How to Perform an Allen Test (Alan B. Lumsden, MD, Cara Chasin, MD)

This session demonstrates the Allen test, a bedside maneuver used to assess adequacy of collateral circulation to the hand via the palmar arch. The radial and ulnar arteries are first identified and simultaneously occluded while the patient repeatedly clenches and relaxes the hand to evacuate blood. Upon opening, the hand should appear blanched, confirming effective occlusion. Release of one artery at a time—first radial, then ulnar—allows assessment of perfusion through each vessel. Rapid return of normal color indicates a patent palmar arch and adequate collateral flow, while delayed or absent reperfusion suggests compromised circulation. This test is essential prior to procedures such as arterial line placement or radial artery harvest, helping reduce the risk of ischemic complications.

KEY LEARNING CONCEPTS
• Indications for Allen test in clinical practice
• Identification and occlusion of radial and ulnar arteries
• Interpretation of blanching and reperfusion
• Assessment of palmar arch patency
• Prevention of ischemic complications

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