COVER STORY The Essentials of Ischemic Wound Care Basic care for ulcerations beyond revascularization. BY JESSICA NEVINS MORSE, MD, AND BRUCE H. GRAY, DO espite continued advancements in revascu- amputation risk, healing potential, and quality of life. larization using both open surgical and Dosluoglu et al confirmed we anecdotally know that endovascular techniques, peripheral arterial necrotic heel ulcerations do poorly, and that even disease (PAD) as a cause for chronic ulcera- with revascularization, the short- and long-term Dtion remains a highly morbid diagnosis. The natural amputation risk is significant.4 The patients who are at history of PAD rivals many forms of cancer, with a 5-year greatest risk are medically debilitated from a nutri- mortality rate of 50%. Patient outcomes can be pre- tional standpoint, nonambulatory, and/or with end- dicted based on their ankle-brachial index (ABI) at stage renal disease.5 presentation. Those with critical limb ischemia (CLI) As vascular physicians, it is imperative to recognize with symptoms including rest pain, ulceration, or gan- the diagnosis of PAD and specifically CLI as the cause grene have the lowest ABI—usually <0.4—and carry of chronic ulceration. Often, poor circulation is com- an annual mortality rate of 20%.1 The risk of limb loss, plicated by peripheral neuropathy, poor skin nutrition, persistent disability, and poor quality of life are more and hygiene. A multidisciplinary approach is required the rule than the exception for these CLI patients. to maximize wound healing. At our wound care insti- Ulcer healing rates have been incompletely studied, tution, we use a three-pronged approach of: but Marston et al showed a 52% healing rate at 12 (1) Noninvasive assessment of the arterial circula- months in ulceration patients treated medically with- tion out revascularization.2 Open revascularization proba- (2) Revascularization when clinically able based on bly improves upon the healing rate at 12 months anatomy and surgical risk (75%), but 19% of patients may lose ambulation sta- (3) Aggressive local wound care both before and tus, and 5% will lose independent living status.3 after revascularization The location of the devitalized tissue also affects These measures, in addition to controlling patients’ ABC Figure 1. Treatment of Wagner IV diabetic foot ulcer in a patient with CLI. Arrival to wound center (A). After revascularization, hyperbaric oxygen therapy, and serial debridements (surgical and enzymatic) (B). After treatment with silver-imbedded calci- um alginate, wound bed is prepared for skin substitute grafting (C). MARCH 2009 I ENDOVASCULAR TODAY I 51 COVER STORY medical comorbidities and maximizing their nutrition- TABLE 1. NONINVASIVE ARTERIAL TESTING al status, give the greatest chance for wound healing, VALUES SUGGESTING INABILITY TO HEAL limb salvage, maintenance of independence, and over- all survival.5 Macrocirculation • ABI <0.4 NONINVASIVE METHODS OF • Ankle systolic pressure <50 mm Hg ASSESSING CIRCULATION Multiple noninvasive modalities exist to predict Microcirculation successful wound healing in the face of PAD by assess- • Toe systolic pressure <30 mm Hg ing the quality of tissue oxygenation surrounding the • Pulse wave amplitude <4 mm wound. These serve as a guide for wound therapy and • Skin perfusion pressure (SPP) <40 mm Hg assist the physician in determining which patients • Transcutaneous oxygen <10 mm Hg may or may not require revascularization. Important • Transcutaneous carbon dioxide >100 mm Hg patient factors that also affect the decision to revas- • Capillary density <20 mm2 cularize include ambulation status, mental status, presence of chronic kidney disease, and the extent and location of necrosis. Bedridden, patients with Calcified tibial arteries can lead to false elevation of dementia are best served with primary amputation the ABI, limiting the utility of this measurement, par- and do not require noninvasive testing. Noninvasive ticularly in diabetics and hemodialysis-dependent arterial testing should be performed in all other cases patients. The TBI is obtained by comparing the great aiding in the objective evaluation of the need for toe pressure (obtained with photoplethysmography revascularization. [PPG]) to the highest brachial pressure obtained with Arterial testing modalities can be subdivided into Doppler ultrasound. Digital arteries are rarely calci- two groups (Table 1): fied, and thus the TBI provides a reliable marker of (1) Assessment of macrocirculation perfusion and healing. A normal TBI is considered 0.7 • ABI and segmental systolic pressures or higher. CLI is defined by TASC II criteria as a toe (2) Assessment of microcirculation pressure <30 mm Hg or <50 mm Hg in a patient with • Toe-brachial index (TBI), skin perfusion active gangrene or ulceration.1 In patients with exten- pressures, transcutaneous oxygen levels, or sive tissue loss or amputation of the great toe, the transcutaneous carbon dioxide levels second toe can be used for TBI. The toe pressure According to the 2007 Trans-Atlantic Inter-Society measurement has been shown to be superior to either Consensus (TASC II) document, it is generally accept- the absolute ankle pressure or transcutaneous oxygen ed that multilevel disease of the macrocirculation is level for identifying CLI and predicting the course of the major determinant for the development of CLI; disease.6 Skin perfusion pressure has been shown to however, disruption in the microcirculation leads to be equivalent to toe pressure measurement in pre- failure of wound healing despite correction of their dicting the healing rate of ischemic ulcerations.7 macrocirculatory disease.1 For this reason, the nonin- The shape and amplitude of the toe PPG waveform vasive assessments of microcirculation have emerged also predicts wound healing and is complimentary to as useful tools predicting healing potential. At our the standard TBI measurement. Pulse wave amplitude wound center, we obtain toe pressures upon initial <4 mm has been associated with the presence of rest evaluation to assess microcirculation of the ischemic pain and ulcerations with a stronger odds ratio than ulcer patient. Also, further investigation of the micro- an absolute toe pressure of <30 mm Hg alone.8 Also, circulation is helpful after revascularization or to fur- in patients with CLI, reduced toe pulse wave ampli- ther evaluate any nonhealing wound. tude of <4 mm has been associated with an increased risk of amputation as well as all-cause mortality.9 TBI and Evaluation of Further pulse wave analysis, such as pulse delay, Photoplethysmography Waveform amplitude reduction, and waveform asymmetry, accu- The ABI is obtained by comparing the highest ankle rately identifies significant PAD. Pulse wave analysis pressure at the anterior tibial, peroneal, or posterior was found to be concurrent with ABI findings 90% of tibial artery with the highest brachial artery Doppler the time and 100% sensitive for detecting high-grade pressure. This ratio when normal is 1, and it is stenoses. Of the parameters studied, pulse wave delay markedly diminished in CLI patients (usually <0.4). showed the greatest accuracy.10,11 52 I ENDOVASCULAR TODAY I MARCH 2009 COVER STORY Skin Perfusion Pressure tions, we have found using a systematic approach to The measurement of SPP was first introduced in local wound care minimizes wound-healing time. A 1967. Since that time, three modalities of determining helpful wound care pneumonic for management of SPP have evolved, all of which measure the exact pres- any chronic wound is DIME: debridement, infection, sure above which skin blood flow ceases when com- moisture control, and edge. pressed externally. Radioisotope clearance relies on Debridement of ischemic wounds should be avoided isotope washout with cuff deflation, whereas PPG before revascularization. It is more favorable to main- monitoring detects resumption of pulsatile flow, and tain a dry wound bed and to minimize the bacterial laser Doppler detects red blood cell flow as cuff pres- load by daily washes with either povidone-iodine or sure decreases. A SPP of >40 mm Hg is considered ade- chlorhexidine. After revascularization, debridement of quate for wound healing.12 slough and eschar is vitally important to stimulate A recent study compared SPP to ankle pressure, toe wound healing by removing a bacterial haven for pressure, and transcutaneous oxygen pressure. Using a growth. Regular debridement reduces the necrotic laser Doppler and 5.8-cm cuff to obtain SPP on the burden and bacterial load and slows the production of dorsum of the foot showed an independent ability to inflammatory cytokines and matrix metalloproteas- predict wound healing, without the limitations of tib- es.16 Although debridement can be performed by sur- ial artery calcification or previous great toe amputa- gical, enzymatic, autolytic, and mechanical means, we tion. The study also showed a strong positive predic- most commonly use serial surgical debridement tive value when combining an SPP >40 mm Hg with a (Figure 1).17 This is particularly important after revas- TBI of >30 mm Hg.13 cularization. Infection is a well-known hindrance to wound heal- Transcutaneous Measures of ing. It should be evaluated when there is a delay in Oxygen and Carbon Dioxide Pressures wound healing despite revascularization. Any patient Transcutaneous oxygen pressure (TcO2) measure- who develops acute changes in pain or exudate should ments are also a well-documented method of assess- be seen promptly