Redistribution of cardiac output during hemorrhagic shock in sheep.
OBJECTIVE
Our goal was to evaluate the robustness of one of the assumptions used by esophageal Doppler monitors to compute systemic stroke volume and cardiac output; i.e., a constant flow proportion between supra-aortic vessels and descending aorta. For this purpose, we measured ascending and descending aortic blood flows during acute hemorrhage in anesthetized ewes.


METHODS
Prospective, experimental study.


METHODS
Animal research facility.


METHODS
Adult ewes.


METHODS
Anesthetized animals were implemented with an aortic pressure transducer and two ultrasound transit time flowmeters placed around ascending and descending aorta, respectively. After baseline measurements, three incremental blood withdrawals were followed by progressive blood restitution in three similar steps.


RESULTS
Ascending and descending aortic blood flows were reduced in a proportional manner after hemorrhage (-48% and -46%, respectively; p < .05 vs. baseline). Following blood restitution, flows were not fully restored, but ascending aortic flow was reduced by 27% with respect to initial control values while descending aortic flow was only 15% below. The agreement between ascending aortic flow and cardiac output calculated as descending aortic flow divided by 0.7 was characterized by a bias of 0.07 L/min and limits of agreement of +1.24 L/min and -1.10 L/min.


CONCLUSIONS
Minor blood flow redistribution between supra-aortic and descending aortic territories was seen only following blood restitution but not during hemorrhage in these anesthetized ewes. This observation supports the robustness of the assumption of constant flow proportion used by the esophageal Doppler monitor to calculate systemic stroke volume from descending aortic flow measurements.
Dumans-Nizard
Virginie
V
Department of Anesthesiology and Intensive Care, Hopital Lariboisiere, Assistance Publique-Hopitaux de Paris, University Paris VII, France.
Nizard
Jacky
J
Payen
Didier
D
Cholley
Bernard P
BP
D000818:Animals; D002302:Cardiac Output; D005260:Female; D012756:Sheep; D012771:Shock, Hemorrhagic / Q000503:physiopathology*