QuestionSBA
QuestionChoice
Warfarin is not used in acute limb ischaemia. Commencement of warfarin would delay any surgical intervention that may be necessary due to its long half-life
32471
d
Warfarin
QuestionChoice
Fondaparinux is not used in acute limb ischaemia. It is commonly used for the management of non-ST elevation myocardial infarctions (NSTEMIs)
32472
e
Fondaparinux
QuestionChoice
An unfractionated heparin infusion is preferable to treatment dose LMWH in the management of acute limb ischaemia. As unfractionated heparin has a shorter half-life than LMWH, patients can be taken to theatre more promptly with reduced bleeding risk
32470
c
Low molecular weight heparin (LMWH)
QuestionChoice
Clopidogrel is not used in acute limb ischaemia. Commencement of clopidogrel would delay any surgical intervention that may be necessary due to its long half-life
32469
b
Clopidogrel
QuestionChoice
This patient has signs and symptoms consistent with acute limb ischaemia. The prominent popliteal pulsation suggests that the aetiology may be embolic disease from a popliteal aneurysm. Medical management of acute limb ischaemia is with high flow oxygen and initiation of an unfractionated heparin infusion. Surgical intervention may be necessary depending on classification using the Rutherford system
32468
a
Unfractionated heparin
QuestionComment
in another question it said LMWH..
27328
QuestionComment
I think UFH IV is the right answer, from what I've found
53497
User
subscriber
Intubation Endoscope
User
subscriber
CEM
Concept
Chapter
# Summary


Acute limb ischaemia (ALI) is a severe, symptomatic hypoperfusion of a limb, typically presenting for less than 2 weeks. This condition is a surgical emergency demanding immediate intervention, ideally within 4-6 hours of presentation. The key signs and symptoms are summarised by the mnemonic "6Ps": pulseless, pain, pallor, paralysis, paraesthesia, and poikilothermia. Important investigations include complete blood count, U&E, group and save, clotting, and ECG. The management of ALI depends on the cause, with strategies varying for thrombotic and embolic causes. In some cases, limb amputation may be necessary.


# Definition


Acute limb ischaemia (ALI) is a severe, symptomatic hypoperfusion of a limb that has been occurring for less than 2 weeks. Although the definition specifies a 2-week period, this condition is considered a surgical emergency and demands urgent intervention, ideally within 4-6 hours, however, missed or delayed diagnosis is common. 


# Epidemiology


In the United Kingdom, acute limb ischaemia (ALI) is not uncommon and presents a significant clinical challenge. Although exact figures vary, incidence rates are estimated at approximately 14 cases per 100,000 persons annually. The condition is more prevalent in older populations, with the majority of cases occurring in individuals over the age of 60. Additionally, factors such as smoking, diabetes, and other forms of cardiovascular disease increase the risk of ALI.


# Aetiology


Acute limb ischaemia can be caused by:


- Thrombosis (80-85%):
- This often results from the rupture of atherosclerotic plaques.
- Cardiac or aortic embolisation 
- This accounts for approximately 10-15% of cases. 
- Seen due to atrial fibrillation or mural thrombus formation post-myocardial infarction. 
- Aortic dissection
- Hypercoagulable states 
- Thrombosis of a pre-existing graft 
- Vasospasm - such as observed in Raynaud's phenomenon.
- External vascular compromise:
- Trauma
- Compartment syndrome


Acute limb ischaemia secondary to thrombosis typically has a sub-acute onset and is associated with features of peripheral vascular disease in the contralateral limb. In contrast, ALI secondary to embolisation has a more acute onset and often results from atrial fibrillation.

Risk factors for acute limb ischaemia are similar to those of general cardiovascular risk factors, such as:

- Smoking
- Diabetes mellitus
- Obesity
- Older age
- Hypertension
- Hypercholesterolaemia

The absence of risk factors for acute limb ischaemia should not exclude ALI from the differential diagnosis, as it can be seen in individuals in the absence of risk factors. 


# Classification 

The Rutherford Classification system is commonly used to grade the severity of acute limb ischaemia.

|**Rutherford Class**|**Sensory Impairment**|**Motor Impairment**|**Doppler Signals**|
|----------------------------|--------------------------------------------------------|----------------------------|------------------------------------------|
|**Class 1**|None|None|**Arterial:** Audible <br> **Venous:** Audible|
|**Class 2a**|Minimal|None|**Arterial:** Audible <br> **Venous:** Audible|
|**Class 2b**|Involves forefoot with possible rest pain|Mild to moderate|**Arterial:** Absent <br> **Venous:** Present|
|**Class 3**|Insensate|Severe, rigorous|**Arterial:** Absent <br> **Venous:** Absent|



# Signs and Symptoms

Acute limb ischaemia most commonly occurs in the lower limbs, but can also occur elsewhere in the body, including the upper limb. 

