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Hypotension and Arteriovenous Shunting: Effects of Intravenous Infusion of Nitroprusside, Nitroglycerin and PhentolamineSection de Chirurgie Cardiovasculaire, Centre de Recherche Pédiatrique, Hôpital Sainte-Justine e Département de Pharmacologie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
Section de Chirurgie Cardiovasculaire, Centre de Recherche Pédiatrique, Hôpital Sainte-Justine e Département de Pharmacologie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
Section de Chirurgie Cardiovasculaire, Centre de Recherche Pédiatrique, Hôpital Sainte-Justine e Département de Pharmacologie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
Section de Chirurgie Cardiovasculaire, Centre de Recherche Pédiatrique, Hôpital Sainte-Justine e Département de Pharmacologie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
Section de Chirurgie Cardiovasculaire, Centre de Recherche Pédiatrique, Hôpital Sainte-Justine e Département de Pharmacologie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada The effects of nitroprusside, nitroglycerin and phentolamine on cardiac dynamics and on the fraction of cardiac output shunted through systemic arteriovenous communi cations, which may explain disparate responses elicited by these systemic vasodilators upon venous return, have been studied in 15 nonanesthetized dogs. Cardiac dynamic parameters were measured by electromagnetic flow probe placed at the root of the aorta. Quantitative measurements of total systemic arteriovenous shunting were determined from the fraction of 9µ radioactively labeled microspheres, injected into the left atrium, recovered in the pulmonary artery. To provide a common basis for comparison, the mean arterial pressure was lowered by 15-20% either with an intravenous infusion of nitroprusside, nitroglycerin or phentolamine. At the fifteenth minute of infusion, nitro prusside produced significant decrease in stroke volume index (23%) and left ventricular power and work (28% and 40%). Nitroglycerin decreased significantly stroke volume index (12%), cardiac index (9%) and left ventricular work (22%). Phentolamine signifi cantly increased heart rate (72%) and left ventricular maximum acceleration (30%) while it decreased stroke volume index (41 %), left ventricular power and work (19% and 55%). Total peripheral resistance was significantly affected only by infusion of phentolamine (-18%). Left ventricular maximum velocity, mean systolic ejection rate and maximum systolic flow did not change significantly under infusion of these systemic vasodilators. Under control conditions, total systemic shunting of cardiac output averaged 8.9- 10% and was not modified by any of the vasodilators used. Arteriovenous O2 difference and oxygen consumption, corroborated these findings since they remained within normal limits before and after infusion of nitroprusside, nitroglycerin or phentolamine. These results indicate that the mechanisms by which venous return is altered during administration of systemic vasodilators in normal subjects are not related to shunting of blood via peripheral arteriovenous anastomoses.
Angiology, Vol. 35, No. 2,
88-96 (1984) |
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