A woman hospitalised with hyperemesis has vomiting of gastric contents. Which single acid-base and electrolyte disturbance is characteristic?

Answer: C. Hypokalaemic, hypochloraemic metabolic alkalosis

Metabolic consequences of hyperemesis

Persistent vomiting of gastric secretions (rich in hydrogen and chloride and with potassium loss) produces characteristic derangements.

Characteristic disturbance

• Hypokalaemia (potassium loss).
• Hypochloraemia (chloride loss).
• Metabolic alkalosis (loss of gastric acid).
• Ketosis if caloric intake is minimal.

Other findings

• Raised haematocrit (haemoconcentration), raised urea, and sometimes mildly abnormal liver enzymes (ALT > AST) and transient hyperthyroidism.

Management

• Rehydrate and replace electrolytes (especially potassium), give antiemetics and thiamine, and monitor.

So a hypokalaemic, hypochloraemic metabolic alkalosis is characteristic.