Body water and electrolyte composition in acute renal failure.

Body water and electrolyte contents have been measured by means of muscle biopsy analysis in 11 patients with untreated acute renal failure and in one patient during the diuretic recovery phase of his illness. Patients with acute oliguric renal failure show two main types of imbalance. One group shows evidence of a reduction in extracellular sodium and chloride with normal intracellular water and electrolytes. These findings are thought to be due to a combination of excess urinary salt loss during the development of oliguric renal failure, and inadequate replacement of extrarenal electrolyte losses. A second group shows overhydration of both extra- and intracellular phases, associated with an excess of sodium and chloride. The intracellular potassium concentration is reduced, owing to the intracellular water excess. The patient studied during the diuretic recovery phase of acute renal failure showed a marked loss of sodium and chloride, which emphasizes the necessity to replace urinary electrolyte losses at this stage of the illness. It is often extremely difficult to assess fluid and electrolyte balance in patients presenting with acute renal failure, and muscle biopsy analysis or isotope dilution studies may be required before accurate replacement therapy is possible.