Assessment of collateral circulation to the hand is required prior to invasive procedures or harvesting of the radial artery (RA). A modified Allen's test (MAT) is commonly used to assess palmar arch collaterals. A variety of non-invasive methods including digital pressures, plethysmography, pulse oximetry and duplex ultrasonography are available to supplement physical examination. However, no consensus exists about the proper role of the MAT and the most appropriate non-invasive test (NIT) in this situation. Interpretation of the MAT and NIT findings are also controversial. This paper reviews the anatomy and the physiologic basis for the MAT and various NITs, the pros and cons of various NITs and recommendations for the assessment of collateral circulation to the hand prior to interventions directed at the RA.
Purpose
Common reasons for avoiding portable noninvasive vascular laboratory (VL) studies include degraded study quality, repetitive stress injuries, the wear and tear of equipment, and inefficiency. We examined the efficiency of portable VL studies in the context of productivity and potential loss of revenue.
Methods
From January 2005 to March 2005, sonographers in the VL recorded the time required to conduct “in-lab” and portable studies with conventional full-size scanners. A blended average based on frequency of portable studies within different areas of the hospital was used to determine the additional time required to conduct a portable study. The sonographer also made a qualitative assessment on the necessity of the portable study in each case.
Results
The VL performed an average of 31 portable studies (18% of total studies) per week. On average, portable testing increased overall study time by 17.7 min per test and 1.8 h per day, resulting in 9.1 h of additional study time lost per week. The potential increase in study volume could result in incremental annual gross revenue of $41,204 to $77,258 for the VL. The sonographers estimated that 24% to 45% of portable procedures could have been conducted in the lab.
Conclusions
In addition to suboptimal imaging and sonographer/equipment wear and tear, the current practice of unrestricted portable tests performed with existing bulky equipment is economically inefficient. New “disruptive” technology, leading to high-quality bedside scanning and limiting portable studies to patients who genuinely need it, will allow for greater productivity, decrease wait time for elective outpatients, and generate incremental revenue for the VL.
Noninvasive testing for patency and completeness of the palmar arch prior to radial artery (RA) harvesting for coronary revascularization is a frequently requested test in the Vascular Laboratory (VL). The sonographer and interpreting physician must be aware of palmar arch anatomy and common variations in order to provide accurate information and avoid hand ischemia. The RA is a favored conduit for coronary revascularization due to good early and mid-term patency rates, which are superior to vein grafts.(1) Cardiac surgeons need precise information on adequate ulnar artery (UA) collateral circulation prior to harvesting the RA to avoid hand ischemia. Since the reliability of the Allen's test is in dispute, noninvasive assessment in the VL is frequently utilized.
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