Studydroid is shutting down on January 1st, 2019

by mtoom


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Where is the body's magnesium?
  • 1% extracellular
  • 33% intracellular
  • 66% bones
What controls magnesium metabolism?
Urinary excretion which is controlled by:
  • Insulin
  • PTH
  • Calcitonin
  • ADH
  • Steroids
What are causes of hypomagnesemia? (3 categories)
  • Alcoholism (common)
  • GI-related
    -malabsoprtion, steatorrhea
    -prolonged fasting
    -fistulas
    -TPN without Mg supplementation
  • Renal
    -SIADH
    -diuretics
    -Bartter's syndrome
    -drugs
    -renal transplantation
What are clinical features of hypomagnesemia?
Similar to hypocalcemia
  • Neuromuscular and CNS hyperirritability
    -muscle twitching, weakness, tremors
    -hyperreflexia, seizures
    -mental status changes
  • Increased risk of hypocalcemia
  • Increased risk of hypokalemia
  • Prolonged QT interval 
What is important about hypomagnesemia with regard to other electrolytes? **
** Low magnesium makes it hard to correct low potassium and low calcium **
What other metabolic derangements are commonly found in the context of hypomagnesemia? (2)
  • Hypocalcemia
  • Hypomagnesemia
How would you treat hypomagnesemia? (2)
  • If mild, oral Mg (ie. magnesium oxide)
  • If severe, IV Mg (ie. magnesium sulfate)
What is the most common cause of hypermagnesemia? (1)
Renal failure
What are other causes of hypermagnesemia? (7)
  • Rhabdomyolysis
  • Burns
  • Trauma
  • Severe ECF volume deficit
  • Excessive Mg intake
  • Adrenal insufficiency
  • Iatrogenic (e.g. treatment of preeclampsia with MgSO4)
What are clinical features of hypermagnesemia? (6)
  • Nausea
  • Weakness
  • Facial paresthesias
  • Progressive loss of deep tendon reflexes
  • Death by respiratory failure or cardiac arrest
  • Somnolence leading to coma or paralysis
How do you treat hypermagnesemia? (5)
  • Stop Mg orders
  • Consider IV calcium gluconate for cardioprotection
  • Saline and furosemide
  • Dialysis if renal failure
  • Intubate if severe respiratory depression
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