Technical and methodological requirements for reliable haemodynamic measurements in the unsedated calf.

The purpose of this study was (1) to evaluate the technical and methodological problems associated with invasive haemodynamic measurements in unsedated cattle; (2) to assess the reproducibility of such measurements both within and between days; and (3) to compare the values with those previously reported. Twenty-one healthy calves, aged from 5.5 to 12 months, were studied. The central venous, the right ventricular, the pulmonary arterial, the pulmonary capillary wedge and the systemic arterial pressures were obtained by means of fluid-filled catheters, and the cardiac output was measured by the thermodilution technique. The heart rate, the stroke volume, the pulmonary and systemic vascular resistances and the pulmonary and systemic ventricular workloads were calculated. An adverse reaction, consisting of severe pulmonary hypertension, tachycardia, tachypnoea and transient weakness, occurred in 7 calves during the catheterization procedures. Such a reaction might be due to a local reflex induced by stimulation of mechano-receptors by the catheter tip. It should be avoided by reducing the manipulation of the catheter as much as possible and by inflating the tip of the balloon when moving it forwards. A comparison of the vascular pressures with those previously reported was difficult because of methodological or technical limitations, such as, for instance, a lack of standardization of the baseline. The reproducibility of the haemodynamic measurements obtained was satisfactory, in contrast to previous studies performed in conscious animals. This was attributed to our animals being better trained to the experimental conditions and emphasizes the importance of reducing mental stress in obtaining reliable haemodynamic measurements in unsedated and potentially uncooperative animals.