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Magnesium Imbalances

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References:

  1. Saunders Comprehensive Review for the NCLEX-RN Examination, 9th Edition, ISBN 978-032-37-9530-2, by Linda Anne Silvestri, Angela E. Silvestri, and Jessica Grimm (Ch. 8, pp. 88-105)

Hypomagnesemia

Normal Serum Magnesium Level: 1.8 to 2.6 mEq/L (0.74 to 1.07 mmol/L)

Hypomagnesemia is a serum magnesium level lower than 1.8 mEq/L (0.74 mmol/L). It may be caused by:

  1. Insufficient magnesium intake: malnutrition and starvation, vomiting or diarrhea, malabsorption syndrome, Celiac disease, and Chron’s disease
  2. Increased magnesium excretion: medications such as diuretics, and chronic alcoholism
  3. Intracellular movement of magnesium: hyperglycemia, insulin administration, sepsis

Assessment

  1. Cardiovascular: tachycardia; hypertension
  2. Respiratory: shallow respirations
  3. Neuromuscular:
    • Hyperreflexia
    • Twitches, paresthesias
    • Positive Trousseau’s and Chvostek’s signs
    • Tetany, seizures
  4. Central Nervous System: irritability; confusion
  5. Laboratory Findings:
    • Serum magnesium level less than 1.8 mEq/L (0.74 mmol/L)
    • ECG changes: tall T waves, depressed ST segments

Interventions

  • Hypocalcemia frequently accompanies hypomagnesemia. Include correction of serum calcium levels in the plan of care.
  • Oral preparations of magnesium may cause diarrhea and increase magnesium loss.
  • Magnesium sulfate through IV may be prescribed in ill clients when levels are low. IM administration causes pain and tissue damage. Initiate seizure precautions, measure serum magnesium levels frequently, and monitor for diminished deep tendon reflexes (suggestive of hypermagnesemia) during administration.

Hypermagnesemia

A serum magnesium level exceeding 2.6 mEq/L (1.07 mmol/L). It may be caused by:

  1. Increased magnesium intake: the consumption of magnesium-containing antacids and laxatives, and excessive magnesium administration through IV.
  2. Decreased renal excretion of magnesium as a result of renal insufficiency.

Assessment

  1. Cardiovascular: bradycardia, dysrhythmias; arrest is possible if severe
  2. Respiratory: respiratory insufficiency if muscles of respiration are involved
  3. Neuromuscular: diminished or absent deep tendon reflexes, skeletal muscle weakness
  4. Central Nervous System: drowsiness and lethargy that progresses to a coma
  5. Laboratory Findings:
    • Serum magnesium level over 2.6 mEq/L (1.07 mmol/L)
    • ECG changes: prolonged PR interval, widened QRS complexes

Interventions

Calcium gluconate is the antidote for a magnesium overdose!

  • Diuretics are prescribed to increase renal excretion of magnesium.
  • Intravenously administered calcium chloride or calcium gluconate may be prescribed to reverse the effects of magnesium on cardiac muscle.
  • Instruct the client to restrict dietary intake of magnesium-containing foods: dark green leafy vegetables, fruits (e.g. bananas, dried apricots, and avocados), nuts (e.g. almonds, and cashews), peas and beans (legumes), seeds, soy products (e.g. soy flour and tofu), whole grains (e.g. brown rice and millet), and milk
  • Instruct the client to avoid the use of laxatives and antacids containing magnesium.

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