Eur J Cardiothorac Surg 2002;21:549-552
© 2002 Elsevier Science NL
The radial hyperaemic response: a new and objective assessment of ulnar collateral supply to the hand
N. Roberts,
S. Ghosh,
M. Boehm,
M. Galiñanes*
Division of Cardiac Surgery, University Hospitals Leicester, Glenfield Hospital, Groby Road, Leicester, LE3 9QP, UK
Received 16 September 2001;
received in revised form 6 December 2001;
accepted 21 December 2001.
* Corresponding author. Tel.: +44-116-256-3031; fax: +44-116-250-2449
e-mail: mg50{at}le.ac.uk
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Abstract
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The assessment of adequate ulnar collateral supply to the hand is mandatory prior to the harvest of the radial artery as a conduit for coronary artery bypass grafting. However, there is currently no one test which is widely used in all centres. We report a new and objective method of assessing ulnar collateral supply to the hand prior to harvest of the radial artery. This technique involves assessing the presence of a hyperaemic flow response to occlusion of the radial artery using an intraoperative transit time flowmeter. We found this technique to be objective and reliable, and would advocate its use in patients with a positive Allen's test.
Key Words: Radial artery • Allen's test • Conduit • Transit time • Flowmeter
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1. Introduction
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The radial artery is gaining in popularity due to encouraging mid term patency results [1]. However, there continues to be concern that radial artery harvest may lead to post-operative hand ischaemia and there is currently no one, widely used test which accurately identifies those patients at risk of ischaemia whilst allowing safe radial artery harvest in all others.
Currently the most commonly used is the modified Allen's test [2]. However, this test is subjective, requires patient co-operation and has been shown to be unreliable in multiple studies [3–5]. Despite this, due to its ease of performance and the reported good results when used as a primary screening test, the modified Allen's test continues to be used in many centres.
We report an objective method for assessing ulnar collateral circulation to the hand using intra-operative transit time flow assessment of hyperaemic responses to arterial occlusion and its comparison to a modified Allen's test.
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2. Subjects and methods
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Fifty-two patients undergoing first time coronary artery bypass grafting entered the study between June 2000 and May 2001. Local ethical committee approval was granted for the study and informed consent obtained.
All patients had a modified Allen's test (MAT) performed pre-operatively. Time to capillary return to the palm of the hand was noted in seconds. The test was deemed positive if blanching of the palm persisted for 7 s or longer.
All patients had radial arteries explored via a small 2–3 cm incision distally and the artery exposed with minimal handling. A transit time flow meter probe (Medistim, Norway) was then passed around the artery and baseline flow measured. The transit time flow principle has been well documented by previous authors as have the techniques for accurate flow measurements which were followed [6].
A standard flow measurement protocol was then followed, firstly both radial and ulnar arteries were occluded by digital pressure distal to the probe for 1 min and then on release of digital pressure the flow-through the radial artery was measured. The flow was allowed to return to baseline and then the radial artery alone was occluded by digital pressure distal to the probe for 1 min and then on release, flow-through the radial artery again was recorded. If suitable the radial artery was harvested as a pedicle and haemostatic clips used on all branches.
All patients were seen in the outpatient clinic between 6 and 8 weeks post-operatively when arms were examined for signs of ischaemia.
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3. Results
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Of the 52 patients studied, nine had positive modified Allen's tests. In the Allen's test-negative group of patients the hyperaemic response seen following the 1-min occlusion of both the radial and ulnar arteries was not seen when the radial artery was occluded alone. In patients with positive modified Allen's test, two distinct groups were identified. As seen in Fig. 1
, four of the nine patients exhibited a hyperaemic response following the occlusion of the radial artery alone that was similar to that seen after occlusion of both forearm arteries. The flow response of the remaining five patients shown in Fig. 2
was similar to the patients with negative modified Allen's test (data not shown).
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Fig. 1. Blood flow in in situ radial arteries following the occlusion of both the radial and the ulnar arteries or the radial artery alone in patients with positive modified Allen's tests in whom the radial artery was not used as a coronary bypass graft conduit (n=4).
