Na+ Flashcards
Would how would Na+ levels change in pts taking large amounts of diuretics w/o drinking water? What would the volume status be?
Hypovolemic hyponatremia
The daily solute load is generally ___-___ mmol/day.
600-1200
Tx for hypervolemic hypernatremia?
Why don’t you want to correct it too fast?
- 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.
What are some examples of scenarios that cause hypervolemic hypernatremia?
Hypertonic fluid administration
Mineralocorticoid excess states
Salt poisoning (and seawater ingestion)
If you decrease your daily excretion of solute by 2/3s, how does your daily urine volume change?
Also decreases by 2/3s (e.g. Beer Drinker’s Syndrome)
In hyponatremia, what’s an eg of a scenario where there is decreased filtration of solute by the glomeruli?
Renal failure
Name some edematous disorder examples.
Congestive heart failure (CHF), liver cirrhosis, renal failure
What are some examples of scenarios that cause hypervolemic hyponatremia?
CHF
Liver cirrhosis
Renal failure
Would how would Na+ levels change in pts administered a large amount of hypertonic saline? What would the volume status be?
Hypervolemic hypernatremia
What is the “normal” urine osmolality and urine output per day? (some ADH present, not too much or too little)
Urine osmolality ~= 400 mmol/kg
Urine volume ~= 1.5 L/day
*Calculations assume that there is excretion of 600 mmol of solute per day
What is the tx for euvolemic hyponatremia?
- Mild?
- *More severe?
- Symptomatic?
- 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!
What is the TBNa+ in pts w/hypo-, eu-, and hypervolemic hypernatremias?
- Hypo: Low TBNa+
- Eu: normal TBNa+
- Hyper: High TBNa+
When evaluating urine Na+ in hyponatremia, what does normal UNa+ (> 20 mmol/L) suggest?
Suggests renal loss of Na+ or excess ADH in the absence of renal sodium avidity, as in SIADH.
What is the tx for hypovolemic hyponatremia?
Hypervolemic hyponatremia?
hypovolemic hyponatremia = nl (isotonic) saline
Hypervolemic hyponatremia = fluid restriction + diuretics
If a person drinks gallon’s of beer without food, why can’t the kidney just get rid of this extra fluid?
Because the kidney needs solute to be able to excrete the fluid (water follows salt)
What are some examples of scenarios that cause euvolemic hypernatremia?
Central diabetes insipidus (trauma, idiopathic, tumor)
Nephrogenic diabetes insipidus (congenital, drugs, hypercalcemia, tubular disease)
Decreased thirst, water intake (“nursing home syndrome”)
Tx for euvolemic hypernatremia?
Water administration (+ ADH in central DI)
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?
- Significant ^^ increase in TBW
- Modest ^ serum Na+
- Hypervolemic hypernatremia
Normal ability to excrete water depends on 3 factors:
- Filtration of solute by the glomeruli
- Delivery of solute to distal (diluting) nephron sites
- Reabsorption of solute but not water in the distal nephron (when ADH is suppressed)
What are some examples of scenarios that cause hypovolemic hypernatremia?
(differentiate renal vs extrarenal causes)
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).
In the absence of ADH, urine osmolality can be as low as ___ mmol/L. The maximal urine osmolality is ____ mmol/L
50
1200
How would SIADH affect total body water?
How would it affect serum Na+?
Would it lead to hyper or hyponatremia? What volume?
- Modest ^ TBW
- no change on serum Na+
- Euvolemic hyponatremia
When evaluating urine Na+ in hyponatremia, what does low UNa+ (< 10 mmol/L) suggest?
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)
What are some examples of scenarios that cause euvolemic hyponatremia?
SIADH – most commonly due to (1) tumor (2) pulmonary disease (3) CNS disease Hypothyroidism Psychogenic polydipsia “Beer drinker’s potomania” Glucocorticoid deficiency
What are some examples of scenarios that cause hypovolemic hyponatremia?
(differentiate renal vs. extrarenal examples)
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
What are the 2 main causes of impaired renal water excretion? (which can lead to hyponatremia)
- Decreased solute excretion (e.g. Beer Drinker’s Syndrome)
2. Impaired urinary dilution (e.g. SIADH, etc)
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?
- modest v in TBW (diuresis, but some water intake)
- vv serum Na+ (due to drug)
- Hypovolemic hyponatremia
Would how would Na+ levels change in pts w/diabetes insipidus? What would the volume status be?
Can’t release (central) or respond to (nephrogenic) ADH, so lots of diuresis, therefore relative increase in Na+ –> euvolemic (?) hypernatremia.
Both thirst and ADH are triggered at a PLASMA osmolality of about ____ mmol/kg and shut off at lower plasma osmolality.
280 mmol/kg
In hyponatremia, what’s an eg of a scenario where there is reduced renal blood flow resulting in stimulation of proximal solute reabsorption
CHF
In hypovolemic hyponatremia, is the TBNa+ increased, decreased, or normal?
Decreased TBNa+
Which is much more common, sustained hyponatremia due to fluid ingestion alone, or due to impaired renal water excretion?
Impaired renal water excretion
In hypervolemic hyponatremia, is the TBNa+ increased, decreased, or normal?
Increased TBNa+
Is ADH more sensitive to changes in osmolality or volume?
Osmolality (but sensitive to both)
In hyponatremia, what’s a drug that would cause inhibition of solute reabsorption in the distal nephron (DCT)?
Thiazides
In euvolemic hyponatremia, is the TBNa+ increased, decreased, or normal?
Normal TBNa+
Tx for hypovolemic hypernatremia?
Hypotonic fluids
What are the physical exam are the main physical signs of hypovolemia?
Euvolemia?
Hypervolemia?
- Hypovolemia: flat neck veins, decreased skin turgor, orthostatic hypotension
- Euvolemia: normal
- Hypervolemia: edema
What type of sodium inbalance is Nursing Home Syndrome a/w?
Euvolemic hypernatremia (due to decreased water intake)
