Magnesium (Mg+) on the NCLEX
Hypomagnesemia and hypermagnesemia: causes, signs, OB mag sulfate context.
Magnesium 1.5-2.5. Often overlooked but important. OB context (pre-eclampsia) is highest-yield.
Hypomagnesemia (<1.5)
Causes: alcoholism, malnutrition, diuretics, PPI long-term. Signs: similar to hypocalcemia (tetany, tremor, seizures). Hypokalemia often refractory until Mg replaced. Torsades de pointes. Treatment: IV MgSO4 (1-2 g over 1 hour for severe). Oral magnesium oxide for mild.
Hypermagnesemia (>2.5)
Causes: renal failure, mag sulfate therapy (OB), antacid abuse. Signs (progressive): decreased DTRs (first) → respiratory depression → hypotension → cardiac arrest. Treatment: calcium gluconate IV (antagonist). Stop magnesium. Dialysis in renal failure.
OB context
Mag sulfate for pre-eclampsia seizure prophylaxis. Therapeutic 4-7 mEq/L. Monitor DTRs, RR, UO closely. Calcium gluconate at bedside.
Frequently asked
Mag and K+ replacement?
Replace Mg first if low, K+ won't correct until Mg corrects.
Mag sulfate toxicity sign sequence?
Loss of DTRs → RR <12 → hypotension → cardiac arrest.
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