Effects of different sufentanil target concentrations on the MACBAR of sevoflurane in patients with carbon dioxide pneumoperitoneum stimulus

Background This study aims to observe the effects of different target controlled plasma sufentanil concentrations on the minimum alveolar concentration (MAC) of sevoflurane for blocking adrenergic response (BAR) in patients undergoing laparoscopic cholecystectomy with carbon dioxide pneumoperitoneum stimulation. Methods Eighty-five patients undergoing laparoscopic cholecystectomy, aged 30-65 years, with American Society of Anesthesiologists physical status I-II, were enrolled in this study. All the patients were randomly divided into 5 groups (S.sub.0, S.sub.1, S.sub.2, S.sub.3, S.sub.4) with different sufentanil plasma target concentration (0.0, 0.1, 0.3, 0.5, 0.7 ng ml.sup.- 1). Anesthesia was induced by inhalation of 8% sevoflurane in 100% oxygen, and 0.6 mg kg.sup.- 1 of rocuronium was intravenously injected to facilitate the insertion of a laryngeal mask airway. The end-tidal sevoflurane concentration and sufentanil plasma target concentration were adjusted according to respective preset value in each group. The hemodynamic response to pneumoperitoneum stimulus was observed after the end-tidal sevoflurane concentration had been maintained stable at least for 15 min. The MAC.sub.BAR of sevoflurane was measured by a sequential method. Meanwhile, epinephrine (E) and norepinephrine (NE) concentrations in the blood were also determined before and after pneumoperitoneum stimulus in each group. Results When the method of independent paired reversals was used, the MAC.sub.BAR of sevoflurane in groups S.sub.0, S.sub.1, S.sub.2, S.sub.3, S.sub.4 was 5.333% (confidence interval [CI] 95%: 5.197-5.469%), 4.533% (95% CI: 4.451-4.616%), 2.861% (95% CI: 2.752-2.981%), 2.233% (95% CI: 2.142-2.324%) and 2.139% (95% CI: 2.057-2.219%), respectively. Meanwhile, when the isotonic regression analysis was used, the MAC.sub.BAR of sevoflurane in groups S.sub.0, S.sub.1, S.sub.2, S.sub.3, S.sub.4 was 5.329% (95% CI: 5.321-5.343%), 4.557% (95% CI: 4.552-4.568%), 2.900% (95% CI: 2.894-2.911%), 2.216% (95% CI: 2.173-2.223%) and 2.171% (95% CI: 2.165-2.183%), respectively. The MAC.sub.BAR was not significantly different between groups S.sub.3 and S.sub.4 when using 0.5 and 0.7 ng ml.sup.- 1 of sufentanil plasma target concentrations. No significant difference was found in the change of E or NE concentration between before and after pneumoperitoneum stimulation in each group. Conclusions The MAC.sub.BAR of sevoflurane can be decreased with increasing sufentanil plasma target concen