Na+

Question 1

Would how would Na+ levels change in pts taking large amounts of diuretics w/o drinking water? What would the volume status be?

Answer 1

Hypovolemic hyponatremia

Question 2

The daily solute load is generally ___-___ mmol/day.

Answer 2

600-1200

Question 3

Tx for hypervolemic hypernatremia?

Why don’t you want to correct it too fast?

Answer 3

• Can be problematic. If severe, it may require both water administration plus either diuretics or dialysis to remove the excess sodium.
• Rate of correction should not exceed 0.5 mEq/L/hr, as too rapid a reduction in serum sodium and osmolality may result in shift of water into the brain and brain edema.

Question 4

What are some examples of scenarios that cause hypervolemic hypernatremia?

Answer 4

Hypertonic fluid administration
Mineralocorticoid excess states
Salt poisoning (and seawater ingestion)

Question 5

If you decrease your daily excretion of solute by 2/3s, how does your daily urine volume change?

Answer 5

Also decreases by 2/3s (e.g. Beer Drinker’s Syndrome)

Question 6

In hyponatremia, what’s an eg of a scenario where there is decreased filtration of solute by the glomeruli?

Answer 6

Renal failure

Question 7

Name some edematous disorder examples.

Answer 7

Congestive heart failure (CHF), liver cirrhosis, renal failure

Question 8

What are some examples of scenarios that cause hypervolemic hyponatremia?

Answer 8

CHF
Liver cirrhosis
Renal failure

Question 9

Would how would Na+ levels change in pts administered a large amount of hypertonic saline? What would the volume status be?

Answer 9

Hypervolemic hypernatremia

Question 10

What is the “normal” urine osmolality and urine output per day? (some ADH present, not too much or too little)

Answer 10

Urine osmolality ~= 400 mmol/kg
Urine volume ~= 1.5 L/day

*Calculations assume that there is excretion of 600 mmol of solute per day

Question 11

What is the tx for euvolemic hyponatremia?

• Mild?
• *More severe?
• Symptomatic?

Answer 11

• Mild asymptomatic hyponatremia should be considered a diagnostic clue but does not mandate treatment.
• More severe asymptomatic hyponatremia (i.e., serum sodium < 125 mmol/L) should be treated with water restriction.
• Symptomatic hyponatremia (confusion, seizures, coma due to hyponatremia) is considered a medical emergency and generally requires hypertonic saline with or without diuretics. Avoid rapid or overcorrection!

Question 12

What is the TBNa+ in pts w/hypo-, eu-, and hypervolemic hypernatremias?

Answer 12

• Hypo: Low TBNa+
• Eu: normal TBNa+
• Hyper: High TBNa+

Question 13

When evaluating urine Na+ in hyponatremia, what does normal UNa+ (> 20 mmol/L) suggest?

Answer 13

Suggests renal loss of Na+ or excess ADH in the absence of renal sodium avidity, as in SIADH.

Question 14

What is the tx for hypovolemic hyponatremia?

Hypervolemic hyponatremia?

Answer 14

hypovolemic hyponatremia = nl (isotonic) saline

Hypervolemic hyponatremia = fluid restriction + diuretics

Question 15

If a person drinks gallon’s of beer without food, why can’t the kidney just get rid of this extra fluid?

Answer 15

Because the kidney needs solute to be able to excrete the fluid (water follows salt)

Question 16

What are some examples of scenarios that cause euvolemic hypernatremia?

Answer 16

Central diabetes insipidus (trauma, idiopathic, tumor)
Nephrogenic diabetes insipidus (congenital, drugs, hypercalcemia, tubular disease)
Decreased thirst, water intake (“nursing home syndrome”)

Question 17

Tx for euvolemic hypernatremia?

Answer 17

Water administration (+ ADH in central DI)

Question 18

How would edematous disorders (e.g. CHF), coupled w/H2O intake, affect total body water?
How would it affect serum Na+?
Would it lead to hyper or hyponatremia? What volume?

Answer 18

• Significant ^^ increase in TBW
• Modest ^ serum Na+
• Hypervolemic hypernatremia

Question 19

Normal ability to excrete water depends on 3 factors:

Answer 19

1. Filtration of solute by the glomeruli
2. Delivery of solute to distal (diluting) nephron sites
3. Reabsorption of solute but not water in the distal nephron (when ADH is suppressed)

Question 20

What are some examples of scenarios that cause hypovolemic hypernatremia?
(differentiate renal vs extrarenal causes)

Answer 20

Renal Na+ losses – diuretics (with inadequate water intake), osmotic or post-obstructive diuresis, tubular injury

Extrarenal Na+ losses – sweating, diarrhea, vomiting (with inadequate water intake).

