Pleural fluid characteristics of patients with symptomatic pleural effusion after coronary artery bypass graft surgery

Background: This study describes the pleural fluid characteristics of patie nts who develop symptomatic pleural effusions after corollary 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 ar tery grafting. Early effusions (<30 days after CABG) occurred in 45 patient s (63%) and late effusions (greater than or equal to 30 days after CABG) de veloped in 26 (37%). Early effusions were bloody (median red blood cell cou nt, 706 x 10(12)/L [706000 mm(3)])with a high eosinophil count (median, 0.3 85), whereas effusions that occurred in the late period were yellow exudate s with predominant lymphocytes (median, 0.68) and monocytes (median, 0.20). The mean pleural fluid level of lactate dehydrogenase was more than 3 time s the upper limit of the reference range in serum in early effusions, where as late effusions had significantly lower lactate dehydrogenase levels. Conclusions: Characteristics of early and late effusions differ significant ly, suggesting a different pathogenesis of the effusions. Patients who deve lop a symptomatic pleural effusion after CABG should undergo a therapeutic thoracentesis; however, further investigations are warranted only in patien ts who have pleural fluid characteristics different from those described.