Exam

Allen Test

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Allen Test, Allen's Test, Wrist Collateral Circulation

  • Epidemiology
  1. Inadequate collateral flow in 3% hospitalized patients
  • Causes of Inadequate Ulnar Circulation
  1. Normal anatomic variant
  2. Hypothenar Hammer Syndrome
  • Indications
  1. Test wrist collateral Blood Flow
  2. Arterial Puncture for Arterial Blood Gas
  • Technique
  1. Patient elevates hand and makes a fist for 20 seconds
  2. Firm pressure held against radial and ulnar arteries
  3. Patient opens hand and should blanche white
  4. Examiner releases only ulnar compression
  • Normal Result
  1. Hand color flushes within 5 to 7 seconds
  • Abnormal result
  • Inadequate collateral circulation
  1. Hand remains white until radial pressure released
  2. Risk of serious hand ischemia if radial vessel spasm
  • Alternative means for assessing collateral circulation
  1. Doppler Ultrasound
  2. Finger plethysmography