Question 21

In the absence of ADH, urine osmolality can be as low as ___ mmol/L. The maximal urine osmolality is ____ mmol/L

Answer 21

50

1200

Question 22

How would SIADH affect total body water?
How would it affect serum Na+?
Would it lead to hyper or hyponatremia? What volume?

Answer 22

• Modest ^ TBW
• no change on serum Na+
• Euvolemic hyponatremia

Question 23

When evaluating urine Na+ in hyponatremia, what does low UNa+ (< 10 mmol/L) suggest?

Answer 23

Suggests extrarenal loss of Na+ or edematous disorder (in which kidneys are avid, and thus causing edema, usually due to a decrease in effective circulatory volume)

Question 24

What are some examples of scenarios that cause euvolemic hyponatremia?

Answer 24

SIADH – most commonly due to (1) tumor (2) pulmonary disease (3) CNS disease
Hypothyroidism
Psychogenic polydipsia
“Beer drinker’s potomania”
Glucocorticoid deficiency

Question 25

What are some examples of scenarios that cause hypovolemic hyponatremia? (differentiate renal vs. extrarenal examples)

Answer 25

Renal Na+ losses – diuretic excess, primary adrenal insufficiency (Addison’s disease), mineralocorticoid difficiency, salt-wasting nephropathies, bicarbonaturia, ketonuria, osmotic diuresis Extrarenal Na+ losses – diarrhea, vomiting, excessive sweating, third-space burns, pancreatitis, traumatized muscle

Question 26

What are the 2 main causes of impaired renal water excretion? (which can lead to hyponatremia)

Answer 26

1. Decreased solute excretion (e.g. Beer Drinker's Syndrome) | 2. Impaired urinary dilution (e.g. SIADH, etc)

Question 27

How would diuretic (w/some water) ingestion affect total body water? How would it affect serum Na+? Would it lead to hyper or hyponatremia? What volume?

Answer 27

- modest v in TBW (diuresis, but some water intake) - vv serum Na+ (due to drug) - Hypovolemic hyponatremia

Question 28

Would how would Na+ levels change in pts w/diabetes insipidus? What would the volume status be?

Answer 28

Can't release (central) or respond to (nephrogenic) ADH, so lots of diuresis, therefore relative increase in Na+ --> euvolemic (?) hypernatremia.

Question 29

Both thirst and ADH are triggered at a PLASMA osmolality of about ____ mmol/kg and shut off at lower plasma osmolality.

Answer 29

280 mmol/kg

Question 30

In hyponatremia, what's an eg of a scenario where there is reduced renal blood flow resulting in stimulation of proximal solute reabsorption

Answer 30

CHF

Question 31

In hypovolemic hyponatremia, is the TBNa+ increased, decreased, or normal?

Answer 31

Decreased TBNa+

Question 32

Which is much more common, sustained hyponatremia due to fluid ingestion alone, or due to impaired renal water excretion?

Answer 32

Impaired renal water excretion

Question 33

In hypervolemic hyponatremia, is the TBNa+ increased, decreased, or normal?

Answer 33

Increased TBNa+

Question 34

Is ADH more sensitive to changes in osmolality or volume?

Answer 34

Osmolality (but sensitive to both)

Question 35

In hyponatremia, what's a drug that would cause inhibition of solute reabsorption in the distal nephron (DCT)?

Answer 35

Thiazides

Question 36

In euvolemic hyponatremia, is the TBNa+ increased, decreased, or normal?

Answer 36

Normal TBNa+

Question 37

Tx for hypovolemic hypernatremia?

Answer 37

Hypotonic fluids

Question 38

What are the physical exam are the main physical signs of hypovolemia? Euvolemia? Hypervolemia?

Answer 38

- Hypovolemia: flat neck veins, decreased skin turgor, orthostatic hypotension - Euvolemia: normal - Hypervolemia: edema

Question 39

What type of sodium inbalance is Nursing Home Syndrome a/w?

Answer 39

Euvolemic hypernatremia (due to decreased water intake)