Background: This study describes the pleural fluid characteristics of patients who develop symptomatic pleural effusions after coronary artery bypass graft surgery (CABG).
Methods: Post-CABG patients who underwent a therapeutic thoracentesis for a symptomatic pleural effusion were included unless another explanation for the pleural effusion was present.
Results: During the study, 71 patients (mean age, 61 years) were identified; 49 were men and 22 were women. All patients underwent internal mammary artery grafting. Early effusions (<30 days after CABG) occurred in 45 patients (63%) and late effusions (>/=30 days after CABG) developed in 26 (37%). Early effusions were bloody (median red blood cell count, 706 x 10(12)/L [706,000 mm(3)])with a high eosinophil count (median, 0.385), whereas effusions that occurred in the late period were yellow exudates with predominant lymphocytes (median, 0.68) and monocytes (median, 0.20). The mean pleural fluid level of lactate dehydrogenase was more than 3 times the upper limit of the reference range in serum in early effusions, whereas late effusions had significantly lower lactate dehydrogenase levels.
Conclusions: Characteristics of early and late effusions differ significantly, suggesting a different pathogenesis of the effusions. Patients who develop a symptomatic pleural effusion after CABG should undergo a therapeutic thoracentesis; however, further investigations are warranted only in patients who have pleural fluid characteristics different from those described.