Effect of ketamine as an adjunct to intravenous patient-controlled analgesia, in patients at high risk of postoperative nausea and vomiting undergoing lumbar spinal surgery.

BACKGROUND: We evaluated the effect of ketamine as an adjunct to a fentanyl-based i.v. patient-controlled analgesia (IV-PCA) on postoperative nausea and vomiting (PONV) in patients at high risk of PONV undergoing lumbar spinal surgery.

METHODS: Fifty non-smoking female patients were evenly randomized to either the control or ketamine group. According to randomization, patients received either ketamine 0.3 mg kg(-1) i.v. or normal saline after anaesthetic induction with fentanyl-based IV-PCA either with or without ketamine mixture (3 mg kg(-1) in 180 ml). The incidence and severity of PONV, volume of IV-PCA consumed, and pain intensity were assessed in the postanaesthesia care unit, and at postoperative 6, 12, 24, 36, and 48 h.

RESULTS: The overall incidence of PONV during the first 48 h after surgery was similar between the two groups (68 vs 56%, ketamine and control group, P=0.382). The total dose of fentanyl used during the first 48 h after operation was lower in the ketamine group than in the control group [mean (SD), 773 (202) μg vs 957 (308) μg, P=0.035]. The intensity of nausea (11-point verbal numerical rating scale) was higher in the ketamine group during the first 6 h after operation [median (interquartile range), 6 (3-7) vs 2 (1.5-3.5), P=0.039], postoperative 12-24 h [5 (4-7) vs 2 (1-3), P=0.014], and postoperative 36-48 h [5 (4-7) vs 2 (1-3), P=0.036]. Pain intensities were similar between the groups.

CONCLUSIONS: Ketamine did not reduce the incidence of PONV and exerted a negative influence on the severity of nausea. It was, however, able to reduce postoperative fentanyl consumption in patients at high-risk of PONV.