Early Experience with Biobranetm for Definitive Coverage of Tangentially Excised Partial-Thickness Thermal Burns

BiobraneTM is a popular biosynthetic semi-permeable skin substitute conventionally applied onto non-excised partial thickness burn wounds to facilitate healing. The use of BiobraneTM for definitive coverage after excision of partial-thickness thermal burns has not been reported. We highlighted our experience of immediate BiobraneTM application for definitive coverage of tangentially-excised partial thickness thermal burn wounds in four patients. This technique is safe and efficient, minimizes painful and costly dressing changes, avoids the complications associated with autologous skin grafting, and eliminates the unpredictability of burns wound conversion. We believe this method expands the indications for BiobraneTM usage, accelerates wound healing, and provides better aesthetic outcomes.


INTRODUCTION
Early excision and autologous skin grafting is the gold standard treatment for burns. 1 However, skin grafting is not without significant morbidity, including donor site bleeding, infection, dysaesthesia, abnormal scarring and dyschromia. The cosmetic appearance of skin grafted sites is also frequently unsatisfactory. 2 Introduced in 1979, Biobrane TM (UDL Laboratories, Rockford, IL) is a highly-conformable synthetic acellular material comprising of a flexible inner trifilament nylon fabric mesh embedded with hydrophilic type I porcine collage and an outer semipermeable silicone membrane. 3,4 When placed on a clean partial-thickness burn, collagen on the inner surface preferentially binds to fibrin from the wound exudate. Adherence of Biobrane TM to the wound reduces pain and permits early joint mobilization. The silicone membrane functions as a protective epidermal barrier against infection and prevents wound desiccation, whilst permitting water vapour permeability to prevent fluid from collecting. 3,4 www.wjps.ir

Guang Ho et al. 120
Over the next 10-14 days, proliferating epithelial cells from hair follicles within the deep dermis migrate across the wound surface, forming everenlarging epidermal islands that eventually become confluent, and in the process causing spontaneous detachment of Biobrane TM from the re-epithelised wound. 3,4 During this period, only the gauze dressings on top of the Biobrane TM is changed, which reduces patient discomfort and duration of hospitalization. As Biobrane TM is transparent, tracking the progress of wound healing and monitoring for potential complications is straightforward. 3,4 Numerous authors have shared their protocols and techniques to maximise successful use of Biobrane TM . [4][5][6] Wound selection is paramount: an exudative wound bed is a prerequisite for adherence, hence Biobrane TM should not be applied to non-exudative deep dermal and full-thickness burns that require excision and skin grafting. Meticulous aseptic wound bed cleaning, as well as removal of unviable blisters and surface debris is also essential to prevent Biobrane TM infection and premature separation from the wound bed. 5 Biobrane TM should be applied within 24-48 hours after the burn injury, beyond which the risks of wound colonization leading to prosthesis infection and failure become significant. [4][5][6] Biobrane TM is primarily utilised as a dressing for non-excised superficial and mid-dermal thermal burns, as well as for skin graft donor sites, to expedite re-epithelization. Biobrane TM has also been deployed for temporary coverage of excised deep dermal and full-thickness thermal burns to prepare the wound for autografting, 7 and has reportedly been used for definitive coverage of partialthickness alkaline burns with good results. 8 The use of Biobrane TM for immediate definitive coverage of thermal burn wounds that have been tangentially excised has not been described in the literature. We reported our experience using this method on four patients with partial-thickness thermal burns.

CASE REPORT
Written informed consent was obtained from each patient. After induction of general anaesthesia and aseptic cleansing, the area of burns to be excised received a subcutaneous injection of tumescent solution (adrenaline 1:250,000, gentamicin 80 mg and lignocaine 3 mg/kg in 500 mL of Ringer's lactate). A tourniquet was not utilized. Ultra-thin tangential excision was performed with an airpowered dermatome (Zimmer Biomet, Warsaw, IN) at 4/1000 inch cutting thickness until uniform punctate bleeding was observed from the wound. Topical adrenaline solution-soaked laparotomy sponges were then applied for hemostasis. Biobrane TM was secured to the wound under slight tension with sterile adhesive tape (Hypafix; Smith&Nephew, Memphis, TN) and surgical staples, and wrapped in gauze soaked with povidone-iodine (Betadine; Pfizer, West Ryde, Australia).

