Clinically documented pleural effusions in medical ICU patients: how useful is routine thoracentesis?

STUDY OBJECTIVES To assess the impact of routine thoracentesis on diagnostic assessment and therapeutic measures in patients with clinically documented pleural effusions. DESIGN AND SETTING Prospective, 1-year, three-center study in medical ICU (MICU) patients with physical and radiographic evidence of pleural effusion. PATIENTS Of 1,351 patients admitted to three MICUs during the study period, 113 patients had physical and radiographic evidence of pleural effusion, yielding an annual incidence of 8.4%. INTERVENTION Routine thoracentesis in 82 patients without contraindications to thoracentesis. MEASUREMENTS AND RESULTS Twenty patients (24.4%) had a transudate, 35 patients (42.7%) had an infectious exudate (parapneumonic, n = 21; empyema, n = 14), and 27 patients (32.9%) had a noninfectious exudate. Laboratory parameters including the leukocyte count, the neutrophil percentage in pleural fluid, and the fluid/serum protein and lactate dehydrogenase ratios differed significantly among the three groups. Thoracentesis yielded improvements in the diagnosis and/or treatment in 46 patients (56%): the presumptive (prethoracentesis) diagnosis was changed in 37 patients (32 patients with certain benefit and 5 patients with probable benefit from thoracentesis), of whom 27 patients received a change in treatment based on the new diagnosis; 9 other patients received a change in treatment although the diagnosis remained the same. The only complications were pneumothorax in six patients (7%), all with a favorable outcome after drainage. CONCLUSION Infection was the main cause of pleural effusions detected based on physical and radiographic findings in our MICU population. Routine thoracentesis proved a simple and safe means of improving the diagnosis and treatment.