Effects of dexmedetomidine versus morphine on surgical stress response and analgesia in postoperative open cardiac surgery

Abstract

Background The aim of this study was to compare between dexmedetomidine and morphine for use as sedative/analgesics and to evaluate their effects on surgical stress response during the first 24 h following open cardiac surgery in the Cardiac Intensive Care Unit (CICU). Patients and methods The present double-blind study was carried out on 30 adult patients 60 years of age or older admitted to the Cardiothoracic Surgery Department of the Alexandria Main University Hospital of ASA physical status grade II and III, scheduled for elective coronary artery bypass grafting surgery under general anesthesia. Immediately after sternal closure at the end of surgery, patients were classified randomly using the closed-envelope technique into two equal groups, started immediately on a continuous intravenous infusion (without a loading dose) of either dexmedetomidine or morphine and continued for 24 h postoperatively. Dexmedetomidine group (group D): dexmedetomidine was prepared at a concentration of 0.1 μg/kg/ml and was infused at a dose of 0.1-0.7 μg/kg/h (equivalent to an infusion rate of 1-7 ml/h). Morphine group (group M): morphine was prepared at a concentration of 10 μg/kg/ml and was infused at a dose of 10-70 μg/kg/h (equivalent to an infusion rate of 1-7 ml/h). Patients were followed up in the CICU for the first 24 h following open cardiac surgery on the basis of hemodynamic changes, plasma interleukin (IL)-6 and cortisol levels, time to successful tracheal extubation, postoperative pain, incidence of delirium, and postoperative nausea and vomiting. Results The mean heart rate values were significantly lower in group D compared with group M during most of the postoperative period. The mean values of systolic blood pressure, diastolic blood pressure, and mean arterial pressure, on comparing the two groups, had showed no statistically significant difference during the entire postoperative period. The mean values of IL-6, cortisol, and glucose were increased significantly in group M relative to group D at 6 and 24 h postoperatively. Time to successful tracheal extubation was significantly shorter in patients of group D than in patients of group M. Visual analogue scale for pain score and Motor Activity Assessment Scale for sedation score showed no significant difference when both groups were compared during the entire postoperative period. The total number of patients with delirium was significantly fewer in group D than group M. The incidences of nausea and vomiting events were insignificantly lower in group D than group M. Conclusion The administration of dexmedetomidine exerted a potent negative chronotropic effect with decreased heart rate. Both dexmedetomidine and morphine equivalently decreased the blood pressure (systolic blood pressure, diastolic blood pressure, and mean arterial pressure) in a range of 15-20% in relation to the preoperative readings. Dexmedetomidine significantly attenuated the surgical stress response and the neuroendocrine response in comparison with morphine through the suppression of the postoperative increase of IL-6 and cortisol, respectively. Dexmedetomidine had promoted earlier recovery and tracheal extubation than morphine, with no accompanying respiratory depression. Both dexmedetomidine and morphine were efficient sedative/analgesics for postoperative cardiac surgery. Dexmedetomidine significantly reduced the incidence and duration of delirium after cardiac surgery.