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Ann Thorac Surg 2000;69:1040
© 2000 The Society of Thoracic Surgeons
DR JAMES R. STEWART (Colorado Springs, CO): I just want to say, I do not really have any questions for you, but based on this information and also similar information from the Mayo Clinic, we have used a regimen with sustained released nifedipine preoperatively and nitroglycerin instead of the standard intravenous diltiazem over the last year in over a hundred patients with radial arteries and have found an excellent result clinically. We have had no problems and it is much easier to manage than the intravenous diltiazem that everybody else seems to be using. We initially used that and are quite accustomed to the perioperative hypotension but find that a single dose of sustained release nifedipine preoperatively with the concomitant nitroglycerin seems to work extremely well.
DR ALLEN S. HUDSPETH (Winston-Salem, NC): I enjoyed your paper. I wonder if based on these studies have you come up with a protocol that is used clinically at your institution and will you tell us about it?
DR ALAA Y. AFIFI (Gulfport, MS): I enjoyed your paper very much. This issue of diltiazem obviously has been around for the past several years with the readvent of the use of radial arteries. The concerns that we have, certainly in my mind, are perioperative administration. One of the things that I always worry about is the hypotensive side effects of these drugs, and one of the new calcium channel blockers that has come out over the past several years that we have been utilizing is nicardipine, or Cardene, intravenously. Have you had any experience at all with Cardene, especially in the perioperative period?
DR W. STEVES RING (Dallas, TX): You demonstrated a slight difference between nifedipine and amlodipine. Do you feel that this is purely a dose effect or is this a true effect between the two agents? And second of all, how would you compare the effects of these agents with the use of IV nitroglycerin, for example?
DR ZELLNER: For the first question, I think that there have been concerns raised and studies have demonstrated some of the negative myocardial effects of nifedipine in patients with congestive heart failure. I think that because a number of the patients that we deal with have reduced ventricular function, the favorable ionic charge of amlodipine may lend itself to be more suitable in patients with reduced ventricular performance. Although there were small differences in the nifedipine and amlodipine groups, we would prefer to use amlodipine.
As far as the second question goes, there have been some recent studies that show better effects: improved prevention of vasospasm in patients who are receiving oral nitrates compared with diltiazem. I think that there are different mechanisms that those act through. We discussed how the calcium channel blockers work in this study. The oral nitrates work through a nitric oxide mechanism in promoting vascular smooth muscle relaxation, and unfortunately we know that this is a very much induced production of nitric oxide to which the vascular smooth muscle rapidly becomes tolerant, and you have to increase the amount of oral nitrates that are used to continue to see the effects of the locally mediated nitric oxide. Patients who are taken off of the oral nitrates in the short term may have some withdrawal effects, which has been noted in some of the other studies. And so this is the reason I do not use oral nitrates in this group long term.
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