Efficacy of buffered local anaesthetics in head and neck infections

Lignocaine is one of the most commonly-used agents to anaesthetise an area preoperatively. It can, however, cause undesirable effects such as burning on injection, relatively slow onset, and unreliable, or lack of, numbness when injected into infected tissues as a result of the acidic pH of commercial preparations (the pH is between 3.5 and 7.0 compared with the physiological pH, which is between 7.35 and 7.45). The aim of this comparative study was to evaluate the efficacy of buffered local anaesthetic on infected areas by altering the pH with 8.4% sodium bicarbonate, to measure the pain before and after the injection, and to record the time of onset of anaesthesia. All 60 patients were given 2% lignocaine hydrochloride with adrenaline 1:80,000 and 30 patients were randomly allocated to have 10:1 dilution of 8.4% sodium bicarbonate (study group). Pain was assessed on a visual analogue scale and a verbal rating scale. There was a significant difference in the amount of pain between control and study groups (p = 0.025). The mean (SD) time (minutes) to onset of local anaesthesia in the study group was 1.06 (0.25) compared with 2.96 (0.81) in the control group (p < 0.001). Our results confirm the efficacy of the buffered local anaesthetic solution in reducing pain on injection and resulting in quicker onset of anaesthesia. Increasing the pH of lignocaine solutions with bicarbonate immediately before use, therefore, should be considered when treating various acute infections of the head and neck.