Crystalloid Coloading Versus Preloading for Prevention of Hypotension After Spinal Anaesthesia in a Mixed Adult Surgical Population: A Prospective Quasi-Randomised Comparative Study

Background: Hypotension is a frequent complication of spinal anaesthesia. Crystalloid preloading and coloading are commonly used fluid strategies, but evidence from mixed surgical populations in sub-Saharan Africa is limited. Methods: This prospective quasi-randomised comparative study was conducted at Bowen University Teaching Hospital, Ogbomoso, Nigeria, from June to August 2025. Ninety-two adults aged 18 to 60 years with American Society of Anesthesiologists physical status I or II were assigned by odd or even surgical-list order to receive 500 mL of 0.9% saline either before spinal anaesthesia (preloading, n = 46) or immediately after intrathecal injection (coloading, n = 46). The primary outcome was any episode of post-spinal hypotension within 60 minutes, defined as absolute systolic blood pressure below 90 mmHg. Unadjusted risk ratios and absolute risk differences were calculated from the reported aggregate counts. Results: Post-spinal hypotension occurred in 15 of 46 patients (32.6%) in the coloading group and 25 of 46 patients (54.3%) in the preloading group. The unadjusted risk ratio was 0.60 (95% confidence interval 0.37 to 0.98), and the absolute risk difference was -21.7 percentage points (95% confidence interval -39.6 to -1.5). Rescue ephedrine was administered to 14 patients (30.4%) after coloading and 25 patients (54.3%) after preloading, corresponding to an unadjusted risk ratio of 0.56 (95% confidence interval 0.34 to 0.93). The reported systolic blood pressure series was broadly similar between groups at most time points, but patient-level repeated-measures analysis was not available. Conclusion: In this single-centre quasi-randomised study, crystalloid coloading was associated with fewer observed episodes of post-spinal hypotension and less rescue ephedrine use than preloading. Predictable allocation, baseline heterogeneity, limited sample size and absence of adjusted and repeated-measures analyses restrict causal interpretation.