The pulmonary microvascular response to infusion of live Escherichia coli in sheep with acutely or chronically prepared lung lymph fistula.

The effects of infusion of live Escherichia coli bacteria in awake sheep with a chronic lung lymph fistula (n = 15) were compared to anesthetized animals (n = 7) receiving the same septic insult after surgical trauma including bilateral thoracotomies for lung lymph cannulation (acute group). During preseptic baseline conditions, pulmonary arterial pressure (Ppa) and central venous pressure (Pcv) were increased and leukocytes decreased in the newly operated animals compared to the sheep with a chronic lung lymph fistula. After i.v. infusion of live E. coli 10(9) X kg-1 b.w. over 20 min, arterial pressure (Psa), cardiac output (Qt), leukocytes, and partial pressure of arterial oxygen (PaO2) decreased in both groups. Ppa peaked after 15 min at 37.2 +/- 2.5 in the chronic and 33.4 +/- 3.3 mm Hg in the acute group. In the chronic group, Ppa remained elevated but not in the acute group during the rest of experiment. Lung lymph flow (QL) increased significantly in both groups during the initial high Ppa, but it increased to a higher level in the chronic group. After 150 min, QL did not differ between the groups but remained elevated over baseline. Lymph-to-plasma concentration ratio (L/P) for total protein decreased in the chronic group during the initial high QL. This decrease was not seen in the acute group that had a significantly higher L/P between 30 and 120 min after sepsis. The high QL with unchanged L/P compared to baseline indicated increased permeability in the pulmonary microvessels in both groups but the changes in permeability, hemodynamics, or respiratory parameters after sepsis were not aggravated by the surgical trauma.