Elucidation on acidity and low glucose concentration in parapneumonic effusion.

Studies were conducted on three consecutive patients with parapneumonic effusions by (a) serial analyses of plasma -pleural fluid glucose, pH, PCO2, and antimicrobial levels, and (b) serial analyses to determine the pH and PCO2 levels of pleural fluids that underwent in vitro incubation, before and after antimicrobial administration. The pleural fluid pharmacokinetics of the three antimicrobials followed a large reservoir model by increasing drug levels gradually, reaching the peak values at about two to seven hours following administration, while serial pleural fluid glucose levels showed a delayed rise or no rise in concentration, respectively. The molecular weights of the three antimicrobials are greater than that of the glucose, thus suggesting that over-utilization of glucose within the pleural cavity is more likely the cause of this situation than the transport defect. In the in vitro incubation study, the serial pleural fluid pH and PCO2 levels before antimicrobial administration progressively decreased, while those following the administration of antimicrobials were stable during the first few hours. The results indicate that, in cases of parapneumonic effusion, the inflamed pleurae and the infectious pleural fluid (empyema) over-utilizes pleural fluid glucose leading to increased fluid acidity.