Comparison of milrinone versus nitroglycerin, alone and in combination, on grafted internal mammary artery flow after cardiopulmonary bypass: effects of alpha-adrenergic stimulation.
OBJECTIVE
To compare changes in blood flow in a grafted internal mammary artery (IMA) after cardiopulmonary bypass (CPB) in response to the administration of milrinone or nitroglycerin and to establish the effects of alpha-adrenergic stimulation.


METHODS
Randomized study.


METHODS
A university medical center hospital and a Veterans Affairs Medical Center hospital.


METHODS
Thirty consenting adults scheduled for elective coronary artery bypass graft surgery.


METHODS
Patients were randomized to receive a 2 microg/kg/min infusion of nitroglycerin (n = 10), a loading dose of 50 microg/kg of milrinone (n = 10), or both drugs combined (n = 10) shortly after CPB. Intravenous phenylephrine was administered to increase mean arterial pressure by 20%. IMA flow was measured with a calibrated laser Doppler flow probe. Hemodynamic and flow measurements were obtained before and after every intervention.


RESULTS
Nitroglycerin and milrinone increased mean IMA flow, but the increase was greater with milrinone. Both drugs combined were superior to nitroglycerin alone but not to milrinone. The addition of phenylephrine to nitroglycerin increased IMA flow in 6 of 10 patients. IMA flow decreased in 4 of 10 patients, however. Phenylephrine significantly increased IMA blood flow in patients receiving milrinone or in those given both drugs combined.


CONCLUSIONS
After CPB, milrinone and nitroglycerin vasodilate the IMA; however, the combination of both drugs was not superior to milrinone alone. When using alpha-adrenergic stimulation, milrinone proved superior to nitroglycerin in preserving IMA flow.
Lobato
E B
EB
Department of Anesthesiology, University of Florida College of Medicine, PO Box 100254, Gainesville, FL 32610-0254, USA. lobato@anest2.anest.ufl.edu
Janelle
G M
GM
Urdaneta
F
F
Martin
T D
TD
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D001783:Blood Flow Velocity; D002315:Cardiopulmonary Bypass; D004359:Drug Therapy, Combination; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007387:Internal Mammary-Coronary Artery Anastomosis; D008323:Mammary Arteries / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000502:physiology; D020105:Milrinone / Q000008:administration & dosage*; D005996:Nitroglycerin / Q000008:administration & dosage*; D010656:Phenylephrine / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000008:administration & dosage*; D014463:Ultrasonography; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000008:administration & dosage*
D000316:Adrenergic alpha-Agonists; D010726:Phosphodiesterase Inhibitors; D014665:Vasodilator Agents; D010656:Phenylephrine; D005996:Nitroglycerin; D020105:Milrinone