Effects of a fentanyl-propofol mixture on propofol injection pain: a randomized clinical trial

BACKGROUND Propofol injection pain is a common problem that can be very distressing for patients. We compared the effects of injection with saline followed by injection with a fentanyl-propofol mixture, injection with fentanyl followed by a propofol injection, and injection with saline followed by propofol alone on propofol injection pain. METHODS The patients were assigned randomly to one of three groups. A rubber tourniquet was placed on the forearm to produce venous occlusion for 1 min. Before anesthesia induction, group C (control, n = 50) and group M (fentanylpropofol mixture, n = 50) received 5 ml of isotonic saline, while group F (fentanyl, n = 50) received 2 µg/kg of fentanyl. After the tourniquet was released, groups C and F received 5 ml of propofol and group M received 5 ml of a mixture containing 20 ml of propofol and 4 ml of fentanyl. At 10 s after the study drugs were given, a standard question about the comfort of the injection was asked of the patient. We used a verbal rating scale to evaluate propofol injection pain. Statistical analyses were performed with Student's t-tests and Fisher's exact tests; P < 0.05 was considered to indicate statistical significance. RESULTS The demographic data were similar among the groups. In group M, the number of patients reporting propofol injection pain was significantly lower than in groups F and C (both P < 0.001). No patient in group F or M experienced severe pain, whereas 24 patients (48%) had severe pain in group C (both P < 0.001). CONCLUSIONS This study shows that a fentanyl-propofol mixture was more effective than fentanyl pretreatment or a placebo in preventing propofol injection pain.