Effect of remote ischemic preconditioning on lung function after surgery under general anesthesia: a systematic review and meta-analysis

Remote ischemic preconditioning (RIPC) protects organs from ischemia–reperfusion injury. Recent trials showed that RIPC improved gas exchange in patients undergoing lung or cardiac surgery. We performed a systematic search to identify randomized controlled trials involving RIPC in surgery under general anesthesia. The primary outcome was the P(a)O(2)/F(I)O(2) (P/F) ratio at 24 h after surgery. Secondary outcomes were A-a DO(2), the respiratory index, duration of postoperative mechanical ventilation (MV), incidence of acute respiratory distress syndrome (ARDS), and serum cytokine levels. The analyses included 71 trials comprising 7854 patients. Patients with RIPC showed higher P/F ratio than controls (mean difference [MD] 36.6, 95% confidence interval (CI) 12.8 to 60.4, I(2) = 69%). The cause of heterogeneity was not identified by the subgroup analysis. Similarly, A-a DO(2) (MD 15.2, 95% CI − 29.7 to − 0.6, I(2) = 87%) and respiratory index (MD − 0.17, 95% CI − 0.34 to − 0.01, I(2) = 94%) were lower in the RIPC group. Additionally, the RIPC group was weaned from MV earlier (MD − 0.9 h, 95% CI − 1.4 to − 0.4, I(2) = 78%). Furthermore, the incidence of ARDS was lower in the RIPC group (relative risk 0.73, 95% CI 0.60 to 0.89, I(2) = 0%). Serum TNFα was lower in the RIPC group (SMD − 0.6, 95%CI − 1.0 to − 0.3 I(2) = 87%). No significant difference was observed in interleukin-6, 8 and 10. Our meta-analysis suggested that RIPC improved oxygenation after surgery under general anesthesia. Clinical trial number: This study protocol was registered in the University Hospital Medical Information Network (registration number: UMIN000030918), https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000035305.