Pulmonary transvascular fluid flux and cardiovascular function in sheep with chronic sepsis

We studied the mechanisms responsible for the changes in lung lymph flow (QL) in chronic sepsis induced by the continuous infusion of endotoxin [lipopolysaccharide (LPS), 10 ng.kg-1.min-1]. Sheep (n = 11) were studied in the unanesthetized state 7 days after preparation, and cardiopulmonary variables were measured. In the control group (n = 5) given lactated Ringer solution, no significant changes were observed in any measured variables. In the LPS group (n = 6), QL increased from 11.7 +/- 3.8 to 54.0 +/- 15.0 (SE) ml/h 24 h after LPS infusion had begun. This elevation in QL was associated with little or no change (P > 0.05) in reflection coefficient (0.80 +/- 0.03 to 0.87 +/- 0.05) or pulmonary microvascular pressure (14.3 +/- 0.4 to 16.7 +/- 1.2 mmHg). The filtration coefficient, however, was significantly elevated (0.018 +/- 0.006 to 0.083 +/- 0.024 ml.min-1.mmHg-1). In association with changes in QL that occur as a result of LPS administration, there was a significant increase in cardiac index (6.1 +/- 0.5 to 10.2 +/- 0.3 l.min-1.m-2) and a reduction in mean arterial pressure (90.2 +/- 4.4 to 73.7 +/- 7.3 mmHg) and systemic vascular resistance index (1,229 +/- 134 to 583 +/- 62 dyn.s.cm-5.m2), findings similar to those noted in septic humans.