Solving the Burn Depth Puzzle

Author(s): 
Laura Bolton, PhD, FAPWCA

Dear Readers:

     Knowing burn wound depth helps determine therapy and predicts healing time and potential for complications such as infection or excessive scarring. Experienced burn surgeons usually determine burn depth clinically with 60%–75% accuracy.1 Burn depth assessment methods include histological biopsy evaluation, thermography, vital dye techniques, video angiography, video microscopy, and laser Doppler flowmetry (LDF). Only LDF, a noninvasive measure of microvascular perfusion, has sufficient evidence of accuracy in predicting burn wound outcomes to merit regulatory clearance for assessing burn depth2 although it still needs to be standardized.2

     This Evidence Corner reviews two recent publications that confirm the validity of LDF as a measure of burn depth among adult Caucasian and pediatric Asian populations. Both studies reinforce the accuracy of LDF in assessing burn wound depth and support the conclusion that partial-thickness burns heal faster than full-thickness burns.

Laura Bolton, PhD, FAPWCA
Adjunct Associate Professor
Department of Surgery, UMDNJ
WOUNDS Editorial Advisory Board Member and Department Editor

LDF-assessed Burn Depth Predicts 21-day Healing

     Reference: Merz KM, Pfau M, Blumenstock G, Tenenhaus M, Schaller HE, Rennekampff HO. Cutaneous microcirculatory assessment of the burn wound is associated with depth of injury and predicts healing time. Burns. 2009 Oct 23. [Epub ahead of print].

     Rationale: Burn surgeons need early, accurate knowledge of burn depth to decide whether or not excision and skin grafting is needed to minimize the risk for infection, scarring, and long hospital stays associated with deep partial-thickness or full-thickness burns as compared to superficial burns. The recognized standard clinical assessment accurately differentiates very superficial burns from full-thickness burns, but is only 50% accurate for intermediate depth burns. Since the first use of LDF on burns in 1984, growing evidence suggests that burns with elevated microvascular perfusion during the first 72 hours post burn will heal without grafting.

     Objective: Use a portable LDF device to noninvasively analyze sequential patterns of microvascular perfusion in superficial and deep partial-thickness burns and identify LDF cut-off values resulting in a high positive predictive value for spontaneous healing by 3 weeks post-burn.

     Methods: A prospective observational study used LDF to measure microvascular perfusion noninvasively on all 28 patients with 173 superficial or deep dermal or full-thickness burn wound sites who were admitted to the Tübingen, Germany burn unit from February 2003–April 2004. A portable LDF unit measured arbitrary units (AU) of blood flow amount and velocity, oxygen saturation, and relative hemoglobin at skin depths of 2 mm and 8 mm on each burn site, and on contralateral unburned sites within 24 hours and at 3 and 6 days post-burn. Treatment decisions were made based on clinical assessment by experienced burn physicians. Superficial burns were treated topically with collagenase ointment and Vaseline gauze. Full-thickness burns were all excised and grafted with split-thickness skin grafts. Intermediate-depth burns were initially treated as superficial until a clinical decision was made that they would not heal in 3 weeks. At that point, they were then excised and grafted as a full-thickness burn. LDF diagnostic and screening validity were calculated respectively as percent of healing outcomes correctly predicted and the percent of burns correctly predicted on admission to heal or not heal spontaneously within 21 days.

References: 

1. Monstrey S, Hoeksema H, Verbelen J, Pirayesh A, Blondeel P. Assessment of burn depth and burn wound healing potential. Burns. 2008;34(6):761–769.
2. Chatterjee JS. A critical evaluation of the clinimetrics of laser Doppler as a method of burn assessment in clinical practice. J Burn Care Res. 2006;27(2):123–130.
3. Tur E. Cutaneous blood flow. Laser Doppler velocimetry. Int J Dermatol. 1991;30(7):471–476.
4. Tur E, Bolton L, Constantine BE. Topical hydrogen peroxide treatment of ischemic ulcers in the guinea pig: blood recruitment in multiple skin sites. J Am Acad Dermatol. 1995;33(2 Pt 1):217–221.
5. Shannon RJ, Bolton L. The use of retinoic acid to minimize skin damage. European Patent Specification EP-0448213. May 15, 1996.





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