[Pre-treatment with ketamine reduces incidence and severity of pain on propofol injection].

The purpose of this study was to evaluate the effect of pre-treatment with ketamine on the reduction of pain during injection of propofol in adult patients. We conducted a prospective, randomized, double-blinded trial. Forty-three patients were randomly allocated to one of two groups according to the agents administered before hand; Group C, normal saline 2 ml and Group K, 1% ketamine 2 ml. The pain on injection was rated as none, mild, moderate, or severe. Sixty-eight percent of patients in the C group experienced pain, while 33% of patients experienced pain in the K group. Thirty-six percent of patients in the C group complained moderate to severe pain but only 9% of patients in the K group. The mechanisms of prevention by ketamine of the pain on propofol-injection could not be clarified from our study, but it may be related to central effects of ketamine. In conclusion, ketamine pre-treatment before propofol administration significantly reduces incidence and severity of pain associated with propofol injection.