Magnesium Sulfate

Magnesium Sulfate

Class:
  • Electrolyte replacement (anticonvulsant, antidysrhythmic)
Actions:
  • Depresses the central nervous system
  • Depresses skeletal and smooth muscles
  • Decreases amount of acetylcholine in neuromuscular synapses
Indications:
  • Torsades de pointes (polymorphic ventricular tachycardia)–1st line drug of choice during cardiac arrest
  • Hypomagnesemia
Pharmacokinetics:
  • Duration: 30 minutes (IV)
Adverse Effects:
  • Flushing, sweating, extreme thirst, sedation, confusion
  • Depressed reflexes, flaccid paralysis, respiratory paralysis
  • Heart block, cardiac arrest
Signs of Toxicity:
  • Paralysis
  • Cardiac arrest
  • Hypermagnesemia (weakness, depressed reflexes, paralysis)
Contraindications:
  • Myocardial damage
  • Heart blocks
  • In pregnancy, IV administration during 2 hours before delivery
  • Safety during pregnancy (Category A).
Dosages & Routes: IV bolus:  (for dysrhythmias or hypomagnesemia)

 

  • Torsades de pointes during cardiac arrest:  1-2 gm diluted to 10 ml with D5W IV or IO over 5 – 20 minutes.
  • Torsades de pointes with pulse or hypomagnesemia: 1-2 gm in 50-100 ml D5W IV infusion over 5 – 60 minutes.  Follow with 0.5 – 1 gm/hour titrated to control torsades.
Nursing Implications:
  • Drug Interactions:
  • Drug Incompatibilities:
  • Check serum magnesium level prior to administration.
  • Cardiac monitor should be used on patients receiving MgSO4 intravenously.
  • Have injectable form of calcium gluconate available to reverse paralyzing effects of magnesium sulfate.
  • Blood pressure may drop if MgSO4  is administered too rapidly.
  • Check blood pressure and pulse every 10-15 minutes during therapy.
  • Normal serum plasma level of MgSO4 is 1.8 – 3.0 mEq/L.  Respiratory paralysis occurs at 12-15 mEq/L.  Cardiac arrest occurs at 25 mEq/L.
  • Assess patellar reflexes hourly to monitor for evidence of toxicity.
  • Monitor hourly urine output.
  • Do not breast feed while receiving MgSO4.

 

References:

American Heart Association. (2006). Handbook of Emergency Cardiac Care (p. 57). Salem, MA: AHA.

Dirks, J.L. (2010) Cardiovascular therapeutic management.  In L.D. Urden, K.M. Stacy, & M.E. Lough's (Eds.) Critical care nursing: Diagnosis and management (6th ed., p. 550).  St. Louis: Mosby Elsevier.

Lehne, R.A. (2010). Pharmacology for nursing care (7th ed., pp. 458-459).  St. Louis: Saunders Elsevier.

Wilson, B.A., Shannon, M.T., Shields, K.M., & Stang, C.L. (2007).  Prentice Hall Nurse's Drug Guide 2007 (pp. 989-991).  Upper Saddle River, NJ: Pearson Prentice Hall.

 

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