Effect of Lidocaine and Epinephrine on Staphylococcus aureus in a Guinea Pig Model of Surgical Wound Infection

Abstract

Postoperative wound infection, most often with Staphylococcus aureus, is of ubiquitous concern in surgical practice, occurring in an average of 1.5 to 5 percent of all procedures. The antimicrobial properties of local anesthetics have been documented over the past 25 years by in vitro studies. This study evaluates the effects of lidocaine preparations on S. aureus in an in vivo setting. In a wound infection model using live albino guinea pigs, S. aureus inoculum was introduced for the reproducible bacterial colonization of clean surgical wounds. One of two sites on the dorsum of each animal was infiltrated with a commercial lidocaine preparation (with and without epinephrine) prior to inoculation with S. aureus (104 cfu/ml). The other site, inoculated with S. aureus without preinfiltration with lidocaine, served as the control. Cultures from the sites treated with lidocaine were then compared with cultures from the control sites. All control sites had a consistent S. aureus presence ≥105 cfu/ml. the threshold for bacterial inhibition of wound healing. Infiltration of the wound with 2 ml of 2% lidocaine prior to inoculation was associated with an average decrease in bacterial count of >70 percent (n = 19). On the other hand, the addition of epinephrine (1:100,000) to lidocaine was associated with a 20-fold increase in bacterial counts compared with control values (n = 10). This is the first study to demonstrate inhibition of S. aureus by a local anesthetic agent in an in vivo model of a surgical wound. This information suggests a possible role for local anesthetics in prophylaxis against surgical wound infection. (Plast. Reconstr. Surg. 110: 1275, 2002.)