Endocrine and Metabolic Critical Care
Endocrine emergencies in the ICU are sequence questions - the marks come from doing the right step in the right order. The Board concentrates on ketoacidosis, hyperosmolar states, adrenal crisis and thyroid emergencies.
Diabetic ketoacidosis
Triad: hyperglycaemia (or euglycaemia with SGLT2 inhibitors), ketonaemia of 3 mmol/L or more, and pH below 7.3 or bicarbonate below 18 with a raised anion gap. Start 0.9% saline and check potassium before insulin. If potassium is below 3.3 mmol/L, give potassium and hold insulin, because insulin drives potassium intracellularly and can precipitate fatal arrhythmia. If potassium is 3.3-5.2, add 20-40 mmol/L and start insulin at 0.1 units/kg/h. Add 10% dextrose when glucose falls below 200-250 mg/dL (11-14 mmol/L) so insulin can continue clearing ketones. Bicarbonate is rarely indicated, only at pH below 6.9. Cerebral oedema is the feared complication in children.
Hyperosmolar hyperglycaemic state
Glucose often above 600 mg/dL, osmolality above 320 mOsm/kg, minimal ketosis, profound dehydration (100-200 mL/kg deficit) and higher mortality than DKA. Restore circulation first, then give insulin more slowly, watching for osmotic shifts.
Adrenal, thyroid and refeeding
Adrenal crisis: hypotension unresponsive to fluids and catecholamines - draw a cortisol sample only if it costs no time, then give hydrocortisone 100 mg IV and 50 mg every 6 hours without waiting for the result. Thyroid storm: PTU plus beta-blockade, iodine at least an hour after PTU, hydrocortisone, supportive care. Myxoedema coma: give hydrocortisone before levothyroxine. Refeeding syndrome is a phosphate shift, so refeed slowly, give thiamine before feeding and monitor phosphate, potassium and magnesium daily.
Worked example
A 22-year-old with DKA has potassium 3.1 mmol/L. Starting the insulin infusion because the protocol says so is the wrong move. Give saline with 40 mmol/L potassium and defer insulin until potassium is above 3.3 - otherwise insulin drives the last extracellular potassium into cells.
Traps
Stopping insulin when glucose normalises without checking ketone clearance. Missing euglycaemic DKA on an SGLT2 inhibitor. Giving levothyroxine before hydrocortisone in a hypotensive hypothyroid patient. Forgetting that hydrocortisone should precede thyroid hormone in any patient with suspected combined failure.