Ann Thorac Surg 2007;84:686-687
© 2007 The Society of Thoracic Surgeons
How To Do It
Three-Digit Allen’s Test
Mohammed Asif, FRCS*,
Pradip K. Sarkar, FRCS
Department of Cardiothoracic Surgery, Northern General Hospital, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom
Accepted for publication November 13, 2006.
* Address correspondence to Dr Asif, Department of Cardiothoracic Surgery, Northern General Hospital, Herries Road, Sheffield, S5 7AU, United Kingdom (Email: m.asif{at}ntlworld.com).
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Abstract
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Hand ischemia after radial artery intervention remains a rare but serious complication. Allen’s test is widely used to assess the adequacy of ulnar collateral circulation to the hand. There have been documented cases of hand ischemia after radial artery intervention even with a negative test. We describe a modification of Allen’s test based on the anatomy of the radial artery branches that could potentially decrease the number of false negative tests.
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Introduction
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The radial artery is a common site for invasive intervention. Cannulation of the radial artery is the gold standard for invasive blood pressure monitoring and serial arterial blood sampling. It is also routinely used for the construction of a radiocephalic arteriovenous fistula for hemodialysis. Procedures such as cardiac catheterization with percutaneous coronary intervention can be performed through the radial artery when the femoral route is contraindicated. Following the work of Acar and colleagues [1] there has been resurgence in the use of the radial artery as a conduit for coronary artery bypass grafting. It is now the arterial conduit of choice after the internal mammary artery [2].
The possibility of hand ischemia after any intervention on the radial artery has made it imperative to establish the adequacy of the ulnar arterial collateral circulation to the hand. Allen [3] first described his test in 1929 but did not indicate a time period after which a test should be deemed positive. Various modifications have been suggested with differing time periods for a positive test ranging from 5 to 15 seconds. We describe a further modification that we believe enhances even further the predictive value of a negative Allen’s test.
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Technique
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The radial artery is located by palpation at the proximal skin crease of the wrist and then compressed with three digits. The ulnar artery is similarly located and then compressed with three digits (Fig 1A). With both arteries compressed, the subject is asked to clench and unclench the hand 10 times (Fig 1B). The hand is then held open, ensuring that the wrist and fingers are not hyperextended and splayed out. The palm is observed to be blanched (Fig 1C). The ulnar artery is released and the time taken for the palm and especially the thumb and thenar eminence to become flush is noted (Fig 1D). If the capillary refill time is greater than 6 seconds we consider the test to be positive and use it as a contraindication to conduit harvest.
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Fig 1. The modified three-digit Allen’s test. (A) The ulnar artery is located by palpation at the proximal skin crease of the wrist and then compressed with three digits. (B) With both arteries compressed the subject is asked to clench and unclench the hand 10 times. The hand is then held open, ensuring that the wrist and fingers are not hyperextended and splayed out. (C) The palm is observed to be blanched. (D) The ulnar artery is released and the time taken for the palm and especially the thumb and thenar eminence to become flush is noted.
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Comment
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We have used this test in more than 600 patients between January 2000 and August 2006 (single surgeon, PKS) prior to harvesting of the radial artery from the nondominant hand for coronary artery bypass grafting. Thus far we have not encountered a single case of postoperative vascular insufficiency to the hand in patients with a negative test. The predictive value of a negative test is 0.8% [4] and therefore we see no reason to substitute more complex examinations. The predictive value of a positive test is only 53% [4]; therefore it requires further investigation. Finger-pulse plethysmography, Doppler flow measurements, and measurement of the systolic arterial pressure in the thumb are alternative methods that can then be used.
When performing the Allen’s test, hyperextension of the hand and wide separation of the fingers can lead to a false positive result (Fig 1C). This is due to occlusion of the transpalmar arch, and parts of the fingers and palm will continue to remain blanched after release of the ulnar artery [5]. To prevent this from occurring the test should be performed with the hand partially open as in Allen’s [3] original description (Fig 1D).
The radial artery has a potentially significant branch proximal to the radial styloid. The palmar carpal branch usually arises near the distal border of pronator quadratus; however it can be given off earlier. It then runs medially to anastomose with the palmar carpal branch of the ulnar artery. It is joined by a branch from the anterior interosseous artery and also by recurrent branches from the deep palmar arch. Together these branches form the palmar carpal arch (Fig 2). If the palmar carpal branch of the radial artery is significant and arises earlier than normal, then the Allen’s test may be falsely negative in the case of ulnar insufficiency. This has been postulated as the mechanism responsible for a false negative Allen’s test prior to radial artery cannulation, which lead to progressive cyanosis of the hand requiring surgical exploration [6]. It is to address this that we routinely perform the Allen’s test using compression with three digits. There have been well documented instances of hand ischemia after radial artery harvest for coronary artery bypass grafting as well as hand ischemia after radial artery cannulation [7, 8]. Although the traditional Allen’s test was negative in many of these cases, the possibility remains of an alternative technique of the test eliciting a different result.
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References
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- Acar C, Jebara VA, Portoghese N, et al. Revival of the radial artery for coronary artery bypass grafting Ann Thorac Surg 1992;54:652-660.[Abstract/Free Full Text]
- Jutley RS, Sarkar PK. Radial artery as a conduit for coronary artery bypass graft Hosp Med 2004;65:589-593.[Medline]
- Allen EV. Thromboangiitis obliterans: methods of diagnosis of chronic occlusive arterial lesions distal to the wrist with illustrative cases Am J Med Sci 1929;178:237-244.
- Husum B, Berthelsen P. Allen’s test and systolic arterial pressure in the thumb Br J Anaesth 1981;53:635-637.[Abstract/Free Full Text]
- Greenhow DE. Incorrect performance of Allen’s test- Ulnar artery flow erroneously presumed inadequate Anesthesiology 1972;37:356-357.[Medline]
- Gandhi SK, Reynolds AC. A modification of Allen’s test to detect aberrant ulnar collateral circulation Anesthesiology 1983;59:147-148.[Medline]
- Manabe S, Tabuchi N, Tanaka H, Arai H, Sunamori M. Hand circulation after radial artery harvest for coronary artery bypass grafting J Med Dent Sci 2005;52:101-107.[Medline]
- Valentine RJ, Modrall JG, Clagett GP. Hand ischemia after radial artery cannulation J Am Coll Surg 2005;201:18-22.[Medline]
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Abstract
Introduction
