Magnesium supplementation in Bartter's syndrome

Bartter's syndrome: a rare cause of a severe metabolic abnormality in a pre-term neonate

A premature neonate with a severe form of Bartter's Syndrome is presented. Clinical features, diagnosis, treatment and prognosis of Bartter's Syndrome are discussed.

A clinical approach to common electrolyte problems: 4. Hypomagnesemia

Magnesium plays a critical role in many cell functions. Hypomagnesemia may occur because of decreased intake or absorption, internal redistribution or increased loss of this element through either renal or nonrenal routes. Manifestations of magnesium deficiency include alterations in calcium, phosphate and potassium homeostasis along with cardiac disorders such as malignant ventricular arrhythmias refractory to conventional therapy, enhanced sensitivity to digoxin and, possibly, coronary artery vasospasm and sudden death. Other features of magnesium deficiency include a host of neuromuscular and neuropsychiatric disorders. In this review we detail mechanisms that may lead to magnesium deficiency, summarize the clinical features of the deficiency and provide a clinical approach to the diagnosis and treatment of this electrolyte disorder.

Biochemical features of dietary chloride deficiency syndrome: a comparative study of 30 cases

The diagnosis in one infant of a severe state of chloride deficiency after ingesting a diet consisting exclusively of a modified cow milk formula containing only 0.5 mEq/100 kcal chloride ion led to the identification of 30 additional infants (age 2.6 +/- 0.7 months) fed the same commercial formula. The total absence of chloride in the urine was used as a biochemical index of subclinical dietary chloride deficiency. Serum and urine values were studied at diagnosis and 10 to 12 days after chloride replenishment, and compared statistically with the values obtained in a control group of 40 infants (age 2.8 +/- 1.2 months) fed exclusively a different modified formula containing an adequate chloride concentration. The outstanding laboratory abnormalities noted in the infants ingesting a low chloride formula were hypochloremia and metabolic alkalosis. Mean serum concentrations of potassium, urea, creatinine, and uric acid were in the normal range, but group values were statistically different from normal. A previously unreported finding was the demonstration of a significant elevation in the serum concentrations of calcium and phosphate and in the urinary excretions of calcium and magnesium, which persisted after almost complete recovery of the remaining biochemical disturbances. These results indicate the potential risk of nephrocalcinosis after dietary chloride deficiency.

Disorders of calcium and magnesium homeostasis

The components of calcium and magnesium balance and the factors responsible for the maintenance of the serum concentration of these cations are reviewed. Within this framework, the causes and treatment of disturbances of the serum concentration are discussed. Hypercalcemia is usually a reflection of increased bone resorption and/or gut absorption with the kidney playing a secondary role. Hypocalcemia is usually due to either a disturbance in the parathyroid hormone-adenylate cyclase system or a disturbance in vitamin D metabolism. As vitamin D is required for expression of the action of PTH at bone and as PTH is a prime regulator of vitamin D metabolism, the absence of either component results in important disturbances in calcium balance. In contrast to calcium homeostasis, the kidney plays a major role in the determination and regulation of serum magnesium. The major causes of hypermagnesemia therefore are associated with loss of renal function, and hypomagnesemia is frequently due to renal magnesium wasting.

Studies on the pathogenesis of Bartter's syndrome

There is no agreement concerning the primary pathogenetic event leading to Bartter's syndrome. Free water clearance and distal fractional chloride reabsorption were abnormally low in our patient with Bartter's syndrome. This series of investigations in this patient with Bartter's syndrome and hypomagnesemia was undertaken to determine if the defect in chloride transport in the ascending limb and the associated renal potassium wasting was specifically related to potassium depletion, increased prostaglandin production or magnesium depletion. Neither potassium repletion, indomethacin administration nor magnesium repletion had an effect on the defect in free water clearance or in distal fractional chloride reabsorption. However, magnesium infusion eliminated renal potassium wasting. These observations suggest that the proximate cause of Bartter's syndrome in this patient is a primary defect in the reabsorption of sodium chloride in the ascending limb and not renal potassium wasting. however, hypomagnesemia may contribute to the renal potassium wasting seen in this syndrome.