Acute Limb Ischemia: A Literal Case of Cold Feet

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Author: Jennifer Reink, MSIV
Ohio University Heritage College of Osteopathic Medicine

Case
A 58-year-old Caucasian male was brought into a community emergency department via ambulance for evaluation of sudden onset left leg pain and right leg numbness. He stated that about five hours earlier, he had begun to experience severe sharp pains shooting down the entire length of his left leg. His right leg had initially felt like pins and needles, but prior to arrival had gone completely numb, to the point that he was unable to lift it. He denied recent trauma, back or abdominal pain, or urinary or stool incontinence. Upon further review, we learned that he had a history of stroke, abdominal aortic aneurysm with graft repair, hypertension, and diabetes. He was taking the associated medications for these conditions, which did not include an anticoagulant. He had no prior history of tobacco, alcohol, or drug use.

On physical exam, he was tachycardic and tachypneic, however, other vitals were within normal limits. He was lying uncomfortably on the cot in significant distress and it was difficult to elicit information. His left leg was pale and his right leg appeared mottled. The temperature of the legs were fairly symmetrical, but with cooler feet and decreased bilateral lower extremity strength. He also had decreased sensation over the right leg and foot. We were unable to palpate any lower extremity pulses. Even before Doppler confirmation, we knew this patient was suffering from limb ischemia and that immediate reperfusion was necessary to salvage his extremities.

What is acute limb ischemia?
Acute limb ischemia is the sudden decrease in limb perfusion causing threat to limb viability.[1,2] It is associated with a high morbidity and mortality rate. As many as 20% of cases may result in amputation of the affected limb and the best predictor of positive outcome is time from onset to treatment.[3] The most common associated causes are thromboembolic events. Thrombotic events are responsible for up to 50% of cases and may be associated with acute plaque rupture, hypovolemia, pump failure, malignancy, thrombophilia, or aneurysm.[4] These are often found in bypass grafts, femoral arteries, or popliteal arteries. Up to 80% of embolic events are associated with a cardiac source including prosthetic heart valves, prosthetic grafts, aneurysmal disease, or post myocardial infarction.[5] The most common locations include the femoral artery bifurcation, aortoiliac arterial system, or the brachial artery. Other common etiologies of acute limb ischemia are compartment syndrome, thoracic outlet syndrome, aortic dissection, severe Raynaud’s syndrome, progressive peripheral vascular disease or vasculitis, or trauma.[3,6]

Presentation and Diagnosis
Risk factors include history of heart attack, diseased or prosthetic valves, large vessel aneurysmal disease, lower extremity revascularization procedures, direct arterial trauma, risk of aortic dissection, generalized arteriosclerosis, deep vein thrombosis, or atrial fibrillation.[2,6] It is important to get a thorough history on any patient you suspect may be having ischemic changes. Physical exam findings include the “6 P’s” or pain, pulselessness, pallor, poikilothermia, paresthesias, and paralysis; paresthesias and paralysis are associated with later stages of disease.[2,4,7] Severity can be identified using a classification system to help determine the viability of the effected limb (Table 1).[2,4]

Class	Category	Prognosis	Sensory Loss	Muscle Weakness	Arterial Doppler Signal	Venous Doppler Signal
I	Viable	No immediate limb threat	None	None	Audible	Audible
IIA	Threatened: Marginal	Salvageable if treated promptly	Minimal (toes)	None	Audible	Audible
IIB	Threatened: Immediate	Salvageable if treated immediately	More than just toes	Mild- moderate	Often audible	Audible
III	Irreversible	Limb loss or permanent damage	Profound anesthesia	Profound paralysis	None	None

Angiography is the gold standard for imaging and allows for concurrent diagnosis and treatment of the occlusion.[7] Ultrasound, computed tomography, and magnetic resonance imaging are also viable imaging modalities, but may be associated with delayed treatment. The benefits of imaging must be weighed against the urgency of revascularization.

Treatment
The most important step an emergency physician can take in treating acute limb ischemia is to immediately consult a specialist.[1,6] The longer it takes for revascularization to occur, the worse the outcome. The specialist will most likely ask that the patient be given a heparin bolus which has been associated with decreased morbidity and mortality. They may also ask for a continuous heparin infusion.[2] The patient should also be given Aspirin which has been shown to decrease the risk of a concurrent vascular event by 25%.[3] The affected extremity should be placed in a position that allows gravity to improve limb perfusion and extreme temperatures should be avoided.[3,6] Adequate pain control should also be achieved.

In spite of optimal therapy, the hospital mortality rate is 20% which is often due to cardiopulmonary complications. There is a one-year mortality rate of 15-20% associated with the medical condition causing the initial event.[6]

Conclusion
For our 58-year-old patient, we contacted the hospital vascular surgeon who had the patient rapidly transferred to another facility for immediate treatment. We provided the heparin bolus, aspirin, and pain control until airlift could arrive. We later learned that this patient’s aortic graft had become occluded leading to bilateral lower extremity ischemia. In the end, our role in the emergency department is to identify acute limb ischemia quickly and activate the surgical team in order to give patients the best chance of limb survival. Next time someone tells you they have cold feet, be sure to check for pulses, because the only thing that may fix it is reperfusion!

References:

1. Creager MA, Kaufman JA, Conte MS. Acute limb ischemia. N Engl J Med. 2012;366(23):2198-206.

2. Mitchell ME and Carpenter, JP. Overview of acute arterial occlusion of the extremities (acute limb ischemia). Sept. 2016. Available at: http://www.uptodate.com/contents/overview-of-acute-arterial-occlusion-of-the-extremities-acute-limb-ischemia.

3. Lin M. Acute limb ischemia. Topics in Emergency Medicine. 2011. Available at: http://www.ucsfcme.com/2012/slides/MEM12001/1.Lin.ALI.pdf.

4. Shishehbor, MH. Acute and critical limb ischemia: when time is limb. CCJM. 2014;81(4):209-216.
Thomas R. Acute limb Ischemia. Available at: https://www.fastbleep.com/medical-notes/surgery/5/272.

5. Purcell D, Salzberg M, and Kan V. Acute limb ischemia: pearls and pitfalls. FOAMED Review. 2015;35. Available at: http://www.emdocs.net/acute-limb-ischemia-pearls-pitfalls.

6. Norgren L, Hiatt WR, Dormandy JA, et al. Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II). J Vasc Surg 2007; 45 Suppl S:S5.