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.