A 70 kg patient undergoing major hepatic resection has received 3 L of normal saline over 4 hours. A repeat blood gas shows Na 145, Cl 115, HCO3 17, pH 7.30. What is the MOST likely type of metabolic acidosis present?

• A Lactic acidosis from tissue hypoperfusion
• B Dilutional acidosis from redistribution of bicarbonate
• C Hyperchloraemic non-anion gap metabolic acidosis from saline administration ✓
• D Ketoacidosis from surgical stress response

Explanation

Normal saline contains 154 mEq/L of both sodium and chloride. Large-volume infusion delivers a chloride load that exceeds renal excretion capacity, leading to hyperchloraemia and a fall in serum bicarbonate via the principle of electroneutrality (raised Cl drives down HCO3). The result is a hyperchloraemic non-anion gap metabolic acidosis. The anion gap here would be: 145 − (115 + 17) = 13, which is at the upper limit of normal (8–12), consistent with a non-anion gap acidosis. Lactate and ketone levels would be normal. Balanced crystalloids like Hartmann's solution or Plasma-Lyte avoid this by containing less chloride.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.