Hypomagnesaemia and Muscle Electrolytes and Metabolites

Ten patients, aged 39–61 years, with hypomagnesaemia due to chronic alcoholism (7 cases) or malabsorption (3 cases), have been investigated by assessing the maximum isometric voluntary contraction force (MVC) of the quadriceps femoris muscle (7 cases), laboratory screening (9 cases) and estimating the electrolyte and metabolite content of biopsy specimens from the quadriceps femoris muscle. The MVC ranged from 0.5 to 34 kp and was significantly lower than in 12 apparently healthy normo-magnesaemic controls (p<0.001). The results of the laboratory screening, apart from a significant lowering of the serum magnesium concentration (p<0.01), were mainly within the range of normal values, apart from signs of liver damage, such as an elevated activity of S-OCT (3 cases), alkaline phosphatase (3 cases), S-ALAT (1 case) and an elevation of bilirubin and blood ammonia (2 cases). Low serum iron-binding capacity occurred in 4 cases, a finding reported in protein-calorie malnutrition. Muscle magnesium content was significantly lower than in healthy controls (p<0.001). Muscle sodium and chloride contents were significantly increased (p<0.05). Total H2O content and the extracellular H2O content were both significantly increased (p<0.05). Pyruvate and lactate values were within the normal range. The apparent equilibrium constant for creatine kinase differed significantly (p<0.01). ATP values were within the normal range, but there were slight decreases for ADP (p<0.05) and creatine phosphate (p<0.01), which is of interest in view of the lowering of the MVC and the diminished capacity for sustained muscular effort in hypo-magnesaemic patients reported earlier.