Studies in pericardial function. I. Cardiovascular effects of assisted ventilation, thoracotomy and pericardiectomy in the anesthetized dog.

In anesthetized dogs, initially breathing spontaneously, the effects of intermittent positive pressure ventilation (IPPV), thoractomy and pericardiectomy on cardiac function, pericardial-ventricular relationships and cardiopulmonary volumes were evaluated. After IPPV stroke volume and work decreased. After thoracotomy there was no further change in cardiac output or work. Pericardiectomy superimposed at this point had no clear-cut effect. End-diastolic transmural pressures (ventricular minus pericardial) and cardiopulmonary volumes were not altered at any stage of the study. In the ventilated open-chest dog the effects of IPPV are greater than those of thoracotomy, and the extent of the effects is related to the level of IPPV. With moderate IPPV and adequate ventilation, the systemic hypotension, marked decreases in cardiac output and reduction of heart volumes reported by previous investigators can be avoided. The removal of the pericardium does not appear to have any deleterious effect in the normal dog.