Abstract: Objective To investigate the effect of preoperative application of magnesium sulfate combined with quadratus lumborum block（QLB）on patients undergoing general anesthesia and its influence on postoperative cognitive function.
Methods 80 patients who underwent laparoscopic inguinal hernia surgery were selected and divided into study group and control group，40 cases in each group.Patients in study group were given routine general anesthesia plus magnesium sulfate combined with quadratus lumborum block，and patients in control group were given routine general anesthesia，then the two groups were compared the differences in terms of clinical efficacy，Tau protein and Aβ42 protein.
Results The analgesia satisfaction of the study group（90.0%）were better than the control group（72.5%）after operation（P<0.05）.The FLACC score（3.7±1.2）and PAED score（3.5±0.5）of T1，the FLACC score（3.3±1.5）and PAED score（2.7±0.8）of T2 in the study group were significantly improved than the control group，which were（2.4±1.5），（2.3±0.8），（2.0±1.0）and （1.7±0.5），respectively（P<0.05）.One week after surgery，the Tau protein and Aβ42 protein of study group were（46.3±12.0）ng/L and（93.6±20.1）ng/L，respectively，which were significantly improved compared with the control group[（55.2±18.1）ng/L and（86.1±18.5）ng/L]，respectively（P<0.05）.After anesthesia，the heart rate[（95.8±7.5）beats / min] and blood pressure[（106.6 ± 8.3）mmHg] of the study group were better than those of the control group，which were（106.8±8.5）beats/min and （115.3±11.5）mmHg，respectively（P<0.05）.
Conclusion Preoperative application of magnesium sulfate combined with QLB has better analgesic effect on patients undergoing laparoscopic inguinal hernia surgery is significant，And it can improve patients' postoperative cognitive function and help maintain the hemodynamic stability of the body.

Key words: magnesium sulfate, quadratus lumborum block, clinical efficacy, serum indexes, postoperative cognitive impairment