Magnesium and Calcium Flashcards
The averge human body(70kg) contain how many moles of Mg2+?
1 mole (25grams) Magnesium
4th most abundant cation in the body and 2nd most abundant cellular ion
Magnesium
% of Magnesium found in the bone
53%
% of Magnesium found in muscle and other organs and soft tissue
46%
% of Magnesium present in serum and Red blood cells
<1%
In the serum, about ___% magnesium is bound to protein, primarily albumin
34%
In the serum, about ___% magnesium exists in the free or ionized state(active)
61%
In the serum, about ___% magnesium is complexed with other ions (phosphate, citrate)
5%
It is the free ion that is physiologically activite in the body
Magnesium
Magnesium Serves as an essential cofactor of enzymes like:
- Amylase
- Acid Phosphatase
- Alkaline Phosphatase
Clinical significance of magnesium
- cardiovascular disorders
- metabolic disorders
- neuromuscular disorders
*others: Hyperaldosteronism Hyperparathyroidism Hyperthyroidism Hypercalcemia Tubular disorder Pyelonephritis Glomerular mephritis
Sources of Magnesium:
Raw nuts Dry cereals Hard drinking water Vegetables Meat Fish Fruit
The ___ ______ may absorb 20-65% of the dietary Magnesium depending on the need and intake
Small intestine
This largely controls the overall Magnesium in the body and also reabsorbs Magnesium in deficiency states or readily excrete excess Mg2+ in overload states
KIDNEY
25-35% of the nonprotein-bound Magnesium (that gets filtered by glomerulus) is reabsorbed by the:
Proximal Convoluted Tubule
This is the major regulatory site where 50-60% of filtered Mg2+ is reabsorbed in the:
Ascending Loop of Henle
2-5% of the filtered Mg2+ is reabsorbed in the
Distal Convoluted Tubule
Renal threshold for Mg2+ is approx.
0.60-0.85 mmol/L (=1.46-2.07 mg/dl)
Normally, only about _% of filtered Mg2+ is excreted in urine per day
6%
This hormone increases the renal reabsorption of Mg2+ in the intestine
Parathyroid Hormone (PTH)
These 2 hormones increases renal excretion of Mg2+
Aldosterone
thyroxine
Causes of hypomagnesemia
- reduced intake
- decreased absorption
- increased RENAL excretion
- increased ENDOCRINE excretion
- increased DRUG INDUCED excretion
- miscellaneous
Causes of Reduced intake of Magnesium
- poor diet
- prolonged magnesium deficient Intravenous(IV) therapy
- chronic alcoholism
Causes of decreased absorption of Mg2+
- malabsorption syndrome
- surgical resection of small intestine
- nasogastric suction
- pancreatitis
- prolonged vomiting and diarrhea
- Laxative abuse
Causes of increased Renal excretion
- tubular disorder
- glomerulonephritis
- pyelonephritis
Causes of Increased ENDOCRINE excretion
- hyperparathyroidism
- hypercalcemia
- hyperaldosteronism (causes paeudohypomagnesia due to increased water reabsorption)
- Hyperparathyroidism
- Diabetic Ketoacidosis (excess urinary loss of Mg associated with Glycosuria)
Causes of Increased DRUG INDUCED Excretion
- dirutecs: Loop diiretics like FUROSEMIDE (increases renal loss of Mg2+)
- thiazide diuretics: require a longer period of use to cause hypomagnesemia
- Antibiotics (gentamicin, cisplatin)
- Cyclosporine: nephrotoxixity, hypertension & neurologic symptoms
- Cardiac Glycosides: digitalis and digoxin
Miscellaneous causes of Hypomagnesemia
- excess Lactation: increased ise and loss thru milk production
- Pregnancy: hyperexcitable uteruS, anxiety and insomnia
Cardiovascular symptoms of Hypomagnesemia
Arrythmia
Hypertension
Digitalis roxicity
Psychiatric symptoms of. Hypomagnesemia
Depression
Agitation
Psychosis
Metabolic disorders causing hypomagnesemia
Hypocalcemia
Hypokalemia
Hyponatremia
Hypophosphatiemia
Treatment of Hypomagnesemia
-oral intake of Magnesium lactate, Magnesium oxide, magnesium chloride or an antacid that contains Magnesium
In severe ill px, this is the preferred tx
Magnesium sulfate solution giver parenterally
Causes of Hypermagnesemia
- decreased secretion
- increased intake
- miscellaneous
Most common cause of hypermgnesemia
Renal failure
Decreased excretion of Mg2+ causes
Acute or chronic renal failure, and hyperthyroidism
Hypoaldosteronism and hypopituitarism( decreased GH and thyroxine)
Increased intake of these drugs leads to Hypermagnesemia
- antacids, enemas, catharics
- therapeutic-eclampsia, MI, cardiac arrythmias
Causes Pseudohypermagnesemia
Dehydration
Treatment of hypermagnesemia
- discontinue Mg2+ source
- for severe Hypermagnesemia: immediate supportive therapy for cardiac, neuromuscular or respiratory abnormalities
- for patients with Renal failure: dialysis
- for normal renal dunction: Diuretic and IV fluid
Specimen for det of Magnesium
Serum (nonhemolyzed)
Plasma (anticoag: Lithium heparin)
Urine (24hrs)
Hemolysis causes falsely ____ Magnesium since Mg is 10x Grater in the intracellular fluid than in Extracellular
Falsely Increased
This is added to remove the presence of Calcium during determination of Magnesium
Calcium shelter
Unacceptable anticoags for determination of mg2+ because theyll bind to Mg2+
Oxalate
Edta
Citrate
Positive result for mAgnesium in FES method
No color imparted to flame
Reference method for measuring Magnesium
AAS- Atomic absorption spectroscopy
3 most common colorimetric methods for Serum Magnesium measurement
Calmagit
Formazen
Methylthymol blue
Positive result for measurement of Mg2+ in calmagite methodq
Reddish violet compound @ 532 nm
Positive result for magnesium in Formazen dye method
Colored complex read @ 660 nm
Positive result for Magnesium in Methylthymol blue method
colored complex
Indicator used in Fluorometric Method for measuring magnesium
8-hydroxyquinoline indicator
Reference Range for serum Mg2+
Serum, colorimetric: 0.63-1.0 mmol/L (1.26-2.10 mEq/L)
