Comparative study of postoperative pain following general anaesthesia with isoflurane and sevoflurane in spine surgery

Introduction: Analgesic requirement following spine surgery is not addressed exhaustively, thus offering immense scope for continued research. Volatile anaesthetics have a biphasic effect on pain sensitivity; they increase sensitivity to pain at low concentrations, and relieve pain at higher concentrations. This study was conducted to compare the differences in post-operative pain severity, duration and analgesic requirements with isoflurane and sevoflurane based anaesthetic regimens in patients undergoing elective spine surgery. We hypothesized that “General anaesthetics administered to provide anaesthesia will not affect postoperative pain and analgesic requirements independently, when analgesics are given in similar doses in the pre- and intra- operative periods.” Methods: This was a prospective, observational study involving a total of 100 patients randomized into two groups - Group S (n = 50), who were maintained on sevoflurane and Group I (n = 50), who were maintained on isoflurane. Severity of pain of all patients was assessed preoperatively and upto 72 hours after extubation or till discharge using VAS scale and compared. Results: The mean preoperative VAS was comparable between the two groups (4.08 and 4.04, p = 0.889) as well as upto 4 hours postoperatively. Beyond 4 hours up to 72 hours, the mean VAS was higher in Group S, the difference being statistically significant (p<0.05 at all times). The mean VAS scores were 5.76, 5.68, 4.28, 2.44, 1.52 in Group I and 6.56, 6.56, 5.36, 4.24, 3.96 in Group S at 6, 8, 24, 48, 72 hours respectively. 17 patients in Group I and 34 patients in Group S needed tramadol in addition to diclofenac postoperatively. Conclusion: Patients anaesthetised with isoflurane for elective spine surgery have significantly less pain and are pain-free earlier as compared to those anaesthetised with sevoflurane.