Increasing the pH of lidocaine decreased pain on injection and augmented patient comfort and satisfaction.
Comparison trial of four injectable anesthetics for laceration repair.
To compare four injectable anesthetics (buffered 1% lidocaine, buffered 1% lidocaine with epinephrine, plain 1% lidocaine with epinephrine, and 0.5% diphenhydramine with epinephrine) for pain of infiltration and effectiveness of anesthesia during suturing of minor lacerations.
                A prospective, randomized, double-blind, comparison trial of the above agents was performed in an urban ED; adults with simple linear lacerations without vascular compromise were enrolled. Physicians and patients ranked the pain of injection and suturing according to a 10-cm visual analog scale (VAS). Fisher's exact and Kruskal-Wallis tests were used to compare demographic data, and Kruskal-Wallis and Newman-Keuls tests were used in analysis of VAS rankings. The power of the study was 0.8 to detect a 1.4-cm difference in VAS readings, and 0.9 to detect a 1.7-cm difference.
                Seven of 200 enrolled patients were excluded due to improper data collection and 13 were removed from final statistical analysis due to need for additional anesthetic (treatment failures), leaving 180 subjects for final analysis. Demographic data were similar for the four groups (p > 0.05). Diphenhydramine with epinephrine was significantly more painful to inject than was buffered lidocaine or buffered lidocaine with epinephrine, according to both the patients (p = 0.0003) and the physicians (p = 0.0037). The two buffered compounds were slightly less painful to inject than was lidocaine with epinephrine, but statistical comparisons did not reach significance. For anesthesia effectiveness, lidocaine with epinephrine and buffered lidocaine with epinephrine were statistically better than buffered lidocaine or diphenhydramine with epinephrine (p = 0.0001 for the patients and the physicians).
                Buffered lidocaine with epinephrine and lidocaine with epinephrine were more effective anesthetics during suturing, according to both the physicians and the patients. There was a tendency toward less pain with infiltration in buffered solutions, compared with plain lidocaine with epinephrine, but the comparisons did not reach statistical significance. Diphenhydramine with epinephrine was more painful to inject than were buffered lidocaine with epinephrine and lidocaine with epinephrine, and was less effective anesthetically than the other three solutions.