Which artery is released first in the Allen test procedure?

In the Allen test procedure, the first artery released is the ulnar artery. This test is performed to evaluate the collateral circulation of the hand. The clinician will apply pressure to both the radial and ulnar arteries simultaneously while the patient makes a fist. This action occludes the blood flow. Once the fist is opened and the clinician observes the color of the hand, the ulnar artery is released first.

Releasing the ulnar artery allows for the assessment of whether adequate blood flow is restored to the hand through the radial artery. If the hand flushes back to a normal color quickly, it indicates that there is sufficient collateral circulation through the ulnar artery to supply the desired blood flow. This is crucial for determining the safety of procedures that may compromise the radial artery, such as arterial line placements or certain vascular interventions.

Proceeding to keep the radial artery compressed while watching the color change allows for further assessment of perfusion status. Thus, the focus on the ulnar artery during the initial release emphasizes its vital role in collateral blood flow, making it the correct artery to release first in this test.