6 - Magnesium Disorders Flashcards
Physiological Roles of
MAGNESIUM
COFACTOR for many enzymatic reactions
ATPase // Glycolysis
Protein Biosynthesis
Metabolism
of Nucleotides / Ca2+ / K+ / energy
Regulator of ION CHANNELS + TRANSPORTERS
in EXCITABLE tissues
Normal Serum Concentration
MAGNESIUM
1.7 - 2.4 mg/dL
*note we use mg/dl , a lot LOWER concentration in the body
Mag GI Absorption
only 30-35% absorbed
POOR ABSORPTION
VVV
So PO admin is NOT good to increase mag levels
Need a Good KIDNEY
Controlling Factors for Magnesium
just the KIDNEY
there is NO Hormone that actively affects magnesium
just Passive diffusion:
Proximal:
Follows Na+ // Water
- *Ascending:**
- *Ca+ // Mag Interaction**
HypoMagnesemia
Serum level
<1.7 mg/dL
Normal is
1.7-2.4
HypoMagnesemia
ETIOLOGY
MALNUTRITION = very COMMON
KetoACIDOSIS / HYPERaldosteronism / HYPERcalcemia / HypoPhosphotemia
REFEEDING Syndrome
Malnourished –> REFED –> use up ALL the MAG when fed
BLOOD TRANSFUSION
Citrate binds to Magnesium
- Decreased GI absorption*
- *Surgery** // Radiation Enteritis / Pancreatic insufficiency
- *Increased GI losses**
- *Chronic Diarrhea /** EXCESSIVE LAXATIVE USE
Renal Losses
Burns / Sweating / Chronic Alcholism
Medications that can cause:
HypoMagnesemia
RENAL LOSSES
Osmotic Agents
Thiazide / Furosemide / Bumetanide
Aminoglycosides / Cyclosporin
Digoxin / Tacrolimus
Amphotericin B
HypoMagnesemia
S/Sx
Moderate = <1.5
Severe = <1.2
Typically MASKED by PRIMARY disease states
(potassium or calcium issues)
but there are 2 symptoms that we can use to DISTINGUISH
MUSCLE FASCICULATIONS
Twitching
TORSADE DE POINTES
life threatening –> need to be treated IMMEDIATELY
Neuromuscular / Neurologic / Psychiatric / Cardiac / Electrolyte
Mechanism of HypoMagnesmia
S/Sx
Neurological Symptoms
NMDA receptor stimulation
Cardiovascular Symptoms
Induce depolarization via EC movement of K+
related to serum DECREASE of K+
Neuromuscular Symptoms
INCREASE Ca binding + release
related to decrease of serum Ca2+
Cardiac Symptoms
of HypoMagnesemia
Arrhythmias
Ventricular / SVT / Digoxin Toxicity
TORSADES DE POINTES
(widening QRS complex)
Heart Failure
HYPERtension
Coronary Artery Vasospasms
Mild / Moderate Asymptomatic
HypoMagnesmia
- *Mild**
- *1.5 - 1.6** mg/dL
- *Moderate**
- *1.2-1.4** mg/dL
- *Treat Both Similarly:**
- *Diet // Oral Supplement // Parenteral**
TREATMENT FOR
Severe OR Symptomatic
HypoMagnesmia
<1.2 mg/dL
Specifically, if life threatening = severe:
LOOK AT EKG for TORSADES DE POINTES
Treat with:
PARENTERAL MAG
2 GM Q15 min
4-8 gm / 100ml D5W or 0.9NS
Continous Infusion > IVPB > IM/IVP is okay too
HypoMagnesmia
DIET TREATMENT
Nuts
Green Veggies
Whole Grain Cereal
MEAT
Mild or Moderate Asymptomatic
1.5-1.6 // 1.2-1.4
