THE EFFICACY OF ADDING A CONTINUOUS INTRAVENOUS MORPHINE INFUSION TO PATIENT-CONTROLLED ANALGESIA (PCA) IN ABDOMINAL-SURGERY

The effect of adding a continuous infusion of morphine I mg/hr to pati ent-controlled intravenous analgesia war; studied in a randomized doub le-blind trial Ninety-six patients scheduled for abdominal surgery wer e enrolled; 38 received PCA and continuous infusion (PCA+C) 45 receive d PCA alone and 13 were excluded because of protocol violations. PCA w as delivered via an ABBOTT 4200 pump with settings of morphine 1 mg bo lus and five-minute lockout in both groups. A separate pump delivered a continuous infusion of morphine 1 mg/ml (PCA+C) or 9% normal saline (PCA) at 1 ml/hr for three postoperative days. Pain was assessed by ho urly verbal pain scores (VPS) and daily visual analog pain scores at r est and on movement (VAS(rest), VAS(more)). PCA delivered morphine and the demand to delivery ratio (D/D ratio) were used as indirect indica tors of pain. These were assessed during daytime (0800-2200 hours), sl eep (2200-0500 hours) and on first waking (0500-0800 hours). Patient d emographics were similar, Patients receiving a continuous infusion had lower pain scores during the first 24 hours but not thereafter (VPS P =0.04, VAS(more) P=0.02). The PCA group delivered more PCA morphine du ring 0500-0800 hours and 0800-2200 hours on the first day only. There was no significant difference in the D/D ratio for any time period dur ing the three days, Total morphine delivery was greater in the PCA+C g roup on the second and third postoperative days (P=0.009 and P=0.0001 respectively)., The incidence of respiratory depression and the total number of complications were significantly higher in those receiving c ontinuous infusion (P=0.04 and P=0.011 respectively.) Adding a continu ous morphine infusion of 1 mg/hr to the described PCA settings for thr ee days following abdominal surgery improved analgesia during the firs t 24 hours but was associated with a greater incidence of complication s.