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.