Providing a roadmap to predict tissue viability.

The Scalpel Cannot See I have long held the notion that while sharps debridement is a necessary and time-honored technique to clear a wound of necrotic and nonviable tissue, themethod is blunt and imprecise. It invariably removes viable tissue and may evenleavebiofilmonthewound. If thedebridement technique is macroscopic, then how do we magnify our visualization to differentiate viable tissue from ischemic, necrotic, and nonviable skin, and subcutaneous, muscle, and extracellularmatrices, in chronic or nonhealing wounds? Towiden our lenses in the evaluation of the pathophysiologic determinants of an acute or chronicwoundhealing,we strive to develop advanced measurement systems. These technologies should have the ability tomeasure neurohumor, arteries, veins, endocrine,andlymphatics (NAVELisahelpfulmnemonic)dynamically and in real time. Toward this goal, significant advancements have taken place in ‘‘mapping out’’ or visualizing these systems, again perhapsmacroscopically through the use of neurography, venography, lymphography, and angiography, in real time. Angiography has been especially useful in mapping out peripheral arterial disease and cardiac and cerebral obstructions. Imaging of human blood vessels was achieved almost 120 years ago in 1896. This was coincidental to the announcement of Roentgen’s (X-ray) discovery, whenHaschek and Lindenthal injected ‘‘Teichmann’s mixture,’’ composed mainly of calcium carbonate, into the blood vessels of an amputated hand, outlining and imaging the vessels. In the intervening nearly century and a quarter, significant advances are allowing clinicians to identify vascularization, tissue perfusion, and viability of the tissues. One of the most noteworthy advancements in visualization of ‘‘real-time’’ blood flow in the tissues of the eyewas the concept of dyeing or tagging the bloodwith a fluorescein dye. The dye is in the formofacid fluorochrome; thesodiumsalt isused insolution to reveal corneal lesions, as a test of circulation in the retina, and even the extremities. Twomedical students at IndianaUniversity are credited for the discovery of the use of fluorescein angiography for retinal imaging in 1960. These historical underpinnings for the use of real-time evaluation techniques using fluorescein angiography are relevant to the modern practice of wound care because of themacrostructures andmicrostructures of interest. Advancing the Scalpel’s Vision Increasingly, wound care practitioners, especially in wound centers, haveaccess to infraredandnear-infrared lightwith various applications for wound assessment (see page 37) and laser Dopplers tomeasure blood flowbymeasuring red blood cells as theymove through the arterial systemusing the ‘‘Doppler effect. ’’ Anewer technologycombining real-time fluorescence imaging to assessperfusionof viable tissue and thedelineationof necrotic tissue for more precise identification for debridement is now available.Applications of intravascular injectionof indocyanine green (ICG) for evaluation of peripheral blood circulation in patients with peripheral arterial disease have been evaluated and found to be effective in delineating ischemic and nonviable tissue in skin flap viability. Advanced technology adds laserinduced fluorescence of ICGas anewmethod for evaluating skin perfusion, which is superior to conventional fluorescein angiography.The advantageofusing fluorescein angiographywith ICG is the mitigation of ionizing radiation and nephrotoxicity associated with other radiopaque dyes used in radiologic imaging. One such device is the LUNA Fluorescence Microangiography System (Novadaq Technologies, Inc,Mississauga, Ontario, Canada), a novel tool that brings this imaging technology to the clinic and the bedside. The system is dubbed the ‘‘LUNA’’ System because it illuminates and differentiates viable tissue from necrotic tissue in real time, allowing the wound care practitioner to visualize the area of interest displayed from a mobile platform and monitor. Recently, the Centers for Medicare & Medicaid Services established vascular angiography as a new reimbursable serviceunder theHospitalOutpatientProspectivePaymentSystem throughAmbulatoryPaymentClassification0397,Vascular Imaging. The rapid tempo of technological advancements enhancing woundevaluation is exemplifiedbyMoore’sLaw. In1965,Gordon Moore, cofounder of Intel Corporation, Santa Clara, California, predicted that computer processor speeds and power would double every 18 months; similarly, our power to visualize tissues of interest in the wound bed and the periphery has advanced exponentially and is now ready for use in the clinic. ‘‘We only see what we know. ’’ V Johann Wolfgang von Goethe (1749Y1832)&