INFLUENCE OF LIDOCAINE ON LEUKOCYTE FUNCTION IN THE SURGICAL WOUND

The inflammatory response of the wound is mediated to a large extent by leukocytes, which play an important role in the wound healing process. Local anesthetics, which are routinely administered before minor skin surgery and for postoperative pain relief, have been shown to have diverse effects on wound healing. Local anesthetics have also been reported to induce potent inhibition of leukocytes in vitro, although their effects on leukocyte activity in the surgical wound have not been elucidated. The present study investigated the in vivo effects of lidocaine on leukocyte function in the surgical wound of rats by sampling leukocytes from hollow titanium implants. The surgical wound was treated with lidocaine or placebo after implantation of the titanium chamber and before skin closure. Leukocyte metabolic activity was measured by chemiluminescense. Cell count was analyzed in a Burker chamber. Results showed progressive increase in leukocyte counts in the wounds of control animals and significantly lower cell counts in the wounds of lidocaine-treated animals 48 h (P < 0.05) and 72 h (P < 0.05) after surgery. A pronounced inhibition of the metabolic response to serum-opsonized zymosan was seen after 8 h in the lidocaine-treated animals versus controls (P < 0.05). After 24 h, leukocyte metabolic activity decreased dramatically in the control group and remained at a low level until 72 h after surgery. In the lidocaine-treated group, the leukocyte response to zymosan remained constantly low throughout the study. The effects of lidocaine were not a result of impaired leukocyte viability. Our results showed that administration of lidocaine in the surgical wound reduced leukocyte migration and metabolic activation in the wound area. These in vivo results suggest, in accordance with previous in vitro studies, a reduced release of tissue-toxic substances such as oxygen free radicals and lysozymes known to impair wound healing. Previous reports on improved wound healing with lidocaine may be explained by the present results.