ACUTE LIMB ISCHAEMIA

INTRODUCTION

Limb ischemia is a severe blockage in the arteries of the lower extremities, which significantly reduces blood flow. Acute limb ischemia is a sudden and rapid decrease in lower limb blood flow. 

TYPES

• Acute limb ischmia
• Chronic limb ischemia
• Critical limb ischemia

Acute limb ischemia

• Acute limb ischemia is a sudden and rapid decrease in lower limb blood flow. 

Chronic limb ischemia

• Chronic limb ischaemia is peripheral arterial disease that results in a symptomatic reduced blood supply to the limbs.
• It is typically caused by atherosclerosis (rarely vasculitis) and will commonly affect the lower limbs (however the upper limbs and gluteals can also be affected)
• Chronic limb ischaemia is a common condition, ranging in severity across the population, associated with several cardiovascular risk factors
• Whilst a clinical diagnosis, it can be quantified by ABPI testing, following by angiogram imaging
• Surgical intervention can be offered if conservative management options fail or those presenting with critical limb ischaemia.

Critical limb ischemia

Critical limb ischaemia is the advanced form of chronic limb ischaemia.

It can be clinically defined in three ways:

• Ischaemic rest pain for greater than 2 weeks duration, requiring opiate analgesia
• Presence of ischaemic lesions or gangrene objectively attributable to the arterial occlusive disease.
• ABPI less than 0.5

There are three main stages of acute limb ischemia: 

• Stage 1: Viable
  • Limb is not immediately threatened
  • No sensory loss
  • No muscle weakness
  • Doppler signals of arteries and veins are audible
• Stage 2: Threatened 
  • Stage 2a: Marginally threatened 
    • Limb is salvageable if promptly treated
    • Minimal sensory loss (toes) or no sensory loss
    • No muscle weakness
    • Doppler signals of arteries are often inaudible; veins are audible
  • Stage 2b: Immediately threatened 
    • Limb is salvageable with immediate revascularization
    • Sensory loss is more than toes, associated with rest pain
    • Mild to moderate muscle weakness
    • Doppler signals of arteries are usually inaudible; veins are audible
• Stage 3: Irreversible 
  • Limb has major tissue loss or permanent nerve damage inevitable
  • Profound sensory loss, numbness
  • Profound weakness, paralysis 
  • Doppler signals of arteries and veins are inaudible

EPIDEMOLOGY

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.

ETIOLOGY

Causes of acute limb ischemia include: 

• Blockage in a blood vessel (embolism) by such as by a blood clot, a fat globule, a bubble of air or other gas, or foreign material
• Blood clot (thrombosis)
• Peripheral artery disease due to atherosclerosis
• Tear in the lining of an aortic or peripheral artery (dissection)
• Major trauma
• Conditions that cause vasospasm 
  • Raynaud phenomenon
  • Shock (e.g., meningococcal sepsis, cardiogenic shock)
  • Administration of vasoactive drugs

Most acute limb ischemia is caused by embolism, thrombosis, peripheral artery disease due to atherosclerosis, or major trauma.

SYMPTOMS

Acute limb ischaemia can occur in patients through all age groups. People who smoke tobacco cigarettes and have diabetes mellitus are at a higher risk of developing acute limb ischaemia.Most cases involve people with atherosclerosis problems.

Symptoms of acute limb ischaemia include:

• Pain
• Pallor (pale appearance of the limb)
• Paresthesias (abnormal sensations in the limb)
• Pulselessness
• Paralysis

DIAGNOSIS

Acute limb ischemia diagnosed with a patient history and physical examination. The blockages associated with limb ischemia are located using one or more of the following methods:

• Auscultation
• Ankle-brachial index (ABI)
• Doppler ultrasound 
• Computerized tomography (CT) angiography
• Magnetic resonance angiography (MR angiography)
• Invasive Angiogram

ALI is diagnosed on the basis of medical history, visual examination, palpation, and Doppler examination of the peripheral arterial pulse using vascular ultrasonography and contrast-enhanced computed tomography (CT) as imaging tests

Investigation –

Suspected cases should be initially investigated with beside Doppler ultrasound scan (both limbs), followed by considering a CT angiography.

If the limb is considered to be recoverable, a CT arteriogram can provide more information regarding the anatomical location of the occlusion and can help decide the operative approach

• In order to treat acute limb ischaemia there are a series of things that can be done to determine where the occlusion is located, the severity, and what the cause was.
• To find out where the occlusion is located one of the things that can be done is simply a pulse examination to see where the heart rate can be detected and where it stops being sensed. Also, there is a lower body temperature below the occlusion as well as paleness.
• A Doppler evaluation is used to show the extent and severity of the ischaemia by showing flow in smaller arteries.
• Other diagnostical tools are duplex ultrasonography, computed tomography angiography (CTA), and magnetic resonance angiography (MRA).
• The CTA and MRA are used most often because the duplex ultrasonography although non-invasive is not precise in planning revascularization. CTA uses radiation and may not pick up on vessels for revascularization that are distal to the occlusion, but it is much quicker than MRA.^[1] In treating acute limb ischaemia time is everything.
• In the worst cases, acute limb ischaemia progresses to critical limb ischaemia, and results in death or limb loss.
•  Early detection and steps towards fixing the problem with limb-sparing techniques can salvage the limb.
• Compartment syndrome can occur because of acute limb ischaemia because of the biotoxins that accumulate distal to the occlusion resulting in edema.

Immediate treatment is needed for limb ischemia to re-establish blood flow to the affected area and to preserve the limb.

TREATMENT

Treatments for acute limb ischemia include: 

• Intravenous (IV) injection of unfractionated heparin (15–20 units/kg)

Upon the diagnosis of ALI, as long as heparin therapy is not contraindicated,an intravenous injection of unfractionated heparin (50–100 units/kg) is immediately administered to prevent the proximal and distal progression of secondary thrombosis to the site of occlusion, and a systemic administration of thrombolytic agents is not recommended. 

• Surgical treatment 
  • Thromboembolectomy
  • Bypass surgery
• Endovascular treatment 
  • Catheter-directed thrombolysis (CDT)
  • Percutaneous thrombus aspiration
  • Stent placement

extensive ischemia due to high occlusion and when time has passed since its onset, there is a high risk of severe ischemia–reperfusion injury; thus, limb amputation might be necessary to prioritize the patient’s life.

• Hybrid treatment that combines both therapies

Hybrid interventions in vascular surgery are defined as the utilization of both open surgical and endovascular techniques simultaneously in a single setting operation.

Red flags

missing stage 2 presentation

Pit falls –

window period causing peripheral limb loss

Pearls –

prompt mangement in stage -1 will save patient limb

• Daibetic control
• Frequent monitoring of limb