EFFECT OF PH MODIFICATION BY BICARBONATE ON PAIN AFTER SUBCUTANEOUS LIDOCAINE INJECTION

OBJECTIVE: TO quantify the pain experienced on subcutaneous injection of lidocaine, lidocaine with sodium bicarbonate (NaHCO3) and saline. D ESIGN: A double-blind randomized prospective study. SETTING: A clinica l research unit in a university-affiliated hospital: PARTICIPANTS: For ty-two healthy adult volunteers who did not have a history of adverse reaction to lidocaine or peripheral neuropathy and were not pregnant. The study was performed in two phases. In Phase 1, 1 mL each of thee s olutions (2 mL of 8.4% NaHCO3 in 20 mL 1% lidocaine, 2 mL saline in 20 mL lidocaine and saline alone) were injected by an investigator, blin ded as to the identity of the solutions, in random order to five volun teers to measure onset and duration of anesthesia and the perceived pa in on injection. In Phase 2, 37 volunteers mere injected with the thre e solutions in random order, by an investigator blinded as to the iden tity of the solutions. MAIN OUTCOME MEASURE: Pain on injection measure d with the visual analogue scale. RESULTS: There were no clinically si gnificant differences between onset and duration of action of lidocain e with and without NaHCO3, as determined by Kruskal-Wallis one-way ana lysis of variance and the Wilcoxon signed-ranks test. Injection of lid ocaine with NaHCO3 was significantly less painful than injection of pl ain lidocaine (p = 0.041). Injection of saline was the most painful. C ONCLUSION: The addition of NaHCO3 to lidocaine produces significant re duction in pain experienced on injection without significantly affecti ng the onset or duration of action.