Trace elements in pleural effusions

When the secretion of pleural fluids exceeds their resorption, liquid (pleural effusion) will accumulate between the visceral and parietal pleura. Pleural effusions derived from the liquid components of blood are expected to contain trace elements and may, as a sink for trace elements, deprive the body of needed essential elements upon their removal by medical intervention. Consequently, patients may be at risk of drifting into trace-element deficiencies. Because the literature is almost devoid of data about trace elements in effusions, the concentrations of 14 trace elements (Ba, Ca, Cd, Co, Cs, Cu, Mg, Mn, Mo, Pb, Rb, Sn, Sr, Zn) were determined simultaneously by inductively-coupled argon-plasma mass spectrometry (ICP-MS) in effusions from 17 patients. The median values for the concentrations of Rb (209 mu g/kg, range 104-334 mu g/kg) and Cs (1.5 mu g/kg, range 0.8-2.4 mu g/kg) in the effusions were almost the same as in the sera. The concentrations of Mg (range 15-22 mg/kg), Ca (range 52-91 mg/kg), Sr (range 12-37 mu g/kg), and Ba (range 1.4-18.2 mu g/kg) were consistently lower in the effusions than in the sera by 18% for Mg, 26% for Ca, 14% for Sr, and 88% for Ba (percentages based on median in serum as 100%). The concentrations of the essential trace elements Co (range 0.16-0.5 mu g/kg), Cu (130-902 mu g/kg), Mn (0.2-2.2 mu g/kg), Mo (0.4-1.5 mu g/kg), Sn (0.4-1.2 mu g/kg), and Zn (27-1931 mu g/kg) in the effusions are generally lower (25-55% based on median) than in the corresponding sera, although a few effusions have higher concentrations of Co, Mn, Mo, or Zn than in the sera. The concentrations of Cd (range 0.2-0.5 mu g/kg) in the effusions were approximately the same as in the sera for three patients, considerably lower than in the sera for four patients, and considerably higher for three patients. The concentrations for lead (range 0.6-45 mu g/kg) in the effusions were generally much higher than in the sera. The effusions were not significantly contaminated with lead-rich erythrocytes. The concentrations of Ca, Cu, and Zn in the effusions correlated positively with the protein concentrations in the effusions. One kilogram of the effusions contains from 10-30% of the trace elements present in the entire volume of serum in circulation.