Cardiac output and redistribution of organ blood flow in hypermetabolic sepsis

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Abstract
Cardiac output (CO) and the distribution of blood flow were studied in chronically catheterized conscious rats during sustained (4 days) sepsis. Septicemia was induced by i.p. administration of a pooled fecal inoculum and tissue blood flow and CO were determined daily with 15-.mu.m radioactive microspheres. Mean arterial blood pressure (MABP, 113 .+-. 2 mm Hg), CO (244.5 .+-. 11.4 ml .cntdot. min-1 .cntdot. kg-1) and total peripheral resistance (TPR, 1.36 .+-. 0.7 mm Hg .cntdot. ml-1 .cntdot. min) were stable in control rats over the 4 days postinoculation. Septic animals showed a consistent tachycardia with MABP significantly reduced only on days 3 and 4 (86 .+-. 4 mm Hg). A hyperdynamic response to sepsis was indicated by an elevated CO (27%) and similarly reduced TPR on day 2. The calculated stroke volume averaged 0.22 .+-. 0.01 ml/beat and did not vary over time or between the 2 groups. There was a 40-70% increase in blood flow to the heart, spleen, adrenal glands and small intestine, and a greater than 6-fold increase in arterial blood flow. The sustained elevation of coronary blood flow observed in septic animals, was independent of myocardial work and is consistent with impaired myocardial function. Pancreas, stomach and skeletal muscle blood flow was consistently comprised (24, 39 and 52%, respectively) during sepsis. Blood flow in other organs remained unchanged over time. Sepsis-induced changes in the fractional distribution of blood flow to various organs were similar to those described for absolute flow. These results document a hyperdynamic state during sustained sepsis in the rat and characterize the distribution of tissue blood flow during this condition.