Deep anaesthesia reduces postoperative analgesic requirements after major urological procedures

Background and objective There is evidence from previous studies that deeper anaesthetic levels reduce postoperative pain along with analgesic requirements. The aim of this study was to confirm this observation during major urological procedures under sevoflurane anaesthesia. Methods Seventy ASA I or II patients undergoing radical prostatectomy or nephrectomy were randomly allocated into two groups: the L-BIS group with BIS (bispectral index scale) values kept within a range of 20-30 and the H-BIS group with values within the range of 50-60. Sevoflurane was the main anaesthetic agent used, along with inhalation of nitrous oxide and continuous remifentanil infusion. Postoperative analgesia was achieved mainly through morphine and ketamine, which was continuously infused by pump, and intravenous parecoxib. Additional analgesics (paracetamol, parecoxib and morphine) were administered in persistent (continuous, lasting longer than predicted and requiring repeated doses of analgesics) postoperative pain. The number of patients who demanded additional analgesia during the first 24 h was recorded, as well as the number of administrations performed, along with visual analogue scale (VAS) scores at 8 and 24 h. Results Sixty patients completed the study, 30 in each group. VAS scores at 8 h were significantly higher in the H-BIS group, both at rest [1 (0-4) vs. 2 (0-8), P = 0.036] and on cough [1 (0-5) vs. 2 (2-9), P = 0.021], but at 24 h were similar between the two groups. Four patients in the L-BIS group and 17 patients in the H-BIS group demanded additional analgesia (P < 0.0009), although the patients in the L-BIS group needed significantly fewer additional doses of analgesics than those in the H-BIS group [0 (0-2) vs. 1 (0-5), P < 0.0008]. Conclusion The results show that intraoperative deep anaesthetic levels during major urological procedures, achieved with high sevoflurane concentrations, lead to reduced postoperative analgesic requirements. Eur J Anaesthesiol 2010;27:801-806