Malnutrition and muscle electrolytes in chronic respiratory failure

Magnesium, potassium and sodium content was measured in the quadriceps femoris muscle of 22 patients with hypercapnic-hypoxemic Chronic Obstructive Respiratory Disease (COPD), as well as in the external intercostal muscles of 14 of the same patients. Nutritional status was also evaluated by means of anthropometric, biochemical, and immunological parameters. Two groups of age- and sex-matched subjects were utilized as controls. Muscle potassium and magnesium content of both types of skeletal muscle was significantly decreased in the COPD patient group as compared to controls; muscle sodium content was increased. No correlation between serum and muscle electrolyte levels was found. Ten COPD patients out of 22 were malnourished; they had reduced muscle potassium and magnesium content values in respiratory and peripheral muscles as compared to both control subject group and COPD patients group with normal nutritional status. The latter patients had, however, low potassium and magnesium values in both respiratory and peripheral skeletal muscles as compared to controls. No relationship was found between serum and muscle electrolyte levels in COPD patients. Important derangements of skeletal muscle electrolyte content are present in COPD patients with respiratory failure, regardless of malnutrition - though magnesium and potassium depletion is more severe if malnutrition coexists.