How is Allen’s test interpreted?
Allen’s test: determining whether the hand can be perfused by a single artery.
Rationale: Determines whether the hand can be perfused from the ulnar artery alone. This needs to be assessed before performing an arterial puncture (blood gas sampling or arterial line placement) or prior to the formation of an upper limb arteriovenous fistula for haemodialysis.
Compress both ulnar and radial arteries until hand becomes pale.
Maintain compression of radial artery.
Release pressure on ulnar artery.
Observe reperfusion of hand.
Positive test: If the hand becomes warm and pink whilst the radial artery is compressed, the test indicates that flow through the ulnar artery is sufficient to maintain independent perfusion of the hand.
When is a carotid–subclavian bypass performed?
Patients with thoracic aortic arch aneurysms that involve the origin of the left subclavian artery (LSA) may undergo endovascular stenting covering the origin of the LSA. If left arm ischaemia develops, a carotid–subclavian bypass may be performed.
When is a carotid–carotid–subclavian bypass performed?
Patients with more proximal thoracic aortic arch aneurysms may require an endovascular stent which covers the origin of the LSA as well as the origin of the left common carotid artery (LCCA). In these cases a bypass is made from the right to left carotid artery and subsequently from the left carotid to the left subclavian artery. In these circumstances the right carotid supplies the entire anterior circulation of the brain as well that of the left upper limb. The carotid–carotid bypass is palpable anterior to the trachea.
What is thoracic outlet syndrome (TOS)?
Thoracic outlet syndrome refers to neurological or vascular symptoms in the upper limb caused by compression of the brachial plexus, subclavian artery or subclavian vein on their course from the neck to the upper limb.
How does TOS present?
Arterial TOS: thromboembolic events in hand
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
