Balance anesthesia using sevoflurane and fentanyl based on site concentration model compared to sevoflurane/N₂O anesthesia for oral surgery

The use of opioids in general anesthesia is a key component in the current notion of "balanced anesthesia". However, concern over opioid side effects can cause practitioners to hesitate to use opioids. Fentanyl is a commonly used opioid in perioperative management, because it allows smooth emergence from anesthesia without coughing and bucking, and provides residual postoperative analgesia. In this study, the adverse symptoms of "balanced anesthesia" using fentanyl and sevoflurane based on site concentration model was compared to those of "traditional anesthesia" using nitrous oxide (N₂O) during oral surgery. Forty patients scheduled to undergo oral surgery (ASA classification 1 or 2) were assigned randomly into one of two groups that were maintained with anesthesia using fentanyl and sevoflurane (group AOS/F, n = 20) and the second group using N₂O and sevoflurane (group GOS, n = 20). Fentanyl was administered intermittently to maintain the effect-site concentration at 2-3 ng/ml using a pharmacokinetic simulation software in the group AOS/F. The time to awake (from the end of surgery to extubation) and the frequency in using an antiemetic drug (metoclopramide hydrochloride) during 24 hours postoperatively were compared between the two groups. At the end of anesthesia, the total dose of fentanyl used and the respiratory rate data were evaluated. There were no significant differences in the time to awake and the use of postoperative antiemetic drug between the two groups (Table 2). In AOS/F group, the total dose of fentanyl was 386 ± 31.5 μg and the respiratory rate was 13.2 ± 0.6 breaths/min at the end of anesthesia. The results indicated that the use of fentanyl based on this pharmacokinetic model did not increase the adverse symptoms known to be related to opioids after general anesthesia, and suggested that fentanyl-based balanced anesthesia could be as safe as traditional GOS anesthesia.