Cardiac Depression in Bacteremia

Abstract

Hemodynamic and respiratory effects of a 5-h i.v. infusion of Pseudomonas aeruginosa at a dose of 108 organisms/ml per min were studied in 6 dogs. Four dogs served as controls. Gram-negative bacteremia, with 70,000 .+-. 1800 organisms/ml of blood, caused a 50% reduction of cardiac output at 3 h. Peripheral vascular resistance increased significantly, but mean heart rate fell below control levels. Decline in mean systemic blood pressure from 150 .+-. 5 mm Hg to 88 .+-. 6 mm Hg was accompanied by a significant increase in pulmonary arterial wedge pressure with normal right atrial and pulmonary arterial pressures. Pulmonary vascular resistance also remained unchanged. With progression of the low output state and development of hypothermia, arteriovenous O2 difference (A-V DO2) fell significantly. Despite a decline in functional residual capacity, venoarterial admixture diminished in the face of reduced pulmonary capillary perfusion, normal arterial PO2 [partial pressure of O2] values, decline in body temperature and finally very narrow A-V DO2. Histologically, ventricular myocardium revealed severe interstitial edema. Myocardial dysfunction may occur early during gram-negative bacteremia and formation of myocardial edema appears to be a significant contributing factor in myocardial failure.