Reduction of propofol injection pain by utilizing the gate control theory

Background: Propofol is the most commonly using intravenous hypnotic for the induction and maintenance of general anesthesia. However, pain on propofol injection is a well known adverse event. Currently, acute and chronic pain can be controlled by utilizing the "gate control" theory. Methods: Patients were randomized to receive lidocaine (0.5 mg/kg; Group L), touch on IV injection site (Group T), combination lidocaine (0.5 mg/kg) and touch on IV injection site (Group B), or normal saline (Group S) with venous occlusion for 1 minute, followed by administration of propofol (0.5 mg/kg) into the largest dorsal vein of the hand. Immediately after administering propofol, an investigator blinded to the group assignments asked the patient about pain at the injection site and assessed pain intensity using a 4-point verbal rating scale (0 = none, 1 = mild, 2 = moderate, 3 = severe). Results: A significant decrease in the incidence of pain on propofol injection was achieved in group L (37%) and group B (23%) compared to either group T (80%) and group S (83%) (P < 0.001). But, the incidence of moderate and severe pain was significantly lower in group L (7%), group T (20%) and group B (0%) when compared to group S (53%) (P < 0.05). Conclusions: Light touch and rubbing reduced pain, although while, they did not reduce the incidence of pain, they reduced the intensity of pain. This method might be considered as an alternative to other treatments but may be contraindicated for use with other drugs.