A-Sodium Concentration

Front 1

Sodium disorders

Describe the regulation of serum Na concentration when you have high water intake?

Back 1

High water intake --> dilution of Na (decrease) --> decrease of ADH release and thirst --> increase water excretion and decrease intake ---> normalization of Na

Front 2

Sodium disorders

Describe the regulation of serum Na concentration when you have LOW water intake?

Back 2

Low water intake --> increase Na conc --> increase ADH and thirt --> decrease renal water excretion and increase intact ----> normalization of NA

Front 3

Sodium disorders

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

Back 3

It will increase ADH release

Front 4

Sodium disorders

Can a large increase or decrease change ADH release even if osmolality hasn't changed?

Back 4

Yes, large changes in BP can override any effect that osmolality has on ADH

Front 5

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?

Back 5

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.

Front 6

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:

Back 6

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.

Front 7

Sodium disorders

What is the pathogenesis of hyponaturemia?

Back 7

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.

Front 8

Sodium disorders

Three causes of HYPOVOLEMIC HYPOnatremia:

Back 8

Hypovolemic hyponatremia: decrease in TBNa due to renal or extrarenal losses
1. diuretics
2. Addison's dz
3. diarrhea/vomiting

Front 9

Sodium disorders

Four causes of EUVOLEMIC HYPOnatremia:

Treatment?

Back 9

Euvolemic Hyponatremia: normal TBNa but incresed TBW
1. SIADH
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

Front 10

Sodium disorders

Four causes of HYPERVOLEMIC HYPOnatremia:

Treatment?

Back 10

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

Front 11

Sodium disorders
REMEBER:
1. low UNA - means?
2. NL UNa - means?

Back 11

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).

Front 12

Sodium disorders

What is hypernatermia and what are three examples of it?

Back 12

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)

Front 13

Sodium disorders
VIP

Does the serum Na concentration give us any reliable information about TBNa?

Back 13

NO!! Should be apparent from this entire lecture

Front 14

Sodium disorders

Hypernatremia is always associated with what?

Back 14

Hyperosmalality

Front 15

Sodium disorders

Four causes of HYPOVOLEMIC HYPERnatremia?

treatment?

Back 15

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

treatment: hypotonic fluids

Front 16

Sodium disorders

How can diuretic, diarrhea, and vomiting all cause both Hypovolemic hyper- and hyponatremia?

Back 16

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

Front 17

Sodium disorders

Three causes of EUVOLEMIC HYPERnatremia:

Treatment?

Back 17

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

Front 18

Sodium disorders

Three causes of HYPERVOLEMIC HYPERnatremia:

treatment?

Back 18

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

Front 19

Sodium disorders

Compare lab findings of a patient with central DI and one with osmotic diuresis?

Back 19

Central DI: urine osmolal < plasma osmolal

Osmotic diuresis: urine osmolal > plasma osmolal

Front 20

Sodium disorders
VIP

What is should the rate of correction be in correcting hypernatremia? Why?

Back 20

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.