The Allen test is a first-line standard test used to assess the arterial blood supply of the hand. This test is performed whenever intravascular access to the radial artery is planned or for selecting patients for radial artery harvesting, such as for coronary artery bypass grafting or for forearm flap elevation.
Buerger's test is used in an assessment of arterial sufficiency
If performed accurately the Allen Test is a very good test to get information about the blood supply of the hand. Normally you have the blood supply of the hand by the ulnar artery (i think 55%) and the radial artery (45%). Both arteries perform two strong connections in the palm - the superficial and the deep palmar arches, which are strong connections between these two arteries. If one of these arteries is closed, the other can supply the whole hand. Normally. In some cases the connections are incomplete or missing or one of the arteries is closed or insufficient.
Before I start the Allen test I perform the Schaefer-Test. The Schaefer Test is to look, if there is a palmaris longus tendon. Patient have to put the tip of the thumb and the tip of the little finger together and then flex the wrist a little bit. that´s the best way to see if there is a palmaris longus tendon or not. If the palmaris longus tendon is missing (8% of all people) then there is a higher change to have vascular variations in the hand (closed ulnar artery, connections of arteries in the palm etc). Then I perform the Allen-Test: about 2-7 cm proximal to the wrist I compress the radial artery of the patient with the 3 fingertips (Index, middle, ring) with my right (left) hand and in the same way the ulnar artery with the other hand. Then the patient have to extent the fingers and make a strong fist for ten times. Then the hand is complete pale. Then I open only one artery (ulnar or radial). The hand is normally pink in some seconds. The same procedure then with the other artery. Ìf the hand is pink in some seconds both arteries are open and both arches are sufficient. If you open one artery and the hand stays pale for more then 20 seconds the artery seems to be not sufficient or closed.
Buergers test is only in the leg. If you are in supine and elevate the leg normally the foot gets pale at 90°. If the leg gets pale at 20 or 30°, the arterial blood supply is not optimal.
Allen's test is to show competancy of the deep palmar arch. First clench the fist and compress both the ulnar and radial arteries at the same time, ensure the hand is not perfused by observation. On releasing either the radial or ulnar artery the hand will instantly reperfuse. If the radial or ulnar artery is incompetent the hand will not reperfuse on the side of the damaged artery.
Buerger's test . With the patient positioned supine, stand at the bottom of the bed and raise both of the patient’s feet to 45º for 1-2 minutes.
2. Observe the colour of the limbs:
- The development of pallor indicates that peripheral arterial pressure is unable to overcome the effects of gravity, resulting in loss of limb perfusion. If a limb develops pallor, note at what angle this occurs (e.g. 25º), this is known as Buerger’s angle.
- In a healthy individual, the entire leg should remain pink, even at an angle of 90º.
- A Buerger’s angle of less than 20º indicates severe limb ischaemia.
3. Sit the patient up and ask them to hang their legs down over the side of the bed:
- Gravity should now aid reperfusion of the leg, resulting in the return of colour to the patient’s limb.
- The leg will initially turn a bluish colour due to the passage of deoxygenated blood through the ischaemic tissue. Then the leg will become red due to reactive hyperaemia secondary to post-hypoxic arteriolar dilatation (driven by anaerobic metabolic waste products).
It's easy and can be performed by alternatively push the radial and ulnar artery and leaving one of them alternatively looking at the capillary refilla at fingertips.
It may be also better assisted by pletismography by the help of an angiologist
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