Perception versus Reality: The Measuring of Pleural Fluid pH in the United States

Abstract

Background: Pleural fluid pH measured by a blood gas analyzer is the only recommended method of pH measurement to guide management for patients with parapneumonic pleural effusions. Not all hospitals use blood gas analyzers for pleural fluid pH determination and it is unknown if physicians are aware of this problem. Objective: To determine if a discrepancy exists between the modality used for measuring pleural fluid pH and how physicians believe it is measured. Methods: We surveyed pulmonologists randomly across the USA by e-mail inquiring how they thought pleural fluid pH was measured at their laboratory. We then independently contacted the laboratory and asked how pleural fluid pH was actually measured. Results: Two hundred and sixty-seven pulmonologists completed the survey. Eighty-six percent of the pulmonologists use pleural fluid pH to manage complicated parapneumonic effusions. Forty-three percent did not recognize blood gas analyzer solely as the most accurate and validated method. Thirty-nine percent of the physicians who use pleural pH to manage effusions and believe that blood gas analyzers are the most accurate were wrong in their assumption that their laboratory was using this tool for pleural pH measurement. Conclusions: Whether it is due to inaccurate knowledge or a perception of how pleural fluid pH is tested, a significant number of pulmonologists, when treating complicated parapneumonic effusions, may be making management decisions based on erroneous information.

Recent developments in the management of pleural infection: A comprehensive review

“…To date, the most powerful clinical indicator to chest tube drainage is a pleural fluid pH < 7.2, a cut‐off universally agreed among international guidelines. The sample for pH should be collected anaerobically in a heparinized blood gas syringe, as the presence of air can falsely elevate pleural fluid pH, as can delay in measurement . Lidocaine is acidic and falsely depresses fluid pH.…”

“…The sample for pH should be collected anaerobically in a heparinised blood gas syringe, as the presence of air can falsely elevate pleural fluid pH, as can delay in measurement. 46 Lidocaine is acidic and falsely depresses fluid pH. Visualisation of frank pus on pleural aspiration is diagnostic of empyema requiring chest tube drainage, and does not require any further confirmatory investigation.…”

A simple weighted scoring system to guide surgical decision-making in patients with parapneumonic pleural effusion

“…Unfortunately, no reliable indicators of the need for surgical intervention have yet been identified. In addition, pH measurements pose some preanalytical challenges (12,13). The results of our study indicated that pleural LDH and glucose levels were increased and decreased, respectively, in patients treated with surgery ( Table 2).…”

Diagnosis of complicated parapneumonic effusion by pleural pH measurement is jeopardized by inadequate physician knowledge and guideline-discordant laboratory practice

“…Assessments of pleural guideline adherence have generally focused on the performance of pleural procedures [7,8]. However, at least one other study examined pleural pH measurements in the United States a decade ago, with very similar findings [9].…”