TY - JOUR
AU - MS, Phillip J. Finley,
AB - Abstract Wound healing after graft closure of excised burn wounds is a critical factor in the recovery process after thermal injury. Processes that speed time to stable wound closure should lead to improved outcomes, shorter lengths of hospital stays, and decreased complications. A randomized clinical trial to test the ability of continuous direct anodal microcurrent application to silver nylon wound contact dressings was designed. Time for wound closure after split-thickness skin grafting was observed. Thirty patients with full-thickness thermal burns were randomized into two groups. The control group received postoperative dressing care using moistened silver nylon fabric covered with gauze after tangential burn wound excision and split-thickness skin grafting. The study group received an identical protocol with the addition of continuous direct anodal microcurrent application. Time to 95% wound closure was measured using digital photography. The digital photographs were evaluated by a burn surgeon blinded to the patient's randomization. An independent t-test was used to analyze the data. The study group experienced a 36% reduction in time to wound closure (mean of 4.6 days) as compared to the control group (mean of 7.2 days). This was statistically significant at a P value of <.05. The use of continuous direct anodal microcurrent decreased time to wound closure after split-thickness skin grafting. Thermal injury is responsible for more than 1 million injuries each year in the United States.1 Tangential excision and split-thickness skin grafting continue to be the mainstay of therapy for full-thickness burn injury. Clinicians and researchers continue to search for mechanisms to speed healing, decrease hospital stays, and decrease complications associated with burn wound care, including infection, scarring with resultant functional loss, and graft failure. In the 1970s, in vitro studies demonstrated that silver ions were an effective antibiotic with a very broad spectrum and favorable quantitative outcomes compared with synthetic antibiotics.2,–5 The potential of silver nylon fabric, filaments, and yarns as an antimicrobial agent was evaluated in a series of in vitro experiments.6,–13 In 1983, keratome-induced wounds (0.3-mm deep) on pigs treated with 50 to 300 microamp anodal direct current applied to silver nylon, found the rate of wound epithelialization to be significantly accelerated.14 Beginning in 1988, the U.S. Army Institute of Surgical Research, San Antonio, Texas, initiated a series of in vivo anodic microcurrent thermal injury animal studies. In all studies, the anodic microcurrent was applied to the treatment site via a silver nylon substrate. The first study, published in 1988, reported the therapeutic and prophylactic benefits of 40-μA anodic microcurrent (direct current) in a rat model of fatal Pseudomonas aeruginosa burn wound sepsis.15 In 1990, the effect of 40-μA anodic microcurrent (direct current) on partial-thickness scald burns, split-thickness grafts taken from these wounds when healed and the resulting donor sites in a guinea pig model showed 1) dorsal scald wounds treated with microcurrent reepithelized by 12 days after injury; 2) split-thickness grafts taken from healed scald wounds showed more rapid revascularization; and 3) grafts and donor sites showed more rapid reepithelization, decreased contraction, improved hair survival, and decreased dermal fibrosis.16 In 1991, the effect of 40-μA of anodic microcurrent (direct current) on the healing time and morphologic maturation of split-thickness grafts placed on tangentially excised deep partial-thickness burn wounds, reported 1) two days for complete revascularization of the grafts (control animals required 7 days); 2) increased epithelial proliferation at the graft-wound interface; 3) grafts firmly adherent within 4 days (controls required 7 days); and 4) 3 months after grafting, grafts expanded with the growth of the animals with abundant hair growth and significantly reduced dermal fibrosis.17 In 1993, the effect of 40-μA of anodic microcurrent (direct current) applied to P. aeruginosa infected burn wounds after excision and coverage with autograft revealed that microcurrent applied to silver nylon dressings may be an effective temporary antimicrobial dressing after burn wound excision.18 In the same year, the effect of 40-μA anodic microcurrent (direct current) on dermal distribution of intravenously injected India ink (Pelikan) after 20% dorsal partial thickness scalds in guinea pigs showed that the depth of circulatory stasis was limited by the direct anodal microcurrent and that the amelioration of the stasis may have explained the reductions in inflammation, fibrosis, scar formation, and final wound contracture previously observed.19 The following year, the effect of 40-μA anodic microcurrent (direct current) on macromolecular extravasation in 20% dorsal full-thickness scald burns in rats indicated a 30% to 50% reduction in the accumulated quantity of dextran or albumin in the burn wound.20 In 1996, the effect of 40-μA anodic microcurrent (direct current) on edema formation after burn injury in rats concluded that immediate application of continuous DC microcurrent reduced burn edema by 48% after burn.21 The same year, the effect of 40-μA anodic microcurrent (direct current) on the survival of autoepidermal-allodermal composite grafts in allosensitized animals reported no second set rejection of meshed composite skin graft with complete epithelialization within 3 weeks with reduced wound contraction.22 Human clinical trials using anodic microcurrent (direct current) was reported in the late 1970s and early 1980s using a standardized clinical technique in open osteomyelitic lesions. Continuous 0.9 volts direct microcurrent was applied to all open wound surfaces by means of a silver nylon fabric with a cathode return electrode applied to uninjured skin.23,24 Initial treatments were limited to 4-hour periods twice a day but later expanded to continuous treatment. The direct anodal microcurrent technique was found to be useful and safe for clinical treatment of acute and chronic wounds.25 Continuous anodic microcurrent stimulation units developed by Flick in the 1980s were applied to a randomized clinical trial in adult patients experiencing full-thickness thermal injuries that required acute split-thickness skin grafting. METHODS Participants Thirty participants were recruited from a level I trauma center in Southern Missouri. Patients admitted to the burn center with full-thickness thermal injury that were older than the age of 18 years were eligible for inclusion. Each patient included in the study provided signed informed consent after Institutional Review Board approval of the protocol. The patients' participation was voluntary, and no compensation was given. The mean age of the participants was 40.0 years with a range of 18 to 68 years. No significant age differences were found between the two groups t(24) = .456, P > .05. Four patients were excluded because of lack of follow-up and failure to follow research protocol. Materials and Design A randomized clinical trial using two groups was designed and Institutional Review Board approval received. After the patients provided consent, they were randomized into one of two groups using a standard randomization table. Both groups received identical preoperative care and underwent tangential excision of their full-thickness burn wound using a Weck knife. Split-thickness skin grafting using autograft obtained with a gas-powered dermatome at a depth of 0.09 inches was performed. The autografts were meshed at 1.5:1, and grafts were secured fully expanded using staples and/or prolene suture. The control group was then dressed at the graft site using silver nylon fabric moistened with sterile water in direct contact with the wound surface and covered with gauze and an elastic bandage. The study group underwent an identical protocol with the addition of continuous direct anodal microcurrent application. The microcurrent was provided by placing an electrical conductive perforated carbon vinyl tape across the outer surface of the silver nylon fabric connected to a microcurrent generator by way of a standard electrode lead. The return electrode was provided via a second electrode placed in an area of uninjured skin remote to the graft or donor site. Gauze dressings and elastic bandage were then placed over the silver nylon/conductive tape surface. The outer appearance of the bandage for both groups was identical. Microcurrent was supplied to the graft area directly by silver nylon cloth manufactured by Carolina Silver Technologies. This fabric was connected to a microcurrent generator compliant with Food and Drug Administration investigational device standards. The microcurrent generators were programmed to provide a constant direct anodal voltage output of 5.0 volts. The current varied between 50 and 100 μA dependent upon the resistance of the wound. The surface of the silver nylon fabric was tested at multiple sites with a voltmeter to assure that voltage spread was uniform and that the delivery system was fully operational. The voltage and current levels were significantly below the threshold of sensation of the patient. Dressings in both arms of the protocol were managed in an identical fashion. Daily outer dressing changes occurred with moistening of the silver nylon fabric using sterile water. Initial wound evaluation occurred at day number 3 postoperatively and then evaluated daily. This continued until the grafted area reached 95% closure. Healing was defined as the time in which 95% of the grafted surface was reepithelailized, including meshed graft interstices.26 Microcurrent generation was initiated immediately after dressing placement and continued until the grafted areas showed 95% closure even if the patient was discharged during this period. Digital photos at 5 megapixels were taken with each dressing change as well as after closure. Photos were blinded to randomized group assignment for review by a burn surgeon. The presence of silver in the systemic circulation was determined by a Thermo Jarrell Ash Trace Analyzer 161-E inductive coupled argon plasma