Effects of isoflurane versus fentanyl-nitrous oxide anesthesia on long-term outcome from severe forebrain ischemia in the rat.

BACKGROUND: This study examined long-term outcome from severe forebrain ischemia in the rat, as a function of anesthetic given during the ischemic injury. METHODS: Rats were subjected to 10 min of near-complete forebrain ischemia while anesthetized with either 1.4% isoflurane or 70% nitrous oxide-fentanyl. Neurologic and histologic outcomes were measured at 5 days, 3 weeks, or 3 months after ischemia. RESULTS: At 5 days, isoflurane-anesthetized rats had less damage than did fentanyl-nitrous oxide-anesthetized rats (mean +/- SD, percent alive hippocampal CA1 neurons = 58+/-29 vs. 20+/-16, respectively; P = 0.011). This was accompanied by improved motor function in the isoflurane group (P = 0.002). At 3 weeks, there was no difference between groups for either outcome variable (percent alive CA1 neurons = 35+/-26 and 36+/-28 for isoflurane and fentanyl-nitrous oxide, respectively). Similarly, at 3 months, there was no difference between groups (percent alive CA1 neurons = 56+/-27 and 60+/-27 for isoflurane and fentanyl-nitrous oxide, respectively). Morris water maze performance at 3 months was similar between anesthetic groups and was also similar to sham performance. The percent alive CA1 neurons in the fentanyl-nitrous oxide group increased with duration of recovery (P = 0.004). There were no differences among isoflurane groups over time (5 days vs. 3 weeks, P = 0.26; 5 days vs. 3 months, P = 0.99; 3 week vs. 3 months, P = 0.32). CONCLUSIONS: This study found no change in the percent alive CA1 hippocampal neurons as a function of duration of recovery from severe forebrain ischemia in isoflurane anesthetized rats. In contrast, the percent alive CA1 neurons in fentanyl-nitrous oxide-anesthetized rats tripled over 3 months of recovery. The natural history of long-term responses to forebrain ischemia requires further study before conclusions can be drawn with respect to the permanence of isoflurane neuroprotection.

Duke Scholars

Author Huaxin Sheng Anesthesiology

Author Robert D. Pearlstein Neurosurgery