Randomized double-blind controlled trial comparing room-temperature and heated lidocaine for digital nerve block.

STUDY OBJECTIVE

To determine whether warming of lidocaine decreases the pain of its injection during digital nerve block.

DESIGN

Prospective, randomized, double-blind, controlled trial.

INTERVENTIONS

Twenty healthy volunteers received bilateral digital nerve blocks of their middle finger. They were first randomly assigned to receive either room-temperature (21 degrees C) or heated (42 degrees C) 2% lidocaine in their first block. They were then randomly assigned to receive the first block in either the right or left hand. The blocks were performed in a standardized fashion by a single physician, who was blinded to which solution was being used. The volunteers rated the pain of each digital block on a 100-mm visual analog scale (VAS). Efficacy of each digital block was tested at 5 minutes.

RESULTS

Heating of the lidocaine was associated with a significantly lower median VAS pain score (31.5 versus 25.0; P < .05). There was no difference in pain score between the two solutions in relation to which hand was used (P = .29) or whether the injection was the first or the second (P = .37). When all factors (temperature, order, and hand) were considered in the ANOVA with respect to VAS pain score, the only significant relation found was that between the temperature of the solution and the VAS pain score (P = .028).

CONCLUSION

Heating of lidocaine decreases the pain of injection during digital nerve block.