Allen test

Indications

• the Allen test is done prior to obtaining samples of arterial blood from the radial artery for arterial blood gas analysis.
• this is to ensure adequate collateral circulation prior to puncturing the radial artery

Procedure

• with the patient resting, palms up, ask the patient to make a fist with one hand
• compress both the radial artery & ulnar artery between your thumbs & fingers
• ask the patient to open his/her hand
• the palm should be pale in color
• release the pressure over the ulnar artery
• the palm should flush in about 3-5 seconds if the ulnar artery is patent
• patency of the radial artery may be checked by repeating the procedure, instead releasing pressure over the radial artery

More general terms

• physical examination technique

Additional terms

• arterial blood gas (ABG)