Effects of anesthesia depth on postoperative cognitive function and inflammation: a systematic review and meta-analysis

Postoperative cognitive dysfunction (POCD) and postoperative delirium (POD) are common postoperative complications in elderly patients. The effect of anesthesia depth on cognitive function remains unknown. We aimed to assess the correlations between anesthesia depth, cognitive function, and inflammation.Literature searches were conducted on Web of Science, PubMed, EMBASE, and Cochrane libraries until August 2019. All studies were randomized controlled trials (RCTs). The STATA 15.0 and trial sequential analysis (TSA) version 0.9.5.10 beta software were used for data analysis. POD and POCD were calculated using a random-effects model. The combined effect estimates are expressed as risk ratios (RR) with 95% confidence intervals (CI).Ten RCTs involving 3142 patients met inclusion criteria. The meta-analysis indicated that the incidence of POCD in the light anesthesia group was significantly lower than the deep anesthesia group on days 1 (RR=0.14, 95% CI: 0.04 to 0.45; I2=0.00, P>0.10), and 90 (RR=0.72, 95% CI: 0.54 to 0.96; I2=0.00,P>0.10). Light anesthesia significantly reduced the risk of POD (RR=0.69, 95% CI: 0.58 to 0.82; I2=0.00, P>0.10). There was no statistical difference in the Mini-Mental State Examination score between the groups on postoperative day 1 (standardized mean difference (SMD)= 0.04, 95% CI: -0.25 to 0.33; I2=0.00, P>0.10).The TSA found that there was insufficient evidence on the effect of anesthesia depth on POCD, but that the conclusions on POD were reliable.Light anesthesia was associated with a decrease in POD and may promote better neurocognitive function postoperatively in comparison with deep anesthesia.