Effects of postoperative background PCA morphine infusion on pain management and related side effects in patients undergoing abdominal hysterectomy

Study ObjectiveTo examine the effects of background morphine infusion via patient-controlled intravenous analgesia (PCA) device.DesignRandomized, controlled, double-blinded study.SettingUniversity-affiliated hospital.Patients60 ASA physical status 1 and 2 patients scheduled for abdominal hysterectomy.InterventionsPatients were randomly allocated to either the PCA group without continuous background morphine infusion (Group 1; n = 30) or the PCA group with continuous background morphine infusion (Group 2; n = 30).MeasurementsPain intensity during movement and at rest, morphine consumption at indicated time intervals, and related side effects were evaluated and recorded for three postoperative days at 12-hour intervals. The degree of patient satisfaction with PCA pain management was elicited and recorded.Main ResultsPain intensity during movement (VASC) at 12 and 36 hours postoperatively and pain intensity at rest from 12 to 60 hours were significantly higher in Group 2 than Group 1. PCA morphine consumption for three days postoperatively in Group 2 was significantly higher. The frequency of vomiting, nausea, and dizziness were higher in Group 2. The frequency of pruritus, urinary retention, and allodynia was similar for both groups. The degree of patient satisfaction with pain management was generally equivalent between the groups.ConclusionA continuous background morphine infusion of 0.5 mg/hr did not lower pain intensity during movement or at rest, but induced higher pain intensity, higher opioid usage, and more complications such as vomiting, nausea, and dizziness.