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


CONCLUSIONS
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.
Conant
Alan R
AR
CardiothoracicCentre, Liverpool NHS Trust, Thomas Drive, Liverpool L14 3PE, UK. Alan.Conant@ctc.NHS.uk
Shackcloth
Michael J
MJ
Oo
Aung Y
AY
Chester
Michael R
MR
Simpson
Alec W M
AW
Dihmis
Walid C
WC
D000316:Adrenergic alpha-Agonists / Q000627:therapeutic use; D000368:Aged; D000804:Angiotensin II / Q000627:therapeutic use; D001026:Coronary Artery Bypass; D004110:Diltiazem / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000627:therapeutic use; D006801:Humans; D008875:Middle Aged; D005996:Nitroglycerin / Q000627:therapeutic use; D009638:Norepinephrine / Q000627:therapeutic use; D010208:Papaverine / Q000627:therapeutic use; D016491:Peripheral Vascular Diseases / Q000517:prevention & control* / Q000601:surgery; D010643:Phenoxybenzamine / Q000627:therapeutic use*; D010726:Phosphodiesterase Inhibitors / Q000627:therapeutic use; D017534:Radial Artery; D013035:Spasm / Q000517:prevention & control*; D013997:Time Factors; D016896:Treatment Outcome; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000627:therapeutic use; D014665:Vasodilator Agents / Q000627:therapeutic use*; D014667:Vasopressins / Q000627:therapeutic use
D000316:Adrenergic alpha-Agonists; D019332:Endothelin-1; D010726:Phosphodiesterase Inhibitors; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D010643:Phenoxybenzamine; D014667:Vasopressins; D000804:Angiotensin II; D010208:Papaverine; D004110:Diltiazem; D005996:Nitroglycerin; D009638:Norepinephrine