spectroscopy with sensitivity to ±0.005 parts per million. Serum specimens, obtained by venipuncture, were obtained before treatment and every other day after the initiation of treatment in both control and treatment groups. If serum silver analysis, determined at the completion of treatment, was positive, all collected serum specimens were analyzed for the presence of silver. Statistical analysis was performed by a statistician utilizing SPSS computer software (SPSS Institute, Chicago, IL). T-test analysis was used to evaluate significance with an assigned P value of <.05. A Cohen's d statistic was calculated and used as an indication of the effect size. Variable analysis of subsets was done to assure that no effect on final outcome was noted. This included age, distribution of wound size, graft area size, percent of graft area, postburn surgery day, site of graft, and presence of diabetes or known cardiovascular disease. RESULTS The data were screened before analysis for accuracy and normality. Time to 95% closure was evaluated and recorded. A significant difference in wound closure time between the microcurrent group (mean = 4.62 days, SD = 1.04) and the nonmicrocurrent group (mean = 7.23 days, SD = 1.83) was observed (t(24) = –4.47, P < .001). The benefit of the microcurrent administration resulted in 36% decrease in time to wound closure. A Cohen's d statistic indicated a large effect size (d = 1.7). Subgroup analysis showed similar medical characteristics between the two groups. No significant differences were found between the two groups on distribution of wound sizes t(23) = .184, P > .05; graft area t(23) = .18, P > .05; percent of graft area t(24) = .56, P > .05; and postburn operative day t(23) = 1.35, P > .05. (See Table 1 for distribution means.) The groups were compared for the following medical demographics: diabetes, vascular disease, and hypertension. Both groups had one patient with diagnosed diabetes, no patients with vascular disease, and a similar number of patients with hypertension. (See Table 2 for distribution of graft sites.) Table 1. Mean distribution of burn and graft areas View Large Table 1. Mean distribution of burn and graft areas View Large Table 2. Demographics of graft site location between groups View Large Table 2. Demographics of graft site location between groups View Large Serum levels, analyzed from post operative day #3, for all participants were between 0.020 and 0.093 µg/ml) with no significant differences in serum silver levels between the microcurrent and nonmicrocurrent groups. DISCUSSION The cumulative evidence from cellular and animal experiments strongly indicates positive associations between direct anodic microcurrent and enhanced wound healing. Such findings have provided a firm underlying basis for the application of direct anodic microcurrent to human wounds. The involved mechanism remains speculative, and large gaps remain in our understanding of the specific cellular and functional targets, therapeutic dose, and regimes to achieve optimal wound healing. This study into the healing effects of anodic microcurrent (direct current) on the healing time on split-thickness skin grafts may provide a basis for continued advances in this still evolving adjunctive therapeutic modality. Anatomic burn locations varied between patient groups. This could potentially account for some of the differences in wound healing outcomes. Research is being conducted to control for this variable by using microcurrent on donor graft sites, thus standardizing the wound area, depth, and location. A more precise definition of healing, using planimetric methods to evaluate degree of epithelial coverage, should be considered in future studies. Extension of the anodic microcurrent (direct current) to other acute wound healing environments such as postsurgical incisions and chronic wound healing environments such as venous stasis ulcerations and diabetic ulcerations should be considered. CONCLUSION The group that received continuous direct anodal microcurrent healed significantly faster than the group without microcurrent (P < .05). Closure after split-thickness skin grafting is accelerated by the use of continuous direct anodal microcurrent applied to silver nylon wound contact dressings. Additional clinical research is recommended to delineate additional potential benefits from continuous microcurrent. REFERENCES 1. American Burn Association. Burn Incidences and Treatment in the US: 2000 Fact Sheet. Retrieved November 20, 2006, from http://www.ameriburn.org/resources_factsheet.php?PHPSESSID=4b287131985ed952ed2641632c9505a8; Internet; accessed July 9, 2007. 2. 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TI - Wound Closure After Split-Thickness Skin Grafting Is Accelerated With the Use of Continuous Direct Anodal Microcurrent Applied to Silver Nylon Wound Contact Dressings
JF - Journal of Burn Care & Research
DO - 10.1097/BCR.0B013E318148C945
DA - 2007-09-01
UR - https://www.deepdyve.com/lp/oxford-university-press/wound-closure-after-split-thickness-skin-grafting-is-accelerated-with-B7blYOpjZy
SP - 703
EP - 707
VL - 28
IS - 5
DP - DeepDyve
ER -