Effect of heparin or fibrinogen depletion on lung fluid balance in sheep after emboli

Abstract

Fibrinogen, fibrin, or their degradation products may be essential for the increased lung vascular permeability to fluid and protein that may occur after microemboli. Anesthetized ventilated sheep (20) lung nymph flow, pulmonary artery and left atrial pressures, thermodilution cardiac output and lymph/plasma protein concentrations were measured. Glass bead microemboli (200 .mu.m diameter) were injected to raise pulmonary vascular resistance to 3 times base-line values and cause increased lung lymph flow with a parallel increase in protein clearance, which is characteristic of increased lung vascular permeability. Neither large doses of heparin (3000 U[units]/kg) nor fibrinogen depletion with viper venom (ancrod, 2 U/kg), alone, affected steady-state pulmonary hemodynamics or lung fluid balance. These treatments prior to giving sufficient amounts of emboli to triple the pulmonary vascular resistance did not prevent the increased lung vascular permeability. Fibrin deposition on degradation is not essential to microembolic lung vascular injury in sheep.