Whole body plasma extravasation in saline and Haemaccel loaded rats: effects of endotoxemia.

Endotoxin causes only a limited increase in plasma leakage in rats. This may be due to a concomitant fall in venous pressure. We therefore studied effects of increases in this pressure on plasma loss. After a 60 min. endotoxin (20 mg/kg. hr E coli 0127-B8) or saline (control) infusion anesthetized rats were volume loaded (3 ml/10 min. 100 g for 10 min.) at t = 120 min. with saline (shock group n = 8; control group n = 8) or Haemaccel (shock group n = 6; control group n = 8). At t = 180 min. the experiments ended. We measured mean arterial and central venous pressure, heart rate, arterial lactate, blood volume (51Cr-labeled red cells), hematocrit (conductivity cell), macromolecular extravasation (125I-HSA) and fluid retention (calculated from change in plasma volume). Whole body transcapillary filtration coefficient (Kf) and interstitial compliance (Ci) were obtained from saline retention curves. During volume loading central venous pressure increased, then fell again. At the end of saline loading (t = 130) 50 and 60% of infused volume remained intravascularly in control and endotoxin treated rats, respectively; at the end of Haemaccel infusion retention was 110 and 120%, respectively. Fifty minutes later (t = 180) it was 25 and 30% after saline loading and 50 and 60% after Haemaccel loading in control and endotoxin treated rats, respectively. Between control and endotoxin group filtration coefficients (Kf; .094 vs .111 ml/min.mmHg.100 g, respectively) and compliances (Ci; 1.90 vs 1.58 ml/mmHg.100 g, respectively) were not significantly different. No increase in leakage of 125I-HSA was found in either group. Increased venous pressure thus did not reveal an increase in macromolecular permeability in endotoxin treated rats.