Effects of a Loading Dose of Morphine for Postoperative Pain Relief in Adult Patients in Post-Anesthetic Care Unit: A Retrospective Analysis in a Medical Center

A loading dose of morphine administered before intravenous morphine titration might improve acute pain relief in the post-anesthesia care unit (PACU). The purpose of this study was to evaluate the effect of a loading dose of morphine retrospectively. Materials and methods: We reviewed a one-year interval PACU records. Patients were divided into two groups, those who received a loading dose (0.5mg/ks) before the end of surgery (group L) and those who did not (group C). Postoperative pain was assessed using the numerical rating scale (NRS; 0 to 10), and a score of ＞3 required another administration of morphine in the PACU. NRS was measured every 15 min up to discharge. Main outcomes evaluations included NRS, morphine consumption, rescue analgesics and incidence of postoperative adverse events. Results: Complete data of 11,048 adult patients discharged from PACU were analyzed. Initial NRS ＞7 occurred less frequently in group L than group C (19.4% vs 37.7%, p＜0.001). NRS ＜3 at discharge also showed favorable result in group L (86.1% vs 72.9%, p＜0.01). The mean equivalent morphine consumption was significantly lower in the group L than group C (5.9±2.6 vs 7.4±3.5mg, p＜0.05). The incidence of requiring rescue analgesics was lower in study group (18.3 vs 21.7%, p＜0.01). The incidences of postoperative events did not differ significantly between groups. Conclusion: A loading dose of morphine before morphine titration provided better acute pain control in PACU. This improvement was not associated with more postoperative adverse events.