Contemporary biochemical analysis of normal pericardial fluid

Objective Biochemical analysis of pericardial fluid (PF) is commonly performed for the initial assessment of PF, and the results are usually interpreted according to Light's traditional criteria for the differential diagnosis of transudates versus exudates. However, Light's criteria have been formulated for the biochemical analysis of pleural fluid. The aim of the present paper is to evaluate the normal composition of PF in candidates for cardiac surgery. Methods Cohort study with analysis of PF from candidates for cardiac surgery. Exclusion criteria were previous pericardial disease or cardiac surgery, prior myocardial infarction within 3 months, systemic disease (eg, systemic inflammatory diseases, uremia) or drug with potentiality to affect the pericardium. Results Fifty patients (mean age was 67 years; 95%CI 64 to 71, 29 males, 58.0%) were included in the present analysis. Levels of small molecules were similar in blood and PF. Total proteins in PF was, on average, 0.5 times lower than corresponding plasma levels (p=0.041), while the level of pericardial lactate dehydrogenase was, on average, 1.06 times higher than plasma (p=0.55). Moreover, mononuclear cells were more concentrated in PF than plasma (p=0.17). Traditional Light's criteria misclassified all PFs as exudates. Conclusions Traditional Light's criteria misclassified normal PFs in candidates for cardiac surgery as exudates. This study suggests their futility for the biochemical analysis of PF in clinical practice.