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

Purpose: Intrathecal morphine administered prior to coronary artery revascu larization (CABG) surgery was studied to determine its effects on the stres s response. Methods: In a single centre, open, randomized clinical trial, first time el ective CABG surgery patients, < 75 yr, were studied. Control subjects (n = 12) received a standardized anesthetic consisting of fentanyl (maximum cumu lative dose of 35 mu g.kg(-1)), propofol, and pancuronium. In addition, spi nal 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. C ontrol subjects received continuous iv morphine at 2 mg.hr(-1) on arrival i n the ICU with iv bolus morphine supplementation as required while spinal s ubjects received bolus iv morphine as required. Changes in plasma cortisol and catecholamine concentrations were measured preoperatively, poststernoto my, on admission to ICU, following tracheal extubation, at 0800 hr on the f irst postoperative day, and 24 and 48 hr after ICU admission. Results: No differences between groups were detected for demographic variab les. The percent change in cortisol concentration relative to preoperative values (control vs spinal; (38 (87) vs -41 (46)%, P < 0.05)) was lower in t he spinal group on admission to ICU. The percent change in plasma epinephri ne 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 di fferent. Conclusion: Intrathecal morphine only partially attenuated the postsurgical stress response in CABG surgical patients.