The influence of injection speed on pain during injection of local anaesthetic

STUDY OBJECTIVE: To determine the influence of injection speed on pain during injection of local anaesthetics. METHODS: In a blinded randomised study with 36 healthy volunteers, each volunteer received three injections of 4.5 ml lidocaine subcutaneously on the abdomen. The injections were given during 15 seconds (0.3 ml/s), 30 seconds (0.15 ml/s), and 45 seconds (0.1 ml/s). The needle tip remained beneath the skin for 45 seconds during all three injections. Participants rated the pain experienced on a 100 mm visual analogue scale (VAS) immediately after each injection. After the last injection, they were asked which injections were the least and most painful. RESULTS: The mean VAS pain score for the 15 seconds injections was 26 (SD = 19), for the 30 seconds injections 24 (SD = 19), and for the 45 seconds injections also 24 (SD = 18) (ns). Eight subjects preferred the 15 seconds injection, 15 preferred the 30 seconds injection, and 10 preferred the 45 seconds injection (ns). CONCLUSION: It is concluded that varying the injection speed between 0.3 ml/s and 0.1 ml/s has no influence on the pain experienced during subcutaneous injection of 4.5 ml lidocaine.