Popham- Natremic Flashcards
What is normal serum Na?
135-145
What is hyponatremia?
Less than 135
What is hypernatremia?
> 145
What is the main contributor to serum osmolality?
Na
If normal plasma/serum osmolality is 285-300 how can you estimate Na, BUN and glucose?
Na (2) + BUN/2.8 + Glucose/18
Are hyponatremia and hypernatremia usually water or salt problems?
almost always WATER problems
What causes the sxs of hypo/hyper natremia?
Alterations in plasma osmolality–>
changes in brain cells
What symptoms do you see with Hyponatremia?
Sxs d/t HYPOOSMOLALITY–> Brain cell swelling
<115: obtundation, seizures, coma
Are symptoms related to hyponatremia usually reversible?
YES!
When are hyponatremic sxs most severe?
If hyponatremia occurs QUICKLY and the brain doesn’t have time to adapt
(If hyponatremia develops gradually–> brain has time to adjust)
How do hyper and hyponatremia affect the brain?
Hypo> HYPOOSMOLALITY–> Brain cell swelling
Hyper> Extracellular hyperosmolality–> brain cell dehydration
What are the symptoms of hypernatremia?
Lethargy weakness irritability twitching seizures coma death
What is commonly seen in the brain with hypernatremia?
Rupture of cerebral vessels due to decrease in brain volume
*Clinically significant water shift occurs with 30-35 mosm/kg osmolar gradient between plasma and brain or a Na elevation of 17 meq
What does ADH do?
Maintains appropriate plasma osmolality
Where is ADH produced and stored?
Produced in HYPOTHALAMUS in supraoptic and paraventricular nuclei, stored in secretory granules>
secretory granules move down supraopticohypophyseal tract to POSTERIOR LOBE of PITUITARY GLAND
What causes the release of ADH?
- Increase in plasma osmolarity
- baroreceptors–> hypovolemia or decreased ECV
- Pain
- Esophageal stimuli
- Various medications
What does ADH bind to and where? What does this do?
V2 receptor in COLLECTING TUBULE>
activates a protein kinase>
Aquaporin 2 to move from cytoplasm to luminal membrane and form water channels
What happens to water if ADH is present?
Water channels are present>
water is returned to blood>
lowers serum osmolality>
urine osmolality will be high
What happens to water in the collecting duct if ADH is absent?
Water channels are absent>
water is excreted in the urine>
raises serum osmolality>
urine osmolality will be low
What is the difference between high and low Posm?
Posm high> thirst, ADH released, CT permeable to water, High Uosm
Posm low> no thirst> no ADH release> Collecting tubules impermeable to water> low Uosm
What is indicated by high and low Uosm?
High Uosm: ADH present, kidney reabsorbing water
Low Uosm: ADH low/absent, kidney is excreting water
What is hte difference between high and low urine Na?
Tells you what the kidney thinks about volume status
High- kidney behaving as if body V is expanded, getting rid of excess Na
Low- kidney behaving as if body is V depleted, reclaiming Na
What is the range of urine osmolality in a normal functioning kidney?
50-1400
- narrower in very old and very young
What happens if Uosm is < 100?
No ADH present and urine is maximally dilute
What happens if Uosm is >100?
the higher the Uosm the more ADH is present
What is the usual daily osmolar load from dietary protein/salt?
500-750 mosm
What is the minimum volume of water excreted daily?
Daily osmolar load/maximal urine osmolarity
500 mosm/day//1000 mosm = .5 L
750 msosm/day//1000 mosm=.75 L daily
What is the maximum volume of water excreted daily?
Daily osmolar load /minimal urine osmolarity
500 mosm/day//50 mosm/l = 10 liters/day
750 mosm/day//50 mosm/l = 15 liters/day
What happens to Na excretion in a steady state?
Dietary intake of Na = urinary excretion of Na