Postoperative analgesia in cardiac surgery: spinal versus intravenous morphine

Objective: To compare the effects of spinal and intravenous administration of morphine to supplement anesthesia with remifentanil in terms of analgesia during early postoperative recovery and considering time until extubation.

Methods: This prospective, randomized, blinded trial enrolled 59 patients scheduled for cardiac surgery. The patients were assigned to receive either a spinal infusion of morphine (15 microg x Kg(-1)) or an intravenous infusion (0.3 mg x Kg(-1)). Anesthesia was maintained with 0.15 to 0.50 microg x Kg(-1) x min(-1) of remifentanil and 2 to 4 mg x Kg(-1) x h(-1) of propofol in perfusion. After the period of extracorporeal circulation, all patients were given an intravenous infusion of 30 mg of ketorolac. Later intravenous ketorolac was ministered at a dose of 30 mg per 8 hours; intravenous morphine (bolus dose of 3 mg) was also administered until pain was relieved.

Results: The same quality of postoperative analgesia and anesthetic recovery was achieved with both spinal and intravenous administration. The incidence of side effects was also similar. Likewise, the extubation times were similar in the 2 groups (spinal infusion group: 294.5 [SD, 150.5] minutes; intravenous group: 325.0 [139.9] minutes; P>0.05). Less postoperative intravenous morphine was administered in the first 24 hours to patients in the spinal morphine group (P<0.05) and fewer patients in that group required intravenous morphine boluses (P<0.05).

Conclusions: Our study suggests that spinal morphine does not offer advantages over intravenous morphine with regard to postoperative analgesia, hemodynamic stability and respiratory parameters, time until extubation, or adverse effects.