Comparison of Intravenous vs. Intramuscular Morphine for Postoperative Pain Relief on the Multidisciplinary Care Path Implemented Ward

Abstract

Objective: To compare the efficacy and side effects of intravenous and intramuscular morphine injection for postoperative pain relief on the multidisciplinary care path implemented ward and to study the attitude of nurses and doctors in using these two routes of analgesia.
Methods: We performed a prospective, single-blind, randomized controlled trial in 80 patients undergoing elective gynecologic surgery. They were randomly allocated into two groups. Group IM received 10 mg morphine intramuscular (IM) injection for pain prn every 4 hours. Group IV received intravenous (IV) morphine for pain prn every 2 hours. The dose of morphine was given based on pain score: < 7 gave 1 mg, ≥ 7 gave 2 mg. In the recovery room (RR) both groups received IV morphine until they felt enough pain relief. We recorded patients’ pain scores at the time discharged from RR, at the time arrival to the ward, 24 and 48 hours postoperation, and the amount of morphine received. We interviewed the patients on their satisfaction for pain relief. The questionnaire was sent to nurses and doctors working in the ward.
Results: The numbers of patients having pain scores ≥ 4 and ≥ 7 within 48 hours in the IV group and the IM group were not different (95% and 42.5% vs. 97.5% and 45%, respectively). More than half of them felt no need to ask for analgesic very often and they received analgesic quite soon. Patients in the IM group had more pain on injection than the IV group (p<0.001). The time they started to experience pain relief after each dose of analgesic was not different in both groups, but more patients in the IV group felt much overall pain relief (p=0.005). The IV group had less nausea, vomiting and dizziness than in the IM group (p=0.002, p<0.001 and p=0.003, respectively). No respiratory depression found in this study. Both groups were satisfied with the treatments. Nurses found no difference in their convenience for administration of morphine between the 2 routes but doctors felt that they were called by nurse for the same patient because of inadequate pain relief more often after the IM route than after the IV route (p=0.007).
Conclusion: There is no difference in postoperative pain relief in 48 hours between giving 2 mg morphine IV prn every 2 hours and 10 mg morphine IM prn every 4 hours in patients undergoing major gynecological operations on the multidisciplinary care path implemented ward. However, patients in the IV group feel less pain on injection, and less nausea and vomiting, although both groups give similar satisfaction scores. Nurses give their opinion of no differences in their convenience for administration of morphine between these two routes. Doctors, however, feel that they are called because of inadequate pain relief more often in the IM group than in the IV group.