6.5- Physiology III - Hypernatremia

omarys's version from 2017-05-27 23:17

Section 1

Question Answer
Hypernatremia is associated with a high ____ ____ due to the _______ ______ of hypernatremia rather than ______ ______.mortality rate ; underlying causes ; hypernatremia itself
T or F- People with severely low ADH will likely develop hypern.False. There's another protective mechanism against hypern.: thirst.
Manifestations of hypern.?Cellular dehydration (cell shrinkage), again in the CNS
Clinical symptoms of hypern.?Neurological mainly, e.g. lethargy, irritability, twitching, seizures (coma and death if severe)
While urea is an ineffective osmole in the plasma, it-does raise osmotic pressure in the lumen of the tubuli, since some of the tubuli cells are impermeable to urea. That's why increased urea levels might cause osmotic diuresis and hypern.
Elevated urea levels inincreased catabolism (a.a. breakdown), increased protein levels
Nephrogenic DI may be the result of (2 electrolyte imbalances)hypercalcemia ; hypokalemia
Nephrogenic DI may be the result of (1 drug and 1 syndrome)lithium ; Sjogren
A major proportion of central DI cases idiopathic (nearly 1/3rd)
What abnormal buildup of biomolecules disease may be a cause of nephrogenic DI?amyloidosis
All hypern.'s share a common mechanism:loss of hypotonic fluid (whether thru the GIT, RT, urine, sweat...)

Section 2

Question Answer
A 3% saline is hypo or hypertonic?Hyper - can lead to hypern. (iatrogenic)
What urine lab values are low in DI?[Na+] and osmolality (NOT a response to dehydration but a result of massive water loss, thus dilution of urine)
Urine output in DI is ____high - no ADH > can't concentrate urine > need higher volume of urine to secrete given amount of solutes
T or F- People with DI are hypovolemic.False. No ADH means no concentration of urine, but not necessarily loss of fluids/dehydration. They THIRST.
T or F- People with DI have low serum [Na+].False, it's normal. No volemic issues going on here (given the patient drinks enough water).

Section 3

Question Answer
Other than elevated urea levels, what can cause osmotic diuresis?Hyperglycemia/unbalanced D
T or F- Both osmotic and secretory diarrhea may cause hypern.False - in secretory diarrhea there is secretion of salts and water. In osmotic diarrhea there's more water loss than salt loss >>> loss of hypotonic fluid >>> hypern.
In both renal and extrarenal loss of water, blood and urine lab findings are identical except for:amount of excreted osmoles per day - will be much higher than 900 mOsm in renal loss (there's osmotic diuresis)
Other than lab findings, what is also common to both renal and extrarenal water loss?Clinical symptoms: dehydration (orthos., low turgor, etc.)
Urine lab results in renal/extrarenal water loss?HIGH osmolality (due to dehydration) and LOW [Na+], just like in hypov. and hyperv. HYPOnatremia. Why? Cuz low ECV that's why (here due to dehydration rather than CHF etc.).

Section 4

Question Answer
In adults, hypern. will ALWAYS be due tothe patient not drinking enough water (if e.g. impaired consciousness, no water available, or -rarely- damage to thirst center/DI)
In polyuria WITH (appropriate) polydipsia, there isnormonatremia
Polyuria and frequent urination areDISTINCT conditions (although the former is usually accompanied by the latter); polyuria is production of large volumes of urine
Polyuria is production of more than ____ L urine/day.3
Indication for water deprivation test?Polydipsia - to dd bwn DI and other causes of polydipsia
People with DI usually do not develop ____, but rather present w/ complaints of ____.hypern. ; polyuria
What findings after water deprivation lead to the elimination of DI as a cause of polydipsia?Concentrated urine (>600 mOsm/L)
Patient presents w/ polydipsia. Next step?Assess urine volume/check for polyuria (24-hour urine collection). If positive, proceed to water deprivation test.

Section 5: Gestational DI

Question Answer
Gestational DI occurs due toVasopressinase. Culprit is placenta
Gestational DI is usuallysubclinical (cuz compensatory ^ in ADH)
When is gestational DI dangerous/clinical?When preggie fasts >>> no water intake and risk of hypern.
Tx isADH analogues resistant to vasopressinase (desmopressin)