The Preemptive Analgesic Effect of Intravenous Ketamine

Hong, Jeong Yeon; Lee, Youn Woo; Park, Wyun Kon; Lim, Woung Choul; Kang, Hee Ryun

Abstract

BACKGROUND: Preemptive treatment with ketamine, a noncompetitive NMDA antagonist, may prevent establishment of postoperative hypersensitivity by blocking the sensory input that induces the central sensitization. The aim of this study was to determine if continuous preemptive administration of intravenous (IV) ketamine decreases postoperative pain.
METHODS
Sixty healthy informed patients scheduled for elective abdominal hysterectomy were randomly divided into two groups of equal size and studied in a double-blind manner. Before surgical incision, patients were given 1 mg/kg of ketamine or equal volume of saline followed by IV infusion of 0.01 mg/kg/min, which was discontinued at peritoneal closure. IV morphine patient-controlled analgesia (PCA) was started in all patients at peritoneal closure. Visual analogue scale (VAS) pain scores and total morphine consumption were recorded at 1, 3, 6, 9, 12, 24, 36, and 48 hours postoperatively.
RESULTS
VAS pain scores at rest were significantly less in the ketamine group than in the saline group at 1, 3, 24, 36, and 48 hr postoperatively. VAS at moving status were less in the ketamine group at 1, 3, 12, 24, 36, 48 hr postoperatively. Patients in the ketamine group had significantly lower morphine consumption throughout the study period, about 20-50% reduction in postoperative total morphine was observed. Only ketamine group experienced severe headache (10 cases), while there were no intergroup differences in other side effects such as pruritus, bad dream, and backache.
CONCLUSION
These results suggest that preemptive continuous IV ketamine decreases postoperative pain intensity and IV morphine requirement, and its action lasts longer than the normal expected duration of action of ketamine.