Pain on injection of propofol. A comparison of cold propofol with propofol premixed with lignocaine.

Propofol is frequently associated with pain on injection. Previous studies have suggested that chilling of the propofol decreases pain significantly. This prospective, randomised, double-blind trial was designed to assess the effectiveness of cold propofol compared with propofol premixed with lignocaine in minimising pain on injection. Patients were allocated to one of four groups: propofol + lignocaine 0.1 mg.kg-1, propofol + lignocaine 0.2 mg.kg-1, cold propofol and a control group consisting of propofol premixed with normal saline and maintained at room temperature. The results of this study show that cold propofol is associated with a very high incidence of injection pain while lignocaine 0.1 mg.kg-1 premixed with propofol significantly decreases the incidence of pain (p < 0.001). Increasing the dosage of lignocaine above 0.1 mg.kg-1, however, does not significantly decrease the incidence of pain further. The addition of lignocaine also significantly decreases the incidence of excitatory side-effects.