A randomized double blind trial to compare pain on digital injection of warm and cold anaesthetic

Local anaesthetics produce pain and burning on subcutaneous infiltration. This transient discomfort often proves to be the most unpleasant aspect of minor surgical procedures. This study aimed to elucidate if warming local anaesthetic to 37°C reduces pain of digital injection. Thirty-six patients attending a department of podiatry for nail surgery participated in this randomized, double blind study. Pain levels were assessed utilizing a visual analogue scale. Each subject was randomly allocated to receive 1 ml of local anaesthetic at either 37°C or 5°C. Pain scores for warm local anaesthetic solution (median 2.6, upper quartile 6.1, lower quartile 1.5) were significantly less painful on digital injection than cold solution (median 9.3, upper quartile 11, lower quartile 8.2) which was confirmed by statistical analysis using SPSS for Windows (Wilcoxon's signed ranks test, matched pairs [z = 2.90, P = 0.0038]).