Exponential increases in pulmonary intravascular and extravascular fluid volumes by overperfusion with dextran 70 in anesthetized dogs.

Abstract

In the lung overperfused by dextran 70, it is not known how intravascular blood volume and extravascular water volume increase as a function of pulmonary microvascular pressure. To determine their characteristics, we produced an overperfusion state (high pressure and high blood flow) by infusing dextran 70 (100 ml/kg over 30 min) into 15 anesthetized dogs. Using the thermal and dye dilution technique, we simultaneously estimated the pulmonary blood volume (PBV) and the extravascular lung thermal volume (EVLTV), and correlated mathematically these variables with pulmonary artery end-diastolic pressure (PAEDP). Here, we defined PAEDP as the pulmonary microvascular pressure. From the values determined before, during and after dextran 70 infusion, we obtained the following exponential relations. PBV(ml/kg) = 30[1-0.902(e-0.021PAEDP(mmHg)) EVLTV(ml/kg) = 5.15(e0.027PAEDP (mmHg)) From these mathematical relations, we conclude that: (1) the pulmonary blood volume increases rapidly at low pressure and slowly at high pressure; and (2) the pulmonary extravascular water volume increases slowly at low pressure and then increases rapidly at high pressure. In addition, this equation indicates that the critical pressure from which the pulmonary extravascular water volume exceeds the upper limit of its normal volume is about 17 mmHg in PAEDP. Infusion of dextran 70 increased plasma macromolecular osmotic pressure from 20.8 +/- 0.6 (mean +/- SD) mmHg before infusion to 43.7 +/- 1.4 mmHg after infusion. Therefore, dextran 70 does not change the critical microvascular pressure against pulmonary edema.