Evaluation of a Low Profile Noncontact Normothermic Wound Dressing for Split-Thickness Skin Graft Donor Site Healing

Feature:
Evaluation of a Low Profile Noncontact Normothermic Wound Dressing for Split-Thickness Skin Graft Donor Site Healing
- Bryan Gawley, MD, and Lisa J. Gould, MD, PhD

Abstract: The ideal split-thickness skin graft (STSG) donor site dressing has yet to be discovered. Ideally, such a dressing would be cost effective, maintain a moist environment to facilitate rapid epithelization, and minimize pain. Noncontact, normothermic wound therapy (NNWT) has been shown to hasten healing time in pressure-related wounds, neuropathic wounds, and venous stasis ulcers. In 1 study, NNWT decreased bacterial counts in pressure ulcers. No studies have looked specifically at NNWT to treat STSG donor sites. The authors conducted a prospective trial to compare a NNWT device (Warm-up® Active Wound Therapy, Augustine Medical Inc, Eden Prairie, Minn) to an impregnated gauze dressing control (Xeroform Petrolatum Gauze, The Kendall Company, Mansfield, Mass) for STSG donor site healing in 5 healthy volunteers. Study subjects served as their own controls. Small split grafts (0.012 in) were taken from the upper buttocks bilaterally and either the study or control dressing was applied. Dressing changes were performed over a 4-week period, during which infection, pain, time to healing, and scar quality were evaluated. All donor sites treated with NNWT dressings took longer to heal (14 days versus 10.8 days), had higher rates of bacterial colonization, and caused more pain. Scar quality was similar. While this type of dressing has shown efficacy in healing chronic wounds, the authors do not support its use on STSG donor sites.

Split-thickness skin graft (STSG) donor sites often can be more painful and uncomfortable for patients than the recipient wound. Ideal donor site dressings facilitate rapid re-epithelization and minimize pain. It is well established that re-epithelization is more rapid in a moist environment.¹ The literature also cites the benefits of warmth on wound healing.^2–7 Noncontact normothermic wound therapy (NNWT) provides a moist wound environment without direct contact between the dressing and wound bed. Additionally, NNWT helps warm the wound toward normothermia and has shown promising results in enhancing the healing of pressure ulcers, venous stasis ulcers, and surgical wounds.^8–16 The authors proposed that NNWT would promote healing of split-thickness donor sites and reduce pain. This study was a pilot trial that used a specifically designed, low-profile NNWT device and compared it to a commonly-used impregnated gauze dressing in healing of STSG donor sites. Time to healing, infection rates, pain, and scar characteristics were assessed.

Materials and Methods

Five healthy volunteers were enrolled in the study after institutional review board approval was received. Each subject served as his or her own control. Split-thickness skin graft donor sites (3 cm x 5 cm intermediate depth, 0.012 in) were created on each subject’s buttocks using sterile technique and an electric dermatome while under local anesthesia. The control group was randomly assigned and covered with petrolatum-impregnated gauze (Xeroform Petrolatum Gauze, The Kendall Company, Mansfield, Mass), a 4 x 4 dry piece of gauze, and transparent film dressing (Op-Site®, Smith & Nephew, Largo, Fla) to maintain moisture. The study group was covered with the low profile, flexible NNWT dressing (Warm-up® Active Wound Therapy, Augustine Medical Inc, Eden Prairie, Minn, Figure 1). A manually activated disposable warming pack was applied (externally) over the noncontact occlusive dressing. This pack provides an operating temperature range of 38ºC to 42ºC for approximately 2 hours.¹⁷ The subjects applied the packs twice daily for 2 hours at a time. Dressings were changed and wound sites were evaluated and photographed every other day for 14 days and then at 4 weeks. Prior to replacing the dressing, each wound was irrigated with 10 cc of sterile normal saline, and saline moistened gauze was used to gently remove nonadherent exudate. Swab cultures were obtained on Days 2, 4, and 8, using the Bornside and Bornside quantitative swab method that utilizes a sterile cotton-tipped swab moistened with 0.1 mL sterile saline solution that is placed in the wound center and rotated clockwise 3 times. Each swab was eluted in 0.9 mL of saline solution. Eluates were then streaked on blood agar and MacConkey’s medium for quantitative bacteriology. Pain was assessed using a visual analog pain scale. After epithelization was complete, as evidenced by lack of drainage, dressing changes were discontinued. Scar quality was assessed subjectively, comparing pliability and color.

Figure 1

Statistical Analysis

Statistical analysis was performed using a student’s t-test. A P value < 0.05 was considered significant for this study.

