Cardiopulmonary response to pseudomonas and E. coli endotoxins

Since many gram negative organisms produce the septic shock syndrome, this study was designed to compare cardiopulmonary responses to endotoxin from Pseudomonas aeruginosa (Ps) with that from E. coli. Accordingly, a Westphal extract of Ps was prepared and given to 13 awake dogs. The data obtained from these animals were compared with data from a group of dogs given E. coli endotoxin under the same conditions. The cardiovascular variables were obtained using 5 cannulae placed under light halothane anesthesia. One cannula was placed in the left ventricle, 2 in the right atrium, and 2 in the thoracic aorta. After total recovery from anesthesia, control values were obtained; endotoxin was administered and the variables were measured immediately and every 1/2 hr thereafter for 6 hrs. Upon comparison, the response seen with Ps was similar to that seen with E. coli. Arterial blood pressure, mean right atrial pressure, left ventricular end diastolic pressure and peak dP/dt followed the same pattern in both groups. Some differeces were seen, however. In the first half of the experiment, the increase in peripheral resistance and the fall in cardiac output were less with Ps than E. coli. The other main difference was an immediate and more severe metabolic acidosis with Ps, evidenced by a greater increase in minute volume, respiratory rate and base deficit and a larger fall in arterial pCO₂ and pH at O and 1/2 hr after the administration of endotoxin. With these exceptions, the picture is the same with both groups.