4. CIS Mechanisms to Adjust Flashcards
When plasma sodium concentration is high, this induces fluid movement ____ cells
out of
Hypernatremia usually greater than 145 mEq/L
In virtually all patients, hyponatremia results from what?
the intake, either oral or intravenous, and subsequent retention of water. A water load normally will be rapidly excreted, but patients with hyponatremia have impairment in renal water excretion, most often due to inability to suppress ADH secretion
What is pseudohyponatremia?
The levels of Na are not really low
Errors in lab measurement of Na that reads hyponatremia due to hyperproteinemia, lipidemia, and cholesterolemia
Also due to water being pulled via osmotic gradient into vasculature with resulting dilutional hyponatremia (hypoglycemia or unmeasured osmol)
Plasma concentration in a patient with hyperglycemia = ?
(2*Na) + (glucose/18) + (BUN/2.8)
What is osmolar gap? What is normal
Difference between plasma osmolality and true plasma osmolality measure with an osmometer. Normal is less than 10 mOsm/kg H2O
Why does a pregnant woman with no symptoms have hyponatremia?
Reset osmostat that most pregnant women have. Body has more fluid and release of ADH and thirst is reset to a lower level.
In normal individual ADH levels are very low when Posm
If plasma osmolality is low and ADH is low, what could you suspect in your patient?
Primary polydipsia and Uosm/Posm is less than 1
If your patient has low plasma osmolality and plasma ADH is high, what can you suspect is happening to your patient?
SIADH
Uosm/Posm greater than 1
If plasma osmolality is high in your patient and plasma ADH is high what can you suspect is going on with your patient?
2 possibilities
- nephro DI if the Uosm/Posm is less than 1
- Dehydration if the Uosm/Posm is greater than 1
If plasma osmolality in your patient is high and plasma ADH is low, what can you suspect is going on with your patient?
Neuro(central) DI
Uosm/Posm is less than 1
What are some causes of true hyponatremia due to high and low ADH?
Dilute urine with low ADH that can be found in pregnancy and psychogenic polydipsia (schizophrenia)
Concentrate urine due to high ADH found in SIADH, cortisol, hypothyroidism, cirrhosis, congestive heart failure
What is desmopressin?
An analog of ADH
What is a main cause of nephrogenic diabetes insipidus?
Lithium treatment
Initially limits the ability of V2 receptors to generate cAMP resulting in diminished biologic activity of ADH.
Chronically, it may also diminish transcription of aquaporin channels and thus renal response to ADH is impaired
When plasma sodium concentration is low, this induces fluid movement _____ cells
into
hyponatremia usually less than 135 mEq/L
What are other common causes for nephrogenic DI besides lithium?
Hypercalcemia and hyperkalemia
