Absence of pulmonary edema during peritonitis and shock in rats

We evaluated the development of pulmonary edema early in the course of peritonitis and shock in rats. Peritonitis was established by cecal ligation and perforation. In a preliminary experiment, sepsis was induced in five animals and five animals served as sham-operated controls. Lungs harvested for gravimetric analysis at 6 hours revealed no significant difference in wet-dry/dry (W-D/D) ratios. In a second experiment, 15 rats were randomized to three groups: septic animals, septic animals infused with 5% albumin, and sham-operated animals. Thermodilution cardiac output and arterial blood gases were sequentially measured over a 6-hour interval. At 6 hours, the lungs were harvested for gravimetric analysis. Lung W-D/D and arterial oxygenation were not significantly different between the three groups. The W-D/D was 3.46 +/- 0.10 in sham-operated rats, 3.37 +/- 0.12 in septic rats, and 3.88 +/- 0.27 in albumin-infused septic rats. The alveolar-arterial oxygen difference at 6 hours was 10 +/- 2 mm Hg in sham-operated rats, 7 +/- 1 mm Hg in septic rats, and 13 +/- 6 mm Hg in albumin-infused septic rats. These data suggest that overt pulmonary edema and arterial hypoxemia may not occur early in septic shock when fluid infusion is not excessive.