Effect of alkalinisation of lignocaine for intraoral nerve block on pain during injection, and speed of onset of anaesthesia

Injections of lignocaine as local anaesthetic for pain control in oral and maxillofacial surgery can themselves be painful. The time of onset of anaesthesia is from 3 to 5 min. Sodium bicarbonate has been used worldwide to reduce both these drawbacks to the injection, so making procedures more acceptable. This randomised prospective trial of 100 patients aged 18–55 years who were given 3 nerve blocks (inferior alveolar, lingual, and long buccal) was designed to assess the effect of alkalinisation of the lignocaine solution with sodium bicarbonate. All patients were given 2% lignocaine hydrochloride with adrenaline 1:80,000 and 50 patients were randomly allocated to be given 8.4% sodium bicarbonate in a 1/10 dilution. Pain was measured on a visual analogue scale (VAS). No patient given the injection with sodium bicarbonate complained of pain, compared with 39/50 (78%) not given sodium bicarbonate (p < 0.0001). The mean (SD) time (seconds) to onset of local anaesthesia in the group given sodium bicarbonate was 34.4 (9.8) compared with 109.8 (31.6) in the control group (p < 0.001). Our results have confirmed the efficacy of the alkalinised local anaesthetic solution in reducing pain on injection and resulting in quicker onset of anaesthesia.