Acute limb ischaemia
|Acute limb ischaemia|
|Classification and external resources|
Acute limb ischaemia occurs when there is a sudden lack of blood flow to a limb.
Acute limb ischaemia is due to either an embolism or thrombosis. Thrombosis is usually caused by peripheral vascular disease (atherosclerotic disease that leads to blood vessel blockage), while an embolism can be due to air, trauma, fat, amniotic fluid, or a tumor. In the United States, it is estimated to occur in 14 out of every 100,000 people per year. The major cause of acute limb ischaemia is arterial thrombosis (85%), while embolic occlusion makes up 15% of causes. Arterial aneurysm of the popliteal artery has been found to create a thrombosis or embolism resulting in ischaemia. With proper surgical care, acute limb ischaemia is a highly treatable condition; however, prolonged or delayed treatment can result in morbidity, amputation, and/or death. Amputation results from the build up of toxins from cell death distal to the blockage.
The New Latin term ischaemia as written, is a version of the British form of the word ischemia, and stems from the Greek term ichein (meaning, 'to hold'). The Greek root word haima contributes to this definition, meaning 'blood'. In this sense, ischaemia refers to the inhibition of blood flow to/through the limb.
Related ischaemic conditions
In addition to critical limb ischaemia, and acute limb ischaemia, there are several other related ischemic conditions which exist. These include the following:
- Renal ischemia (nephric ischemia)
- Mesenteric ischemia
- Cerebral ischemia
- Cardiac ischemia
- Critical limb ischaemia (CLI), an advanced stage, is defined as the combination of evidence of ischaemia together with any of ischaemic rest pain, non-healing ulcers, or gangrene. CLI is the point at which the lack of blood flow is no longer considered acute, and has crossed a threshold, threatening the sustainability of the limb (or part of the limb). This condition has a negative prognosis within a year after the initial diagnosis, an amputation rate of 14-20% and a death rate of 25% within the first year and 50% within five years.
Signs and symptoms
Acute limb ischaemia can occur in patients through all age groups. Patients that smoke 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:
- Pale in color
- Perishing cold- Freezing cold feeling, a painful cold temperature.
- Paraesthetic feeling such as burning or tingling
Diagnosis and prognosis
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 more quick than MRA. 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 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.
Thrombolysis allows for the treatment of ALI by dissolving the clot through the following methods:
In the past, streptokinase was the main thrombolytic chemical. More recently, drugs such as tissue plasminogen activator, urokinase, and anisterplase have been used in its place. Mechanical methods of injecting the thrombolytic compounds have improved with the introduction of pulsed spray catheters—which allow for a greater opportunity for patients to avoid surgery. Pharmacological thrombolysis requires a catheter insert 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.
Another type of thrombolysis disrupts the clot mechanically using either saline jets or, more recently, ultrasound waves. Saline jets dislodge the clot using the Bernoulli effect. Ultrasound waves, emitted at low frequency, create a physical fragmentation of the thrombus.
Open surgical revascularization involves clamping off arteries and creating a "bypass" around the clot by inserting a graft. This creates an alternate route to allow blood flow around the clot.
Considerations in treatment
The best course of treatment varies from case to case. The physician must take into account the details in the case before deciding on the appropriate treatment. No treatment is effective for every patient.
Treatment depends on many factors, including:
- Location of lesions
- Anatomy of lesions
- Patient risk factors
- Procedural risk
- Clinical presentation of symptoms
- Duration of symptoms
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