Postoperative effects of low-dose intrathecal morphine in coronary artery bypass surgery

Intrathecal morphine has been used in hopes of providing long-lasting postoperative analgesia in patients after cardiac surgery. The aim of this study was to evaluate the effects of 7 micro/kg intrathecal morphine administration in coronary bypass surgery in the postoperative period.

We conducted a prospective, randomized, blinded, and controlled study. Twenty-three patients, who underwent primary elective coronary bypass surgery, were randomly allocated to receive morphine 7 micro/kg intrathecally, before the induction of general anesthesia (Group M, n = 12) or no intrathecal injection (Group C, n = 11). Pain scores, determined by visual analogue scale (VAS), were recorded immediately after extubation upon admission to the intensive care unit (ICU), at the 2nd, 4th, 6th, and 18th hour after extubation. Pethidine was administered if the patient's VAS > or = 4 and consumption was recorded. Extubation time and ICU length of stay were also recorded.

VAS scores were lower in the Group M at each measured time than the control group (p = 0.016, 0.023, 0.004, 0.0001, and 0.001, respectively). According to the VAS scores, pethidine requirement was lower in the Group M than the control (p = 0.001). Extubation time (3.58 +/- 1.57 vs. 4.86 +/- 1.38 hours, p = 0.045) and ICU length of stay (16.25 +/- 2.70 vs. 19.30 +/- 2.45 hours, p = 0.014) were also significantly shorter in the Group M than the control group. No significant complications were seen in this group of patients.

Intrathecal morphine provided effective analgesia, earlier tracheal extubation and less ICU length stay after on-pump coronary bypass surgery. The influence on ICU length of stay requires further evaluations.