Postoperative analgesia in Cardiac Surgery

Overview

Introduction:
Prospective study comparing four methods of postoperative analgesia with regard to the following criteria: pain relief during bed-restand rehabilitation; the effect on ventilation and the occurrence of side effects.Study population and types of intervention: Ninety-two patients scheduled for cardiac surgery via sternotomy were enrolled in the study during theperiod from autumn 1998 to spring 1999. The patients were randomized into four groups. Balanced general anaesthesia was administered. Withinfirst 48 hours after the completion of surgery, patients were periodically assessed in 6–12 hours intervals and also during rehabilitation. We assessedpain according to VAS, hemodynamic parameters, spirometric values, arterial blood gases, depth of sedation and side effects of pain control.Following types of analgesia were compared:a) Mixture of ketamine 400 mg and sufentanil 100 mcg in 50 ml syringe, administered in a continuous infusion, rate of infusion 0.5–3.5 ml/hr(group A)b) Mixture of bupivacaine 0.5% 12.5 ml and sufentanil 50 mcg in 50 ml syringe, administered epidurally, rate of infusion 3–8 ml/hr (group B)c) Morphine administered by nurse in 2 mg boluses prn (group C)d) Morphine administered using PCA system: 10 mg/20 ml, bolus dose 1 ml, lock-out interval 5 min (group D).Results: We found statistically significant less pain during bed rest and rehabilitation in patients treated with epidurally administered analgesicmixture. During the postoperative period, in all groups spirometric functions decreased; the least decrease was in the group treated epidurally. Thosepatients had also higher oxygenation index; however, that value did not reach statistical significance. Sedation was equal in all groups. The mostcommon adverse effect of pain control was nausea; in two cases in group A we observed respiratory depression.Discussion: We fail to reach ideal postoperative analgesia of 3 and less according to VAS. We confirmed literary data on beneficial effect of epiduralanalgesia on ventilation and rehabilitation. With respect to this, we prefer that type of analgesia. PCA suited to the patients but not all of them wereable to operate the device by themselves. There were also technical difficulties with that particular type of syringe pump. Intermittent bolusadministration of morphine administered by nurse as requested leads to more frequent pain outbreak episodes, possibly caused by significant fluctuationof plasma level of the given drug.

Key words:
epidural analgesia - patient controlled analgesia ketamine - morphine