Pain on intradermal injection with lignocaine. The effect of concentration.

Twenty ASA 1 volunteers were each injected intradermally with four solutions containing 0.2 ml of 0.5%, 1%, and 2% lignocaine and 0.9% saline to determine whether the pain experienced on injection was related to the concentration of local anaesthetic. A 10 cm linear analogue pain scoring system was used, and the solutions were ranked from most painful to least painful. There were no differences between the different concentrations of lignocaine and 0.9% saline in the severity of pain experienced. We conclude that any concentration of lignocaine may be used intradermally before inserting intravenous catheters without affecting the degree of pain experienced by that injection.