Changes in pleural PH, Po2, PCo2, and HCo3 following the thoracocentesis

Determining the pleural PH and PCo2 could be helpful in differential diagnosis of pleural effusion. Usually pleural fluid PH and Pco2 are measured immediately following the thoracocentesis and in case of any delay samples will be preserved on ice, meanwhile, PH could be remained unchanged under special situations in vivo and at room temperature. The present study was conducted with the aim of determining the changes in pleural PH, Po2, PCo2, and HCo3 immediately following the thoracocentesis and one hour later at room temperature. For this descriptive study, 84 patients with pleural effusion referring to Shaheed Beheshti Hospital in Kashan were included. Pleural aspiration was carried out in sitting position, then samples were examined for pleural PH, Po2, PCo2, and HCo3. To differentiate transudate and exudate blood samples were also obtained. There was no significant difference between PH and Hco3 of samples immediately obtained following the thoracocentesis and one hour later, however this difference was observed in Po2. Of 84 patients, 33 had transudative pleural effusion, whereas the remaining 51 had exudative pleural effusion. Among transudative pleural effusion PH, PCo2, and Po2 were significantly differed between T0 and T60, however this significant relation was not found in HCo3. Among exudative patients we have found significant association between Po2 T0 and Po2 T60. The pleural fluid PH, PCo2, and HCo3 of samples kept at room temperature does not change significantly during the first hour following the thoracocentesis. Po2 is increased in transudative and exudative pleural effusion within the first hour following the thoracocentesis. Meanwhile, changes in PH, Po2, and PCo2 of transudate samples were more than exudate samples.