Electrolyte: MAGNESIUM (Mg++)
Second Most Abundant Cation in ICF (Normal: 1.3 – 2.3 mEq/L)
LOW
COMPARE &
CONTRAST
HYPOMAGNESEMIA
Mg < 1.3 mEq/L
1/3 bound to protein, 2/3 free cation
 GI loss r/t alcoholism: ↓ dietary
intake, impairs renal conservation,
intestinal malabsorption,
intermittent D/V
*Chronic alcoholism most common cause
due to poor dietary intake
 Intestinal malabsorption syndromes
 Diarrhea
 Diuretics
 Prolonged adim. of Mg free IVF/TPN
 NG suction
 Renal or liver disease
 Diabetic ketoacidosis
*Usually occur Mg < 1.0 mEq/L
 Most are neuromuscular:
hyperexcitability w/ muscle
weakness, tremors & athetoid
movements, tetany, + Trouseau’s &
Chvostek’s, seizures, laryngeal
stridor, signs of low hypocalcemia r/t
low PTH, alterations in mood
(apathy, depression, agitation,
dizziness, insomnia, audio or visual
hallucinations, psychoses), Digoxin
toxicity
Cardiac Changes
 Predisposes to dysrhythmias (PVC or
V-fib), ↑ risk for digoxin toxicity, ECG
(prolonged PR & QT intervals,
widening QRS complex, depressed ST
segment, flattened T waves,
prominent U waves)
*Closely monitor Dig levels
 Mg < 1.3 mEq/L
 Potassium
May also be low
 Calcium
 ECG
 Urine Mg level
Terms
Definition
Causes
Signs & Symptoms
Cardiac
Respiratory
Neurological
General
HIGH
HYPERMAGNESEMIA
Mg > 2.5 mEq/L
*rare electrolyte abnormality
 Hemolyzed blood samples
 Renal failure (most common cause)
 Addison’s Disease
 Excessive use of antacids & laxatives
 Untreated ketoacidosis
 Excessive infusion
 Hypothermia
 Lithium toxicity
Acute Elevations
 Depression of CNS
Mild Increases
 Low BP, N/V, facial flushing, sensations
warmth
Higher Increases
 Lethargy, dysarthria (poorly articulated
speech), drowsiness, loss of deep
tendon reflexes, muscle weakness &
paralysis, depressed respirations,
coma
Cardiac Changes
 Sinus bradycardia, prolonged PR & QT
intervals, tall T waves, widened QRS,
heart block, cardiac arrest in diastole
*Primary symptoms occur as the result of
peripheral & central nervous system
depression
Lab & Diagnostic Tests
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Mg > 2.5 mEq/L
ECG
K+ increased
Ca++ increased
Creatinine clearance decreases to less
than 3.0 ml/min
Diet (Mg rich foods – see below)
 Can be used alone for mild ↓ Mg
Mg Replacement
 Assess renal function – route of Mg
elimination
 PO Slow-Mag – diarrhea possible side
effect
 IV or IM
 Monitor BUN & creatinine
Admin. of Mg Sulfate IV
 Monitor rate closely – too rapid →
risk for cardiac arrest; dose based on
severity; rate not to exceed 150
mg/min or 67 mEq over 8 hours
(severe)
 Contraindicated in heart block
 Monitor kidney function & check
deep tendon reflexes before admin.
 Monitor urinary output – 100 ml q 4
hr (at least)
 Assess patellar reflexes
 Monitor respiratory status – risk for
respiratory arrest
 Identify & monitor pt. at risk
 Assess for digoxin toxicity
 Seizure precautions
 Monitor airway
 Safety for confusion & psychosis
 Pt. education: diuretics & laxative
use; diet
Treatment
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
Nursing Interventions
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T – tetany
A – anorexia
Monitor pt. at risk
Monitor VS – low BP & shallow resp.
with apnea
 Assess patellar reflexes – absent
reflexes implies Mg > 7.0
 Monitor LOC – drowsy, lethargy, coma
*Low BP & periods of apnea – CALL doctor
Magnesium Rich Foods
HYPOMAGNESEMIA
S – seizures
Prevention is key
Avoid administration of Mg in renal
failure patients
 Hemodialysis
Emergency treatment if resp. or cardiac
problems develop
 Ventilator support
 Calcium Gluconate
→ Direct antagonist to Mg
→ 5-10 mEq may reverse cardiac
or respiratory problems
→ Lasix
→ NaCl or LR
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Green vegetables (*spinach)
Meat
Seafood
Nuts/seeds/legumes
Whole grains
Peanut butter
Cocoa
R – rapid heart rate
V – vomiting
KEY POINTS:
E – emotional lability
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D – deep tendon reflexes are increased
Mg is important for neuromuscular function
Activator for enzymes
Carbohydrate & protein metabolism
Vasodilation in peripheral arteries
Found in bone & tissue
Eliminated by kidneys
Regulators for Mg – GI & urinary systems