Radial artery cannulation

The radial artery is most frequently chosen because it is accessible and has good collateral blood flow. Allen's test, used to confirm the ulnar arterial blood supply, is not reliable.

Technique of cannulation

The wrist is hyperextended and the thumb abducted. After skin cleansing local anaesthetic (1% plain lidocaine) is injected into the skin and subcutaneous tissue over the most prominent pulsation. The course of the artery is noted and a 20G Teflon cannula is inserted along the line of the vessel. The usual technique is to enter the vessel in the same way as an intravenous cannula would be inserted. There is usually some resistance to skin puncture. To avoid accidentally puncturing the posterior wall of the artery, the skin and artery should be punctured as two distinct manoeuvres. Alternatively, a small skin nick may be made to facilitate skin entry.

In the case of elderly patients with mobile, atheromatous vessels a technique that involves deliberate transfixation of the artery may be used. The cannula is passed through the anterior and posterior walls of the vessel, thus immobilising it. The needle is removed and the cannula withdrawn slowly into the lumen vessel, before being advanced forward.

Seldinger-type kits are also available for arterial cannulation. A guidewire is first inserted through a rigid steel needle. The indwelling plastic cannula is then placed over the guidewire.

The cannula should be connected to a continuous flushing device after successful puncture. Flushing with a syringe should be avoided since the high pressures generated may lead to a retrograde cerebral embolus.

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