General anesthesia does not reduce life expectancy in aged rats.

A recent clinical study demonstrated that deep anesthesia, as measured by Bispectral index monitoring, was associated with increased 1-yr mortality among middle-aged and elderly surgical patients. We have previously demonstrated impaired cognitive performance in aged rats for weeks after general anesthesia with 1.2% isoflurane-70% nitrous oxide-30% oxygen. However, the effects of 2 h of anesthesia with 1.2% isoflurane-70% nitrous oxide-30% oxygen on rodent life expectancy are unknown and may have confounded our results. Accordingly, we designed this study to determine if general anesthesia alters life expectancy in aged rats. Sixteen 22-mo-old Fischer 344 rats were randomized to anesthesia for 2 h with 1.2% isoflurane-70% nitrous oxide-30% oxygen or a control group that received 30% oxygen (n = 8 per group). Rats recovered in an enriched oxygen environment and then were placed in their home cage under routine conditions. The number of days between anesthesia administration and death were recorded and Kaplan-Meier survival curves generated and compared statistically using the log-rank test and bootstrap method. There was no difference in long-term survival between the control and anesthesia groups. Hence, general anesthesia with 1.2% isoflurane-70% nitrous oxide-30% oxygen does not reduce life expectancy in aged Fischer 344 rats.