Magnesium Disorders

Question 1

What are causes of decreased magnesium reabsorption

Answer 1

Volume expansion, hypercalcemia, hypophosphatemia, metabolic acidosis

Question 2

What are causes of increased magnesium reabsorption

Answer 2

Volume depletion, hypocalcemia, metabolic alkalosis

Question 3

Who is at high risk for hypomagnesemia

Answer 3

Malnutrition, alcoholism, CHF

Question 4

Causes of hypomagnesemia d/t deficient intake, GI losses, renal losses, and redistribution

Answer 4

Deficient intake: ETOH, TPN
GI loss: Diarrhea, celiac, IBD, small bowel resection, PPI
Renal loss: loop diuretics, volume expansion, osmotic dieresis, tubular dysfunction
Redistribution: acute pancreatitis, hungry bone syndrome

Question 5

Cardiovascular, neuro, and metabolic clinical manifestations of hypomagnesemia

Answer 5

Cards: torsades
Neuro: muscle weakness, tetany, seizures
Metabolic: hypokalemia, hypocalcemia

Question 6

Management of hypomagnesemia including torsades

Answer 6

Torsades or v fib: 2g mag IV push with STAT CMP
Less urgent: Mag sulfate 1-4 grams, check K, po mag oxide 240-1600 QD-QID

Question 7

Hypermagnesemia causes

Answer 7

Compromised renal function, enteral or TPN, massive mag intake, hypothyroidism, hyperparathyroidism, Addison’s disease, lithium treatment

Question 8

Cardiovascular, GI, and neuro clinical manifestations of hypermagnesemia

Answer 8

Cards: hypotension, bradycardia, HB, asystole
GI: N/V, ileus
Neuro: hyperreflexia, flaccidity, skeletal muscle paralysis, respiratory muscle weakness/paralysis, lethargy, coma, urinary retention

Question 9

Treatment plan of hypermagnesemia (asymptomatic, symptomatic, vs chronic RF)

Answer 9

Asymptomatic: no treatment, remove exogenous source, saline added, loop diuretics
Symptomatic: calcium gluconate 1g IV over 5 mins
Chronic RF: HD

Question 10

Role of Phosphate in normal physiology

Answer 10

Skeletal integrity, energy economy, formation of high energy phosphate bonds, structure of nucleic acid, lipids, and proteins

Question 11

Regulators of phosphate levels

Answer 11

Parathyroid hormone: increases excretion
Fibroblast growth factor: Increases excretion
Extracellular volume expansion
Acute hypercalcemia
Common diuretics

Question 12

Redistribution causes of hypophosphatemia

Answer 12

Respiratory alkalosis, Sepsis, Rapid refeeding, leukemia, DKA, anorexia, alcoholism

Question 13

Causes of increased excretion of hypophosphatemia

Answer 13

Primary hyperparathyroidism, extracellular volume expansion, diuretics

Question 14

Causes of decreased absorption hypophosphatemia

Answer 14

Hyperparathyroidism, ethanol, glycosuria, phosphate binders, antacids, chronic diarrhea, chronic alcoholism

Question 15

Hypophosphatemia clinical manifestations

Answer 15

Hemolysis
Rhabdo
Seizure
Coma

Question 16

Treatment plan for hypophosphatemia including Prevention, Mild-mod, and Severe cases

Answer 16

Prevention: recognition and correction
Mild-mod (1.5): oral replacement via skim milk or sodium phosphate tabs
Severe (<1.5): IV phos replacement 2.5-5mg/kg over 6 hours, monitor ionized calcium

Question 17

What level is considered hyperphosphatemia

Answer 17

> 5.0

Question 18

What is hyperphosphatemia most commonly associated with

Answer 18

Renal dysfunction

Question 19

Redistribution causes of hyperphosphatemia

Answer 19

Tumor lysis syndrome, rhabdo, acute on chronic respiratory acidosis, acute pancreatitis, DKA, Lactic acidosis

Question 20

Increased intake causes of hyperphosphatemia

Answer 20

Laxatives in elderly
Parenteral phosphorous supplementation
Increased interstitial uptake of vitamin D with decreased PTH

Question 21

Clinical manifestations of hyperphostphatemia

Answer 21

Hypocalcemia
Ectopy
Increased anion gap

Question 22

Hyperphosphatemia treatment plan

Answer 22

Reduce phosphate intake <800mg/dl
Phosphate binders
Diamox
HD