Effect of intraoperative depth of anesthesia on postoperative pain and analgesic requirement: A randomized prospective observer blinded study

Background: Intraoperative depth of anesthesia may affect postoperative pain relief. This prospective, randomized, and observer-blinded study assessed the effect of intraoperative depth of anesthesia on the postoperative pain and analgesic requirements in patients undergoing laparoscopic cholecystectomy.

Materials and methods: A total of 80 patients were randomly divided into two groups of 40 each. A standard technique for anesthesia was followed in all patients. Depth of anesthesia was monitored by bispectral index (BIS) and adjusted with 0.5 to 1.5% isoflurane in group S by addition of propofol in group B, if required, to maintain a BIS value of 45 to 40. Postoperative analgesia was provided by tramadol 1 mg/kg every 6 hours and rescue analgesia by morphine boluses. Postoperative pain was assessed by Visual analogue scale score at 0, 8, 16, and 24 hours.

Results: The demographic characteristics were comparable in both groups. The mean BIS value in Group S was 63.32 ± 11.43 and 45.06 ± 15.31 in Group B, well in the range of 40 to 60, reflecting adequate hypnotic effect for general anesthesia. The mean arterial pressure was low in group B throughout the surgery (P<0.05-0.001). The pain score were lower in group B at 0 and 8 hours postoperatively when compared with group S (P<0.05). The rescue analgesic requirement was less in group B, compared with group S (P<0.05).

Conclusion: Maintaining BIS to a value of 45 to 40 throughout the surgery results in better postoperative pain relief and decreased requirement of rescue analgesic without any untoward effect.