A sufficient supply of blood and nutrients is essential for tissue integrity and function. In the absence of adequate blood supply, wound healing stages experience delayed progression which leads to the development of chronic wounds in ischemic tissues. 6.5 million people in the United States suffer from Peripheral Arterial Disease which is associated with the presence of chronic, ischemic wounds.1 Wound care specialists and podiatrists should be able to recognize the early signs of ischemia in a wound to provide effective wound care and early intervention that can help preserve tissue integrity.

What Are Ischemic Wounds? 

Ischemic wounds occur due to a compromised or obstructed blood supply to a tissue. They are most commonly associated with lower leg ulceration in patients with peripheral arterial disease (PAD) and chronic limb ischemia. Peripheral arterial disease is characterised by narrowing of the distal blood vessels which compromises the blood supply. These wounds most often tend to occur on the shin, tips of toes and sides of the feet. Ischemic wounds have the characteristic features of chronic ischemia which include pale skin, pulselessness, paraesthesia and cold skin. Ischemic wounds are extremely painful and present with yellow exudate and necrotic debris in the tissue bed.

As ischemic wounds have low tissue perfusion, this favours bacterial colonisation and infections.2 Therefore, the majority of ischemic wounds are accompanied by abscesses and gangrene. A combination of tissue hypoxia and infections halts the normal progression of wound healing stages which ultimately leads to tissue death. Therefore, it's not a surprise that over 66% of patients diagnosed with chronic limb ischemia undergo leg amputation within 4 years of diagnosis.3 Podiatrists and wound care specialists should therefore be vigilant in detecting early signs of ischemia in patients with peripheral arterial disease and diabetes.

Assessment of Ischemic Wounds

After obtaining a comprehensive history, the following bedside tests can help in the diagnosis of ischemic wounds:

• Capillary Refill Time - A capillary refill time greater than 2 seconds might indicate insufficient arterial supply.
• Ankle-Brachial Pressure Index (ABPI) - this involves the comparison of blood pressure at the arm and ankle using a Doppler. A ratio of <0.9 is indicative of ischemia in the limbs.
• Transcutaneous oximetry - this can help assess the oxygen content in the skin surrounding the wound. A value of <40 mmHg represents a vascular compromise, and any value less than 20 mmHg represents severe disease.
• Buerger test - the patient is asked to raise the affected leg at 45 degrees for about 1 minute. The patient’s leg starts turning pale in the setting of arterial insufficiency and returns to its normal colour when lowered.

Wound Care Principles For Ischemic Wounds

An adequate blood supply is a prerequisite for optimal wound healing. Therefore, the management strategies for ischemic wounds are directed towards restoring tissue perfusion to aid wound healing. 

• General Management: Patients should be advised to quit smoking as it helps halt the progression of peripheral arterial disease. Moreover, they should be advised to exercise regularly to help relieve the symptoms of claudication. Compression therapy is not recommended in patients with ischemic wounds as it might further compromise blood flow to the tissues.4
• Management of Infection: Ischemic wounds are prone to bacterial colonisation due to prolonged ischemia. Wound infection can further delay wound healing and can damage healthy granulation tissue. Therefore, effective infection control is necessary for wound healing. Topical treatment with silver dressings might be suitable for superficial infections. However deep infections require systemic antibiotic therapy. 
• Wound Dressing: The skin surrounding ischemic wounds is fragile and would require non-adherent dressings to avoid damage to the skin. Dressings should also be infused with antimicrobial properties to help manage the infection. 
• Regular Cleaning: Normal saline is recommended for wound irrigation and cleansing as it is non-toxic to the granulation tissue. It helps remove necrotic debris and helps accelerate the wound healing process.5
• Pharmacological Management: Antiplatelet drugs should be prescribed to patients as they limit the progression of peripheral vascular disease. Vasodilator drugs like Cilostazol can be effective in improving peripheral blood circulation.6 Given the painful nature of ischemic wounds, effective painkillers should be prescribed. Another adjunct to the treatment of ischemic wounds include statins that can help reduce the severity of the peripheral vascular disease.
• Surgical Management: Critical limb ischemia can lead to tissue death and subsequent amputation in the lower limbs. Therefore, surgical management might be indicated to restore perfusion to the tissues. Before surgery, distal vessel patency should be assessed using CT angiography. A bypass graft is constructed using the patient's saphenous vein that helps bypass the obstruction in blood flow. Alternatively, endovascular interventions can be used to restore perfusion. Endovascular procedures are associated with fewer complications compared to open surgical procedures for revascularization.7

Use of Telehealth For Ischemic Wounds

Telehealth allows clinicians and wound care experts to provide effective wound care to vulnerable patients. The COVID-19 pandemic has highlighted the need for alternatives to traditional face-to-face consultations. Through readily available access to expert advice, patients can greatly benefit and receive adequate wound care. Telemedicine can also help improve patients’ compliance to treatment and can help in the early detection of wound deterioration.

References 

1. CDC. Peripheral arterial disease (PAD) [Internet]. Cdc.gov. 2021 Available from: https://www.cdc.gov/heartdisease/PAD.htm
2. Shai A, Maibach H. Etiology and mechanisms of cutaneous ulcer formation. In: Wound Healing and Ulcers of the Skin: Diagnosis and Therapy—The Practical Approach. New York: Springer-Verlag Berlin Heidelberg; 2005:30-52.
3. Reinecke H, Unrath M, Freisinger E, Bunzemeier H, Meyborg M, Lüders F, Gebauer K, Roeder N, Berger K, Malyar NM. Peripheral arterial disease and critical limb ischaemia: still poor outcomes and lack of guideline adherence. European heart journal. 2015 Apr 14;36(15):932-8.
4. Bonham PA, Flemister BG, Goldberg M, Crawford PE, Johnson JJ, Varnado MF. What's New in Lower-Extremity Arterial Disease?: WOCN's 2008 Clinical Practice Guideline. Journal of Wound Ostomy & Continence Nursing. 2009 Jan 1;36(1):37-44.
5. Maklebust J, Sieggreen M. Pressure ulcers: Guidelines for prevention and management. Lippincott Williams & Wilkins; 2001.
6. Money SR, Herd JA, Isaacsohn JL, Davidson M, Cutler B, Heckman J, Forbes WP. Effect of cilostazol on walking distances in patients with intermittent claudication caused by peripheral vascular disease. Journal of vascular surgery. 1998 Feb 1;27(2):267-75.
7. White CJ, Gray WA. Endovascular therapies for peripheral arterial disease: an evidence-based review. Circulation. 2007 Nov 6;116(19):2203-15.

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