Magnesium Flashcards
What is the 4th most abundent cation in the body?
Magnesium
How often can you repeat doses of calcium?
every hour
What is the clinical effect like?
immediate, but transient
What does IV calcium do?
it directly antagonizes the NM and CV effects of hypermagnesemia
How do you treat a patient with severe hypermagnesemia?
with IV calcium
How can most cases of hypermagnesemia be anticipated?
renal failure patients should not be given mg meds, parenteral mg should be monitored
When do you see muscle paralysis, respiratory paralysis, cardiac arrest?
above 10
When do you see bradycardia, ecg changes, hypotension?
10-Jun
When do you see drowsiness, flushing and headache?
mg- 4-6
What 3 symptoms can be seen if potassium exceeeds 4 meq/L?
NM, CV, hypocalcemia
How can mild hypermagnesemia occur?
hyperparathyroidism, hypothyrodism, diabetic ketoacidosis, tumor lysis syndrome, theophylline intoxication, lithium ingestion, dead sea water poisoning
Where is the magnesium absorbed with magnesium enemas?
in the large bowel
Other than giving a massive dose, how else can mg be increased orally?
Give an example of these disorders
by a GI disorder that enhances magnesium absorption
ulcer disease, gastritis, colitis
What Is the 2nd most prevalent intracellular cation?
Magnesium
What are two ways patients can be given exogenous magnesium?
laxatives and antacids
What is the level for patient with end stage renal disease?
2.4-3.6
What is considered hypermagnesemia?
When is this usually seen?
> 2.1
impaired renal function, large doses of magnesium given iv, orally or as an enema
What can larger doses of mg precipitate?
diarrhea which exacerbates hypomagnesemia
When should IM be used?
How should they be diluted?
only if IV is limited access and severe hypomagnesemia
20% before injection to prevent venous sclerosis and pain
What is the IV bolus administration associated with?
flushing, sweating, and sensation of warmth
How much should you use for non life threatening?
1 Meq/kg
How much should you use for life threatening symptoms?
2g MgSO4
What does magnesium replacement depend on?
the severity of the clinical manifestation
give examples of NM?
weakness, seizures, tetany, coma, depression, tremor, spasm
Why is magnesium important?
it is a cofactor required for nearly all biochemical and enzyme systems
What are the dominant organ systems involved in hypomagnesemia?
NM nad CV
What is symptomatic hypomagnesemia often associated with?
multiple electrolyte abnormalitites including hypokalemia, hypocalcemia, and metabolic alkalosis
What do nephrotoxins do?
Which medications are included in this?
produce urinary magnesium wasting
aminoglycosides, antibiotics, cisplatin, amphotericin B, cyclosporine, foscarnet, tacrolimus, and pentamidine
What does hypovolemia do?
stimulates proximal sodium, water, and magnesium reabsorption
What are examples of diuretics?
How do they do this?
loop and thiazide diuretics
inhibit mg reabsorption, produce mild hypomagnesemia
Name two classes of drugs that can cause mg loss?
diuretics, and nephrotoxins
What is one other way mg can be lost?
drugs
What are examples of hormone induced renal loss?
hyperparathyroidism, hyperthyroidism, aldosteronism, hungry bone syndrome
What are examples of tubular disorders?
postobstructive diuresis, renal tubular acidosis, Bartters syndome, primary renal magnesium wasting, glomeruloneprhitis
What reactions is it involved in?
transfer of phophate groups, all reactions that require ATP, replication and transcription of DNA and the translation of mRNA
How man Meq does a 70-kg adult have of Mg?
2000
What are the two groups of renal losses?
primary tubule disorders, hormone induced renal losses
give examples of GI losses?
prolonged nasogastric suctionling, acute and chronic diarrhea, malabsorption syndromes, extensive bowel resection, alcoholism, intestinal fistule, malabsorption,
What are the 2 major mechanisms by which hypomagnesemia can be induced?
gastrointestinal or renal losses
Where does hypomagnesemia occur commonly?
in inpatient settings
What is classified as hypomagnesemia?
<1.4 Meq/L
what does hypomagnesemia do?
stimulates transport
How much is in the bone?
50-60%
How much of extracellular magnesium accounts for the total body magnesium?
1%
What does hypermagnesemia do
inhibits loop transport
what is a major regulator of magnesium reabsorption?
the plasma concentration
Where does 15-25% of magneisum get reabsorbed?
in the proximal tubule
where does 60-70% of magnesium get absorbed?
in the thick ascending loop of henle
Where is homeostasis regulated?
in the kidney through glomerular filtration and reabsorption
How much of the ingested magnesium is absorbed in the small bowel?
30-40%
What does magnesium balance depend on?
GI absorption and renal excretion
What are the normal serum magnesium concentrations?
1.4-2.1 meq/L
