Ann Thorac Surg 2002;74:271-272
© 2002 The Society of Thoracic Surgeons
How to do it
Intraoperative confirmation of ulnar collateral blood flow during radial artery harvesting using the "squirt test"
Inderpaul Birdi, FRCS(CTh)*a,
Andrew J. Ritchie, FRCSa
a Papworth Hospital, Papworth Everard, Cambridge, United Kingdom
Accepted for publication February 17, 2002.
* Address reprint requests to Dr Birdi, Papworth Hospital, Papworth Everard, Cambridge CB3 8RE, UK
e-mail: inderuk{at}hotmail.com
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Abstract
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Hand ischemia is a major concern after radial artery harvesting for coronary revascularization. Although a number of preoperative tests have been described to assess the adequacy of ulnar collateral blood flow, many of them are subjective and unreliable. In addition, the presence of arterial connections between the radial and ulnar systems in the elbow and forearm and variability in forearm angiology imply that assessment of alternative blood supply to the hand can only be made once collateral branches of the radial artery have been divided. We describe a technique for intraoperative assessment of ulnar collateral blood flow after mobilization and division of collateral branches of the radial artery.
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Introduction
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Improved radial artery harvesting techniques have stimulated resurgence in the use of this conduit for coronary revascularization. Concerns still remain, however, regarding the potential for serious hand ischemia as a result of inadequate ulnar collateral blood flow.
A number of preoperative tests have been used in an attempt to identify patients at risk, including the Allen test, ultrasound examination of palmar arch flow, digital pressure measurements, and digital oxygen saturation [1–4]. Many of these tests are subjective and unreliable and have yet to be validated.
Anatomic studies have shown that collateral branches exist between the radial and ulnar arteries at the level of the elbow and forearm [5]. In addition, variations in the development of forearm blood supply also exist [6]. These issues have major implications for interpretation of noninvasive tests of collateral blood supply to the hand. Occlusion of the ulnar artery at the wrist, for example, cannot reliably account for the delivery of blood to the radial artery through collaterals in the proximal upper limb that may result in inadequate delivery of blood to the hand after surgical mobilization of the radial artery. Thus, adequacy of ulnar collateral flow can only be made after surgical division of the forearm branches of the radial artery intraoperatively.
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Technique
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We have been using a simple technique that allows intraoperative assessment of ulnar artery blood supply to the hand before removing the radial artery from the forearm.
Radial arteries were exposed using a modified protocol similar to that described by Reyes and colleagues [7], after preoperative confirmation of a positive Allen test. Care was taken to identify the bifurcation of the brachialartery into radial and ulnar branches. A swab soaked in glyceryl-trinitrate (0.5 mg/mL) was wrapped around the artery to minimize spasm. The radial artery was mobilized and separated from its branches. After systemic anticoagulation with heparin, and before cardiopulmonary bypass (ensuring physiologic pulsatile flow), a delicate artery occlusion clip was applied to the mid portion of the radial artery, and a small, longitudinal arteriotomy was made at its distal point. The presence of pulsatile flow and a "squirt" height greater than 1.5 cm during systole were arbitrarily used as evidence of adequate collateral flow (Fig 1).
Under these circumstance the radial artery was removed, and the arm was closed in a routine fashion.
We have now used the squirt test in 700 patients, in whom 695 radial arteries were successfully harvested. No episodes of hand ischemia were experienced when assessed clinically and by digital oxygen saturation measurements. At 6 weeks’ follow-up, all patients reported normal hand function. In 79 nondominant limbs, thenar muscle power was assessed preoperatively and at 3 months [4]. A small but significant decrease in thenar muscle power was observed, without any objective clinical evidence of hand dysfunction. All of these patients demonstrated a positive preoperative Allen test.
Inadequate squirt test measurements were recorded in only 1 patient with a positive preoperative Allen test. In this patient, the arteriotomy was easily repaired, and the arm was closed without radial artery removal. Full recovery was achieved. In all remaining patients, the squirt test suggested adequate collateral flow, and the radial artery was harvested without any ischemic sequelae.
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Comment
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The squirt test has proven to be a very useful tool for intraoperative assessment of collateral arm blood flow before radial artery harvest. A positive squirt test ensures that the assessment of alternative blood supply to the hand is not reliant on collateral supply from the radial artery through the elbow and forearm, and is the only sure way to determine adequacy of the superficial palmar arterial supply to the hand.
Our experience offers compelling evidence that demonstration of an adequate squirt test, as defined by the measurements described above, provides the clinician with the reassurance that radial artery harvesting is unlikely to lead to major hand morbidity. Further evaluation and validation of the squirt test in comparison to preoperative ultrasound investigation and intraoperative thenar pressure measurements are underway.
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References
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- Ruengsakulrach P., Brooks M., Hare D., et al. Preoperative assessment of hand circulation by means of Doppler ultrasonography and the modified Allen test. J Thorac Cardiovasc Surg 2001;121:526-531.[Abstract/Free Full Text]
- Rodriguez E., Ormont M., Lambert E., et al. The role of preoperative radial artery ultrasound and digital plethysmography prior to coronary artery bypass grafting. Eur J Cardiothorac Surg 2001;19:135-139.[Abstract/Free Full Text]
- Starnes S., Wolk S., Lampman R., et al. Noninvasive evaluation of hand circulation before radial artery harvest for coronary artery bypass grafting. J Thorac Cardiovasc Surg 1999;117:261-266.[Abstract/Free Full Text]
- Grossebner M., Arifi A., Bourov Y., et al. No change in oxygen saturation but measurable difference in thenar flexor power after radial artery harvest. Eur J Cardiothorac Surg 1999;16:160-162.[Abstract/Free Full Text]
- Roderiguez-Niedenfuhr M., Sanudo J.R., Vasquez T., et al. Anastomosis at the level of the elbow joint connecting the deep, or normal, brachial artery with major variations of the upper limb. J Anat 2000;196:115-119.
- Roderiguez-Niedenfuhr M., Sanudo J.R., Vasquez T., et al. Median artery revisited. J Anat 1999;195:57-63.
- Reyes A., Frame R., Brodman R. Technique for harvesting the radial artery as a coronary artery bypass graft. Ann Thorac Surg 1995;59:118-126.[Abstract/Free Full Text]
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Circulation,
January 4, 2005;
111(1):
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Abstract
Introduction