The signs and symptoms of ALI are represented by the mnemonic "6Ps":


- **Pulseless**
- Peripheral pulses may be difficult to palpate or impalpable.
- **Painful**
- The pain is described as constant and severe. It occurs at rest. 
- If it is worse on passive movement, this may be a sign of compartment syndrome, a severe complication of acute limb ischaemia. 
- **Pallour**
- The limb may also have cyanosis or mottling. 
- **Poikilothermia**
- This is also referred to as "perishingly cold" 
- **Paraesthaesia**
- Loss of sensation occurs before loss of motor power due to the smaller diameter of sensory nerves compared to motor nerves. 
- **Paralysis**
- Patients may have a reduction or complete loss of muscular power. 


If a limb has already lost motor and sensory function, which are late signs seen in acute limb ischaemia, it is generally considered unsalvageable.

### Distinguishing Signs and Symptoms based on Cause

The signs and symptoms of acute limb ischaemia vary slightly depending if the underlying cause is embolism or thrombosis.

|**Characteristic**|**Thrombosis-Related ALI**|**Embolism-Related ALI**|
|----------------------------------------|-------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------|
|**Onset**|Gradual onset. Chronic peripheral arterial disease stimulates collateral vessel development.|Acute onset symptoms.|
|**Ischemia Border**|No clear border of ischemia due to the presence of chronic peripheral arterial disease.|Well-demarcated area of ischemia, may have a mottled appearance.|
|**Appearance of Unaffected Limb**|Signs of peripheral arterial disease, such as ulcers and reduced pulses, likely present.|Vascular exam of the other leg is typically normal.|



# Differential Diagnosis


The main differential diagnoses for acute limb ischaemia include:


- **Critical Limb Ischaemia**: This is limb ischaemia which has been occurring for more than 2 weeks. It will also have reduced or absent pulses, but will have ulcers and signs or gangrene. These limbs may have a pink colouration due to collateral formation and compensatory vasodilation surrounding the stenosis. 
- **Compartment syndrome** - Symptoms typically include severe pain, pallor, paresthesia, pulselessness, and paralysis.
- **Deep vein thrombosis (DVT)** - Symptoms can include unilateral leg swelling, pain, and redness.
- **Raynaud's phenomenon** - Symptoms are episodic and include pallor, cyanosis, and rubor in response to cold or stress.




# Investigations


Initial investigations should include:

- Handheld Doppler ultrasound to determine arterial flow of peripheral vessels
- This can be used to calculate the ankle-brachial index (ABI). This is where blood pressure is calculated in the ankle and the arm, and then applied to the following equation to determine the ABI. 
- ABI = Highest ankle systolic pressure (dorsalis pedis or posterior tibial) / Highest brachial systolic pressure (left or right arm)
- < 0.7 is indicative of poor prognosis 
- ECG
- This is particularly useful to detect atrial fibrillation, suggesting an embolic cause for ALI.
- Bloods to include:
- Full blood count (FBC), urea and electrolytes (U&E), creatinine kinase, blood grouping and save, clotting profile

Imaging may include:

- Digital subtraction angiogram (DSA)
- This is considered the standard investigation as it allows determination of the cause of the ischaemia and management can be initiated at the same time. 
- Crescent-shaped occlusion, also referred to as the meniscus sign suggests embolic cause 
- Thrombotic ALI is associated with atherosclerosis of other vessels and the presence of collaterals
- Duplex Doppler ultrasound
- CT angiogram 
- Enables visualisation of arteries perfusing the lower limb, however, is contraindicated in those with poor renal function due to the use of dyes. 
- MR angiogram 
- This also uses a dye as during the arterial phase of a contrast bolus the arteries can be visualised. 


# Management

Acute limb ischaemia is a medical emergency which requires urgent assessment by a vascular surgeon.

In all cases, all patients should be kept nil by mouth in preparation for potential surgical interventions. Whilst awaiting definitive management, the patient should have:

- Intravenous heparin to prevent thrombus propagation (dependent on local protocols and based on surgeons' advice)
- Oxygen 
- Analgesia
- NSAIDs should typically be avoided as many patients are vasculopaths and NSAIDs have an associated risk of cardiovascular events.
- Intravenous fluids 
- Patients are commonly dehydrated, and risk renal damage due to the release of intracellular components.

