Hypotension after unilateral versus bilateral spinal anaesthesia

BACKGROUND Spinal anaesthesia is frequently used in surgical procedures involving the lower abdomen and extremities, however, the occurrence of hypotension remains a common and clinically important adverse effect. Unilateral spinal anaesthesia seems to be a promising approach to minimise this complication but the effectiveness of this remains controversial. OBJECTIVE A meta-analysis was undertaken to evaluate the superiority of unilateral spinal anaesthesia over bilateral spinal anaesthesia with regard to the incidence of hypotension and other complications. DESIGN Systematic reviews and meta-analysis of randomised controlled trials (RCTs). DATE SOURCES PUBMED, Embase, Web of Science and Cochrane Central Register of Controlled Trials databases were searched from their inception to 5 March 2024. ELIGIBILITY CRITERIA Randomised controlled trials (RCTs) comparing unilateral spinal anaesthesia with bilateral spinal anaesthesia were eligible for inclusion. Observational studies, case reports, case series, and studies not conducted in humans were excluded. The incidence of hypotension, vasopressor requirement, and other complications were compared. Heterogeneity was assessed by subgroup analyses and sensitivity analysis. RESULTS Twenty-one trials involving 1358 patients undergoing unilateral lower extremity surgery or lower abdominal surgery were included in the meta-analysis. Hyperbaric solutions were used in most trials. The Mantel–Haenszel random-effect model was used for the analysis of binary endpoints, reported as relative risk (RR) with a 95% confidence interval (CI). The incidence of hypotension was significantly lower in the unilateral spinal anaesthesia group compared with the bilateral spinal anaesthesia (RR 0.38, 95% CI 0.27 to 0.55; P < 0.001; I 2 = 38%). Subgroup analysis shows that the occurrence of hypotension was significantly lower in the unilateral subgroup, regardless of dosage, surgical site, adjuvants to the local anaesthetics, and different definitions of hypotension. CONCLUSIONS Unilateral spinal anaesthesia is associated with a significant reduction in the occurrence of hypotension, despite variations in the definition of hypotension, adjuvants, and site of surgery. These results favour the use of lateral spinal anaesthesia in patients undergoing unilateral lower abdominal or lower limb surgery. However, the GRADE assessment of the quality of evidence was ‘low’ due to the high risk of bias and heterogeneity. All the results should be treated with caution.