A 58-year-old man undergoes a 6-hour laparotomy for small bowel obstruction. On post-operative day 2, he has received 6 litres of 0.9% normal saline. Serum sodium is 148 mEq/L, chloride is 118 mEq/L (normal 98-106), bicarbonate is 18 mEq/L, and pH is 7.28. Which fluid-related complication best explains this biochemical picture?

• A Hyperchloremic normal anion gap metabolic acidosis from excess saline ✓
• B High anion gap metabolic acidosis from lactic acid accumulation
• C Metabolic alkalosis from third-space fluid sequestration
• D Respiratory acidosis with metabolic compensation from atelectasis

Explanation

Large-volume 0.9% normal saline causes hyperchloremic normal anion gap metabolic acidosis because saline contains 154 mEq/L of chloride, exceeding the serum chloride threshold. The elevated chloride level displaces bicarbonate, producing a non-anion gap acidosis. This is a well-documented complication of saline resuscitation and is a major reason balanced crystalloids (Ringer's lactate) are preferred in large-volume resuscitation.

Reference: Sabiston Textbook of Surgery, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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