SERIAL OBSERVATIONS AFTER HIGH-DOSE TALC SLURRY IN THE RABBIT MODEL FOR PLEURODESIS

The mechanisms leading to a pleurodesis after the intrapleural injecti on of a sclerosing agent are not completely understood. The purpose of the present study was to make serial observations over 28 days on the pleural fluid findings and the gross and microscopic changes in the p leura after talc slurry administered intrapleurally at a high dose. Si xty-six rabbits received 400 mg/kg talc slurry. Ten to 12 rabbits were sacrificed 1, 2, 4, 7, 14, and 28 days after the intrapleural injecti on. At sacrifice the pleural fluid was measured and analyzed, and the pleural surfaces were studied grossly and microscopically. The intrapl eural injection of 400 mg/kg talc slurry resulted in an acute exudativ e pleural effusion that persisted for 4 days. There was a progressive increase in the gross and microscopic fibrosis over the 28 days, Talc was present at the time of sacrifice in all animals. At 28 days there was a clinically significant pleurodesis in all rabbits; pleurodesis w as not observed before this time, From this study we conclude that the intrapleural injection of 400 mg/kg talc slurry leads to an acute exu dative pleural effusion and clinically significant pleurodesis that is present on day 28 but not day 14. It appears that the production of a pleurodesis requires higher doses of talc in rabbits without a chest tube than in humans with a chest tube.