Effects of nitroglycerin and nitroprusside on the pulmonary hemorrhagic edema induced by cerebral compression and epinephrine.

In vagotomized and pentobarbital-anesthetized rats, massive pulmonary hemorrhagic edema was produced by cerebral compression (CC) or an injection of epinephrine (EP) 0.25 mg/kg. The pulmonary changes were induced following severe Cushing reaction manifested by systemic hypertension. We determined the dose-effect relationship of nitroglycerin (NTG) and nitroprusside (NPS) on the changes in systemic arterial pressure and lung pathology. The drugs were given by iv infusion 5 min before CC or EP and continued throughout the experiment. NTG, 5 micrograms/kg/min, did not affect the pressor response and the pulmonary damage. In a dose of 10 micrograms/kg/min, the CC- and EP-induced changes were partially blocked. A dose of 20 micrograms/kg/min almost completely prevented the CC- and EP-induced pulmonary changes despite partial blockade of the pressor response. NPS exerted more potent effects than NTG on such changes. A dose of 5 micrograms/kg/min was capable of decreasing the pressor response by about 20% and the lung changes by about 50%. In a dose of 10 micrograms/kg/min, the pulmonary changes were almost completely prevented. The results suggest that vasodilators such as nitroglycerin and nitroprusside can block the pressor response and pulmonary pathology subsequent to CC or EP. The effects may be attributed to the ventricular unloading action of these vasodilators that decrease the preload and afterload of the heart. In this respect, nitroprusside is more potent than nitroglycerin.