Electrolyte abnormalities

Question 1

What are two causes of hypernatremia

Answer 1

1. ) Dehydration - treat with normal saline

2. ) Diabetes insipidus - treat with ADH or underlying cause if it is nephrogenic or hydrochlorothiazide

Question 2

What is the algorithm for hyponatremia

Answer 2

Need to determine volume status first

1.) Hypervolemic hyponatremia - occurs because kidneys not perfused, so they retain water and sodium
- Cirrhosis
- Nephrotic syndrome
- CHF
Tx - Treat underlying cause

2.) Hypovolemic hyponatremia - occurs because lose salt and water but patient only replaces water
- Diuretics
- Vomiting and diarrhea
- Burns and sweating
Tx - Replace with normal saline

3. ) Euvolemic hyponatremia
   - SIADH
   - Hypothyroidism
   - Psychogenic polydipsia
   - Hyperglycemia

Question 3

What medications can cause SIADH

Answer 3

Sulfonylureas or SSRI’s

Question 4

What are the lab values associated with SIADH

Answer 4

1. ) High urine sodium (>20)
2. ) High urine osmoality (>100)
3. ) Low serum osmolality (less than 290)
4. ) low uric acid in serum

Opposite for diabetes insipidus

Question 5

What is the treatment for hyponatremia

Answer 5

Mild - Restrict fluids

Moderate to severe with symptoms - saline infusion, loop diuretics, possibly hypertonic saline if really bad

If chronic SIADH - use either demeclocycline or use conivaptan/tolvaptan

Question 6

What are obscure causes of hyperkalemia that I should know

Answer 6

1. ) Beta blockers
2. ) Digoxin toxicity
3. ) ACE inhibitors - block aldosterone
4. ) Type 4 renal tubular acidosis
5. ) Renal failure - prevents potassium excretion

Question 7

What is the order in which cardiac EKG changes present with hyperkalemia

Answer 7

1. ) Peaked T waves
2. ) Loss of P wave
3. ) Widened QRS complex

Question 8

What are causes of hypokalemia that I should know

Answer 8

1. ) DIuretics that are not potassium sparing
2. ) Dietary insufficiency **
   3) Vomiting - via loss of hydrogen ions, and transcellular shift
3. ) Amphoterin - cause RTA
4. ) Bartter syndrome - loop of Henle cannot absorb sodium and chloride - causes secondary hyperaldosteronism and renal potassium wasting

Question 9

What is the treatment for hypokalemia

Answer 9

Replace potassium, and avoid glucose containing fluids that would promote insulin release and cause transcellular shift

Question 10

Metabolic acidosis: Why is lactic acidosis important and what is the treatment

Answer 10

It indicates hypoperfusion (i.e. shock) causing cells to shift to glycolysis and create lactic acid

Treatment: Underlying cause

Question 11

What does aspirin overdose cause and what is the treatment

Answer 11

First: Respiratory alkalosis from hyperventilation
Later: Metabolic acidosis from poisoning of mitochrondria with lactic acid formation

Treatment: Bicarbonate

Question 12

How does methanol intoxication present

Answer 12

Intoxicated patient with visual disturbance because of formic acid and formaldehyde production

Treatment: Fomepizol or ethanol

Question 13

How does ethylene glycol intoxication present

Answer 13

Intoxicated patient with renal abnromality

Treatment: Fomepizol or ethanol

Question 14

What are the only two causes of metabolic acidosis with a normal anion gap

Answer 14

1. ) Diarrhea

2. ) Renal tubular acidosis

Question 15

Why does diarrhea cause a normal anion gap

Answer 15

Lose potassium and bicarbonate in diarrhea, but increases chloride reabsorption (hyperchloremia)

Get metabolic acidosis that is hyperchloremic, hypokalemic

Question 16

What is special about RTA type 1, and what is its diagnosis and treatment

Answer 16

Urine alkaline so stone formation likely

Diagnosis: Give acid, urine pH stays basic
Treatment: Give bicarbonate

Question 17

What is special about RTA type 2, and what is its diagnosis and treatment

Answer 17

Low serum bicarbonate leeches calcium out of bones so osteomalacia develops

Diagnosis: Give bicarbonate, this person cannot reabsorb bicarbonate so it makes urine pH basic
Treatment: Thiazide diuretic - volume contracts, raises bicarbonate concentration in serum

Question 18

What is RTA type 4

Answer 18

Decreased aldosterone production or effect. Diabetics with normal anion gap metabolic acidosis will have this, this time hyperkalemic

Diagnosis: Lose sodium in urine
Treatment: Fludrocortisone

Question 19

How do you differentiate between RTA and diarrhea

Answer 19

This time, check urine anion gap

Sodium - Chloride

Kidneys can normally secrete NH4Cl, so in diarrhea, will see negative UAG, and in RTA will see positive UAG