HypoMagnesemia
DOSE of Oral Treatment
NUTS / GREEN VEGGIES / CEREAL / MEAT
Highest Elemental Mag:
OXIDE > Hydroxide > GLuconate > Chloride
300-600mg ELEMENTAL Mag Daily
various salt forms, look at the Elemental Mag
Dosed FOUR TIMES A DAY
because of poor GI absorption
SLOW onset of ACTION
ADR:
DIARRHEA // N/V
Mild / Moderate HypoMagnesemia
- *PARENTERAL TREATMENT**
- typically only give IV if LIFE THREATENING = TDP*
@1 gm / hr
We have to give it SLOW, b/c kidney will eliminate it if fast
& HypoTension
Mild = 1.5-1.6
1-2 gm/ 100mL
Mag SulfateinD5Wor0.9NS
Moderate = 1.2 - 1.4
2-4 gm/100ml
1gm Mg Sulfate = 8.12 mEq elemental Mg
Parenteral Magnesium Supplement
Routes of Admin + ADR
Parenteral Dose is 30-50% of ORAL Dose
Since Oral dose is lost due to poor GI absorption
CONTINUOUS INFUSION
Can exceed renal threshold // HypoTension (<1g/hour)
IVPB is also possible
IM - Painful
IVP - Flushing / Sweating / Warm Sensation
HYPERmagnesemia
Levels
>2.4 mg/dL
Normal is:
1.7-2.4
CAUSES of HYPERmagnesemia
not as Common as HypoMagnesemia
EXCESSIVE MAGNESIUM INTAKE
(MOST COMMON)
Antacids // Cathartics (especially with CKD)
- *GFR < 30 mL/min**
- *POOR KIDNEY FUNCTION**
Lithium Therapy
HypoThyroidism
Addison’s Disease
treatment of Eclampsia
HYPERMagnesemia
S/Sx
Most Sympsoms come from
- *Calcium / Potassium disorders**
- Except for:*
Cardiac
CUTANEOUS VASODILATION
Neuromuscular
HypoReflexia // Muscle Paralysis
Symptoms may occur when:
Moderate = 4.1 - 12.5 mg/dL
Severe = >12.5 - 32 mg/dL
Mild / Moderate Asymptomatic
HYPERmagnesemia
Treatment Algorithm
- *Mild Asymptomatic**
- *2.5 - 4 mg/dL**
- *Moderate Asymptomatic**
- *4.1 - 12.5 mg/dL**
Same Treatment, NO DRUGS that SPECIFICALLY REMOVE MAG
Saline Infusion
Furosemide
Hemodialysis
Severe OR Symptomatic
HYPERMagnesemia
Treatment Algorithm
LIFE THREATENING
Muscle Paralysis / Cutaneous Vasodilation
>12.5 mg/dL
Calcium
to FIX EKG
Saline Infusion
Hemodialysis
HYPERmagnesemia
TREATMENT
- *Mg Restriction**
- no drugs to DIRECTLY remove MAG*
CALCIUM Cl or Glu
this is for the CV effects = EKG Change
1gm over 5-10 min
(HYPERK is 1gm over 2-3 min)
Furosemide
Saline Diuresis = 0.9% NaCl
To introduce MORE sodium to kidneys –> eliminate both Mag + Na+
Hemodialysis
if poor kidney fxn
How to treat SEVERE HypoMagnesemia
<1.2 + Symptoms
4-8 gm/100ml
Mag Sulfate in D5W or 0.9Ns
@2gm q15min
then SLOW DOWN
1gm / 1 hour
for the rest of the mag
Which Electrolytes affect MAGNESIUM’s
Excretion & Reabsorption?
Mag mainly follows SODIUM
↓ CALCIUM = Neuromuscular
Modulates Ca2+ binding and release from the sarcoplasmic reticulum (SR)
Interaction w/ Mag+Calcium in ASCENDING loop
POTASSIUM = ↓K
Blocks outward movement of K+ through K+ channels in cardiac cells
