Malignant pleural effusions: meaning of pleural-fluid pH determination

In 36 patients with malignant pleural effusions, we determined the pH and the glucose concentration of the pleural fluid. Twenty-one of 36 patients (58.3%) had a low pH (less than 7.30) and 15 had a normal pH (greater than or equal to 7.30; 7.13 +/- 0.12 vs. 7.37 +/- 0.05; p less than 0.0005). The patients with low pH had significantly lower glucose concentrations than those with normal pH (2.7 +/- 1.4 vs. 6.3 +/- 2.9 mmol/l; p less than 0.0005). Twenty-one of 34 patients (61.7%) had a glucose concentration lower than a cut-off value of 4.4 mmol/l; of these, 17 (81%) had a low pH. The mean survival in the low-pH group was 4.8 +/- 4.4 months, whereas the mean survival in the normal-pH group was 5 +/- 8 months (p greater than 0.4). Twelve of 36 patients (33.3%) were treated with intrapleural Corynebacterium parvum (CBP) injections. Fourteen of 21 low-pH patients (66.6%) survived more than 2 months, and 4 of them are still alive. Six of 15 normal-pH patients (40%) survived more than 2 months, and 1 of them is still alive. Three of the 5 living patients were treated with CBP (2 in the low-pH group and 1 in the normal-pH groups). Our results confirm that pH and glucose concentrations in the pleural fluid of patients with malignant effusions are frequently low. However, the survival and the response to CBP pleurodesis in patients with low-pH malignant effusions are the same as those in patients with normal-pH malignant effusions.