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Simplifying Non-invasive Assessment of Hand Ischemia

Hand ischemia is a serious and well known complication of arteriovenous (AV) access creation. It occurs in 5-10% of all cases of AV creation, especially when the brachial artery is used as the inflow (1-3). AV induced hand ischemia causes significant pain and discomfort, as well as potentially leading to digit or even hand loss. The development of ischemic symptoms distal to an AV access can occur in the early or late post-operative interval. Three distinct etiologies of hand ischemia have been reported; (a) arterial occlusive disease proximal or distal to the AV anastomosis causing blood flow restriction; (b) excessive flow into the AV conduit with or without arterial occlusive disease; and (c) lack of vascular collateralization to the increased flow demand (4). In other cases, distal arteriopathy as a result of generalized vascular calcification and diabetes is the cause. Treatment should start with a detailed history and physical examination to help rule out other nonischemic causes of hand pain. Non-invasive testing is the next crucial step in the diagnosis of hand ischemia. A variety of non-invasive exams such as digital pressure measurement, digital/brachial index (DBI) measurement, digital plethysmography and duplex ultrasonography, are available to assist in the evaluation of hand ischemia. Confirmatory testing can be performed utilizing digital photoplethysmography (PPG) with the fistula open and after manual compression of the fistula. Although it is normal to have a reduction in the amplitude of digital waveforms distal to a patent proximal fistula, the non-ischemic hand should demonstrate normal pulsatile waveforms (5, 6). Patients with pronounced ischemia have monophasic, or flat, waveforms that augment with the compression of the fistula. Once confirmed, non-invasive testing can also be utilized with a high degree of accuracy to access for the cause of the ischemia and may in some cases, replace the need for angiography (7). The presence of a proximal inflow stenosis contributes to the steal syndrome in 20-30% of patients who present with distal extremity ischemia (8). Duplex imaging is ideal for evaluating hemodynamically significant stenoses of inflow vessels, as well as within the AV circuit. Evaluation of the blood flow volume and hemodynamics of an AV access can be performed with high reliability and relative ease. The use of a DBI of less than 0.6 has been reported as a reliable predictor for symptoms of steal syndrome after surgery (9). Non-invasive testing is a critical and important step in the evaluation and treatment of hand ischemia. It is important to have a clear understanding of the causes of AV access induced hand ischemia. It is also critical to have knowledge of the normal and abnormal parameters for an upper extremity non-invasive examination. A systemic approach with a clearly defined protocol and algorithm can help improve efficiency and outcomes in the diagnosis and treatment of hand ischemia.