Cardiovascular performance with E. coli challenges in a canine model of human sepsis

We investigated cardiovascular dysfunction by injecting lethal and nonlethal bacterial challenges into conscious dogs. E. coli bacteria of varying numbers were placed in a peritoneal clot. Cardiovascular function was studied with simultaneous radionuclide scans and thermodilution cardiac outputs. In surviving animals, the number of bacteria in the clot increased as the corresponding systolic cardiac function decreased (P = 0.01). Cardiac function was measured by left ventricular (LV) ejection fraction (EF) and LV function curves [LV stroke work index (LVSWI) vs. end-diastolic volume index (EDVI), and peak systolic pressure vs. end-systolic volume index]. Furthermore, the diastolic volume-pressure relationship of survivors shifted progressively to the right [i.e., increasing EDVI (P less than 0.02) with minimal change (P = NS) in LV filling pressure]. This increase in LV size was associated with maintenance of measures of cardiac performance [stroke volume index (SVI) and stroke work index (SWI)] at similar levels. Death occurred only in the group with the highest bacterial dose. Compared with survivors receiving the same number of bacteria, nonsurvivors had a decrease in (P less than 0.05) LV size, a leftward shift (P less than 0.01) in LV diastolic volume-pressure relationship, and a decrease in both LVSWI and SVI (possibly related to volume and/or LV functional status). Data from survivors suggest that increasing the number of bacteria produces changes in myocardial compliance and contractility. These changes increase LV size (preload), a major determinant of cardiac performance that possibly enhances survival.