Fluid balance in ANTU-injured lungs during crystalloid and colloid infusions

A controversy exists as to the preferred solution for plasma volume replacement and cardiac output maintenance in the presence of lung injury. To evaluate these responses, crystalloid and colloid infusions were compared in dogs treated with 5 mg/kg of alpha-naphthylthiourea (ANTU), which produces a predictable increase in vascular permeability and extravascular water (QW) in the lung. A tracheobronchial lymphatic from the left lung was cannulated and left atrial (Pla) pressure, lymph flow, lymph-to-plasma protein concentration ratios, and thermal dilution cardiac output were monitored. Test infusions were either 15 ml/kg of 6% dextran 70 (DX) or 60 ml/kg of normal saline (NS) infused over 20 min. Solutions were infused 3 h after ANTU as follows: group I (DX); group II (NS), group III (DX, constant Pla); and group IV (NS, constant Pla). In groups III and IV, Pla was maintained constant by bleeding into a reservoir during an exchange transfusion. Postinfusion QW increased to 9.01 and 9.14 g/g blood-free dry wt for groups I and II, respectively, but there was no significant postinfusion increase in QW for groups III and IV compared with the 3-h preinfusion values. However, cardiac output was significantly higher at 5 h in group III compared with group IV. These studies indicate that capillary hydrostatic pressure was the major determinant of QW during the infusions but that DX maintained cardiac output significantly higher because of vascular retention of the colloids.