Lung water increases with fluid administration during CPPV after pulmonary microembolization

Abstract

Hypoxemia created by pulmonary microemboli is improved by continuous positive-pressure ventilation (CPPV) but at a cost of reducing cardiac output (Q̇). In this high pulmonary vascular resistance (PVR), pulmonary edema setting, the authors attempted to increase the Q̇, which had been reduced by CPPV, with an infusion of dextran. In 14 dogs, 0.125 g/kg of starch microemboli (63-74 μm in diameter) were infused. CPPV at 15 cm H2O then was applied and Pa(O2) increased from 53 ± 4 to 69 ± 3 mmHg, but Q̇ decreased from 2.9 ± 0.2 to 1.7 ± 0.2 l/min. Seven of these dogs (control group) were monitored for 3 h. In the remaining seven dogs (volume group), dextran 40 was infused until Q̇ returned to pre-CPPV values, and monitoring was continued for 3 h. With return of Q̇ to pre-CPPV levels, indices of tissue oxygenation (O2 transport, Pv̄(O2) O2 consumption and metabolic acidosis) were significantly improved. However lung water was increased significantly by the volume infusion, so that at 3 h lung water in the volume group was double the value in the control group. The authors conclude that the volume infusion in the face of a high PVR may correct the reduced Q̇ of CPPV and improve tissue oxygenation, but it also may increase pulmonary edema.