A Comparative Study of the Effects of Two Different Levels of End-Tidal Carbon Dioxide Pressure on Cognitive Dysfunction in Elderly Patients, after Cataract Surgery under General Anesthesia

Background: This study aimed to compare the effect of two different levels of end-tidal carbon dioxide on cognitive impairment in elderly patients undergoing surgery. Methods: In this clinical trial study, 240 patients over 65 years of age were randomly distributed into two groups. In the first group, the end-tidal carbon dioxide (ETCO2) pressure was maintained in the range of 35-40 mmHg, and in the second group in the range of 40 to 45 mmHg. Patients' cognitive scores before surgery, and 24 hours, one week, and six weeks later were compared between the two groups. Findings: In the first 24 hours, the incidence of cognitive impairment was 12.5 and 11.7 percent in first and second groups, respectively; while at the first week after surgery, this rate was 6.7 and 11.7 percent, and at the sixth week, 5.0 and 9.2 percent, respectively, based on the short test of mental status. In all cases, the difference between the two groups was not statistically significant. Conclusion: ETCO2 in the range of 35 to 45 mmHg has no effect on the cognitive impairment of elderly patients under cataract surgery with general anesthesia. Therefore, further studies on the effects of different extents of ETCO2 on cognitive impairments are necessary.