Lidocaine via lontophoresis in laceration repair: A preliminary safety study

Iontophoresis is a painless technique for topical anesthesia that uses an electric field to drive charged ions across an epithelial surface. The safety of this technique for laceration repair has never been demonstrated. The purpose of this study was to investigate the effect of iontophoretic fields on rapidly proliferating cells involved in laceration wound healing. The study was a prospective single-blinded animal study using a guinea pig model. Twelve guinea pigs each received four induced, uncontaminated lacerations. Each guinea pig was randomly assigned to 1 of 3 groups (4 guinea pigs in each group). One group received lidocaine via iontophoresis, one group received injected lidocaine, and one group received half iontophoresis and half injected lidocaine. After anesthetic treatment, wounds were then repaired in a standard fashion. The wounds were examined grossly on a daily basis and on day 10 the incised skin containing the laceration was examined by a pathologist blinded to the treatment group. A total of 48 wounds were assessed for wound healing, 24 of which received lidocaine via iontophoresis and 24 lidocaine via injection. The power of the study to determine a 40% difference between the two groups was 0.8. There was significantly more granuloma and granulation tissue formation in the iontophoresis group than in the injected lidocaine control group (P = .0004, Fisherʹs exact test). There were no statistically significant differences in degree of inflammation between the two groups (lidocaine via injection v lidocaine via iontophoresis) measured by amount of dermal fibrosis (P = .14, Fisherʹs exact test), giant cell formation (P = .21, Fisherʹs exact test), and presence of acute and/or chronic inflammation (P = .17, Wilcoxonʹs rank sum test). Wound healing proceeded normally with 100% in both groups having normal scar formation and healing at day 10. In conclusion, iontophoresis appears to be a safe method of anesthesia delivery in this guinea pig model with lacerations. Increased granuloma and granulation tissue formation may indicate an enhancement of wound healing via iontophoresis.