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08/06/2014 13:19Allen's test - Wikipedia, the free encyclopedia

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Arteries of the hand

Allen's testFrom Wikipedia, the free encyclopedia

In medicine, the Modified Allen's test , also the Modified Allen test ,

1. The hand is elevated and the patient/person is asked to make a

fist for about 30 seconds.

2. Pressure is applied over the ulnar and the radial arteries so as

to occlude both of them.

3. Still elevated, the hand is then opened. It should appear

blanched (pallor can be observed at the finger nails).

4. Ulnar pressure is released and the colour should return in 7

seconds.

If color returns as described above, the Allen's test is considered tobe "positive." If color fails to return, the test is considered "negative"and the ulnar artery supply to the hand is not sufficient. The radialartery therefore cannot be safely pricked/cannulated.

Anatomical basis

The hand is normally supplied by blood from the ulnar and radial arteries. The arteries undergo anastomosisin the hand. Thus, if the blood supply from one of the arteries is cut off, the other artery c an supply adequateblood to the hand. A minority of people lack this dual blood s upply.

Significance

An uncommon complication of radial arterial blood sampling/ cannulation is disruption of the artery(obstruction by clot), placing the hand at risk of ischemia. Tho se people who lack the dua l supply are atmuch greater risk of ischemia. The risk can be reduced by per forming Allen's test beforeh and. People whohave a single blood supply in one hand often have a dual supp ly in the other, allowing the practitioner totake blood from the side with dual supply.

Allen's test is also performed prior to heart bypass surgery. Th e radial artery is occasional ly used as acond uit for b ypass surgery, and its patency lasts longer in com parison to the saphenous ve ins. Prior to heartbypass surgery, Allen's test is performed to assess the suitability of the radial artery to be used as a conduit.A result of less than 3 seconds is considered as good and suitable. A result of between 3-5 seconds isequivocal, whereas the radial artery will not be considered for grafting if the result is longer than 5 seconds.

The utility of the Allen's test is questionable, [1] and no direct correlation with reduced ischemiccomplications of radial artery cannulation have ever been proven. In 1983, Slogoff and colleagues reviewed1,782 radial artery cannulations and found that 25% of them resulted in complete radial artery occlusion,

without apparent adverse effects. [2] A number of reports have been published in which permanent ischemic

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8/12/2019 Allen's Test (Wikipedia)

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08/06/2014 13:19Allen's test - Wikipedia, the free encyclopedia

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sequelae occurred even in the presence of a normal Allen's test. [3][4] In addition, the results of Allen's tests

do not appear to correlate with distal blood flow as demonstrated by fluorescein dye injections [5][6]

Modifications to the test have been proposed to improve reliability. [7]

References1. ^ Jarvis MA, Jarvis CL, Jones PR, Spyt TJ (October 2000). "Reliability of Allen's test in selection of patients for

radial artery harvest" (http://linkinghub.elsevier.com/retrieve/pii/S0003-4975(00)01551-4). Ann. Thorac. Surg. 70

(4): 13625. doi:10.1016/S0003-4975(00)01551-4 (http://dx.doi.org/10.1016%2FS0003-4975%2800%2901551-4).

PMID 11081899 (https://www.ncbi.nlm.nih.gov/pubmed/11081899).

2. ^ Slogoff, S; Keats AS; Arlund C (1983). "On the safety of radial artery cannulation.". Anesthesiology 59: 427.

doi:10.1097/00000542-198307000-00008 (http://dx.doi.org/10.1097%2F00000542-198307000-00008).

3. ^ Thompson, SR; Hirschberg A (1988). "Allen's test re-examined.". Crit Care Med 16: 915.

4. ^ Wilkins, RG (1985). "Radial artery cannulation and ischaemic damage: A review.". Anaesthesia 40: 896899.doi:10.1111/j.1365-2044.1985.tb11055.x (http://dx.doi.org/10.1111%2Fj.1365-2044.1985.tb11055.x).

5. ^ McGregor, AD (1987). "The Allen test an investigation of its accuracy by fluorescein angiography.". J Hand

Surg (BR) 12: 8285. doi:10.1016/0266-7681(87)90065-9 (http://dx.doi.org/10.1016%2F0266-

7681%2887%2990065-9).

6. ^ Stead, SW; Stirt JA (1985). "Assessment of digital blood flow and palmar collateral circulation.". Int J Clin Monit

Comput 2: 29. doi:10.1007/bf02915870 (http://dx.doi.org/10.1007%2Fbf02915870).

7. ^ Asif M, Sarkar PK (August 2007). "Three-digit Allen's test" (http://linkinghub.elsevier.com/retrieve/pii/S0003-

4975(06)02283-1). Ann. Thorac. Surg. 84 (2): 6867. doi:10.1016/j.athoracsur.2006.11.038(http://dx.doi.org/10.1016%2Fj.athoracsur.2006.11.038). PMID 17643672

(https://www.ncbi.nlm.nih.gov/pubmed/17643672).

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