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The flashcards below were created by user
marshenski
on FreezingBlue Flashcards.
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Where is most of the Mg found in our bodies?
ICF, about half found in muscles
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How much Mg found in the plasma?
<1%
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Normal Value?
1.8-2.5 mg/dl 1.5-1.9 mEq/L
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How much of the Mg is ionized?
- 55% ionized
- 30% bound to protein
- 15% bound to anions
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What do we use Mg for?
- Enzyme synthesis
- DNA and protein synthesis
- energy metabolism
- glucose utilization
- Fatty acid synthesis and breakdown
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Name some of the channel/pump that Mg influences?
- Na/K ATPase pump
- Na/Ca ATPase pump
- Ca leak channel
- others
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Why is Mg referred to as an endogenous antagonist of Ca?
- maintenance of Ca leak channels=norm vascular tone
- prevention of vasospasm
- prevention of Ca overload in tissue
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Is Mg involved in enzyme reactions?
Yes, it is often a Co-factor
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What interaction does Mg have with PTH?
- PTH partially responsible for the absorption of Mg
- controls end organ sensitivity to both PTH and Vit D
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Why will abnormalities in Mg result in abnormalities of Ca metabolism?
Mg is responsible for control of Vit D
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What role in K metabolism does Mg have?
regulation of the Na/k ATPase pump particularly in K depleted states
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Does Mg help regulate cell membranes?
Yes
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Where is Mg found as a structural component?
Cell membranes and bones
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How does hypo Mg effect axonal transmission?
Mg stabilizes neural fiber. In low Mg stated transmission speed is increased and more excitable
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How does Mg effect the release of nuerotransmitters?
competition with Ca inhibits Ca entry into presynaptic terminal
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How will the muscles react to a low Mg state?
contract more to a smaller stimulus, this leads to tetany
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When would hypermagnesemia be used theraputically?
- Premature labor
- Pre-eclampsia & eclampsia
- Torsades
- Prevents vasospasm via blocking release of catechols
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Most pt's will begin to show symptoms of a Mg level below?
1.2 mg/dl
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Will low levels of Mg increase Dig toxicity?
yes
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How is it that levels are usually low?
- excessive loss via GI tract
- failure of kidneys to conserve Mg
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How many of hospitalized alcoholic pt's will have low levels of Mg?
30%
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What drug can lower Mg levels?
- aminoglycosides
- chemo
- cardiac glycosides
- diuretics
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When might an intracellular shift of phos be noted?
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Why would low levels of Mg cause Dig tox?
Mg regulates the Na/K ATPase pump thereby decreasing the effectiveness. This could lead to K wasting in the kidneys and Low K increases dig tox.
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If a pt is hypo Mg and hypo K is it likely that you would have to replace both lytes?
yes
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If we were going to treat Mg with IV bolus what dose would we give?
8-16 mEq in bolus over an hour, followed by 2-4 mEq/hr, followed by 1 mEq/min
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When replacing Mg do we need to use a monitor?
Yes
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What is the most common cause of hyperMg?
- Iatrogenic: Antacids, enemas, parenteral nutrition
- Renal failure
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what are some of the less common causes of HyperMg?
- Addsions disease
- lithium tox
- hypothyroidism
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Why would we see a depressed musculoskeletal function in lieu of hyperMg?
Mg is a competitive inhibitor of Ca, so more Mg would mean that there is less Ca to help with the release of acetylcoline
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How does hyperMg effect the muscle relaxants that we might use?
- it potentates the effect of the nondepolarizing musc relaxants
- reduces the release of K when used with Succ
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How would we treat acute neuro and cardiac toxicities associated with hyperMg?
5-10mEq Ca IV, ECF fluid expansion and lasix to increase secretion,dyalysis
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Is the emergency treatment of hyperMg with Ca a definitive treatment?
not really, only buys us time to work on underlying cause
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