No morphine sparing effect of ketamine added to morphine for patient-controlled intravenous analgesia after uterine artery embolization

Background: Pain following embolization of the uterine arteries (UAEs) is variable and may be very severe requiring large doses of parenteral opioids for relief. The present study tested the hypothesis that the addition of ketamine to IV patient-controlled morphine reduces the amount of morphine required for pain-control during the first 24 h after UAE embolization. Methods: Fifty-six patients undergoing UAE embolization for treatment of symptomatic uterine leiomyomata were randomized to receive either 2 mg/ml of morphine (Control group, n=30) or 2 mg/ml of both morphine and ketamine (Ketamine group, n=26) by IV patient-controlled analgesia (IV-PCA). Pump settings were bolus dose 1 ml, lockout 10 min, no background infusion. In addition, all patients received diclofenac and acetaminophen for pain relief. Pain scores, morphine consumption and adverse events like nausea, vomiting, itching, visual disturbances, anxiety, dreaming and hallucinations, if any, were recorded for 24 h after embolization. Results: The mean ± SD 24-h consumption of patient-controlled morphine was 38.3 ± 21.0 mg in the Ketamine group vs. 33.3 ± 18.3 mg in the Control group (NS). The difference between the means was 5.0 mg (95% confidence interval: −5.7; 15.6). One patient in the Ketamine group vs. none in the Control group experienced auditory hallucinations. Conclusion: Studying an unselected group of patients undergoing embolization of the UAEs for treatment of symptomatic uterine leiomyomata under conditions of basal analgesia with acetaminophen and diclofenac, we failed to demonstrate any morphine-sparing effect of IV-PCA ketamine and morphine compared with IV-PCA morphine alone.