Medical Aspects of Chemical Warfare (2008) - The Black Vault

Vesicantsries because of the unique nature of the agent and theunique progression of the injury.Noninvasively examining cutaneous blood flowcan greatly assist the physician in making depth ofinjury determinations. Laser Doppler perfusion imaging(LDPI) and indocyanine green (ICG) fluorescenceimaging may prove to be very valuable tools in prognosticatingoptimal wound healing of cutaneous HDinjuries. 138Laser Doppler flowmetry and LDPI have been usedfor prolonged, noninvasive monitoring of tissue viabilityand wound healing, and for the assessment ofperipheral vascular disease, inflammation, ischemia,reperfusion, skin graft acceptance (take), and burndepth. Brown et al found that laser Doppler perfusionimages of vesicant vapor burns on the backs ofswine correlated well with histopathological findings(thrombosis and necrosis of subepidermal capillaries)between 1 hour and 7 days postexposure and suggestedthat clinical management decision making onhow to treat early vesicant burns could be aided byLDPI. 162 Chilcott et al used several noninvasive bioengineeringmethods to monitor wound healing in alarge white pig model for 7 days following exposureto HD and lewisite vapors. 163 They found LDPI to bea promising prognostic tool.ICG fluorescence imaging is a minimally invasiveprocedure that requires the placement of an intravenousline. The fluorescence of intravenous ICG hasbeen shown to estimate burn depth in small animals. 164In contrast to fluorescein fluorescence, ICG fluorescenceis capable of distinguishing superficial and deeppartial-thickness burns from full-thickness burns. 165The fluorescence intensity of ICG decreases exponentiallywith burn depth for burns of similar age. 166 ICGfluorescence was successfully used to estimate burndepth in a porcine model. 167 An imaging system witha diagnostic algorithm was developed at the WellmanLaboratories of Photomedicine (Boston, Mass); thesystem accurately diagnosed burns that healed within21 days with minimal scarring from those that tooklonger to heal by secondary means. The algorithmwas shown to be dependent on the age of the burn andindependent of the location of the burn. This technologyshowed promise in plastic surgical applicationsand accurate determination of thermal burn depth inhumans. 168–170 ICG fluorescence imaging also showspromise in diagnosing depth of HD injury. 171 UnlikeLDPI, multiple images over large areas can be capturedin a relatively short period of time. Images are typicallycollected 5 to 10 minutes after ICG injection to allowuptake and distribution. The dye is then excited (eg,780 nm), and the resultant fluorescence emission (eg,810 nm) immediately captured and saved by a computerand analyzed for burn/normal skin fluorescenceratio. ICG binds strongly to plasma globulins, limitingboth extravasation within burn-injured vascular epitheliaand extravascular transport to areas nearby. 166Large signals are thought to be the result of vasodilationand hyperemia, and smaller signals are thought tobe attributable to vascular occlusion and edema. 164,166Treatment of deep injuries. Previous animal studieshave shown that surgically aggressive approaches areneeded to prevent or minimize significant cosmeticand functional deficits that result from deep HD injury.For the best outcome, deep dermal/full-thicknesscutaneous HD injuries require full-thickness debridement followed by autologous split-thickness skingrafting. 172,173 To be successful, the skin grafts must beplaced on a hemostatically secure wound bed, devoidof blood clots, debris, or necrotic tissue. The recipientbed must have an adequate blood supply to nourishthe skin grafts, and the grafts must be protected fromshearing forces, motion, and mechanical disruption. Avariety of modalities are available for achieving initialgraft adherence and subsequent acceptance (“take”).These include sutures, surgical staples, fibrin glue, tieoverbolsters, compression dressings, and a variety ofantishear dressing techniques. The choice of fixationand dressing technique is determined by the size andlocation of the wounds, and the experience and preferencesof the surgeon. 138In thermal burn management, deep burns aregrafted to promote timely wound closure and improveoutcome with minimal cosmetic and functionaldeficits. The decision to graft is based upon depth ofinjury, and deep HD injuries will require surgicallyaggressive approaches. As with thermal burns, depthof HD injury should be accurately assessed beforetreatment begins. Reported long-term effects such asfragile skin and scarring likely indicate that injurydepth was not accurately diagnosed and treatmentwas not sufficiently aggressive.Treatment of partial-thickness injuries. Epidermaland superficial dermal HD injuries may have greaterclinical relevance on the battlefield than deep injuries.Partial thickness injuries need debridement, butnot grafting. The standard treatment, after assessingthe injury and deroofing frank blisters, is to performadequate debridement of partial-thickness injuries,then treat the lesions like chronic cutaneous ulcers orpartial-thickness thermal burns using contemporarymedical approaches. Debridement is followed by oneor more treatment adjuncts. Examples of adjunctsunder consideration are dressings, growth factors,skin substitutes, and Vacuum-Assisted Closure (VAC)Therapy (KCI, San Antonio, Tex).Debridement. Experimental approaches to vesicant283