Pleural fluid pH
Pleural fluid pH can be used to differentiate between a simple parapneumonic effusion (pH >7.20) and a complicated parapneumonic effusion (pH <7.20).
|Additional Information||Pleural fluid forms a film about 10 um thick between the visceral and parietal pleural surfaces and is usually <1 mL in volume. A proportion of patients who are hospitalised with pneumonia develop a pleural effusion (an excessive collection of fluid in the pleural cavity). This is referred to as a simple parapneumonic effusion. When the pleural fluid has developed features of infection but is not yet overtly purulent, this is referred to as complicated parapneumonic effusion. Pleural fluid containing frank pus (infection + white cells) is referred to as empyema. A simple parapneumonic effusion can be treated by antibiotics alone, whereas both a complicated parapneumonic effusion and frank pus require chest tube drainage. The British Thoracic Society (Thorax 2003;58(Suppl II):ii8-ii17) recommends fluid pH as a means of differentiating between a simple parapneumonic effusion (pH>7.2) and a complicated parapneumonic effusion (pH <7.2).|
|Send to||pH on blood gas analyser|
|Collection Con||This test requires anaerobic heparinised samples, most conveniently collected using a blood gas syringe. Exposure to air or mixing with air will decrease the sample pCO2 and therefore increase the sample pH. As a result, samples should NOT be sent through the air tube. Samples should be hand delivered, and must reach the laboratory within 30 minutes of collection. Minimum sample volume is 1 mL.|
|Telepath||PHF1L / PHF1J|