Results

Time to healing was significantly prolonged in the NNWT group compared to the control group (mean 14 and 10.8 days, respectively; standard deviation [SD] 1.22 and 0.84, respectively; standard error of the mean [SEM] 0.55 and 1.87, respectively; P < 0.03). Figure 2 shows time to healing (in days) for both groups. Sequential comparisons between the wounds consistently showed exudate covering the NNWT treated wound. Although no wounds were grossly cellulitic, the NNWT wound cultures demonstrated significantly more Staphylococcus aureus colonization than control (mean = 8 x 10³ cfu, and 0.6 x 10² cfu, respectively; SEM 1990 and 40; P = 0.012). Figure 3 shows culture results for each group. Generally, study participants rated the NNWT dressing as more painful than control. Scar quality at 4 weeks was comparable in terms of color and pliability. One patient suffered from a reaction to the NNWT dressing adhesive. No other significant untoward events occurred.

Figures 2-3

Discussion

In 1962, Winter¹ and Chang et al¹⁸ demonstrated that moisture enhances wound re-epithelization. Winter’s study utilized a porcine model to demonstrate that occlusive dressings that maintain moisture and warmth were optimal for healing. More recent studies have looked specifically at the effects of warming on wound healing. Local warming increases local perfusion and oxygen tension, supports enzymatic reactions, and increases the availability of immune cells.^2-4,6,7,19 Other studies have shown that warming of wounds decreases bacterial counts and increases fibroblast activity.^2,3 Noncontact normothermic wound therapy has been shown to be effective in the treatment of chronic wounds—pressure, venous stasis, and diabetic ulcers—but no studies have evaluated the efficacy for healing acute wounds.^{8–16,19–21}
The present study evaluated the efficacy of NNWT for healing STSG donor sites. The study hypothesis was that NNWT should be ideal for healing STSG donor sites because the warm, moist environment would maximize re-epithelization and reduce pain. However, the results suggest that this type of wound dressing is inferior to commonly used impregnated gauze dressings. It appears that the warmth and moisture provided by the NNWT dressing is not enough to achieve optimal healing. Compression, exudate absorption, and antimicrobial activity are important components the NNWT dressing lacks.²² The noncontact or noncompressive nature of the therapy allows exudate to form over the wound surface, which slows healing. An overabundance of exudate rich in matrix metalloproteinases (MMPs) and inflammatory cells may hinder epithelization. In particular, the authors noted that the region under the plastic “bubble” that was in contact with the overlying foam divider healed the fastest (Figure 4D).

Figure 4

A major critique of this study is that the wound bed was disturbed periodically to evaluate wound progress. Impregnated gauze used on donor sites is usually applied and left undisturbed until the wound is healed. For the purposes of the study, the dressings were changed every 2 days. This resulted in disruption of the wound bed, pain during dressing changes, and increased opportunity for bacterial contamination. Dressing changes were performed in the clinic using aseptic technique, and each wound was gently cleansed with sterile saline, which should have decreased bacterial counts. Another potential critique is that petrolatum-impregnated gauze has mild bacteriostatic activity and is not the standard of care for a clean, partial-thickness wound. Dressings that maintain a moist wound interface, including hydrocolloids, have been shown to produce faster healing than conventional fine mesh gauze.^23–25 In selecting a control dressing, the authors thought it was important to utilize the simplest, most commonly used dressing while continuing to maintain a moist wound interface between the skin graft donor site and the dressing. Petrolatum-impregnated gauze continues to be used due to its low cost, ease of application, and availability in most operating rooms. Occlusive film dressings are also used but are difficult to use on large donor sites due to fluid collection that occurs under the dressing. Thus, the authors compromised and used a hybrid dressing that has gained popularity at the authors’ hospital: petrolatum-impregnated gauze covered with dry gauze to absorb exudate, topped with an occlusive film dressing to maintain moisture. In the end, despite these critiques, NNWT resulted in delayed healing and increased pain compared to petrolatum-impregnated gauze with an occlusive secondary dressing despite removing the impregnated gauze every 2 days. The fact that this occurred in healthy volunteers rather than in patients who would be even more susceptible to infection and impaired healing adds concerns regarding the use of NNWT for STSG donor site healing.
The beneficial effects of NNWT better target the obstacles to healing that are commonly seen in chronic wounds (ie, decreased local blood flow, high bacterial counts, and low oxygen tension). In an acute, superficial wound, such as a STSG donor site, there is sufficient, if not increased, local blood flow, a sterile environment, and adequate oxygen tension for normal healing. Therefore, the characteristics of NNWT as evaluated in the present model are not optimal for STSG donor site healing.

Conclusion

This study demonstrates that NNWT does not provide any benefit over moist occlusive dressings for STSG donor site healing. The ideal donor site dressing will provide a moist, warm environment, minimize bacterial colonization, and manage exudate.19,22 The combination of a bacteriostatic impregnated gauze dressing that prevents adherence to the wound, a secondary gauze dressing to manage exudate, and an occlusive dressing to maintain moisture balance remains the authors’ choice for use on large STSG donor sites.

