Exchange of alkali trace elements in hemodialysis patients: A comparison with Na+ and K+

Background: In the past, nephrologists have been troubled by electrolyte di sturbances and consequently focused their attention on the importance of ma intaining the concentrations of electrolytes within the normal range. Howev er, information about the potential role of trace elements in chronic renal failure is scarce. Methods: During hemodialysis sessions, the concentratio ns of the five alkali metal cations lithium (Li), sodium (Na), potassium (K ), rubidium (Rb), and cesium (Cs) have been determined in plasma and dialys is fluids of chronic hemodialysis patients by inductively coupled plasma ma ss spectrometry (Li, Rb, Cs) and by ion-sensitive electrodes (Na, K). Stric t quality control schemes were applied to all analytical procedures to ensu re accuracy and precision of the results. Results: The plasma concentration s of the elements Li, Cs, Rb, and K distinctly decreased to 29, 50, 69, and 71%, respectively, of their initial values during hemodialysis. Simultaneo usly, the concentrations of these elements in dialysis fluids at the outlet of the dialyzer increased approximately 13-fold for Rb, Ii-fold for Li, 3- fold for Cs, and 2-fold for K as compared with the inlet values. The concen trations of Na in plasma and dialysis fluids were almost identical and did not change during hemodialysis. Conclusions: Li, Rb, and Cs were depleted i n hemodialysis patients, although the plasma concentrations of these trace elements still remained within the reference ranges for healthy adults. Con sequently, further studies are needed to elucidate the clinical importance and long-term effects of these trace element imbalances - for example, CNS disturbances associated with diminished concentrations of Rb - in hemodialy sis patients.