Allen's test is used to detect the patency of which of the following ?

Allen's test, also Allen test, is used to test blood supply to the hand, specifically, the patency of the radial and ulnar aeries. It is performed prior to radial aerial blood sampling or cannulation. Allen's test is also performed prior to hea bypass surgery. The radial aery is occasionally used as a conduit for bypass surgery, and its patency lasts longer in comparison to the saphenous veins. Prior to hea bypass surgery, Allen's test is performed to assess the suitability of the radial aery to be used as a conduit. The modified Allen's Test *The hand is elevated and the patient/person is asked to make a fist for about 30 seconds. *Pressure is applied over the ulnar and the radial aeries so as to occlude both of them. *Still elevated, the hand is then opened. It should appear blanched (pallor can be observed at the finger nails). *Ulnar pressure is released and the color should return in 7 seconds. Inference: Ulnar aery supply to the hand is sufficient and it is safe to cannulate/prick the radial If color does not return or returns after 7-10 seconds, the test is considered positive and the ulnar aery supply to the hand is not sufficient. The radial aery therefore cannot be safely pricked/ cannulated.