Experimental pleurodesis in rabbits induced by silver nitrate or talc - 1-year follow up

Study objective: To compare the pleurodesis results from the intrapleural i njection of silver nitrate and talc slurry over an observation period of 12 months in rabbits. Design: Rabbits were randomized to receive 2 mL of 0.5% silver nitrate or 4 00 mg/kg of talc slurry in 2 mL intrapleurally. Ten rabbits in each group w ere killed at 1 month, 2 months, 4 months, 6 months, 8 months, 10 months, a nd 12 months after intrapleural injection. The degree of gross pleurodesis and the amount of microscopic pleural fibrosis and inflammation were graded on a scale of 0 to 4. Results: The mean +/- SEM gross pleurodesis score in the 70 rabbits that re ceived silver nitrate was 3.34 +/- 0,08, which was significantly higher tha n the score of 2.32 +/- 0.09 in the 70 rabbits that received talc. The mean gross pleurodesis score was significantly higher at each of the observatio n times (p < 0.05), except at 2 months, in the rabbits that received silver nitrate, The pleurodesis was distributed throughout the thorax in the rabb its that received silver nitrate, while it was only in the ventral thorax i n the rabbits that received talc slurry. The gross pleurodesis scores showe d no tendency to decrease during the 12-month observation period in either treatment group. The persistence of talc in the pleural space did not lead to chronic inflammatory changes because the inflammation scores were simila r in both groups at ah observation times. The microscopic pleural fibrosis score tended to decrease with time in the silver nitrate group but not in t he talc slurry group. Conclusions: The intrapleural injection of 2 mL of 0.5% silver nitrate prod uces a better pleurodesis than does the intrapleural injection of 400 mg/kg of talc slurry in rabbits. The pleurodesis induced by silver nitrate persi sts for at least 1 year. The efficacy of silver nitrate as a sclerosing age nt in humans should be evaluated.