ATI Unit 12 Posterior Pituitary Disorders Flashcards
what does the posterior pituitary gland secrete and what does under- and oversecretion of this do?
- secretes vasopressin or ADH (antidiuretic hormone)
- oversecretion = SIADH (syndrome of inappropriate ADH) where you hold on to too much water and there’s little urine outpus
- undersecretion of ADH = diabetes insipidus, always too much urine output, hypotension, thirst
(both often result in fluid/electrolyte imbalances)
what are the three types of diabetes insipidus
1) primary = hypothalamus or posterior pituitary messed up
2) nephrogenic = inherited problem in renal tubules (don’t react to vasopressin/ADH)
3) drug-induced = lithium carbonate (Lithium) or demeclocycline (Declomycin)
what two drugs can induce diabetes insipidus?
- lithium carbonate (Lithium)
2) demeclocycline (Declomycin)
- changes how kidneys respond to ADH
so what are some assessments you want to check out with diabetes insipidus?
- are they taking lithium or demeclocycline
- is there anything cranial related: think tumors, trauma, cranial surgery, and infection (meningitis, encephalitis)
- dehydration/decreased thirst response
- people with renal failure/insufficiencies
- are they using diuretics?
- dysphagia/poor food intake
subjective and objective findings of diabetes insipidus
Subjective
- polyuria (output of 4-20 L/day of dilute urine)
- polydipsia (excessive thirst, 2-20L/day)
- nocturia
- fatigue
- dehydration EVB thirst, weight loss, muscle weakness, headache, constipation, dizzinesss
Objective
- sunken eyes
- tachycardia
- hypotension
- loss of skin turgor
- dry mucous membranes
Lab tests for diabetes insipidus
Urine (DILUTE)
Decreased urine…..
- urine specific gravity (less than 1.005)
- urine osmolality (less than 300 mOsm/L)
- pH
- Na+, K+
(as urine volume increases, osmolality decreases)
Serum (CONCENTRATED)
- increased everything (as serum volume decreases, osmolality increases)
Radioimmunoassay - decreased ADH
using a water deprivation test for diabetes insipidus
- basically withhold fluids and see if urine still stay diluted despite this
- if postural hypotension, dizziness, tachycardia develop, STOP, patient is dehydrated
using a vasopressin test for diabetes insipidus
- a subq vasopressin shot is given and if patient has diabetes insipidus, urine output after shot will be increased specific gravity
- differentiates nephrogenic from central DI
if a patient has diabetes insipidus what’s a food to avoid?
caffeine - diuretic effect
if a patient with DI develops constipation what foods would help?
bulk food and fruit juices
what meds are given for DI?
- ADH replacement agents (desmopressin acetate or DDAVP; aqueous vasopressin or Pitressin)
- synthetic ADH
- teachings: weight, I/O match, electrolytes, specific gravity - ADH stimulants - carbamazepine (Tegretol)
- anticonvulsants stimulate release of ADH
- monitor for thrombocytopenia (bruising, fever, sore throat) - vasopressin (Pitressin)
- the hormone
- can cause vasoconstriction so caution in clients with CAD
- water intoxication: headache, confusion
- lifelong therapy
what weight gain should a client report?
greater than 0.9kg (2lb)
what is the general change in the body that SIADH causes?
- posterior pituitary releasing too much ADH
- water is reabsorbed
- renin-angiotensin system blocked and sodium still secreted
Leads too….
water intoxification
dilutional hyponatremia
cellular edema (can cause decreased serum osmolality b/c of fluid shifts)
so what are the risk factors in a patient with SIADH?
- malignant tumors like the oat-cell lung cancer can cause hypersecretion
- another is increased intrathoracic pressure like with positive pressure ventilation
other: cranial trauma, meningitis, stroke, pain, stress, meds
NOTE
diuretics can further complicate sodium losses
which meds can cause SIADH
- alcohol
- lithium carbonate
- phenytoin
