Abstract
Summary
In 32 hemodynamic studies on 26 unanesthetized normal calves (average weight 103 kg) lying restrained on their side abdominal inferior vena cava (IVC) and right atrial (RA) pressures obtained by catheter withdrawal under fluoroscopy were 15 ± 0.9 and 2 ± 0.5 mm Hg, respectively. The change in pressure occurred at the level of the diaphragm. Positive and negative variations in RA pressure corresponding to the respiratory cycle were not observed in the IVC pressure recorded below the diaphragm. In 5 calves IVC pressure was 2 ± 1.7 mm Hg standing and 16 ± 1.5 mm Hg while restrained on their side. In 17 calves with Brisket disease (BD) restrained on their side RA pressure was 36 ± 2.0 mm Hg without an IVC to RA gradient. The data suggest that significant narrowing of the IVC occurs at the level of the diaphragm in normal calves lying on their side presumably related to the effect of the weight of the abdominal contents on the IVC transmural pressure. The absence of an ICV to RA pressure gradient in calves with elevated RA pressure due to BD emphasizes the important role of outflow pressure in the vascular waterfall phenomenon.
The technical assistance of Mr. Don Anton is greatly appreciated.
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