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Modification of pleural fluid pH by local anesthesia
D Jiménez Castro1, G Díaz, E Pérez-Rodríguez
1Respiratory Disease Service, Hospital Universitario Ramón y Cajal, Madrid, Spain.
Chest
|August 24, 1999
Summary
Anesthetizing patients before thoracentesis can alter pleural fluid pH. This change may misclassify parapneumonic effusions, especially small ones (<15%), potentially affecting treatment decisions.
Area of Science:
- Pulmonary Medicine
- Anesthesiology
- Diagnostic Procedures
Background:
- Thoracentesis commonly involves local anesthesia.
- The impact of anesthesia on pleural fluid pH is not well understood.
Purpose of the Study:
- To investigate if local anesthesia affects pleural fluid pH measurements.
- To determine the clinical significance of anesthesia-induced pH changes.
Main Methods:
- Compared pleural fluid pH before and after local anesthesia (mepivacaine) in 50 patients.
- Analyzed pH data for classification of parapneumonic effusions and need for chest tube.
- Stratified results by effusion volume (<15% and >15% hemithorax occupancy).
Main Results:
- A statistically significant decrease in pleural fluid pH was observed after anesthesia (7.32 vs. 7.28, p<0.0001).
- Discordance in effusion classification occurred in 45% of cases.
- In small effusions (<15%), anesthesia led to 80% classification discordance and 100% misprediction of chest tube need.
Conclusions:
- Local anesthesia can significantly alter pleural fluid pH.
- Anesthesia-induced pH changes may lead to misclassification of parapneumonic effusions, particularly small ones.
- Clinical decisions regarding chest tube placement may be impacted by pre-procedure anesthesia.