ADH Flashcards
antidiuretic hormone disorders
SIADH, diabetes insipidus
what does SIADH stand for
syndrome of inappropriate anti diuretic hormone
what is SIADH
abnormal production or sustained secretion of ADH
what is SIADH characterized by
fluid retention
serum hypoosmolality and hyponatremia
concentrated urine
cause of SIADH
malignant tumors like small cell carcinoma of lung
central nervous disorders like head trauma, stroke
drug therapy like morphine, SSRI, some chemo
miscellaneous conditions like hypothyroidism, infection
pathogenesis of SIADH
inc ADH
inc water reabsorption in the renal tubules (inc permeability of distal tubule–>reabsorb water)
inc intravascular fluid volume
causes dilutional hyponatremia and dec serum osmolality
SIADH osmolality
urine osmolality and specific gravity: high
serum osmolality: low
serum sodium: low
urine output: low
wt: gained
pt gaining wt by gaining water without salt
SIADH clinical manifestations
depend on severity and rate of onset of hyponatremia
- dyspnea, fatigue
- water shifts from blood to cells
- neuro: dulled sensorium, confusion, lethargic, muscle twitching, convulsions
- GI: impaired taste, anorexia, vomiting, cramps
- severe: unrepairable neurological damage
is SIADH be lethal
yes from water intoxication
- serum Na level lower than in the cells, water shifts into cells causing cells to swell
- swelled cells in the brain can lead to herniate
pharm for SIADH
drugs not used rather treat underlying cause
- discontinue meds that inc ADH
- chronic SIADH: demecyclocline–> counteracts
- can be give loop diuretics to dec water but must monitor Na frequently so it doesnt drop too low
demeclocyline classification
tetracycline broad spectrum anb
demeclocycline indications
abx
chronic SIADH
demeclocycline moa
interferes with renal response to ADH
- kidneys don’t respond to ADH so water wont be reabsorbed
demeclocycline adverse effects
photosensitivity
teeth staining
nephrotoxic
what is diabetes insipidus
deficiency of ADH (from posterior pituitary) or
a dec renal response to ADH
what is diabetes insipidus characterized by
excessive water loss in the urine
inc plasma osmolality
what are the two forms of DI
neurogenic (aka central, lesion of part of brain that interferes with release, most common)
nephrogenic (kidneys dont response to ADH)
what is the cause of neurogenic DI
damage to the hypothalamus
damage to the pituitary gland
what is neurogenic DI associated with
stroke
tramuatic brain injuries
cerebral infections
brain surgery
what is the onset of neurogenic DI? permanent?
sudden and typically permanent
what is the cause of nephrogenic DI
loss of kidney function
often drug related (lithium)
what are the associated disorders with nephrogenic DI
chronic kidney disease
what is the onset/course of nephrogenic DI
slow onset and progressive disease
pathogenesis of DI
dec ADH
dec water reabsorption in renal tubules
dec intravascular volume leading to
- inc serum osmolality (hypernatremia)
- excessive urine output
