Acute Limb Ischemia Flashcards
What condition is marked by a sudden decrease in limb perfusion that threatens the viability of the limb, often caused by embolism or thrombosis.
Acute Limb Ischemia (ALI)
What are risk factors for acute limb ischemia?
Atrial fibrillation, recent myocardial infarction, heart failure, peripheral artery disease, hypercoagulable states, vascular trauma, patients with a history of coronary artery disease with a previous anterior wall myocardial infarction, heart failure with reduced ejection fraction, hypertension, and hyperlipidemia or peripheral artery disease.
What are the main etiologies of acute limb ischemia (ALI)?
- Thrombosis (e.g., at the site of atherosclerosis or aneurysm)
- Embolism
- Phlegmasia (extensive venous backup, very rare)
- Trauma
What is the most common source for embolism leading to ALI?
Cardiac sources such as atrial fibrillation, left ventricular thrombus, or endocarditis (septic emboli).
What are the six Ps of acute limb ischemia?
Pain, Pallor, Pulselessness, Poikilothermia (coldness or ambient temperature), Paresthesia, and Paralysis.
What are the early and severe clinical features of ALI?
Sensory symptoms (paresthesia) are early, while motor loss and paralysis are severe and indicate advanced ischemia.
What are the typical physical exam findings in acute limb ischemia?
Coolness to touch, delayed or absent capillary refill, absent arterial pulses, and sensory or motor deficits in severe cases.
How is acute limb ischemia classified based on limb viability?
- Viable limb: No sensory loss, minimal pain, normal capillary refill, audible Doppler signals.
- Threatened limb: Very painful, Delayed capillary refill, partial sensory/motor deficits, inaudible arterial Doppler signals.
- Nonviable limb: Absent capillary refill, complete sensory and motor loss, irreversible tissue damage.
How is acute limb ischemia classified by severity and intervention?
- Viable (Class I):
Mild pain, intact capillary refill and pulses, no intervention needed. - Marginally threatened (Class IIa):
Moderate pain, diminished pulses, possible sensory deficits, requires urgent revascularization. - Immediately threatened (Class IIb):
Severe pain, sensory/motor deficits, absent pulses, requires emergent revascularization. - Irreversible ischemia (Class III):
Complete paralysis/no sensation, signs of dead tissue, requires amputation.
What is the initial medical management for suspected ALI?
Intravenous heparin infusion to prevent thrombus propagation.
Patients with ALI diagnosed via clinical examination should be immediately given anticoagulation (eg, intravenous heparin infusion). Anticoagulation prevents further arterial thrombus propagation, as well as distal arterial and venous thrombosis (from stasis), while the patient undergoes further diagnostic imaging or awaits surgical intervention. For some patients, anticoagulation may result in clinical improvement. However, many patients require percutaneous thrombolysis (eg, alteplase) or surgical thrombectomy to restore perfusion to the threatened limb.
What diagnostic tests are used for acute limb ischemia?
Doppler ultrasound to assess arterial and venous flow; in some cases, CT angiography or MR angiography to evaluate the site of occlusion.
When is catheter-directed thrombolysis appropriate in ALI?
For patients with a viable limb (audible Doppler signals, no sensory or motor deficits), typically caused by extensive thrombosis rather than embolism.
What is the time window for emergency surgical revascularization in ALI?
ALI can cause irreversible tissue damage (myonecrosis) within 4-6 hours if untreated, making immediate surgery essential regardless of comorbid conditions.
What is the first-line treatment for a threatened limb in acute limb ischemia?
Emergency surgical revascularization.
What is the role of transthoracic echocardiography (TTE) in ALI?
TTE can be used after stabilization to evaluate for cardiac sources of embolism, such as left ventricular thrombus or valvular disease.
What are the potential complications of untreated ALI?
Irreversible myonecrosis, limb amputation, metabolic acidosis, hyperkalemia, rhabdomyolysis, and death.
What is the role of high-intensity statins and antiplatelet therapy in ALI?
They are used for long-term secondary prevention of atherosclerotic events but are not part of the acute management of ALI.
How does delayed capillary refill help differentiate ALI severity?
Delayed capillary refill is a hallmark of a threatened limb, indicating the need for emergency intervention to restore perfusion.
Why should serial Doppler examinations not delay surgical revascularization in ALI?
In a threatened limb, delaying intervention can lead to irreversible damage within hours.
What is reperfusion injury in ALI, and what are its clinical features?
Reperfusion injury occurs after restoring blood flow to ischemic tissue, causing oxidative damage, metabolic acidosis, hyperkalemia, and myoglobinuria.
What anticoagulant is preferred in the acute management of ALI, and why?
Heparin is preferred due to its rapid onset of action and ability to prevent clot propagation.
What is the diagnostic imaging modality of choice for ALI?
Computed tomography angiography (CTA).
What is the recommended initial management for ALI?
- Start intravenous heparin, 2. Administer fluids, 3. Place the affected limb in a dependent position to improve perfusion.
