Choice of bicarbonate-buffered solution versus compound sodium lactate as the intraoperative crystalloid solution during abdominal surgery remains unclear

1. This trial did not establish non-inferiority of bicarbonate-buffered solution versus compound sodium lactate (CSL) for end-of-surgery standard base excess (SBE), and results should not be interpreted as evidence of equivalence.

2. Lower lactate with bicarbonate-buffered solution was an exploratory finding unaccompanied by acid-base or clinical benefit, so routine substitution for CSL cannot yet be recommended pending larger, adequately powered trials.

Evidence Rating Level: 1 (Excellent)

This single-center, open-label, randomized non-inferiority trial (n=50) compared bicarbonate-buffered solution with compound sodium lactate (CSL) as the intraoperative crystalloid in high-risk adults undergoing elective major abdominal surgery. Bicarbonate-buffered fluids avoid exogenous lactate, but comparative physicochemical data against CSL in this setting have been limited. The primary estimand was the mean difference in end-of-surgery standard base excess (SBE), with a prespecified non-inferiority margin of −1.5 mEq/L. In the intention-to-treat analysis (multiple imputation for two missing CSL values), the mean SBE difference was −0.42 mEq/L (95% CI, −1.92 to 1.09), and the per-protocol complete-case estimate was −0.48 mEq/L (95% CI, −2.02 to 1.06); both lower bounds fell below the margin, so non-inferiority was not established, though neither interval indicated inferiority or superiority. Sensitivity analyses (Hodges–Lehmann estimate, observed-range imputation scenarios) yielded consistent conclusions. End-of-surgery lactate was lower with bicarbonate-buffered solution (median 0.9 vs 1.2 mmol/L, unadjusted P=0.031), without corresponding differences in SBE, pH, or clinical outcomes.

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