Medical, Metabolic, and Multisystem Emergencies
Concepts to master
This domain covers diabetic emergencies (DKA versus hyperosmolar hyperglycemic state), hypoglycemia, thyroid storm and myxedema coma, adrenal crisis, electrolyte disturbances, sepsis and septic shock, anaphylaxis, toxicologic emergencies, and multisystem conditions such as heat illness and rhabdomyolysis. You must understand that sepsis is a time-dependent syndrome and that anaphylaxis is a clinical diagnosis treated with epinephrine, not antihistamines.
Distinguishing features
DKA typically features hyperglycemia, ketosis, and anion-gap metabolic acidosis with Kussmaul respirations; HHS features profound hyperglycemia and hyperosmolality with minimal ketosis. Both cause total-body potassium depletion even when serum potassium appears normal or high; insulin shifts potassium intracellularly, so potassium must be watched during treatment. Toxicologic emergencies require knowing toxidromes and antidotes at a recognition level.
Traps to watch
- Giving insulin before checking potassium in DKA.
- Treating anaphylaxis with antihistamines or corticosteroids first instead of intramuscular epinephrine.
- Assuming a normal serum potassium means total-body potassium is normal in DKA.
- Missing sepsis because the patient is not febrile or is normotensive early.
Rule of thumb
For undifferentiated altered mental status, check glucose first. For shock with fever or suspected infection, start antibiotics and fluids early rather than waiting for cultures to return.
Worked example: A patient with DKA has a serum potassium of 5.0 mEq/L. Insulin is appropriate only with close potassium monitoring, because insulin will drive potassium intracellularly and may precipitate hypokalemia.