### Definitive Management 

The management of acute limb ischaemia varies based on the patient's comorbidities, underlying cause and severity and duration of symptoms. Management options include:

- Endovascular techniques such as:
- Percutaneous catheter-directed thrombolysis 
- Thrombolytic drugs (i.e. alteplase) are used to dissolve the thrombus. 
- Percutaneous mechanical thrombectomy 
- The thrombus is removed using endovascular tools. 
- Surgery may be indicated due to severity or if endovascular techniques have failed. Options include:
- Surgical thromboembolectomy
- Endarterectomy
- Bypass surgery 
- The occluded vessel is bypassed using a graft to restore perfusion. 
- Fasciotomies
- These are commonly performed prophylactically for severe ALI with a high risk of developing compartment syndrome. 
- Amputation 
- Used when the limb is considered to be non-viable or if other treatments have failed. 


### Use of Rutherford Classification

Acute limb ischaemia can be further classified according to the Rutherford criteria, which can help stratify management:

* Stage I: Viable limb. There is an arterial signal that can be picked up with Doppler.
* Stage IIa: Mild sensory deficit and no motor deficit.
* Stage IIb: Severe sensory deficit; usually more than just the toes. There may also be rest pain and a motor deficit. 
* Limb salvage depends on immediate treatment.
* Fasciotomies are often required.
* Stage III: Irreversibly non-viable limb.
* Sometimes patients with stage III undergo amputation due to significant risk of complications such as reperfusion injuries and high mortality. 
* Very early treatment can rarely result in some degree of reversal.


### Follow Up

Following the immediate management of an acutely ischaemic limb, follow-up should include:

- Smoking cessation advice
- Management of diabetes if present
- Diet and exercise advice for weight loss 
- Lipid-lowering therapy should be considered 
- Use of anti-platelet agents for those with peripheral arterial disease should be started long-term 


# Complications

Individuals with ALI risk having the following complications:

- Reperfusion injury:
- Ischaemia causes tissue death. When perfusion is restored to the limb, potassium and hydrogen ions can be released, resulting in hyperkalaemia and acidosis. 
- Hyperkalaemia can result in weakness and cardiac arrhythmias. 
- Damage to the muscle causes the release of myoglobin, which can cause acute kidney injury. 
- Compartment syndrome: 
Reperfusion of previously ischaemic tissue can cause oedema. This increases the pressure within a restricted fascial compartment, resulting in compartment syndrome. 
- This is an emergency which requires urgent fasciectomy to treat and reduce the loss of muscle. 
- Peripheral nerve injury:
- Prolonged ischaemia can result in long-term damage to the nerves, resulting in chronic pain pathology. 
- Amputation:
- If not diagnosed and treated within a timely manner, the limb may require amputation. 
- This is more common in cases caused by thrombosis due to the underlying peripheral arterial disease.


# Prognosis

Acute limb ischaemia is associated with an up to 20% mortality rate, which is often the result of reperfusion injury. A poorer prognosis is associated with more severe arterial disease and prolonged time to perfusion. This is seen as prolonged ischaemia time is associated with higher rates of amputation, as a 24-hour delay between symptom onset and reperfusion is associated with a 20% amputation rate. 

# NICE Guidelines

[NICE Guidelines Peripheral Arterial Disease](https://bestpractice.bmj.com/topics/en-gb/431?q=Peripheral%20arterial%20disease&c=recentlyviewed) 


# References

[NHS Peripheral Arterial Disease](https://www.nhs.uk/conditions/peripheral-arterial-disease-pad/) 

[BMJ Best Practice Peripheral Arterial Disease](https://bestpractice.bmj.com/topics/en-gb/431?q=Peripheral%20arterial%20disease&c=recentlyviewed) 

[Royal College of Emergency Medicine: Acute Limb Ischaemia](https://www.rcemlearning.co.uk/reference/acute-limb-ischaemia/) 

[European Society for Vascular Surgery 2020 Guidelines](https://esvs.org/wp-content/uploads/2021/08/Acute-Limb-Ischaemia-Feb-2020.pdf) 

[Patient Info: Limb Embolism and Ischaemia](https://patient.info/doctor/limb-embolism-and-ischaemia)
789
828
Acute limb ischaemia
Topic
126
Vascular Surgery
Video
Concept
828
Acute limb ischaemia
12
XJvR3iz
images/videos/surgery.png
Acute limb ischaemia
Video
Concept
828
Acute limb ischaemia
315
eNd6PcR
images/videos/surgery.png
Quesmed Tutorial: General and Vascular Surgery SBAs 
6494
Medical management of acute limb ischaemia is with high flow oxygen and initiation of an unfractionated heparin infusion.
A 56-year-old man with a background of type 2 diabetes, hypertension and ischaemic heart disease presents with a cold and painful left foot.

He reports that the symptoms came on suddenly around two hours ago. On examination, the left foot is pale and cold with absent dorsalis pedis and posterior tibial pulses; however, a prominent popliteal pulse is detected. Sensation and movement of the foot are preserved.

Which of the following is the most appropriate intervention whilst awaiting diagnostic imaging?
a