Anterior quadratus lumborum blocks for postoperative pain treatment following intra-abdominal surgery: A systematic review with meta-analyses and trial sequential analyses

Background: The anterior quadratus lumborum (QL) block may be used for postoperative pain management for intra-abdominal surgeries, but the evidence is uncertain. We aimed to investigate the benefit and harm of the anterior QL block compared to placebo/no block for intra-abdominal surgery. Methods: We searched Medline, Embase, and CENTRAL for randomized controlled trials investigating anterior QL block for postoperative pain management for adult patients undergoing any intra-abdominal surgery. The two co-primary outcomes were cumulative 24-h opioid consumption and serious adverse events. We performed meta-analysis, trial sequential analysis (TSA), assessed the risk of bias, and present the certainty of evidence with the Grading of Recommendations, Assessment, Development and Evaluation approach. Results: Thirty-five trials randomizing 2418 patients were included in the meta-analyses. Anterior QL block may reduce cumulative 24-h intravenous opioid consumption compared to placebo/no block (MD −10.42 mg, 96.7% CI −14.83 to −6.01, TSA-adjusted CI −17.03 to −3.82, p <.01). Two trials reported on SAEs. Anterior QL block may have little to no effect on the number of serious adverse events compared to placebo (RR 1.49, 96.7% CI 0.19 to 11.47, p =.68), but the evidence is very uncertain. All trial results were assessed as being high risk of bias. Conclusions: The anterior QL block may reduce cumulative 24-h opioid consumption. Reported serious adverse events were few and the anterior QL block may have little to no effect on the number of SAEs, but the evidence was very uncertain.