Tissue plasminogen activator and DNase in empyema.

To the Editor: Rahman and colleagues (Aug. 11 issue)1 found improved fluid drainage in patients with pleural infections and a reduced frequency of surgical referral and duration of hospital stay after combined therapy with intrapleural tissue plasminogen activator (t-PA) and DNase. In pleural effusions, the viscosity correlates with the concentrations of albumin, protein, and lactate dehydrogenase.2,3 In an experimental model, the peak in lactate dehydrogenase levels occurs about 12 hours after the peak in numbers of inflammatory cells in the pleural fluid.4 Hence, antibiotic treatment before randomization might have had an influence on the pleural inflammatory response and consequently on the results. Can the authors provide information about antibiotic treatment before randomization and chest-tube drainage?