Collateral Circulation Testing of the Hand– Is it Relevant Now? A Narrative Review

Abstract

Testing for collateral circulation of the hand before any radial artery procedure has been a subject of many controversies. Neither the Allen's test (AT) nor the plethysmography based Barbeau test, adequately and reliably test for collateral circulation. With growing interest in radial approaches for vascular procedures, its common use for arterial monitoring and blood gas sampling, there has been a growing interest in the relevance of assessing collateral hand circulation. Multiple studies now refute the utility of collateral testing, yet it continues to be propagated as an essential triaging assessment tool by educators. Allen's, or modified Allen tests (MAT) are operator dependent and often subjected to observational bias. Barbeau test is more objective, however, it fails to show added benefit in assessing pre-procedural patency. Despite studies questioning the validity of collateral circulation assessment, these tests continue to preclude radial approach. There is no standardization for being considered an abnormal test across literature and the significance of an abnormal test translating into a clinical outcome has not been investigated in prior studies. This may be attributed to the robust vascular supply of the hand, connections at the digital circulation level and vessel recruitment in an event of occlusion. We reviewed this topic extensively and make an argument that non-invasive collateral testing should be abandoned as a triage tool for radial artery procedures such as arterial punctures, arterial monitoring, and transradial vascular procedures.

Introduction

The Allen test (AT) was first described in 1929 and for many years after, was deemed an essential procedure before any radial artery intervention. It was initially described to detect arterial occlusion in thromboanginitis obliterans.^1,2 In a typical AT, the patient was asked to make a fist for one minute to squeeze blood out of the hand. For checking for patency of either the radial or ulnar artery, each artery was compressed individually, and flow through the uncompressed artery was measured by replacement of pallor with capillary blush (Figure 1).³ The test was considered positive if there was no return of rubor. Both hands were examined at the same time. However, false-positive results were noted with this test especially when the hands were hyperextended to more than 20-degrees because of the mechanical compression of the carpal structures or the stretching of the skin. ^4,5 In the 1950s, the test was modified for use by Irving S. Wright and became known as the modified Allen test (MAT). It was specifically used to determine the adequacy of collateral hand circulation.⁶ In MAT, the examiner compresses both arteries when the subject's fists are clenched. When the patient opens the hand, the adequacy of circulation is evaluated upon releasing one of the arteries. Both AT and MAT require a visual assessment of the hand and are often subject to interobserver variation.⁷ Barbeau et al. in 2004 introduced the idea of plethysmography (PL) and pulse oximetry (OX) to objectively measure collateral circulation.⁸ To perform this test, PL and OX were recorded with a pulse oximeter with the clamp sensor applied to the thumb. The PL readings were recorded before and immediately after radial artery compression for 2 min (the 2 min mark was arbitrarily chosen). PL readings were then divided into 4 types: A, no dampening of pulse tracing immediately after radial artery compression; B, dampening of pulse tracing; C, loss of pulse tracing after occlusion and recovery within 2 min; D, loss of pulse tracing without recovery. Oximetry testing was either positive or negative during radial artery compression.⁸ This approach gained traction in the transradial cardiac catheterization field and was termed as the Barbeau test (Figure 2). Reverse Barbeau test is the plethysmographic assessment of blood flow during ulnar artery compression.