pH-adjustment and discomfort caused by the intradermal injection of lignocaine

One hundred adult day-case patients who required intravenous access had cannulae inserted using local anaesthesia with 1% lignocaine, 1% lignocaine with adrenaline or the corresponding pH-adjusted solutions. The local anaesthetic solutions were modified by the addition of 1 ml 8.4% sodium bicarbonate to 10 ml lignocaine. Pain scores at different stages of cannulation were noted and showed a significant reduction after use of pH-adjusted solutions (p less than 0.02 for the plain lignocaine, and less than 0.001 for the lignocaine with adrenaline). Modification of the pH of lignocaine solutions by the addition of sodium bicarbonate is a simple method significantly to reduce the discomfort caused by the infiltration of the local anaesthetic.