Vasodilator and oxidant scavenger in the neurogenic pulmonary edema induced by cerebral compression

In vagotomized rats, cerebral compression (CC) produced marked increase in arterial pressure and pulmonary hemorrhagic edema (PHE). We studied the effects of a vasodilator and an oxidant scavenger to delineate the role of hemodynamic and permeability factors in this type of neurogenic PHE. Infusion of sodium nitroprusside at a dose of 5 micrograms/kg/min significantly reduced the CC-induced pressor response by 14% and the lung edema by 41%. A dose of 10 micrograms/kg/min blocked the pressor response by 51%, and completely prevented the lung injury. Dimethylthiourea (DMTU), a potent scavenger for oxidants such as hydroxyl radical and hydrogen peroxide, in doses of 300 and 600 mg/kg was pretreated 15 min before CC. Although DMTU was shown to block the permeability lung damage caused by phorbol myristate acetate (a neutrophil activator), this agent did not exert any effect on the CC-induced pressor response and lung injury. The data indicate that granulocyte-mediated oxidants such as hydroxyl radical and hydrogen peroxide do not appear to be involved in this type of neurogenic lung pathology. The results support the concept that PHE induced by intracranial hypertension is initiated by hemodynamic changes in the systemic and pulmonary circulation. Hydrostatic effect plays a major role in this type of neurogenic lung pathology.