SAQ 364 – Obstetrics – hyperemesis gravidarum with mixed acid-base disturbance

Obstetrics – hyperemesis gravidarum with mixed acid-base disturbance.

a. Acid-base interpretation

• Mixed metabolic acidosis and metabolic alkalosis.
• Anion gap = 132 – (17 + 86) = 29, consistent with high anion gap metabolic acidosis.
• Delta ratio = (29 – 12) / (24 – 17), greater than 2, consistent with concurrent metabolic alkalosis.
• Expected CO2 = 8 + 1.5 x 17 = approximately 32, so respiratory compensation is appropriate.
• Electrolyte abnormalities: hypokalaemia and hypochloraemia.
• Normal lactate and creatinine are relevant to the differential.

b. Diagnosis and confirmation

• Hyperemesis gravidarum with starvation ketoacidosis causing HAGMA and vomiting causing metabolic alkalosis.
• Confirm with ketone level.

c. Management

• Antiemetic such as metoclopramide 10 mg IV.
• Correct hydration, initially with IV Hartmann's, then enteral fluids when tolerated.
• Correct ketoacidosis with dextrose infusion.
• Replace electrolytes, especially KCl with or without magnesium sulphate.