Hyponatremia, Hypernatremia, and Fluid Therapy

Question 1

serum osmolality equation

Answer 1

= 2 (Na+) + (glucose/18) + (BUN/ 2.8)

Question 2

rule for correcting [Na] in dilutional hyponatremia from excess glucose?

Answer 2

True [Na] = increase of 1.6 mEq/L for every 100 mg/dl increase in glucose above 100 mg/dl

Question 3

how do serum osmolality and blood volume influence ADH secretion?

Answer 3

ADH released in response to 1-2% increase in osmolarity and/or > 10% decrease in volume

Question 4

consequence of raising serum Na concentration too quickly or too high

Answer 4

Central Pontine Myelinosis

Question 5

neurogenic factors that stimulate ADH release

Answer 5

cold, nausea, nicotine, pain

Question 6

receptor involved in thirst response

Answer 6

AT1 receptor for Ang II

Question 7

how does ADH secretion differ in response to hypovolemia compared to hyperosmolarity

Answer 7

hypovolemia - exponential increase

hyperosmolarity - linear increase

Question 8

cellular changes with acute and chronic hyponatremia?

Answer 8

acute - water moves into ICF from ECF, cells swell

chronic - solute (KCl) moves out of cell, no swelling

Question 9

cellular changes with acute and chronic hypernatremia?

Answer 9

acute - water moves from ICF to ECF, cells shrink

chronic - idiogenic osmoles produced in cells drive re-entry of water into cells, cell volume remains same

Question 10

Treatment of hypovolemic hyponatremia?

Answer 10

isotonic saline or blood products to raise ECF volume

Question 11

Treatment of hypervolemic hyponatremia?

Answer 11

treat cause of edema (CHF, cirrhosis)

Question 12

what do you worry about in giving a patient with SIADH isotonic saline?

Answer 12

worsening hyponatremia

Question 13

Treatment of acute and chronic SIADH

Answer 13

acute - 3% saline

chronic - demeclocycline or tolvaptan, NEVER 3% saline

Question 14

Treatment of hypernatremia

Answer 14

Water

hypernatremia ALWAYS represents water deficiency

Question 15

cause of primary polydipsia

Answer 15

water intake without sufficient solute.
no osmoles driving dilution of urine.
results in decreased serum osmolality and polyuria

Question 16

Which class of IV fluids are mainly confined to vascular space?

Answer 16

colloids

Question 17

Which drug repletes total body water? Useful in true dehydration

Answer 17

D5W

Question 18

Which drug is useful in treating hypertonic ECF volume depletion?

Answer 18

1/2 NS (in D5W)

• D5W for hypernatremia
• NS for ECF volume depletion

Question 19

What is the reason for using colloid infusion?

Answer 19

raises VS volume while decreasing excess IS volume

Question 20

Side effects of hydroxy-ethyl starch?

Answer 20

1. proximal tubule cell swelling
2. Acute kidney injury
3. increases risk of bleeding following surgery