Expansion
Hypothermia, hypoventilation, hyponatraemia and reduced consciousness
Expansion
Features, all reflecting a profound fall in metabolic rate:
- Hypothermia, often without shivering
- Bradycardia and hypotension, with reduced cardiac output
- Hypoventilation with type 2 respiratory failure, from reduced central drive and respiratory muscle weakness
- Hyponatraemia, from impaired free water clearance
- Hypoglycaemia
- Reduced consciousness, seizures, non-pitting oedema, ileus
Precipitants: infection, cold exposure, sedatives or opioids, surgery, stroke, myocardial infarction, and stopping thyroxine.
Treatment
- Hydrocortisone first, before thyroid hormone, because coexisting adrenal insufficiency is common and thyroxine accelerates cortisol clearance
- Thyroid hormone: intravenous levothyroxine, sometimes with liothyronine
- Passive rewarming, since active rewarming causes vasodilatation and collapse
- Ventilatory support, cautious fluids, treat the precipitant
Drug metabolism is slowed, so sedatives and opioids must be used with great caution.