CASE 1
A 27-year-old male construction worker sustained 15.5% total body surface area (TBSA) partial-thickness thermal burns from a flash fire at an industrial site ( Figure 1A). The time interval from accident to surgery was 48 hours. After removal of blisters and aseptic cleansing, the lateral aspect of his right forearm (approximately 1% TBSA) was noted to have sluggish capillary refill ( Figure 1B). This area was tangentially excised until punctate bleeding was seen. Biobrane TM was then applied to all burns. The area of excised burns was observed to be healing well underneath the Biobrane TM dressings ( Figure 1C) on post-operative day (POD) 10, and had fully epithelized by POD 15 ( Figure 1D).

CASE 2
A 57-year-old female waitress presented six days after sustaining 10% TBSA partial-thickness thermal burns from being scalded by boiling soup at work. After debridement of blisters, her right thigh and upper shin (6% TBSA) and left calf (4% TBSA) were found to be poorly blanching with multiple areas of fixed-staining (Figure 2A and B). These areas were tangentially excised until punctate bleeding was seen from the dermis of the wound ( Figure 2C and D). Biobrane TM was then applied to these excised areas. Her wounds were observed to be healing well on POD 7 ( Figure 2E and F), and epithelization was complete by POD 11 ( Figure 2G and H). A summary of the 4 cases is provided in Table 1.
The study was performed in accordance with the principles of the Declaration of Helsinki. Written informed consents were obtained. Institutional review board/ethics committee approval was not required for retrospective case reports. Patients provided written informed consent for the publication and the use of their images. Written informed consent was obtained from the patient for publication of this case series and accompanying images. A copy of the written consents was available for review by the Editor-in-Chief of this journal on request.   www.wjps.ir/Vol.9/No.3/September 2020

