BACKGROUND: Midazolam has been reported to decrease postoperative nausea and vomiting (PONV). We studied the antiemetic effect of midazolam in patients receiving intravenous patient-controlled analgesia (PCA) using morphine after total abdominal hysterectomy.

METHODS: Group C (n = 27) received bolus of morphine 5 mg and PCA of morphine 1 mg/ml. Group M1 (n = 27) received bolus of morphine 5 mg and midazolam 1 mg and PCA of midazolam 0.2 mg/ml mixed with morphine 1 mg/ml. Group M2 (n = 27) received bolus of morphine 5 mg and midazolam 1 mg and PCA of midazolam 0.4 mg/ml mixed with morphine 1 mg/ml. The PCA delivery system was programmed to deliver 1 ml of the test solution per demand with a 10 min lockout interval and no background infusion. The incidence of PONV, metoclopramide and ketorolac usage, morphine and midazolam consumption, pain, sedation, and other side effects were assessed at 1, 4, 8, 16, 24, 36 and 48 h after the operation.

RESULTS: The incidences of PONV were 19 (70%) in Group C, 14 (52%) in Group M1 and 10 (37%) in Group M2. The incidence of PONV in Group M2 was significantly lower than that in Group C (P < 0.05). Patients in Group M2 experienced more sedation than those in Group C (P < 0.05). No severe sedation was observed in all groups.

CONCLUSIONS: Combination of midazolam 0.4 mg per morphine 1 mg in PCA had more effective antiemetic efficacy than control without significant adverse effects.