Acute limb ischaemia

Symptoms of acute limb ischemia can occur anywhere from minutes to days. they are commonly mis-attributed to compartment syndrome. Symptoms may also include intermittent claudication or pain at rest. In late stages, paresthesia is replaced by anesthesia (numbness) due to death of nerve cells. In severe cases, gangrene can occur suddenly and spread rapidly, and should be treated within six hours of ischaemia. Embolic occlusions should be considered when patients present with a sudden and severe onset. Acute arterial occlusions may also lead to arterial spasms, causing a "marble" white appearance. Patients who have an embolic (small piece of debris that breaks off from somewhere else in the body, such as the heart) cause of ALI often present with unilateral decreased pulses, whereas those with a thrombotic (clot that forms directly in the blood vessel) cause of ALI such as atherosclerosis often present with bilateral decreased pulses. == Causes ==

Most acute limb ischemia is caused by thrombosis (40% of the cases), embolism (30%), vascular graft thrombosis (20%), thrombosis by popliteal artery aneurysm (5%), and major trauma (5%). In a patient with otherwise no known risk factors, atrial fibrillation with embolism should be suspected. This leads to an occlusion of the artery and thus ischemia. Unlike embolic causes of limb ischemia, thrombosis is progressive and develops over time. In hypercoagulable states, thrombosis can occur in areas without atherosclerosis, and usually presents in patients with malignancy, increased tendency for blood to clot, or low blood flow. Vascular graft thrombosis Thromboses as a result of cardiac interventions has become increasingly common. Clots may form at the sheath or catheter tip, potentially causing embolism during sheath removal. Aneurysm Thromboses forming within aneurysms are most frequently seen in the popliteal artery. Acute limb ischemia due to a popliteal artery aneurysm has been reported to have a 20-60% chance of limb loss and 12% mortality rate. Trauma Acute limb ischemia may also be caused by traumatic disruption of blood flow to a limb, which may present with either hard signs or soft signs of vascular injury. Hard signs include pulsatile bleeding, expanding hematomas (collections of blood), or absent distal pulses, and must be taken to surgery emergently. Soft signs include reduced pulses or nerve damage. ==Diagnosis==

Once signs and symptoms of acute limb ischemia are identified, the cause and location of the occlusion and its severity need to be addressed. A clinical pulse examination can be done to detect the location of the occlusion by finding the area where the pulse is detected until the area where the pulse disappears. The skin temperature would also be colder in the pulseless area compared to the areas where the pulses are present. Patients with clinical suspicion of ALI should also receive a chest X-ray and echocardiogram to evaluate for cardiac embolism, cardiac thrombus, myocardial infarction, and cardiac function. == Prevention ==

The primary prevention of acute limb ischemia starts with awareness of peripheral artery disease (PAD). In patients with PAD, smoking cessation, weight control, blood pressure control, diabetes control, physical activity, and rhythm control in those with atrial fibrillation should be encouraged. Lifestyle modifications such as exercise, healthy eating, weight management, and stress management are all important in decreasing inflammation and other risk factors for PAD. Medical therapy such as antihypertensives, lipid-lowering therapy, antidiabetic therapy, and antithrombotics can be considered when lifestyle modifications are not enough. Antiplatelets are recommended with 1C level of evidence for patients with symptomatic PAD, with a preference of clopidogrel over aspirin. The VIVA trial demonstrated a 7% reduction in mortality of using ankle-brachial index (ABI), blood pressure management, and ultrasonography for vascular disease screening. ==Treatment==

Initial anticoagulation with heparin is usually first recommended to prevent further development of the clot and help reduce ischemia. Pharmacological thrombolysis requires a catheter to be inserted into the affected area, attached to the catheter is often a wire with holes to allow for a wider dispersal area of the thrombolytic agent. These agents lyse the ischemia-causing thrombus quickly and effectively. However, the efficacy of thrombolytic treatment is limited by hemorrhagic complications. Plasma fibrinogen level has been proposed as a predictor of these hemorrhagic complications. However, based on a systematic review of the available literature until January 2016, the predictive value of plasma is unproven. After the clot has been dissolved or removed, a stent or balloon may be placed to keep the artery open and prevent further ischemia. Major complications of thrombolysis include intracranial hemorrhage, major bleeding, compartment syndrome, and failure of thrombolysis. Other options include a vascular bypass to route blood flow around the clot. Medical management For secondary prevention of ALI, long-term anticoagulation and management of atherosclerosis must be considered. ==Prognosis==

There is a high risk of mortality and cardiovascular events in those with critical limb ischemia. At one year, around 20-25% will die and 25-30% will need major amputation. ==Epidemiology==

The major cause of acute limb ischaemia is arterial embolism (80%), while arterial thrombosis is responsible for 20% of cases. In rare instances, arterial aneurysm of the popliteal artery has been found to create a blood clot or embolism resulting in ischaemia. ==References==