Influence of diuretics on the concentration of proteins and other components of pleural transudates in patients with heart failure

PURPOSE: Diuretic therapy increases the total protein and lactate dehydroge nase concentrations in pleural fluid in patients with transudates due to he art failure, but the effect of diuresis on other substances in pleural flui d constituents is not known. SUBJECTS AND METHODS:Twenty-one patients with transudative pleural effusion s due to congestive heart failure were prospectively studied. Repeated diag nostic thoracentesis (mean +/- SD = 3 +/- 1; range, 2 to 6) was performed u ntil the effusions were radiographically unapparent (5 +/- 2 days). Thirty- one patients with congestive heart failure who underwent only a single thor acentesis after diuretic therapy served as controls. We measured the concen trations of various components of pleural effusions in the serum and in the pleural fluid, and determined the serum-pleural fluid gradient (serum conc entration minus pleural fluid concentration) and ratio (serum concentration divided by pleural fluid concentration). RESULTS: The pleural concentrations of most components increased significan tly (P <0.001) from the initial specimen to the final specimen: total prote in, from 23 +/- 7 g/L to 33 +/- 9 g/L; albumin, from 13 +/- 4 g/L to 18 1 6 g/L; lactate dehydrogenase, from 177 +/- 62 U/L to 288 +/- 90 U/L; cholest erol, from 31 +/- 16 mg/dL to 52 +/- 22 mg/dL; and cholinesterase, horn 1,3 04 +/- 616 U/L to 1,884 +/- 674 U/L. Expressed as percentage change, the in creases in the serum-pleural fluid gradients for albumin (12% +/- 22%) and total protein (11% +/- 12%) were significantly less than the increases in t heir concentrations in pleural fluid (albumin, 47% +/- 49%; total protein, 48% +/- 40%) or in their pleural fluid/serum ratios (albumin, 27% +/- 29%; total protein, 38% +/- 34%). CONCLUSIONS: The concentrations of the biochemical components commonly meas ured in pleural fluid increase progressively during diuretic therapy. Calcu lation of the serum-pleural fluid gradients for protein and albumin may be the most useful way to distinguish transudates from exudates in patients wi th congestive heart failure who have undergone diuresis. Am J Med. 2001;110 :681-686. (C) 2001 by Excerpta Medica, Inc.