Magnesium Flashcards
How abundant is Mg?
- 4th most abundant in body
- 2nd most abundant intracellular
How is Mg distributed in the body?
- 53% in bone
- 46% in muscle and soft tissue
- <1% in serum and RBC’s
Mg ions in the serum
- 33% bound to protein (mostly albumin)
- 61% free (ionized- physiologically active)
- 5% complexed w/ free ions
Name some roles of Mg
- Essential cofactor for >300 enzymes
- Transcellular ion transport
- Synth of carbs, proteins, lipids and nucleic acids
- Release of/response to hormones
- Neuromuscular transmission, muscle contration, metabolic function
How is Mg obtained?
Dietary:
- Rich; raw nuts, dry cereal, “hard” water
- Other: beggies, meat, fish, fruit
NOTE: processed foods are low
Which organ is responsible for Mg regulation?
- By kidneys
- Renal threshold; 0.60-0.85
- Non-protein bound is filtered by glomerulus (25-30% reabsorbed in PCT, 2-5% in DCT, 50-60% reabsorbed in loop of henle
What hormones play a part in regulation of Mg?
(Related to Ca+Na regulation)
- PTH (increases renal absorption along with Ca; enhances absorption in the intestines
- Aldosterone and thyroxine (increase renal excretion)
When is hypomagnesemia most common?
In hospitalized patients (ICU, diuretic therapy, digitalis therapy(heart conditions))
Name symptoms of hypomagnesemia
< 0.5mmol/L:
- Cardiovascular and neuromuscular (faulty ATPase pump)
- Neuromuscular (Ca uptake after muscle contraction and reg of acetylcholine impaired-weakness, tremors, tetany, paralysis, coma)
- Psychiatric (depression, psychosis)
- Metabolic (impairs PTH release/target tissue response)
NOTE: strong association w/ hypokalemia, hyponatremia, hypophosphatemia
How is hypomagnesemia treated?
Usually orally (Mg lactate, Mg oxide, MgCl2 Mg-containing antacid - Severely ill: parenteral (npo) MgSO4 solution
Mg treatment alone may fix other hypos.
When is hypermagnesemia seen?
Most common in renal failure
Most severe: decreased renal func + increased intake of antacids, enemas or cathartics
Pseudo- due to dehydration
When is MgSO4 used theraputically?
- Cardiac arrhythmia and myocardial infarction
- Antacids, enemas, cathartics
- Preeclampsia; decreases hyperactivity, increases uterine blood flow, neonatal hypermagnesemia may occur due to immature kidneys
Name symptoms of mild to moderate/ critical hypermagnesemia
MM- hypotension, bradycardia, skin flushing, nausea
Crit- ECG cahnges, aystole (flat line), coma, respiratory depression/arrest, paralysis
Other symptoms of hypermagnesemia
- May inhibit PTH release (hypocalcemia, hypercalcuria)
- Hemostasis inhibited due to competition b/w increased MG and Ca
Treatment of hypermagnesemia
- Discontinue source of Mg (increased intake)
- Immediate supportive therapy for severe
- Diuretics and IV fluid if normal renal func
- Hemodialysis with renal failure
