Partial lung bypass reduces pulmonary edema induced by kerosene aspiration in dogs

Kerosene aspiration causes severe pulmonary capillary leak in dogs that is reduced by lowering pulmonary vascular pressures with plasmapheresis. In this study, we tested the possibility that partial lung bypass (PLB) with a veno-arterial extracorporeal circuit previously used for membrane oxygenation (ECMO) would decrease kerosene-induced pulmonary edema. Twelve dogs having a stable pulmonary capillary wedge pressure (Ppw) of 10 tort received 0.25 mL/kg of kerosene into each mainstem bronchus. After 1 hour, the dogs were separated into two equal groups: a control group (C) in which Ppw was maintained at 10 torr until 5 hours after injury, and a PLB group in which PLB reduced Ppw to 5 torr, associated with a 25% reduction in pulmonary blood flow. The blood was pumped back into the distal aorta with blood gas tensions matched by ECMO to the values exiting the lungs as sampled in the left ventricle. In the C group, extravascular thermal volume (ETV) increased from 8.7 ± 4.7 mL/kg to 32.9 ± 26.2 mL/kg between 1 and 5 hours postinjury (P < .05). In the PLB group, ETV increased less between 1 hour (11.7 ± 3.3 mL/kg) and 5 hours (16.5 ± 6.8 mL/kg). Therefore, the values at 5 hours were different between the groups (P < .05). The wet lung weight to body weight ratios of lungs excised at 5 hours were also much less (P < .05) in PLB (20 ± 5 mL/kg) than in group C (40 ± 18 mL/kg). We conclude that PLB reduces edema formation during a pulmonary capillary leak state by reducing pulmonary vascular pressures and/or flows. This supports a therapeutic approach to kerosene pneumonitis that seeks the lowest Ppw compatible with adequate cardiac output and oxygen transport, and suggests an additional benefit of the ECMO circuit in pulmonary vascular leak over and above supporting inadequate lung oxygen exchange at reduced FIO₂ and oxygen toxicity.