Bis-guided evaluation of dexmedetomidine vs. midazolam as anaesthetic adjuncts in off-pump coronary artery bypass surgery (OPCAB)

Abstract

Background. To assess the efficacy of midazolam and dexmedetomidine as induction agents and adjuncts to anaesthesia during OPCAB surgery. Patients and Methods. 107 patients scheduled for elective OPCAB surgery between 1st of January 2005 to 31 st of December 2007 were enrolled. Patients were randomly allocated into two groups Midazolam group (Group M, n=57) and Dexmedetomidine group (Group D, n=50). Patients in Group D (Dexmedetomidine group) received dexmedetomidine as initial i.v loading dose of 1 µg kg -1 over 1 minute (min) before induction of anaesthesia and 60 µg hr -1 continuous infusion thereafter until the end of surgery. Patients in group M (Midazolam group) received midazolam 0.1 mg kg -1 over 1 min before induction of anaesthesia and 2.5mg hr­ 1 continuous infusion thereafter until the end of surgery. Anaesthesia was maintained with continuous i.v infusion of sufentanil 0.2 µg kg -1 h -1 , study drug infusion at a rate of 10 ml h -1 , and rocuronium 0.5 mg kg-1 h -1 supplemented with sevoflurane as required. Induction doses as well as anaesthetic maintenance supplementation doses were guided by the BIS reading near 50. Data collection included haemodynamic parameters (HR, MAP, CI & SVR), BIS readings (T0-T7) and sevoflurane concentrations (T3-T7) were recorded at the following data points, T0= baseline pre-induction, T1= immediately post-induction T2= during laryngoscopy & intubation, T3= skin incision, T4= sternotomy, T5= during revascularization of the left anterior descending (LAD) artery, T6= during revascularization of the obtuse marginal (OM) artery, T7= with chest closure at conclusion of surgery. Results. 5 patients in Group M and 3 patients in group D were excluded due to diversion to on pump technique. All baseline parameters were comparable among both groups. In group M (52 patients) SVR and BP had significantly decreased following induction (T1) compared to baseline (T0, p<0.0001), while HR and CI had significantly increased during T1 compared to baseline (T0, p<0.0001). Also parameters recorded thereafter were comparable to baseline values. In Group D (47 patients) all parameters recorded were comparable to baseline values with exception of HR that decreased significantly from T1-T7 compared to T0. BIS values recorded were comparable among both groups, however sevoflurane concentrations was significantly higher in Group M compared to group D (P<0.0001). Conclusion. Midazolam can alter hemodynamic response following induction of anaesthesia; however such changes are reversible and returned to baseline. Dexmedetomidine is more haemodynamic stable and more potent anaesthetic adjuvant compared to midazolam in patients undergoing OPCAB surgery.