Differences in postoperative opioid consumption in patients prescribed patient-controlled analgesia versus intramuscular injection.

The purpose of this study was to examine differences in opioid consumption in patients prescribed patient-controlled analgesia (PCA) versus intramuscular injection (IMI) in the early postoperative period after open abdominal surgery. A retrospective audit of 115 patients elicited demographic and clinical data. No significant differences were found between the demographic variables of the PCA and IMI groups. There was a significant difference in the mean opioid dose used during the first 3 postoperative days (p < .01). Mean opioid consumption was 136.89 mg for the PCA group and 50.79 mg for the IMI group. Although there was a reduction in the amount of opioid consumed over the first 3 postoperative days, the PCA group consistently consumed more opioid analgesia compared with the IMI group. Furthermore, there was a disproportionate reduction in opioid consumption between the two groups from Day 1 (r = .34; p < .01) to Day 3 (r = .14; p = .14). This study shows that the amount of analgesia consumed during the postoperative period by patients who had abdominal surgery varied markedly depending on the mode of analgesia (PCA or IMI). The difference in analgesic consumption was also found to increase throughout the 3-day postoperative period. This divergence in the amount of opioid consumption between patients who were prescribed PCA and patients who were prescribed IM analgesia heightens the need for vigilance in assessment and management of pain during the early postoperative period, particularly in patients prescribed IM analgesia on an "as-needed" basis.