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J Thorac Cardiovasc Surg 2003;126:448-454
© 2003 The American Association for Thoracic Surgery

Cardiopulmonary support and physiology

Phenoxybenzamine treatment is insufficient to prevent spasm in the radial artery: the effect of other vasodilators

Alan R. Conant, PhDa,b,*, Michael J. Shackcloth, FRCSa, Aung Y. Oo, FRCS (CTh)a, Michael R. Chester, MRCP, MDa, Alec W. M. Simpson, DPhilb, Walid C. Dihmis, FRCS (CTh)a

a Cardiothoracic Centre,a Liverpool NHS Trust, Liverpool, UK
b Department Human Anatomy and Cell Biology,b University of Liverpool, New Medical School, Liverpool, United Kingdom

Received for publication September 24, 2002; revisions received October 25, 2002; revisions received November 8, 2002; accepted for publication November 11, 2002.

* Address for reprints: Alan Conant, PhD, The Cardiothoracic Centre, Liverpool NHS Trust, Thomas Drive, Liverpool L14 3PE, United Kingdom
Alan.Conant{at}ctc.NHS.uk

OBJECTIVES: After its reintroduction as an arterial graft in coronary artery surgery, the radial artery is now established as an alternative arterial conduit, with good early and midterm patency. However, because of the concern about its vasospasticity, numerous vasodilator strategies have been used. Recently the use of the irreversible {alpha}-adrenergic antagonist phenoxybenzamine has been proposed. Although this treatment is effective in eliminating the vasoconstriction mediated by noradrenaline, the contribution of other circulating vasoconstrictors to vasospasm could be as important. This study investigates the response of radial arteries treated with phenoxybenzamine to vasoconstrictor stimuli and possible preventative strategies.

METHODS: In vitro, sections of radial artery, pretreated with phenoxybenzamine after harvesting, were stimulated with maximal concentrations of the vasoconstrictors noradrenaline, vasopressin, angiotensin II, KCl, and endothelin-1. In matched segments of artery, vasoconstrictor responses were recorded in the presence of diltiazem, glyceryl trinitrate, and papaverine and compared with phenoxybenzamine-treated samples.

RESULTS: Phenoxybenzamine-treated radial artery failed to respond to noradrenaline but did respond to vasopressin, angiotensin II, endothelin-1, and KCl. Diltiazem was largely ineffective against contractile stimuli apart from KCl. Glyceryl trinitrate and papaverine significantly reduced responses to all of the vasoconstrictors tested.

CONCLUSION: In phenoxybenzamine-treated sections of radial artery, circulating vasoconstrictor agonists may still contribute to the induction of spasm. Additional vasodilator strategies may be required to completely prevent vasospasm.






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