A 34-year-old woman with a history of duoden ulcer disease presents with progressive vomiting of partially digested food eaten days earlier. She is dehydrated. Serum sodium is 132 mEq/L, potassium 2.8 mEq/L, chloride 88 mEq/L, bicarbonate 38 mEq/L, pH 7.52. Which acid-base disturbance is most likely?

• A Hyperchloremic metabolic acidosis
• B Respiratory alkalosis with metabolic compensation
• C Hypokalemic, hypochloremic metabolic alkalosis ✓
• D High anion gap metabolic acidosis

Explanation

Gastric outlet obstruction causes repeated loss of hydrochloric acid in vomitus, producing hypochloremia and metabolic alkalosis. Secondary hyperaldosteronism from volume contraction drives urinary potassium loss, causing hypokalemia, and paradoxical aciduria appears late. Hyperchloremic acidosis is seen after ureterosigmoidostomy or severe diarrhea, not gastric vomiting. The anion gap here is normal at about 6 mEq/L, which excludes option D.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

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