Effects of colloid or crystalloid solutions on edemagenesis in normal and thrombomicroembolized lungs

We studied the effects of crystalloid (75 ml/kg of Ringer's lactate) or colloid (6% dextran-70, 6% hydroxyethyl starch, or 25 ml/kg of 5% human serum albumin) fluid infusions or no treatment (control) on the calculated lung capillary (Pc)-plasma oncotic pressure (pi c) gradient and pulmonary edema. Two sets of mongrel dogs were studied: uninjured (n = 25; 14 to 22 kg) and pulmonary fibrin-microembolized (n = 25; 15 to 23 kg). In both sets of experiments, left atrial pressure was controlled (15 mm Hg) throughout the 4-h plus experimental period. In the uninjured set, the Pc-pi c gradient averaged +1.0 and -0.2 mm Hg in the hydroxyethyl starch and dextran groups, +0.7 and +2.3 mm Hg in the human serum albumin and control groups, and +6.2 mm Hg in the Ringer's lactate group. In the fibrin-microembolized group, this gradient averaged 2.6, 2.4, 3.0, 5.3, and 9.5, respectively. The extravascular lung water to bloodless dry lung wet weight ratios in the no-fluid treatment group of the uninjured and microembolism groups with increased pressure (3.8 +/- 0.3 to 4.1 +/- 0.4 [SEM]; NS) are consistent with interstitial or perivascular edema. There were, however, no significant differences noted between the respective control groups or any fluid treatment group in either set of experiments. These data support the view that infusion of either colloid or crystalloid solutions in normal or pulmonary fibrin-microembolized lungs does not produce sufficient change in the Pc-pi c gradient to elevate edemagenesis when pulmonary capillary pressure is limited to 22 mm Hg in dogs.