Increasing the pH of lidocaine decreased pain on injection and augmented patient comfort and satisfaction.
Effects of alkalinization of lidocaine on the pain of skin infiltration and intravenous catheterization.
To test the hypothesis that alkalinization of lidocaine decreases the pain of skin infiltration in surgical patients.
                Double-blind, randomized, prospective study.
                Preoperative holding units, Brigham and Women's Hospital.
                184 adult surgical patients.
                We compared the efficacy of 1% lidocaine with and without 0.1 mEq/ml of sodium bicarbonate (NaHCO3) for relief of pain of (1) skin infiltration and (2) intravenous (i.v.) catheterization prior to surgery.
                Patients evaluated the intensity of pain using a 100 mm visual analog scale (VAS). There were no differences between study groups (lidocaine with NaHCO3, n = 89; lidocaine alone, n = 95) with respect to site of catheterization or catheter gauge used. Lidocaine plus NaHCO3 caused significantly less pain on skin infiltration (median VAS = 4; range = 0 to 51) than did lidocaine alone (VAS = 8; range = 0 to 48; p < 0.008). Pain of i.v. catheterization also did not differ between groups. There was a weak correlation between catheter gauge and pain of i.v. catheterization (r = -0.19; p = 0.01).
                Pain resulting from skin infiltration of lidocaine solutions can be diminished by adding NaHCO3. However, catheter size is more important than the presence or absence of NaHCO3 in determining the pain of i.v. catheterization.