Acute upper limb ischemia occurs when there is a sudden deterioration of blood supply to the upper arm. Besides trauma and iatrogenic causes, the two main causes of acute limb ischemia are embolism and thrombosis within blood vessels. Embolism results when non dissolvable material pass on to finer arteries and occlude the lumen.
Hence blood cannot circulate as physiologically needed. The main source of emboli is usually from the left atrium of the heart which is mainly due to fibrillation and mural thrombus. The other source is from proximal large artery arteriosclerotic debris which can dislodge and occlude smaller arteries.
Thrombosis, is caused by progressive atherosclerotic obstruction, hypercoagulability, and dissection of arteries. Atherosclerosis is a chronic process which lead to progressive arterial lumen narrowing. Atherosclerotic plaque can also develop in the upper limb arteries and develop acute thrombosis if the plaques is dislodged and lands on the already narrowed artery. This is better explained in Fig 1.
Fig. 1: Formation of Atherosclerotic plaques-The process
Acute upper limb ischemia(AULI) is one of the most difficult challenges that a vascular surgeon may face. The initial assessment and diagnosis are largely done clinically.
Patients often present with numbness, pain and a cold arm. Diagnosing AULI is mainly clinical but it is usually confirmed by an arterial duplex or CT angiogram scan.
Acute upper limb ischemia is an uncommon vascular emergency; however, it can lead to severe morbidity if patient don’t get treated successfully. The main cause of AULI is due to sudden arterial occlusion as a result of embolic events, thrombotic events, trauma, arterial dissection and aneurysm.
Clinically the features of AULI is similar to lower limb ischemia which is the known as the 6 P’s which is Pulselessness, Pain, Pallor, Parasthesia, Paralysis and Perishing cold. Normally the patient would have 6 hours from the time of onset of symptoms so that treatment could be started.
A number of studies have shown that the most common site of acute arterial occlusion is at the brachial artery (61%), axillary artery (23%), radial and ulna artery (23%) and subclavian artery (11.7%).
After initial anticoagulation the arm often improves and a decision performing a surgical embolectomy can be difficult. 50% of patients may have persistent late symptoms of arm pain if they are treated only conservatively. However, when in doubt if limb is threatened with compromised viability an urgent embolectomy should be performed. Should the patient not fit enough, it should be done under local anaesthesia.
There are a number of modalities of treatment for acute upper limb ischemia. They are as follows: Surgical thromboembolectomy, Surgical by pass using vein graft or synthetic graft, catheter driven thrombolysis, percutaneous aspiration thrombectomy, mechanical thrombectomy and medical management.
There is a lack of evidence about the management of acute upper limb ischemia (AULI). The studies that have been done so far are mostly observational studies of small cohort of patients. AULI has been found out to only 2-18% of the total number of procedures for limb ischemia. Despite prompt diagnosis and management, studies have shown that the rate of amputation and death is usually quite high in contrast to other major vascular interventions.
In the recent past, AULI can be treated by various endovascular procedures apart from conservative management with or without open surgery. Given the various treatment modalities, this systematic review focuses on the first line treatment of acute upper limb ischaemia. Therefore, a good clinical assessment of upper limb and a management guideline from bigger studies is of vital importance.
By Dr Raj Seeburrun, vascular surgeon in UK.