Analgesic effectiveness of transversus abdominis plane blocks after hysterectomy: a meta-analysis

To determine the effectiveness of transversus abdominis plane blocks in gynecological surgery by systematic review and meta-analysis. Embase, MEDLINE and the Cochrane Library (CENTRAL) bibliographic databases were searched using a Cochrane Library search strategy modified for gynecological surgery. We included randomized controlled trials comparing transversus abdominis plane block with no block or placebo block. We retrieved 681 citations from which we included five published studies (225 randomized participants) which fulfilled our inclusion criteria, and identified a further six ongoing studies. Quality was assessed across six risk of bias domains: randomization sequence generation, allocation concealment, blinding, missing outcome data, selective reporting and other biases. Data were meta-analyzed where possible and presented as mean differences with 95% confidence intervals. Study quality was moderate. Compared with no block or saline placebo, transversus abdominis plane block provided significantly less postoperative pain at rest on a 10 cm visual analog scale at 2h (mean difference -2.14 cm, 95% confidence interval (CI) -3.57 to -0.71) but not at 24h postoperatively (-0.52 cm, 95% CI -1.49 to 0.45). Pain on movement showed similar results. Transversus abdominis plane block resulted in significantly less postoperative requirement for morphine use at 24h (-11.76 mg, 95% CI -18.77 to -4.75) but not at 48 h (-16.01 mg, 95% CI -39.40 to 7.39). Evidence exists for the short-term efficacy (within 24 h) of transversus abdominis plane blocks during hysterectomy in terms of reported pain and morphine consumption, which may not be sustained at 48 h. Updates to this review should be undertaken periodically, and until further robust evidence is available, anesthetists should not rush to adopt this procedure into routine practice.