The Glucose-pH Relationship in Parapneumonic Effusions

Both a low pleural fluid glucose concentration and pleural fluid acidosis are markers of severe pleural inflammation, but the relationship between these phenomena has not been defined clearly. Therefore, we measured simultaneous pleural fluid glucose concentrations and pH in 25 consecutive parapneumonic pleural fluids. Seventeen effusions had a glucose concentration > 60 mg/dl (group 1, 126 ± 7 mg/dl, mean ± SEM), while eight had a pleural fluid glucose < 60 mg/dl (group 2, 15 3 mg/dl,P<.01). Pleural fluid pH was 7.35 ± 0.03 in group 1 compared with 6.83 ± 0.09 in group 2 (P<.01). A significant correlation between pleural fluid glucose and pH was found (r=.81,P<.01). Low-glucose, low-pH effusions were complicated (either loculated or empyemas). Uncomplicated effusions had glucose concentrations > 60 mg/ dl and a pleural fluid pH > 7.30. The concomitant occurrence of low pleural fluid glucose and pH suggests that the mechanisms leading to these phenomena are interrelated. (Arch Intern Med138:1378-1380, 1978)