The pH of sclerosing agents: a determinant of pleural symphysis.

The rate of success in producing pleural symphysis with intrapleural instillation of sclerosing agents has been variable. Differences in the designs of studies probably account for some of the variability, but the reasons for the remainder are not clear. Since a low pH of the pleural fluid is associated with pleural adhesions and loculations, the pH of the commonly used solutions of sclerosing agents was determined, both in their usual concentrations and when diluted with large quantities of exudative pleural fluid. The buffered solution of tetracycline hydrochloride had the most acidic pH (2.0) and showed little change when diluted by pleural fluid. A 0.5 percent solution of sodium hydroxide had the highest pH (13.0). The remainder of the sclerosing solutions showed a range of pH from 4.3 to 8.7. Experimental and clinical experience suggests that tetracycline consistently has the highest rate of success in producing pleural symphysis. It appears that when proper technique is employed, the pH of the solution of the sclerosing agent is an important determinant of the production of pleural symphysis.