The impact of spinal versus general anesthesia on the variability of surgical times: a systematic review and meta-analysis.

backgroundWith spinal anesthesia, when cases are taking longer than usual, there may be behavioural tendencies for surgical teams to work more quickly. We conducted a systematic review with meta-analysis to examine standard deviations of surgical times for single-dose spinal anesthetics versus general anesthesia. We compared ratios of mean surgical times as a secondary endpoint.

methodsWe included randomized trials of humans where general or spinal anesthesia was used for one category of surgical procedure (e.g., hip arthroplasty) and the article reported the means and standard deviations of operative durations. We used statistical methods suitable for surgical times following log-normal distributions. We used generalized confidence intervals to calculate point estimates of ratios and standard errors for each study, followed by pooling among studies using DerSimonian and Laird random-effects meta-analysis with Knapp-Hartung adjustment.

resultsAmong the 77 included studies, 96% were of high quality for our endpoint (i.e., had a low risk of bias), as no (0%) study focused on comparing variability of surgical times and none had surgical time as the primary endpoint. Spinal anesthesia was associated with 6.6% smaller standard deviations than general anesthesia (95% confidence interval, 15.8% smaller to 1.9% larger, P = 0.13). By meta-regression, there was no significant association of the ratios of standard deviations with study quality (P = 0.39), year of publication (P = 0.76), or categories of procedures (all five P ≥ 0.28). Spinal anesthesia was associated with 1.1% smaller means than general anesthesia (95% confidence interval, 3.7% smaller to 1.5% larger, P = 0.42). There were no significant associations between the ratios of means and study quality (P = 0.47), year of publication (P = 0.95), or categories of procedures (all five, P ≥ 0.63).

conclusionsThe results of this systematic review and meta-analysis show with high confidence that the effect of choosing spinal anesthesia on variability in surgical time, if present, is sufficiently small to have no substantive direct economic effect. The same conclusion applies to mean surgical time. Therefore, although anesthetic choice has a clinical (biological) impact and affects anesthesia times, the direct effects on surgical times and workflow are minimal at most. Anesthetic choice does not influence operating theatre productivity via changes to surgical times. The impact of spinal anesthetic effects is limited to nonoperative times (e.g., reducing anesthesia-controlled times by using a block room before the patient enters the operating room). STUDY REGISTRATION: PROSPERO ( CRD42023461952 ); first submitted 8 September 2023.