Cardiovascular studies on normal calves

Abstract

Physiologic measurements of several circulatory parameters were made in 15 normal unanesthetized calves by cardiac catheterization. Fifty-four observations were made in the ‘resting’ state during 27 separate studies. The calves were restrained in the right lateral decubitus position in a calf chute. Oxygen consumption (Vo2) was measured by collecting expired air through a cuffed endotracheal tube. Cardiac output was determined by the direct Fick (Q·f) and/or the dye dilution (Q·d) techniques. Pulmonary artery (PAP), right heart and carotid artery (CAP) pressures were measured routinely while pulmonary artery wedge, left ventricular and central aortic pressures were obtained in a few animals. Under the conditions of the study, it is unlikely that the animals were in a truly resting state. However, absence of a statistically significant difference between two consecutive measurements of various parameters in 11 studies and good agreement between 17 paired Qf and Qd determinations suggests that the animals were in a reasonably steady state. Mean ± Sx values of the more important parameters measured were as follows: Qd 7.30 ± 0.23, Qf 7.10 ± 0.42 l/min/m2; Vo2 365 ± 29 cc/min/m2; PAP 21.6 ± 1.4, CAP 131 ± 4.5 mm Hg; pulmonary vascular resistance 2.34 ± 0.27 mm Hg/l/min/m2.