Indications

Allen’s test is used to determine the efficiency of the ulnar arterial collateral circulation (blood flow) to the hand. This test is often used before interventions like arterial blood gas (ABG) assessment, before obtaining blood samples for laboratory purposes and before invasive blood pressure monitoring is done.

Procedure

  1. Place the hand in a position wherein the palm is facing forward.
  2. Find the radial and the ulnar pulses. The radial artery is found below the thumb along the proximal skin crease of the wrist. The ulnar artery is found below the smallest finger along the proximal crease of the wrist.
  3. With your fingers and thumb, compress the radial and the ulnar pulses firmly.
  4. Tell the patient to make a fist with the hand and open it for ten times. After clenching and unclenching the hand, the palm should turn pale.
  5. Release your fingers and thumb from the radial and ulnar pulses and count how many seconds it takes for the palm and the thumb to return to their normal pink color.
Allen's test for the hand

Locate the ulnar and radial pulses and firmly place your fingers over the pulses.

For sedated patients and for those who are unable to follow instructions, the Allen’s test is used together with a pulse oximeter.

  1. Place the hand in a position wherein the palm is facing forward.
  2. Attach the pulse oximeter to any finger of the hand.
  3. Find the radial and the ulnar pulses. The radial artery is found below the thumb along the proximal skin crease of the wrist. The ulnar artery is found below the smallest finger along the proximal crease of the wrist.
  4. Use your fingers and thumb to compress the radial and ulnar pulses firmly. You will know that you are applying a firm pulse when there is no wave on the pulse oximeter monitor.
  5. Release your fingers from the ulnar artery and count the seconds for the pulse oximeter wave form to return on the monitor.

Interpretation

Positive Allen’s Test

Within 3 to 5 seconds, the palm returns to its normal pink color; this means that the artery is patent. If using a pulse oximeter, within 3 to 5 seconds, the pulse oximeter wave form returns completely; this means the ulnar artery is patent.