The Circulatory Effects of Isoproterenol, Acetylstrophanthidin, and Volume Loading in Acute Pericardial Tamponade

AUTHORS ’ SYNOPSIS. In 13 dogs with experimentally-induced acute pericardial tamponade, volume load increased cardiac output by 170 % as pericardial and right arterial pressure increased. Acetyl-strophanthidin did not sigiiicantly change stroke volume or cardiac output. Isoproterenol augmented cardiac output by 240 % and reduced venous pressure. Pericardial tamponade produces marked limitation in cardiac function. The physiological basis for the abnormal circulatory state is the high intraperi-cardial pressure which limits diastolic expansion of the ventricles and thereby impedes venous return, with consequent reduction in cardiac output and arterial pressure. Pericardiocentesis is the therapy of choice, but under certain circumstances it may be advantageous to assist the circulation before removal of the pericardial fluid. Several workers have studied the haemodynamic effects of therapeutic manoeuvres other than peri-cardiocentesis. Kuno (191 7) reported that adren-aline in one dog with cardiac tamponade caused an increase in cardiac output and an elevation of arterial pressure. He postulated that the adrenaline reduced intrapericardial pressure by diminishing the volume of the heart. Isaacs, Berglund, and Sarnoff (1954) showed that an increase of blood volume significantly increased aortic pressure and cardiac output in mild to moderate tamponade, but that, in severe tamponade, volume infusion pro-duced little improvement. Other authors have speculated about the value of pressor or sympa-thomimetic agents, but no studies are available. Similarly the literature contains no satisfactory information concerning the use of digitalis in the treatment of pericardial tamponade.