BACKGROUND: Surgical site infections are common, with an incidence of 1.5% to 5% for all types of surgery. In vitro studies suggest an antimicrobial effect of local anesthetic. We hypothesized that subcutaneous infiltration of local anesthetic before surgical incision would reduce the incidence of postoperative wound infection.
METHODS: In a wound infection model using 4- to 6-week-old female mice, Staphylococcus aureus and Escherichia coli were inoculated in surgical wounds infiltrated with local anesthetic or saline. On day 5, the mice were killed and tissues were evaluated for viable bacterial numbers, presence of bacteria histologically, and degree of inflammation on a scale of 0 to 3 based on number and types of inflammatory cells and presence of necrosis.
RESULTS: A one-way between-subjects analysis of variance with Tukey honestly significant difference post hoc comparisons showed no statistically significant difference in the degree of inflammation in mice infiltrated with lidocaine, lidocaine mixed with bupivacaine, or saline (p = 0.994, p = 0.337, and p = 0.792, respectively). A Tukey honestly significant difference post hoc analysis demonstrated that the saline (p = 0.038) and lidocaine mixed with bupivacaine (p = 0.006) had significantly lower degrees of inflammation than did the lidocaine group. A Bonferroni post hoc test demonstrated that those in the lidocaine (p = 0.003) and lidocaine mixed with bupivacaine (p = 0.008) groups had significantly higher inflammation than those in the saline group after controlling for the condition of the inocula.
CONCLUSIONS: Infiltrate, whether saline, lidocaine, or lidocaine mixed with Marcaine, did not result in significantly different bacterial presence or higher degree of inflammation when controlling for experimental condition of bacterial inocula. Thus, subcutaneous infiltration of local anesthetic before a surgical incision is made does not reduce the incidence of bacterial growth or influence the degree of inflammation which alters infection rates.
From the Department of Surgery (V.G.S., C.M.L., M.K., J.N., M.H.G., B.J.D.) and UT Health Science Center and School of Veterinary Medicine (P.C., D.B., K.K.), Graduate School of Medicine and Department of Statistics (P.B.), University of Tennessee Medical Center, Knoxville, Tennessee.
Submitted: November 30, 2011; Revised: February 9, 2012; Accepted: March 30, 2012.
This research was presented at the University of Tennessee Medical Center Department of Surgery Resident Research Day June 2011, the University of Tennessee Medical Center Graduate School of Medicine Resident Research Day May 2011, the University of Tennessee Comparative and Experimental Medicine and Public Health Research Symposium June 2011, the Tennessee Chapter of the American College of Surgeons Annual Meeting July 2011, and the 25th annual meeting of the Eastern Association for the Surgery of Trauma, January 10–14, 2012, Lake Buena Vista, Florida.
Address for reprints: Valerie G. Sams, MD, MPA, Department of Surgery, 1924 Alcoa Hwy Box U-11, Knoxville, TN 37920; email: firstname.lastname@example.org.