After 6 litres of 0.9% saline over 24 hours, a patient develops pH 7.28, bicarbonate 18 mEq/L, and serum chloride 118 mEq/L with a normal anion gap. Which property of a balanced crystalloid such as Ringer lactate accounts for avoiding this complication?

• A Lower sodium concentration than plasma
• B Higher osmolality than 0.9% saline
• C Presence of glucose as a caloric source
• D Chloride content closer to plasma with a buffer precursor such as lactate ✓

Explanation

Large-volume 0.9% saline delivers 154 mEq/L of chloride, far exceeding plasma levels around 103 mEq/L. The excess chloride reduces the strong ion difference and lowers bicarbonate, producing hyperchloraemic non-anion-gap acidosis. Balanced solutions such as Ringer lactate contain chloride near physiologic concentrations plus a metabolisable anion like lactate, which regenerates bicarbonate. Their sodium content and osmolality are broadly similar to saline, so those options do not explain the difference.

Reference: Sabiston Textbook of Surgery, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.