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Fig. 2. Blood flow in in situ radial arteries following the occlusion of both the radial and the ulnar arteries or the radial artery alone in patients with positive modified Allen's tests in whom the radial artery was used as a coronary bypass graft conduit (n=5). *P<0.05 vs. corresponding radial artery alone occlusion group.
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If a hyperaemic response was elicited to radial artery occlusion alone, the ulnar collateral supply was deemed inadequate and the radial artery was not harvested. If no hyperaemic response was elicited to radial occlusion alone, the radial artery was harvested independently of the modified Allen's test result.
There were no complications of hand ischaemia in any of the arms in which radial arteries were harvested.
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4. Discussion
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It is agreed throughout the cardiac surgical community that some assessment of adequate ulnar collateral supply to the hand should be used prior to harvest of the radial artery. There is, however, no consensus on how this should be achieved. Historically the Allen's test has been used but this has received wide-ranging criticism for its subjectivity and potential false-negative and false-positive results.
There are many reports of no ischaemic complications following harvest of radial arteries with normal Allen's tests [2,7] and this would suggest the usefulness of the Allen's test as a simple primary screening test, a view supported by our results and by Ruengsakulrach et al. [8]. When presented with a positive Allen's test (e.g. beyond 6–10 s) the operating surgeon has the choice of further evaluation of ulnar collateral supply to the hand or rejection of the radial artery as a conduit. The latter strategy will undoubtedly deprive some patients of the potential benefit of an arterial graft in patients not at risk of hand ischaemia. Our study has shown that more than half of the patients with a positive Allen's test did not have a hyperaemic flow response to radial artery occlusion alone (Fig. 2), and these patients went on to have their radial artery harvested without ischaemic complications.
Our study suggests that transit time flow assessment of the radial hyperaemic response is a safe and objective method of assessing ulnar collateral supply to the hand using readily available technology and its use in patients with a positive Allen's test is advisable.
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Footnotes
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Presented at the joint 15th Annual Meeting of the European Association for Cardio-thoracic Surgery and the 9th Annual Meeting of the European Society of Thoracic Surgeons, Lisbon, Portugal, September 16–19, 2001.
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Appendix A. Conference discussion
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Dr C. Muneretto (Brescia, Italy): We currently use the radial artery in a great majority of our patients. We did more than 500 radial arteries in this way without any complication. My question is, do you evaluate at baseline this radial artery only with the Allen's test or do you associate the Allen's test, for example, to a Doppler measurement of the lump ulnar flow or to a pulse oximetry at the end?
Mr Roberts: We only evaluated with the transit time flowmeter around the artery. We didn't use any other methods apart from the traditional Allen's test and the transit time flowmeter.
Mr D. Ngaage (Leeds, UK): The radial artery can be sensitive and once you put your probe around it, it goes into spasm and can give a false reading on your flowmeter. Realizing this, how did you treat the radial artery?
Secondly, I would like to know for how long you followed up these patients. You said there was no complication in both patients. Did the group of patients with a positive Allen's test and the flowmeter and hyperemic test showed that you could use their radial artery have any complications?.
Mr Roberts: Firstly, we didn't find that the radial artery went into spasm. We only dissected out maybe 1 cm around the other side. If anyone has used the transit time flowmeter for measuring flow through coronary grafts, if you apply a lot of gel around, then it didn't stimulate the radial artery to spasm in any way.
And secondly, there were no complications of ischemia in the Allen's test positive patients. The assessment of those patients was purely clinical; we asked the patients if they had any symptoms. And as has been described and in some recent publications, one can detect minor abnormalities of hand gripping in anyone who has had a radial artery harvested, but in all the tests that we have looked at, in all the papers that we have looked at, symptoms following radial artery harvest, the patients haven't complained of very much. The only abnormality we could detect was on very sensitive testing, and all we did was a clinical examination, and they didn't have any symptoms.
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References
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Abstract
1. Introduction
