Muscle water and electrolytes in uremia and the effects of hemodialysis.

The effects of acute uremia and hemodialysis on water and electrolyte distribution and intracellular pH (pHi) of skeletal muscle were studied in dogs. Acute uremia resulted in an increase in intracellular muscle water and Ca++ content, and a fall in both intracellular Na+ concentration and the calculated muscle membrane potential (EM). Muscle pHi did not change. The increase in muscle Ca++ content was prevented by previous parathyroidectony. The administration of parathyroid extract to previously parathyroidectomized uremic animals resulted in a rise in muscle Ca++ content to levels similar to those observed in intact uremic animals. Hemodialysis with standard dialysate resulted in a normalization of both muscle Em and Ca++ content but did not affect either muscle intracellular water, Na+ concentration, or pHi. Hemodialysis with hypertonic dialysate (glycerol or mannitol) resulted in a slight fall in intracellular muscle water content toward normal but did not change muscle intracellular Na+ concentration or pHi. The muscle membrand permeability of Na+ relative to K+ (PNa/PK) was not changed by hemodialysis with either standard dialysate or dialysate with mannitol added. Glycerol, however, appeared to increase PNa/PK to about 10 times the normal value. The observed changes in muscle water and solute content may be related to the increased muscle irritability seen in acute uremic patients. These changes, however, are only partially corrected by hemodialysis with standard or hypertonic dialysate.