Profound hypothyroidism typically presenting with hypothermia, bradycardia and impaired level of conciousness.
Hypothermia must be corrected by aggressive rewarming and with warmed fluids.
Hypotension must be managed by careful assessment of fluid status, usually requiring central venous pressure monitoring. Warmed fluids and pressors may be required.
Mechanical ventilation may be necessary for hypopnoea.
Blood glucose must be monitored and hypoglycaemia corrected appropriately.
A septic screen should be undertaken and broad spectrum antibiotics given if appropriate.
Cardiac status must be assessed and if myocardial infarction or dysthrhythmia are detected, appropriately treated.
Prophylactic anticoagulation should be given.
Care must be taken with pressure areas.
100mg intramuscular hydrocortisone should be given and continued 6 hourly until coincident glucocorticoid deficiency has been ruled out.
Patients with severe hypothyroidism are unstable and so require very careful initiation of therapy. Liothyronine is short acting and may be started in extremely low doses in such cases.
Tiny doses as low as 1.25mcg may be used in very severe cases, though 5mcg is a reasonable first dose to give in most cases.
Liothyronine should be given enterally (usually via a nasogastric tube) in all cases due to the increased risk of tachyarrhythmia with intravenous replacement. If this is tolerated, a repeat dose can be given at 6 hours. If this too is tolerated, the dose may be increased to 10mcg 12 hourly.
After a further 24hours, levothyroxine may be introduced at a dose of 25mcg daily, with an anticipated increase to 50mcg after 6 weeks depending on the individual case. Liothyronine should be continued in parallel with the levothyroxine for approximately 1 week.