Combining the Modified Allen’s Test and Pulse Oximetry for Evaluating Ulnar Collateral Circulation to the Hand for Radial Artery Catheterization of the ED Patient

Radial artery catheterization for the purpose of continuous blood pressure monitoring and frequent blood gas sampling is regularly performed in the emergency department (ED) and in the intensive care unit (ICU). In the operating room, anesthesiologists generally have the benefit of a conscious and cooperative patient, and the modified Allen’s test can be performed before catheterization of the radial artery to assure adequate collateral circulation. In contrast, patients in the ED and ICU are frequently unable to follow commands due to sedation or to a significantly altered level of consciousness. Under such circumstances the modified Allen’s test cannot be accurately performed and the radial artery is often catheterized without assessing the collateral circulation of the hand. ED and ICU patients are frequently hypotensive and are often being treated with vasoconstricting medication. Furthermore, many of these patients have peripheral vascular disease. Under these circumstances cannulation of the radial artery may carry a greater risk for causing limb ischemia. We discuss how pulse oximetry may be used to perform the modified Allen’s test in these patients to evaluate collateral circulation and potentially reduce the risk of iatrogenic hand injury.