An audit of postoperative intravenous patient-controlled analgesia with morphine: evolution over the last decade

The development and refinement of an acute pain service based on the increased availability of clinical evidence would be expected to improve the quality of postoperative pain control. This report reviews the application of postoperative patient-controlled analgesia (PCA) using intravenous morphine in a single institution between 2002 and 2005. More than 5000 patients were evaluated and the results were compared with a similar study performed 10 years ago. Prescription of PCA had increased by more than threefold. Morphine consumption from post-operative day 1 to day 3 (19.1 vs. 26.1, 8.6 vs. 18.1 and 4.5 vs. 19.0 microg/kg/h, respectively), demand-to-delivery ratio (1.35-1.76 vs. 2.4-2.8) and the incidence of respiratory depression (0.06% vs. 2%) were significantly reduced (p<0.001), but there was no improvement in pain relief. A substantial proportion of patients still experienced postoperative nausea (47%) and vomiting (18.5%) despite a reduction in morphine consumption. Most patients ranked PCA as good and only 0.3% were dissatisfied. We conclude that, in our institution over the last decade, PCA has become more popular for postoperative pain management but with no attendant improvement in pain relief or reduction in side effects. Using PCA alone may result in poorer quality postoperative analgesia. Our findings add to the growing body of evidence that postoperative pain management has not substantially improved despite increased adoption of acute pain services.