The Comparison of Preventive Analgesic Effects of Ketamine, Paracetamol and Magnesium Sulfate on Postoperative Pain Control in Patients Undergoing Lower Limb Surgery: A Randomized Clinical Trial.

BACKGROUND: In considering the importance of postoperative pain management and its consequences on its related secondary outcomes including nausea, vomiting, and operation-related complications, we aimed to compare the effectiveness of the three analgesic agents including ketamine, paracetamol, and magnesium sulfate for postoperative pain relief and associated consequences in this trial.

MATERIALS AND METHODS: In this double-blinded randomized control clinical trial, patients scheduled for elective lower extremity orthopedic surgery under general anesthesia were enrolled and randomized into four groups for receiving intravenous ketamine (0.25 mg/kg), paracetamol (15 mg/kg), magnesium sulfate (7.5 mg/kg), and placebo (normal saline), immediately after the induction of anesthesia. Postoperative pain scores, analgesic, and metoclopramide use, and frequency of vomiting and satisfaction score of studied patients in the four studied groups during the 6 h, 6-12 h, and 12-24 h after recovery were recorded and compared.

RESULTS: In this trial, thirty patients randomized in each studied groups. Mean of postoperative pain score was significantly lower in ketamine group than others during 24 h after recovery ( P < 0.001). Mean of additive analgesic use was significantly lower in ketamine group during 12 h after recovery ( P < 0.001), but it was not significantly different during 12-24 h after recovery ( P = 0.12). Mean of vomiting frequency and metoclopramide use was not different between groups ( P > 0.05). Excellent and good satisfaction score were significantly higher in ketamine group than other groups ( P = 0.04).

CONCLUSIONS: Ketamine has more superior effect for during recovery and postoperative pain controlling and analgesic use than paracetamol and magnesium sulfate.