Chapter 2: Ischemic Wounds

INTRODUCTION

Most ischemic wounds are caused by moderate to severe peripheral arterial disease (PAD); however, there are several systemic disorders that can also cause skin hypo-perfusion which results in non-healing wounds, e.g. arterial entrapment, thrombus, adventitial cyst, embolism, fibromuscular dysplasia, dissection, trauma, vasculitis, and vasospasm.¹ Successful treatment of any ischemic wound depends first upon treatment of the underlying disease, be it PAD or some other malady such as pressure, chronic venous insufficiency, autoimmune diseases, trauma, diabetes, or infection. Evaluation of any wound that presents below the knee must include a thorough vascular screening to rule out PAD as a contributing factor. This chapter illustrates ischemic wounds caused by both PAD and systemic disorders, as well as signs and symptoms for a differential diagnosis.

CLASSIFICATION

The American College of Cardiology/American Heart Association Practice Guidelines classify the presentation of PAD into four categories: asymptomatic, claudication, critical limb ischemia, and acute limb ischemia.² Frequently the first sign that an asymptomatic patient may have PAD is a non-healing wound on the distal foot even though no other symptoms are present. Claudication is characterized by fatigue, discomfort, heaviness, or pain in the lower extremities with a predictable amount of exercise; it is relieved by rest and best treated with supervised exercise therapy.³ Critical limb ischemia (CLI), caused by moderate to severe PAD, is characterized by rest pain, nocturnal recumbent pain, or ischemic lesions that are typically present for at least 2 weeks. Acute limb ischemia can occur up to 2 weeks from the onset of symptoms and is characterized by the 6 “Ps”—pain, paralysis, paresthesia, pulselessness, poikilothermia (inability to regulate one’s core body temperature), and pallor.¹

The Society for Vascular Surgery has developed a risk stratification system based on Wound, Ischemia, and foot Infection (WIfI) that takes into account the wound size, the degree of perfusion, and the presence of infection. WIfI is the first PAD tool to take into consideration all three aspects of a lower extremity wound and is especially useful for diabetic foot ulcers which frequently have an arterial component. The WIfI lower extremity threatened limb classification is depicted in Figure 2-1. Although it is used primarily by vascular surgeons and podiatrists, the WIfI classification can be a useful guide for any clinician in assessing the severity of a patient’s condition when presenting with a lower extremity wound. For example, a patient with a small lesion on the foot with palpable pulses and no signs of infection will probably respond to standard wound care as described in Chapter 1. Any patient who has diminished pulses should be referred to a vascular specialist; any patient with signs of infection should be assessed and treated appropriately, with either topical antimicrobial dressings or systemic antibiotics. Table 2-1 lists the signs of local and systemic infection.