Evaluation of Mean Pulmonary Artery Pressure Following Experimental Pulmonary Embolism in Dogs

ABSTRACT

In various autopsy series, overdiagnosis as well as underdiagnosis of pulmonary embolism has been reported. During the past decade, mortality rate has not declined despite advances in diagnostic methods. To evaluate the hypothesis that changes of hemodynamic parameters responded by mean pulmonary arterial pressure differences are of paramount importance to guide prognosis, experimental model of anesthetized dogs was used. Six dogs were anesthetized with 15 milligrams per kilogram of pentobarbital sodium, given intravenously and paralyzed with 2 milligrams of pancuronium bromide. 0.3 to 0.8 gram per kilogram of autologous blood clot was infused into the right atrium through a left external jugular vein. The dogs after embolization were divided into group A(mean pulmonary arterial pressure 33mmHg) and group B(mean pulmonary arterial pressure 43 mmHg). Each group of three dogs was monitored for a total of 4.5 hours. A 7F Swan-Ganz catheter was positioned and used to measure with fluid-filled transducer pulmonary capillary wedge pressure, mean pulmonary arterial pressure and mean right atrial pressure. Cardiac ouput was measured in triplicate by thermodilution and divided by weight to obtain the cardiac index. Blood gases, pH and saturation of arterial blood were measured. White blood cell and platerlets were counted in arterial blood. The results are as follows 1) Changes in mean arterial pressure showed no significant differences between group A and group B following embolization. 2) Changes in mean pulmonary arterial pressure showed significant differences between group A and group B(p<0.05). 3) Changes in cardiac index showed significant differences between group A and group B after 45 minutes following embolization(p<0.05). 4) Changes in total pulmonary resistance showed significant differences between group A and group B after 45 minutes following embolization(p<0.05). 5) PaO2 showed significant differences between group A and group B after one hour following embolization(p<0.05), but arterial pH showed no significant difference. 6) Changes in mean pulmonary capillary wedge pressure, mean right atrial pressure and heart rates showed no significant differences between group A and group B following embolization. In conclusion, changes in mean pulmonary arterial pressure, cardiac index, total pulmonary resistance and PaO2 showed significant differences between group A and group B following embolization.