CONTROL OF PULMONARY EDEMA WITH SILICONE AEROSOLS

¹ Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, Michigan

Aerosols of dimethylpolysiloxane emulsions with antifoaming properties have been studied with respect to their ability to control pulmonary edema due to vascular factors (intravenous injection of epinephrine in rabbits) or respiratory tract irritation (inhalation of Cl₂ in rats).

Preliminary in vitro experiments revealed that although several silicone preparations have marked antifoaming properties, the emulsion XEC 151 is the most effective and easily handled. This agent is capable of preventing foaming in a 10 per cent serum solution when added in concentrations as low as 0.02 microgm./ml. of the emulsiomi (6 x 10^-9 concentration of the silicone).

Inhalation of an aerosol of an aqueous emulsion containing 10 per cent XEC 151 caused rapid subsidence of respiratory distress in rabbits injected intravenously with 0.25 to 2.0 mgm./kgm. of epinephrine, and provided essentially complete protection against death from doses of epinephrine of 1.0 mgm./kgm. or less, and 60 per cent protection against death from 2.0 mgm./kgm. Emulsion XEF 215 provided only slightly less protection than did XEC 151. These aerosols also afforded protection against death from pulmonary edema following Cl2 inhalatiomi, although the range of exposure within which death was prevented was much narrower than in the case of epinephrine. It is suggested that the limits. of dosage of epinephrine or chlorine against which the silicone aerosols can protect is determined by toxic actions of these agents other than the production of pulmonary edema.

Inhalation of the silicone aerosol did not alter oxygen transfer in the lungs of dogs amid daily administration for as long as 28 days did not produce inflammatory or granulomatous changes in the lungs of rats. Other workers have reported the extremely low toxicity of these materials after both acute and chronic- administration by various routes.

A comparison of the action of these aerosols with that of other agents proposed for the local control of pulmonary edema indicates many points of superiority of the silicone emulsion aerosols and suggests that these agents should be given a serious clinical trial in the control of pulmonary edema in man.

It is also suggested that the silicone emulsions can be employed safely to reduce foaming in aerated isolated organ chambers containing serum or other proteinaceous materials.