Warming lignocaine to reduce pain associated with injection

Abstract

Objective - To investigate the effect of warming lignocaine on the pain associated with subcutaneous injection. Design - Double blind, randomised, crossover study. Setting - Hospital clinic. Subjects - 40 healthy volunteers. Interventions - Subcutaneous injection with 1 ml of 1% lignocaine at 20°C and 1 ml of 1% lignocaine at 37°C. Main outcome measures - Pain assessed by linear analogue pain scores and subjects' comparison of pain on injection. Results - 25 subjects (89%; 95% confidence interval 72% to 98%) thought that lignocaine at 20°C was more painful and 3 (11%; 2% to 28%) thought that lignocaine at 37°C was more painful (p<0·0001); 12 subjects did not express a difference. Median pain score for injection at 20°C was 11·00 and at 37°C was 3·25 (p<0·001). Median difference was 8·25 (4·00 to 13·50). Conclusions - The simple procedure of warming to 37°C reduced the pain associated with subcutaneous injection of lignocaine.