Does intrathecal morphine alter the stress response following coronary artery bypass grafting surgery?

Purpose: Intrathecal morphine administered prior to coronary artery revascularization (CABG) surgery was studied to determine its effects on the stress response. Methods: In a single centre, open, randomized clinical trial, first time elective CABG surgery patients, < 75 yr, were studied. Control subjects (n = 12) received a standardized anesthetic consisting of fentanyl (maximum cumulative dose of 35 mu g.kg(-1)), propofol, and pancuronium. In addition, spinal subjects (n=13) received 1.0 mg (age > 60 yr) or 1.5 mg (age less than or equal to 59 yr) intrathecal morphine prior to induction of anesthesia. Control subjects received continuous iv morphine at 2 mg.hr(-1) on arrival in the ICU with iv bolus morphine supplementation as required while spinal subjects received bolus iv morphine as required. Changes in plasma cortisol and catecholamine concentrations were measured preoperatively, poststernotomy, on admission to ICU, following tracheal extubation, at 0800 hr on the first postoperative day, and 24 and 48 hr after ICU admission. Results: No differences between groups were detected for demographic variables. The percent change in cortisol concentration relative to preoperative values (control vs spinal; (38 (87) vs -41 (46)%, P < 0.05)) was lower in the spinal group on admission to ICU. The percent change in plasma epinephrine levels (control vs spinal) on admission to ICU (285 (337) vs -10 (37)%) and 0800 hr after surgery (314 (341) vs -4 (37)%) was also significantly different. Conclusion: Intrathecal morphine only partially attenuated the postsurgical stress response in CABG surgical patients.