Endocrinology & Metabolism
Endocrinology and metabolism tests diabetic emergencies, adrenal and thyroid crises, sodium disorders and stress hyperglycaemia.
Core rules
- DKA: glucose >13.9 mmol/L, ketonaemia, pH <7.3 or bicarbonate <18 mmol/L, raised anion gap. HHS: glucose >30 mmol/L, osmolality >320 mOsm/kg and minimal ketones.
- DKA: give isotonic fluid and IV insulin 0.1 U/kg/h after checking potassium. If K <3.3 mmol/L, hold insulin and replace potassium.
- Adrenal crisis: hydrocortisone 100 mg IV then 50 mg every 6 h, fluids and treatment of the precipitant.
- Thyroid storm: beta-blocker, PTU, iodine after PTU, glucocorticoid and supportive care.
- SIADH: euvolaemic hyponatraemia with low serum osmolality and high urine osmolality; treat with fluid restriction.
Worked example
A DKA patient has K 3.0 mmol/L. Do not start insulin: insulin drives potassium intracellularly and can precipitate arrhythmia. Replace potassium first, then start insulin when K >3.3 mmol/L, while continuing fluid resuscitation and hourly glucose and potassium monitoring.
Traps
- Giving bicarbonate routinely in DKA; reserve it for pH <6.9.
- Missing HHS because ketones are low.
- Treating adrenal crisis with fludrocortisone first; hydrocortisone is immediate.
- Correcting hyponatraemia too fast, causing osmotic demyelination.