title: Effect of local anesthetic on microorganisms in a murine model of surgical site infection.
abstract: 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.
authors: Department of Surgery, University of Tennessee Medical Center, Knoxville, Tennessee, USA. vsams@utmck.edu
authors: Valerie G
authors: VG
authors: Sams
authors: Christy M
authors: CM
authors: Lawson
authors: Patricia
authors: P
authors: Coan
authors: David
authors: D
authors: Bemis
authors: Kimberly
authors: K
authors: Newkirk
authors: Michael
authors: M
authors: Karlstad
authors: Jamison
authors: J
authors: Norwood
authors: Patrick
authors: P
authors: Barlow
authors: Mitchell H
authors: MH
authors: Goldman
authors: Brian J
authors: BJ
authors: Daley
mesh_terms: D000704:Analysis of Variance; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D004195:Disease Models, Animal; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D005260:Female; D015994:Incidence; D007279:Injections, Subcutaneous; D008012:Lidocaine / Q000494:pharmacology; D051379:Mice; D008815:Mice, Inbred Strains; D050296:Microbial Viability / Q000187:drug effects*; D011300:Preoperative Care / Q000379:methods; D011897:Random Allocation; D012016:Reference Values; D012680:Sensitivity and Specificity; D013211:Staphylococcus aureus / Q000187:drug effects; D013530:Surgical Wound Infection / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control*
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine