Propofol infusion rate does not affect local pain on injection

Background: Local pain at the site of an i.v. injection of propofol is a well-known problem, particularly in infants. This randomised investigator-blinded crossover study was designed to assess the effect of the i.v. bolus infusion rate on propofol-induced pain at the site of injection. Methods: Thirty unpremedicated patients scheduled for ear-nose-throat or plastic surgery at Malmo University Hospital, Sweden, were given two consecutive 2.0ml injections of propofol 10mg/ml (Diprivan((R)), AstraZeneca, Sweden/UK), at different infusion rates (0.2 or 1.0ml/s), immediately before induction of general anesthesia. Half of the patients (n=15) received the first bolus of propofol over 2s and the second bolus over 10s, and the other half (n = 15) had their injections in reversed order. After each injection, the patient was asked by an investigator to indicate pain intensity on a visual analog scale (VAS) and to report the times of the appearance, maximum point and disappearance of pain. The injections were given approximately 2 min apart. The investigators scoring pain intensity, as indicated by the patients on a 10-point numerical rate scale, were blinded to the order in which the injections were given, as were the patients themselves. Results:, There were no statistically significant differences in the incidence (both 86%) of intensity (median; 25th; 75th percentiles, in VAS units: 3.1; 1.0; 5.3 and 3.3; 1.4; 5.0, respectively) or duration (66 +/- 31 and 73 +/- 26s, respectively) of pain between the faster (1.0ml/s) and slower (0.2ml/s) bolus infusion rates of propofol studied. Conclusions: We conclude that the i.v. bolus infusion rate of propofol does not influence drug-induced local pain on injection, at least not within the infusion rate interval studied. Therefore, adjusting i.v. injection speed does not seem to be a clinically useful tool for reducing the intensity or duration of propofol-induced pain at the site of administration.