The effect of injection speed on the pain of lidocaine infiltration

Objective: To determine whether reducing the speed of injection is effective in reducing injection pain for buffered and unbuffered lidocaine solutions. Methods: A prospective, single-blind, randomized, crossover, laboratory study was performed. Adult volunteers were recruited from ED staff at an urban teaching hospital to serve as subjects. Twenty-nine subjects each received 4 1 -mL injections into the dorsum of the hands. Each subject received fast and slow injections of buffered and unbuffered lidocaine. Subjects rated the pain of each injection on a lOQ-mm visual analog scale (VAS). Mean pain scores for each intervention were compared using analysis of variance. Results: The mean pain VAS score for fast injection of buffered lidocaine was 14.1 mm. For slow buffered injection, the mean pain score was 11.4 mm (p = 0.98). For unbuffered lidocaine, the means were 28.7 mm for fast injection and 22.2 mm for slow injection (p - 0.40). Conclusions: Reducing injection speed did not produce a statistically significant change in injection pain for either buffered or unbuffered solutions.