All are true about the Allen's test except:
|A||Is performed by occluding the radial and ulnar arteries and releasing the latter while observing the capillary refill|
|B||Is considered to be normal if capillary refill is noted with in 10-15 seconds|
|C||Test the patency of transpalmar arch|
|D||Is impossible to perform adequately in anaesthetized person|
|E||May produce a false abnormal result with wrist in flexion.|
Is impossible to perform adequately in anaesthetized person
a. Allen's test is done before radial artery cannulation to see the patency of ulnar artery/collateral circulation (trans palmar arch) of hand.
b. In this test after exsanguination of hand, pressure is applied on radial and ulnar artery till hand is blanched from pressure.
c. Now release the ulnar artery still maintaining pressure on radial artery. If ulnar artery is patent the normal colour of hand should return in < 7 seconds. 7-15 seconds is considered border-line and> 15 seconds is abnormal. Acute flexion or extension may produce false results.