THE EFFECTS OF HYALURONIDASE ON THE EFFICACY AND ON THE PAIN OF ADMINISTRATION OF 1-PERCENT LIDOCAINE

Despite current clinical practice, there is no objective evidence to d emonstrate the efficacy or pain on injection when hyaluronidase is add ed to lidocaine as an anesthetic combination for local anesthesia. To evaluate the usefulness of hyaluronidase added to lidocaine in affecti ng pain on injection and effectiveness of local anesthesia, a prospect ive, randomized, double blind study comparing 1% lidocaine preparation s with and without hyaluronidase (15 U/cc) was conducted. A paired exp eriment was done with each subject receiving both treatments. Solution s of these local anesthetics were prepared. A 0.5-cc intradermal injec tion of each was administered to the dorsum of the nondominant hand of 25 volunteers. After showing study participants a standard pain with a peripheral nerve stimulator, pain of anesthetic infiltration was rat ed by the subject using a visual analog scale. The amount of tissue de formation on injection was assessed. The area of anesthetized skin sur rounding each injection was measured at 1/2, 1, 2 1/2, 4 1/2, 8, and 1 2 minutes after injection. The area of anesthesia achieved by 1% lidoc aine infiltration can be significantly enhanced by the addition of hya luronidase at a concentration of 15 U/cc (p = 0.0003). This raises the pH of the anesthetic to a slightly more physiologic level (6.33 versu s 6.20) and makes the pH closer to the pK of the lidocaine. In additio n, the hyaluronidase additive significantly decreases the amount of ti ssue distortion (p < 0.0001) without decreasing the efficacy of anesth etic action (p = 0.01). However, adding hyaluronidase to 1% lidocaine significantly increased the pain on injection (p = 0.0002). The inject ions of small amounts of hyaluronidase-containing solutions in this ex periment did not produce any visible effects at 5 to 7 days after inje ction; however, the effect of hyaluronidase upon wound healing was not studied.