fluids from the start; her temperature drops fast.
Crisis
The spinal failed and she had a GA. Forty minutes into recovery she's barely rousable: temp 34.1 °C, RR 7, SpO2 89% on 4 L, PaCO2 68 mmHg. What do you do?
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- Delayed emergence with hypoventilation: drug effect, cold, sodium, glucose, and her thyroid. Crisis
- Airway and breathing first: bag-mask support, and intubation if she can't protect her airway.
- Nerve stimulator for residual block, reversed if present.
- If opioid is suspected, naloxone 40 mcg at 2-minute intervals, to a 200 mcg total.
- Glucose, sodium and a blood gas now, and I correct what's abnormal.
- Rewarm her; if this is myxoedema coma, I conserve heat with covers rather than warming blankets.
- ICU for ventilation, with IV thyroid hormone and hydrocortisone continued. After surgery
Fatal mistakes
- A full induction dose in a myxoedematous patient.
- Starting thyroid hormone with no steroid cover.
- Sedative premedication before she reaches theatre.
Checked against: Stoelting 8e · Miller 10e · Barash 9e · Faust
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