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20 Cards in this Set

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Sodium disorders

Describe the regulation of serum Na concentration when you have high water intake?
High water intake --> dilution of Na (decrease) --> decrease of ADH release and thirst --> increase water excretion and decrease intake ---> normalization of Na
Sodium disorders

Describe the regulation of serum Na concentration when you have LOW water intake?
Low water intake --> increase Na conc --> increase ADH and thirt --> decrease renal water excretion and increase intact ----> normalization of NA
Sodium disorders

What will a small increase in effective osmolality (Na + glucose) do to ADH release?
It will increase ADH release
Sodium disorders

Can a large increase or decrease change ADH release even if osmolality hasn't changed?
Yes, large changes in BP can override any effect that osmolality has on ADH
Sodium disorders

Explain why a patient with a urine osmolality of 80 releases 10L of urine a day but someone with an osmolality of 400 only releases 2L of urine a day?
The patient with the low urine osmolality is in water diruresis so NO ADH is being released.

However the higher osmolality (400) induces ADH to reabsorp water from the urine so you get less, only 2L, of urine since body is thinking it needs to concerve volume.
Sodium disorders

Hyponatremia is defined as decreased [Na] from excess total body water relative to TBNa+. What are three different ways you you can have hyponatremia:
1. high TBW with nL TBNa
(ADH is too high - SIADH syndrome of inappropriate ADH) ADH is high so wate intake will still be retained

2. low TBW with very low TBNa
(diuretics - renal loss of Na and water; this would also cause ADH release)

3. very high TBW with high TBNa (edematous disorders - CHF, liver cirrhosis, renal failure) even here ADH is released because of a decreased effective blood vol (CO) so kidney responds by conserving Na and water.
Sodium disorders

What is the pathogenesis of hyponaturemia?
Hyponaturemia is almost always do to impaired renal water excretion (excess ADH, renal failure, CHF) since you would have to intake over 12L of fluid to cause hyponaturemia on your own.
Sodium disorders

Three causes of HYPOVOLEMIC HYPOnatremia:
Hypovolemic hyponatremia: decrease in TBNa due to renal or extrarenal losses
1. diuretics
2. Addison's dz
3. diarrhea/vomiting
Sodium disorders

Four causes of EUVOLEMIC HYPOnatremia:

Euvolemic Hyponatremia: normal TBNa but incresed TBW
2. Hypothyroidism (if severe)
3. Psychogenic polydipsia
4. "Beer drinkers potomania"

Treatment: mild = no treatment
severe and asymptomatic = water restiction
symptomatic (seizures/confusion) = intially treat with hypertonic saline, then loop diuretic
Sodium disorders

Four causes of HYPERVOLEMIC HYPOnatremia:

Hypervolemic Hyponatremia: increased TBNa and TBW (body thinks it has low BP from low CO)
1. CHF
2. Liver cirrhosis
3. nephrotic syndrome
4. renal failure

Treatment: diuretics and fluid restiction
Sodium disorders
1. low UNA - means?
2. NL UNa - means?
1. low UNa: extrarenal losses of Na or edematous disorder (since it needs to take the Na in to get the water)
2. nL UNA - can be still caused by excess ADH secretion (doesn't need to take in Na to get water).
Sodium disorders

What is hypernatermia and what are three examples of it?
Hypernatremia: increased [Na] caused by a decrease in EBW relative to TBNa.

1. Low TBW with nL TBNa
(dehydrated, DI in which ADH is impaired)
2. Very low TBW with low TBNa
(sweat, GI tract loss, kidney loss)
3. Nl TBW with high TBNa
(in setting of administration of hypertonic fluids in renal water loss -- give to much Na)
Sodium disorders

Does the serum Na concentration give us any reliable information about TBNa?
NO!! Should be apparent from this entire lecture
Sodium disorders

Hypernatremia is always associated with what?
Sodium disorders

Four causes of HYPOVOLEMIC HYPERnatremia?

Hypovol Hypernat
1. diuretics (lose more water than Na)
2. tubular injury
3. sweating
4. diarrhea/vomiting

treatment: hypotonic fluids
Sodium disorders

How can diuretic, diarrhea, and vomiting all cause both Hypovolemic hyper- and hyponatremia?
In both, both TBW and TNa are lost. It all depends which is lost the fastest.

If more Na is lost = hyponatremia

If more water is lost = hypernatremia
Sodium disorders

Three causes of EUVOLEMIC HYPERnatremia:

Euvolemic Hypernatremia
1. Central DI (trauma, idopathic, tumor -- not making ADH)
2. Nephrogenic DI (congenital, drugs) - not responsive to ADH
3. Decreased water intake ("nursing home syndrome")

Treatment? water administration
Sodium disorders

Three causes of HYPERVOLEMIC HYPERnatremia:

Hypervolemic hypernatremia:
1. administration of hypertonic fluid
2. hyperaldosteronism (mineralocorticoid excess causes mild hypernatremia)
3. salt poisoning (sea water ingestion)

treatment: can be a problem; water administration and diuretic to remove Na
Sodium disorders

Compare lab findings of a patient with central DI and one with osmotic diuresis?
Central DI: urine osmolal < plasma osmolal

Osmotic diuresis: urine osmolal > plasma osmolal
Sodium disorders

What is should the rate of correction be in correcting hypernatremia? Why?
The rate of correction should be no more than 0.5meq/L/hr or else the reduction of serum sodium and osmolality can cause a shift of water into the brain --> brain edema.