• C Arzola and P M Wieczorek.
• Department of Anesthesia and Pain Management, Mount Sinai Hospital and University of Toronto, 600 University Avenue, Room 1514, Toronto, ON, Canada M5G 1X5.
• Br J Anaesth. 2011 Sep 1; 107 (3): 308-18.

AbstractSpinal anaesthesia is the preferred anaesthetic technique for elective Caesarean deliveries. Hypotension is the most common side-effect and has both maternal and neonatal consequences. Different strategies have been attempted to prevent spinal-induced hypotension, including the use of low-dose bupivacaine. We conducted a systematic search for randomized controlled trials comparing the efficacy of spinal bupivacaine in low dose (LD ≤8 mg) with conventional dose (CD >8 mg) for elective Caesarean delivery. Thirty-five trials were identified for eligibility assessment, 15 were selected for data extraction, and 12 were finally included in the meta-analysis. We investigated sources of heterogeneity, subgroup analysis, and meta-regression for confounding variables (baricity, intrathecal opioids, lateral vs sitting position, uterine exteriorization, and study population). Sensitivity analysis was performed to test the robustness of the results. In the LD group, the need for analgesic supplementation during surgery was significantly higher [risk ratio (RR)=3.76, 95% confidence interval (95% CI)=2.38-5.92] and the number needed to treat for an additional harmful outcome (NNTH) was 4 (95% CI=2-7). Furthermore, the LD group exhibited a lower risk of hypotension (RR=0.78, 95% CI=0.65-0.93) and nausea/vomiting (RR=0.71, 95% CI=0.55-0.93). Conversion to general anaesthesia occurred only in the LD group (two events). Neonatal outcomes (Apgar score, acid-base status) and clinical quality variables (patient satisfaction, surgical conditions) showed non-significant differences between LD and CD. This meta-analysis demonstrates that low-dose bupivacaine in spinal anaesthesia compromises anaesthetic efficacy (risk of analgesic supplementation: high grade of evidence), despite the benefit of lower maternal side-effects (hypotension, nausea/vomiting: moderate grade of evidence).

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