Allens test for integretiy of palmar arch tests which of the following?

ANSWER: (C) BothREF: Harrison's 18th ed chapter 230Repeat from December 2010 CET PrimaryAllen's test, also Allen test, is used to test blood supply to the hand, specifically, the patency of the radial and ulnar arteries. It is performed prior to radial arterial blood sampling or cannulationAlien s test is also performed prior to heart bypass surgery. The radial artery is occasionally used as a conduit for bypass surgery, and its patency lasts longer in comparison to the saphenous veins. Prior to heart bypass surgery, Allen's test is performed to assess the suitability of the radial artery to be used as a conduitThe modified Allen TestThe 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 arteries 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 artery supply to the hand is sufficient and it is safe to cannulate/prick the radialIf color does not return or returns after 7-10 seconds, the test is considered positive and the ulnar artery supply to the hand is not sufficient. The radial artery therefore cannot be safely pricked/cannulated.