Lymphatic transport of pericardial effusate in sheep

In this report, we quantified fluid loss from the pericardial cavity during simulated saline effusions and determined what proportion of this loss occurred through lymphatics. Fifty or 100 ml of Ringers lactate solution [containing 0.5% sheep albumin and (131)I-human serum albumin (HSA)] was injected into the pericardial cavity of sheep. Pericardial pressures, systemic arterial pressures, and plasma/pericardial fluid concentrations of the radioactive tracer were measured. Lymph transport of pericardial fluid was estimated from the plasma recovery of tracer using a mass balance equation. Plasma recoveries were corrected for tracer loss using a coefficient of elimination calculated from the plasma disappearance curve of intravenously administered (125)I-HSA. Over 4 h, 27.6 +/- 4.9 (+/-SE) and 36.7 +/- 4.2 ml were lost from the pericardial cavity in the 50- and 100-ml effusion series, respectively, of which 5.2 +/- 0.8 (20.2 +/- 3.8% of volume lost) and 7.7 +/- 1.6 ml (21.5 +/- 3.3% of volume lost) could be attributed to lymphatic transport. We conclude that lymphatic transport is one of the factors that contribute to pericardial "reserve" function by helping to restore pericardial fluid volume to resting levels.