References

1. Winter GD. Formation of the scab and the rate of epithelisation of superficial wounds in the skin of the young domestic pig. 1962. J Wound Care. 1995;4(8):366–371.
2. Jia C, Yang Y, Hughes MA, Cherry GW. The effect of intermittent radiant warming on the contraction of collagen lattices populated with human dermal fibroblasts and on the proliferation of ulcer fibroblasts in monolayer: an in vitro pilot study. WOUNDS. 2004;16(4):124–133.
3. Lee ES, Caldwell MP, Talarico PJ, Kuskowski MA, Santilli SM. Use of a noncontact radiant heat bandage and Staphylococcus aureus dermal infections in an ovine model. Wound Repair Regen. 2000;8(6):562–566.
4. Park HY, Shon K, Phillips T. The effect of heat on the inhibitory effects of chronic wound fluid on fibroblasts in vitro. WOUNDS. 1998;10(6):189–192.
5. Plattner O, Akca O, Herbst F, et al. The influence of 2 surgical bandage systems on wound tissue oxygen tension. Arch Surg. 2000;135(7):818–822.
6. Rabkin JM, Hunt TK. Local heat increases blood flow and oxygen tension in wounds. Arch Surg. 1987;122(2):221–225.
7. Xia Z, Sato A, Hughes MA, Cherry GW. Stimulation of fibroblast growth in vitro by intermittent radiant warming. Wound Repair Regen. 2000;8(2):138–144.
8. Cherry GW, Wilson J. The treatment of ambulatory venous ulcer patients with warming therapy. Ostomy Wound Manage. 1999;45(9):65–70.
9. Kloth LC, Berman JE, Dumit-Minkel S, Sutton CH, Papanek PE, Wurzel J. Effects of a normothermic dressing on pressure ulcer healing. Adv Skin Wound Care. 2000;13(2):69–74.
10. Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. Study of Wound Infection and Temperature Group. N Engl J Med. 1996;334(19):1209–1215.
11. Melling AC, Ali B, Scott EM, Leaper DJ. Effects of preoperative warming on the incidence of wound infection after clean surgery: a randomised controlled trial. Lancet. 2001;358(9285):876–880.
12. Price P, Bale S, Crook H, Harding KG. The effect of a radiant heat dressing on pressure ulcers. J Wound Care. 2000;9(4):201–205.
13. Robinson C, Santilli SM. Warm-Up Active Wound Therapy: a novel approach to the management of chronic venous stasis ulcers. J Vasc Nurs. 1998;16(2):38–42.
14. Santilli SM, Valusek PA, Robinson C. Use of a noncontact radiant heat bandage for the treatment of chronic venous stasis ulcers. Adv Wound Care. 1999;12(2):89–93.
15. Scott EM, Leaper DJ, Clark M, Kelly PJ. Effects of warming therapy on pressure ulcers—a randomized trial. AORN J. 2001;73(5):921–927, 929–933, 936–938.
16. Whitney JD, Salvadalena G, Higa L, Mich M. Treatment of pressure ulcers with noncontact normothermic wound therapy: healing and warming effects. J Wound Ostomy Continence Nurs. 2001;28(5):244–252.
17. Warm-up Wound Therapy System [company brochure]. Eden Prairie, Minn: Augustine Medical Inc; 1999.
18. Chang H, Wind S, Kerstein MD. Moist wound healing. Dermatol Nurs. 1996;8(3):174–176, 204.
19. Whitney JD, Wickline MM. Treating chronic and acute wounds with warming: review of the science and practice implications. J Wound Ostomy Continence Nurs. 2003;30(4):199–209.
20. Alvarez OM, Rogers RS, Booker JG, Patel M. Effect of noncontact normothermic wound therapy on the healing of neuropathic (diabetic) foot ulcers: an interim analysis of 20 patients. J Foot Ankle Surg. 2003;42(1):30–35.
21. McCulloch J, Knight CA. Noncontact normothermic wound therapy and offloading in the treatment of neuropathic foot ulcers in patients with diabetes. Ostomy Wound Manage. 2002;48(3):38–44.
22. Lionelli GT, Lawrence WT. Wound dressings. Surg Clin North Am. 2003;83(3):617–638.
23. Feldman DL, Rogers A, Karpinski RH. A prospective trial comparing Biobrane, Duoderm, and xeroform for skin graft donor sites. Surg Gynecol Obstet. 1991;173(1):1–5.
24. Horch RE, Stark GB. Comparison of the effect of a collagen dressing and a polyurethane dressing on the healing of split thickness skin graft (STSG) donor sites. Scand J Plast Reconstr Surg Hand Surg. 1998;32(4):407–413.
25. Steenfos H, Partoft S, Timshel S, Balslev E. Comparison of SureSkin®, DuoDerm E® and Jelonet® Gauze in split skin donor sites—a clinical and histological evaluation. J Eur Acad Dermatol Venereol. 1997;8(1):18–22.

Wounds - ISSN: 1044-7946 - Volume 18 - Issue 10 - October 2006 - Pages: 294 - 299