Hypomagnesemia (Mg^2 +<1.4 mEq/L)
CAUSES
■ Inadequate intake/absorption
■ Malnutrition
■ Inadequate supplementation in IV fluids
■ Malabsorption
■ Alcoholism
■ Pancreatitis
■ Endocrine disorders
■ Aminoglycosides
SYMPTOMS
■ Lethargy
■ Muscle spasms
■ Seizures
EXAM
■ Neuromuscular
■ Irritability
■ Hyperreflexia, tremor, tetany, or carpopedal spasms
■ Cardiovascular
■ Hypotension
■ Arrhythmias: Digoxin potentiation for toxicity
■ QT and PR prolongation
■ Widened QRS
■ ST depression
■ T-wave flattening and inversion
■ Hypokalemia
■ Hypocalcemia
TREATMENT
■ Emergent replacement of life-threatening dysrhythmias or seizures should
include 1–2 g of MgSO 4 IV over 1–5 minutes.
■ Nonemergent magnesium replacement rate is 1–2 g over 1 hour, followed
by 0.5 g/hour.
■ Check and correct for associated hypokalemia and hypocalcemia.
Hypermagnesemia (Mg^2 +>2.2 mEq/L)
CAUSES
■ Iatrogenic, most commonly from administration to preeclamptic patients
■ Renal failure
■ DKA
■ Adrenal insufficiency
ENDOCRINE, METABOLIC, FLUID, ANDELECTROLYTE DISORDERSYou respond to a code on the floor to find an elderly man seizing. After
treating the seizures you review the chart to see the patient has been ad-
mitted for pneumonia and has been receiving IV fluids for the last few
days. With a basic metabolic panel that shows a normal sodium and
potassium, what electrolyte abnormality could cause the seizure?
This patient likely has iatrogenic hypomagnesemia.