Muscle water and electrolytes in patients undergoing continuous ambulatory peritoneal dialysis

Muscle water and electrolytes were determined in percutaneous muscle biopsy material from m. quadriceps femoris in 33 uremic patients undergoing continuous ambulatory peritoneal dialysis (CAPD) for 1-38 months, and in 34 normal subjects. The patients showed increased muscle contents of water, sodium, and chloride relative to fat-free solids (FFS); both intra- and extracellular water contents were increased. The total water content was inversely correlated with the duration of CAPD. The muscle potassium content was increased, both relative to FFS and to magnesium, whereas the intracellular potassium concentration was normal. Despite hypermagnesemia, the muscle content of magnesium was normal and the intracellular concentration was even slightly decreased due to the increase in intracellular water. We conclude that muscle water and electrolyte status is abnormal in CAPD patients, but the alterations appear to be less marked than in uremic patients undergoing other forms of therapy.