DISCUSSION
Contemporary guidelines on Biobrane TM usage recommend that to be applied to newly-burnt, exudative, partial-thickness wounds that have been carefully prepared. [4][5][6] This maximises adherence and reduces the risks of wound colonization and consequent prosthetic infection and failure that plagued many earlier studies. 9,10 Our case series demonstrated that ultra-thin, tangential excision allowed conversion of an older (>48 hours) burn to a fresh burn which permitted successful application of Biobrane TM . Not only does this remove colonizing bacteria, the raw excised surface also produces renewed exudate, enhancing the adherence of Biobrane TM to the burn wound. 5 As illustrated above, this technique lends itself well to burns of homogenous or heterogenous depth. If capillary refill is uniformly reduced across the burn, the entire wound is tangentially shaved and Biobrane TM is applied. If a part of the wound is poorly-blanching, only that particular area requires tangential excision, and Biobrane TM can then be applied to the entire wound (excised as well as nonexcised). The latter extends the "trial-of-life" concept, where Biobrane TM is applied over burns of uncertain dermal depth in a wound that is hopefully still capable of spontaneous healing. 5 Numerous groups, 11,12 including our own 13 have shown that Biobrane TM has reduced the need for autologous skin grafting in partial-thickness burns. By improving adherence of Biobrane TM to areas of deeper injury, this novel technique potentially decreases the need for autologous skin grafting (and its attendant cosmetic and functional complications) even further. Nonetheless, it is imperative that patients should be counselled pre-operatively that Biobrane TM may not adhere or "take" over the excised areas and that subsequent re-excision with autologous skin grafting may be necessary.
Caution should be exercised when applying this technique to deep dermal and full-thickness burns, in these wounds it is highly unlikely that the remnant dermis will be able to produce enough exudate to allow sufficient Biobrane TM adherence after tangential excision. Laser Doppler imaging may be a useful adjunct in determining burn depth (and the suitability of this technique), if uncertainty persists after clinical assessment. 14 Greenwood et al. have warned about the risk of applying Biobrane TM to an excised wound, with blood clots and subsequent fibrovascular ingrowth into the nylon scaffold making removal difficult. 5 .
We thus paid meticulous attentiontowards achieving hemostasis using a combination of adrenaline-containing tumescent infiltration, bipolar electrocautery and manual pressure. Biobrane TM was only secured onto the raw wound surface, once all visible bleeding had been arrested. We did not encounter any problems related to spontaneous detachment of Biobrane TM from the wound, once epithelization had occurred. It has been demonstrated that Biobrane TM is capable of controlling bacterial growth in wounds with an initial bacterial count of less than 10 5 per gram of tissue, and wounds with a bacterial count exceeding 10 5 per gram of tissue precludes Biobrane TM "take". 4,6,15 As burn wounds become progressively colonized by bacteria with time, most authors advise that Biobrane TM is applied within 48 hours of injury, 4-6 with a recent retrospective cohort study showing evidence of significantly faster re-epithelization and decreased need for skin grafting, if Biobrane TM is applied within 12 hours. 12 Nonetheless, there is no conclusive evidence that its use is contraindicated in older burns. 4,6 We successfully performed ultra-thin tangential excision with immediate Biobrane TM coverage on burns with a mean age of 105.5 hours (4.4 days; range: 48-168 hours) from the time of injury without any infectious complications. Nonetheless, we do not recommend that this technique is attempted on burn wounds that display overt clinical signs of infection.
This approach allows more definitive intervention on burns of equivocal healing potential, the excized surface exudes fibrin that promotes binding to collagen on the inner surface of Biobrane TM . This promotes greater adherence of Biobrane TM to the wound, and in so doing facilitates accelerated re-epithelisation. 5,6 The correlation between burns healing time and subsequent development of hypertrophic scarring and contractures has been widely reported, with burns taking more than 21 days to heal at significantly greater risk of hypertrophic scarring and its sequelae (e.g. unsatisfactory cosmesis, pain, itching, and joint contractures). 2 More recent work has shown that the rates of hypertrophic scar are multiplied by 1.138 for every additional day taken for the burns to heal (even within the 21 day period); therefore, every effort should be made to accelerate wound healing. 16 In our study, all excised wounds re-epithelised after an average of 9.75 days (range 7-13 days), and none had developed hypertrophic scarring at 12 months of follow-up. Biobrane TM was shown to be a versatile alternative to conventional dressings in the management of thermal burns. While its cost, benefit ratio has yet to be fully elucidated; Biobrane TM permits reduced frequency and discomfort of dressing changes, potentially reduces the extent of and the need for skin grafting, as well as decreases hospitalization time. 5,6,[17][18][19] However, current recommendations may restrict its usage. Although the small population and descriptive nature of this series make it impossible to perform any meaningful statistical analysis, these promising early results challenge the widelyaccepted doctrine that application of Biobrane TM should be limited to superficial to mid-dermal partial-thickness thermal burns within 48 hours of injury. Preparatory tangential excision expands the indications for Biobrane TM use, allowing earlier definitive treatment of equivocal burns, whilst simultaneously avoiding the complications of skin grafting and retaining the benefits of Biobrane TM that have made it so popular. Larger prospective case-controlled studies are required to further establish the average time to wound healing, costeffectiveness, outcomes (functional and aesthetic) and complications of this novel technique.

CONCLUSION
Ultra-thin tangential excision of partial-thickness thermal burns with equivocal capacity for spontaneous healing followed by immediate definitive coverage with the biosynthetic dressing Biobrane TM can achieve good functional and cosmetic results. Contrary to existing guidelines, this technique can be successfully employed on burns that are more than 48 hours from the time of injury. This accelerates re-epithelisation, minimizes the complications of delayed wound healing and may reduce the need for patients to undergo autologous skin grafting.