Warming lignocaine to reduce pain associated with injection.

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 degrees C and 1 ml of 1% lignocaine at 37 degrees 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 degrees C was more painful and 3 (11%; 2% to 28%) thought that lignocaine at 37 degrees C was more painful (p < 0.0001); 12 subjects did not express a difference. Median pain score for injection at 20 degrees C was 11.00 and at 37 degrees 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 degrees C reduced the pain associated with subcutaneous injection of lignocaine.