Objective: To study neuroendocrine response during cholecystectomy under general anesthesia with fentanyl and under general anesthesia with nitrous oxide plus thoracic epidural block, by determining plasma levels of ACTH and beta-endorphin.
Patients and methods: This was a prospective study of 2 randomly chosen groups of 7 patients each who were undergoing cholecystectomy. One group received general anesthesia with fentanyl at initial doses of 10 micrograms/kg-1 followed by perfusion of 5 micrograms.kg-1.h-1. The other group received general anesthesia with 60% nitrous oxide in oxygen combined with bupivacaine 0.5% for thoracic epidural blockade. Plasma levels of ACTH and beta-endorphin were determined at the following moments: A, upon arrival in the operating theater; B, after anesthetic induction and intubation; C, after incision; D, 30 minutes after start of surgery; E, after surgery but before extubation, and F, after arrival in the recovery room. Also recorded were mean arterial pressure and heart rate.
Results: In both groups we found significantly higher levels of beta-endorphin throughout surgery. The increase was greater, however, in the group receiving combined anesthesia at moments D (p = 0.008) and E (p = 0.008). ACTH levels rose significantly during surgery (p = 0.004) in the combined anesthesia group, whereas there was only a slight increase in the group receiving only general anesthesia (p = NS). beta-endorphin levels increased proportionally more than ACTH levels during combined anesthesia. Hemodynamic stability was acceptable in both groups.
Conclusion: General anesthesia with fentanyl at the dose used in this study was more effective that combined anesthesia in mitigating the release of ACTH and beta-endorphin during cholecystectomy.