Pulmonary vasoconstriction in a canine model of neurogenic pulmonary edema

The intracisternal administration of veratrine to the chloralose-anesthetized dog produces pulmonary hypertension (PH) and neurogenic pulmonary edema (NPE). To determine whether pulmonary vasoconstriction, mediated by a circulating agent, contributes to the PH, the left lower lung lobe (LLL) perfusion of seven splenectomized (to keep hematocrit and blood viscosity constant) dogs was isolated so the LLL could be perfused at constant flow and outflow pressure with blood pumped from the pulmonary artery. The LLL was denervated by removing it from the dog. Veratrine (40-160 micrograms/kg) increased LLL arterial pressure by 39.2% and produced large increases in plasma catecholamine concentrations. The double-occlusion technique indicated that 74% of the increase in the LLL arteriovenous pressure gradient was due to an increase in venous tone. This pattern of vasoconstriction was similar to that previously observed during the infusion of exogenous catecholamines and suggested that catecholamines mediated the LLL response. The more severe degree of PH observed in the intact animal in NPE, however, suggests that passive rather than active changes in pulmonary hemodynamics are predominantly responsible for the development of PH in this disorder.