Randomised double-blind comparison of morphine vs. a morphine–alfentanil combination for patient-controlled analgesia

In a randomised, double-blind study, we compared a combination of morphine and alfentanil with morphine alone for patient-controlled analgesia (PCA) after Caesarean section under spinal anaesthesia. After surgery, patients were randomly allocated to receive PCA with a bolus dose of either morphine 0.75 mg plus alfentanil 0.125 mg (Group MA, n = 40) or morphine 1.5 mg alone (Group M, n = 37) with a lockout interval of 8 min and no hourly dose limit. Clinical assessments were made in the first 24 h, after which patients completed a written questionnaire. There were no differences between groups in PCA usage or visual analogue scale pain scores measured at 2, 4, 6 and 24 h. There was a low incidence of side-effects in both groups. In the questionnaire, patients in Group MA scored higher compared with Group M when asked to grade speed of onset and effectiveness of analgesia after a PCA bolus; there were no differences in grading for duration of analgesia or overall patient satisfaction. Addition of alfentanil to morphine may have advantages for PCA.