Hypernatremia Flashcards
Is ADH release more sensitive to small increases in tonicity or EABV?
plasma tonicity
is ADH release more sensitive to LARGE increases in tonicity or EABV?
EABV
As tonicity increases and EABV decreases, how does ADH sensitivity change?
increases
What is the SNa cutoff for hypertonic hypernatremia?
145 mEq/L
When do most adults begin showing symptoms of hypernatremia?
SNa > 160 mEq/L
What are symptoms of hypernatremia?
seizures, coma, somnolence, lethargy, thirst
When is aggressive treatment for hypernatremia started?
when SNa is above 155 mEq/L , regardless of symptoms
What is the rapid adaptation to hypernatremia in the brain?
Swelling by accumulating electrolytes, increasing osmolality
What is the slow adaptation of hypernatremia in the brain?
accumulation of organic osmolytes
How fast should SNa fall when treating hypernatremia, so as to avoid cerebral edema?
< 8 mEq/L/day
Does isotonic volume depletion or hypertonicity cause cellular dehydration?
hypertonicity
Can dehydration by itself produce recognizable volume depletion? Why?
No - water is lost from ECF in smaller amounts compared to hypertonic dehydration, which loses greater amounts from BOTH ICF and ECF - this is much more likely to cause a very elevated SNa
In the absence of ADH, what happens to water diuresis in the setting of volume depletion or decreased renal solute?
it’s impaired
How can you develop hypertonic hypernatremia? (2)
intake of hypertonic salt OR persistent water loss without replacement
What do you always know about the patient if they have persistent hypertonic hypernatremia?
they either have absent thirst or they cannot access water in their living situation
Who is most likely to be hypertonic/hypernatremic?
elderly, infirm, infants, and intubated
What are the 3 classes of hypertonic hypernatremia?
hypertonic Na Gain
polyuric
non polyuric
what are the 2 kinds of polyuric hypernatremias?
solute diuresis and pure water diuresis
what are the two types of pure water diuresis polyuric hypernatremias?
central and nephrogenic diabetes insipidus
Drinking sea water, hypertonic feeding, hypertonic enemas, 3% saline, Bicarb infusion, and primary aldosteronism are all examples of what kind of hypernatremia?
hypertonic sodium gain
elevated glucose, mannitol, urea, diuretics, NaCl and bicarb are examples of what cause for hypernatremia?
solute diuresis leading to polyuria
What are some causes of central diabetes insipidus?
alcohol pituitary tumors post brain surgery trauma cysts granulomatosis pregnancy meningoencephalitis genetic mutations in ADH
What are some causes of nephrogenic diabetes insipidus?
hypercalcemia hypokalemia renal disease drugs genetic mutations in V2R and AQP2
hypodipsia, fever, sweating, vomiting, diarrhea and cathartics all cause what class of hypernatremias?
non polyuric - no intake and therefore no replacement for free water clearance/loss
What kind of hypernatremia can cause brain shrinakge, cerebral blood vessel tears, limbic demyelination, eABV elevation and acute pulmonary edema?
hypertonic sodium gain
Who is most likely to have hypodipsia?
elderly adults who are infirm, with diminished thirst and no access to water
Are most liquid losses in the body hypotonic or hypertonic? what does this mean for SNa?
hypotonic - they cause hypernatremia through free water loss
What is the only kind of liquid loss in the body that is isotonic?
secretory diarrhea
Persistent inhibition of ADH is: central or nephrogenic diabetes insipidus?
central
tubular unresponsiveness to ADH is: central or nephrogenic diabetes insipidus?
nephrogenic
As urine flow rate increases,w hat happens to pure water diuresis?
the urine osmolarity will drop because there is less time to remove solutes
As urine flow rate increases, what happens to solute diuresis?
it increases, because osmolarity increases as flow rate increases
As urine flow rate increases, are urine losses relatively water rich or poor?
rich - causes hypernatremia by leaving residual TBW hypertonic
Why is hypokalemia common in hyperglycemic polyuria?
tubular flow rate and solute load have increased, washing out solute gradient. Meanwhile, ENac takes up sodium, which produces a relative electronegativity near the CCD
When can primary polydipsia be excluded in the water deprivation test?
when Sna > 145 mEQ/L and/or Uosm > Posm
What does the water deprivation test in the setting of polyuria help us differentiate between?
central and nephrogenic diabetes insipidus, polydipsia
Why do you measure UV, Uosm, weight, SNa, and Posm repeatedly during the water deprivation test?
to see when the patient reaches steady state
When do you stop the water deprivation test and administer desmopressin?
When 1. Uosm is > 600, 2. Uosm is stable for 2 or 3 hours despite rising Posm , or 3. Posm is > 295 or SNa > 145
When do you give desmopressin in the water deprivation test?
When Uosm is stable for 2 or 3 hours despite rising Posm , or Posm is > 295 or SNa > 145
If the response to desmopressin is a Uosm that rises > 100%, what is the diagnosis?
central diabetes insipidus
If the response to desmopressin is a Uosm that rises 15-50% (> 300 mOsm), what is the dix?
partial central diabetes insipidus
If the response to desmopressin is no change to Uosm, what is the dx?
nephrogenic diabetes insipidus
If the response to desmopressin is a small rise in Uosm (< 300 mOsm), what is the dx?
partial nephrogenic diabetes insipidus
How should acute Na intoxicatin with neurologic symptoms be treated?
D5W
- if within 24 hours, then the goal is to correct SNa to 145
- if longer than 48 hours, SNa should not fall faster than 8 mEq/L/day
How do you estimate target water deficit in hypernatremia?
current TBW x (SNa/140 - 1)
What is TBW in men?
0.6 lean body weight
What is TBW in women?
0.5 lean body weight
what is TBW in the elderly?
0.45 lean body weight
How should SNa be corrected with high serum glucose?
SNa + (glucose - 100/100) x 2)
How should hypernatremia caused by sweating , GI losses or solute diuresis be treated?
0.9 saline or 0.45 saline + potassium
How can you calculate rate of fall SNa from a 1L infusion?
(infused Na + infused K) - SNa/TBW + 1L
HOw do you treat acute central DI?
with 2 mcg desmopressin IV x 12 hours
How is nephrogenic DI treated?
low Na/low protein diet
thiazide diuretics
NSAIDs
HOw is x linked V2r treated (experimentally)?
vaptans
What are normal insensible water loss for a 70 kg person?
500 ml/day/m2 or 800 ml/day
How should IV infusions be given in treating hypernatremia?
water and sodium infusions should be separate
