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*HYPOMAGNESEMIA

* Normal serum Magnesium range: 1.7-2.4 mg/dL (= 1.4-2.0 mEq/L = 0.70 -1.00 mmol/L);
 - to convert mg/dL to mmol/L (SI units): multiply by 0.4114

Assoc. lytes abnormality: hypocalcemia, hypokalemia, hypophosphatemia, hyponatremia. (Ref: Arch IM 1992/01;152:40)

Cardiac Sx: Digitalis toxicity, Arrhythmia (V tach, V Fib, PVC, Torsades de pointes, PAC, Multifocal atrial tach.

RX:
In arrhythmic hypomagnesemic pt: 10-15 ml of 20% MgSO4 be infused in 1 min (8 -12 mmol of Mg), followed by 500 ml of 2% MgSO4 (40 mmol) over 5 h.
A second 500 ml of the solution given over a 10 h period may be necessary.

In convulsing hypomagnesemic pt: MgSO₄ 4 g (16 mmol of Mg) IV, followed by 12 g (48 mmol) for the remainder of day 1, then 6 g/d IV for days 2-5.

In non-convulsing hypomagnesemic pt: give 8-12 g/day in divided doses as MgSO₄ 1-2 g IV over 30-60 min or 1 g IM q4-6h; or MgCl₂ 50 mmol/day (100 mEq Mg²⁺/day) IV infusion.
   

Diff. Dx:
A. Decreased intake or absorption
1. Protein calorie malnutrition
2. Losses of GI fluids
3. Malabsorption syndromes
4. Primary hypomagnesemia

B. Renal losses
1. Diuretics
2. Non azotemic tubular dysfunction
3. Primary & secondary aldosteronism
4. Idiopathic hypomagnesemia

C. Magnesium depletion & miscellaneous disorders
1. Chronic alcoholism
2. Diabetic ketoacidosis
3. Bone resorption
4. Hyperthyroidism or primary hyperparathyroidism
5. Amphotericin B toxicity

*HYPERMAGNESEMIA
1. Severe renal failure
2. Moderate renal failure on magnesium containing antacids

04182001