TREATMENT OF CANINE ACUTE PULMONARY EMBOLIC SHOCK : Effects of Isoproterenol and Norepinephrine on Hemodynamics and Ventricular Wall Motion

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To determine indications for isoproterenol and norepinephrine, the effects of each drug on acute pulmonary embolic shock were compared with those of mechanical occlusion of the descending aorta (AO). In 18 dogs, we measured the changes in the hemodynamics and the ventricular wall motion in experimental pulmonary embolic shock. When the left ventricular systolic pressure decreased to 70 mmHg (shock), dogs were treated with isoproterenol, norepinephrine or AO. At the shock, the difference between the left and right ventricular pressures became negative. The changes in the left and right ventricular septum-free wall diameter (LVD. RVD) resulted in a significant leftward shift of the interventricular septum (IVS), and systolic shortening in LVD was extremely diminished. Isoproterenol administration decreased left and right ventricular end-diastolic pressure (LVEDP. RVEDP), but did not improve the reversion in RVEDP and LVEDP. The leftward shift of the IVS was not restored to normal. Following either norepinephrine administration or AO, the difference between the left and right ventricular pressures was restored to normal. Improvements in left ward shift of the IVS and systolic shortening of each diameter were observed. The similarity of norepinephrine administration to AO suggests that in the treatment of acute pulmonary embolic shock, restoration of systemic pressure for the maintenance of coronary perfusion, may be of primary importance. We concluded that norepinephrine is superior to isoproterenol for improvement of hemodynamics and ventricular wall motion in severe pulmonary embolic shock.