Allen test

(ăl′ĕn)


1. A bedside test used to evaluate the patency of the arteries of the hand before arterial puncture. The patient elevates the hand and repeatedly makes a fist while the examiner places digital occlusive pressure over the radial and ulnar arteries at the wrist. The hand will lose its normal pink color. Digital pressure is released from one artery (usually the ulnar), while the other, i.e., the radial, remains compressed. If there is normal blood flow through the unobstructed artery, color should return to the hand within 10 sec. The return of color indicates that the hand has a good collateral supply of blood and that arterial puncture of the compressed artery can be safely performed.
2. A procedure to identify the presence of thoracic outlet compression syndrome caused by tightness of the pectoralis minor muscle. With the patient seated, the examiner abducts the involved shoulder to 90° and flexes the elbow to 90°. While palpating the radial pulse, the examiner externally rotates the humerus while the patient actively rotates the head to the opposite side. A diminished or absent radial pulse is indicative of the pectoralis minor muscle's compressing the neurovascular bundle. This procedure often produces false-positive results.

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ALLEN TEST ; SEE: thoracic outlet compression syndrome.

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