Categorizing risk for poor outcome in patients with parapneumonic effusions

* pH is the preferred pleural fluid chemistry test, and pH must be determined by a blood gas analyzer. If a blood gas analyzer is not available, pleural fluid glucose should be used (P0 = glucose ≥60 mg/dL; P1 = glucose <60 mg/dL). The expert panel cautions that the clinical utility and decision thresholds for pH and glucose have not been well-established.
¥ Clinical experience indicates that effusions of this size do not require thoracentesis for evaluation, but will resolve.
** If thoracentesis were performed in a patient with A0 category pleural anatomy and P1 or B1 status found, clinical experience suggests that the P1 or B1 findings might be false-positive. Repeat thoracentesis should be considered if effusion enlarges and/or clinical condition deteriorates.
†† If clinical condition deteriorates, repeat thoracentesis and drainage should be considered.
¥¥ Regardless of prior antibiotic use.
*** Larger effusions are more resistant to effective drainage, possibly because of the increased likelihood that large effusions will also be loculated.
††† Pleural loculations suggest a worse prognosis.
¥¥¥ Thickened parietal pleura on contrast-enhanced CT suggests presence of empyema.