Exam 4 - Hypoadrenocorticism Flashcards
what is the general cause behind primary hypoadrenocorticism?
destruction/infiltration of adrenal cortices
what is the most common pathogenesis of primary hypoadrenocorticism?
immune-mediated destruction
what is ‘classic’ hypoadrenocorticism?
mineralocorticoid & glucocorticoid deficiency
what is ‘atypical’ hypoadrenocorticism?
some dogs with primary hypoadrenocorticism that only suffer from a lack of cortisol - > 25% of cases
can be from lack of acth production
why does secondary hypoadrenocorticism occur? is it common?
lack of ACTH production - nope
signs reflect lack of cortisol because secretion is entirely dependent on acth, with aldosterone production unaffected
why may we see iatrogenic hypoadrenocorticism?
may be the result of abrupt withdrawal of exogenous steroids - signs occur due to lack of cortisol
may occur with therapy for cushings with trilostane or mitotane - signs are due to lack of cortisol +/- aldosterone
what are some examples of metabolic processes that are affected by cortisol?
gluconeogenesis
immunologic function
hepatic synthesis of albumin
effective hematopoiesis
what are some general signs seen that are attributed to a lack of cortisol?
anorexia, vomiting, diarrhea
lethargy & depression
weight loss
abdominal pain
signs are exacerbated by stressors
what is aldosterone essential for in the body?
end point of the RAAS system - essential for sodium retention & adequate extracellular fluid volume & regulates potassium by promoting excretion by kidneys (save sodium & pee potassium)
what are some general signs attributed to aldosterone deficiency?
weakness, hypotension
dehydration & pre-renal azotemia
cardiac consequences of hyperkalemia - bradycardia, irregular beats, & sinus arrest
what is the common signalment of dogs affected by hypoadrenocorticism?
young (4-6 years old), female (70% of cases)
portuguese water dog, standard poodles, & westies
T/F: even though there is a poster child for addison’s. a dog is never too young, too old, too big, or too small for the disease
true
T/F: most dogs with addison’s are examined at least 3 times before a diagnosis is made
true
what are some chief complaints that are seen in addisonian patients?
often vague - ADR
commonly suggests gi disease - vomiting, diarrhea, anorexia, bloody vomit & diarrhea are common
unlocalized abdominal pain
regurgitation
seizures & collapse
T/F: clinical signs of addison’s may be triggered by a stressful event such as boarding, travel, house guests, & surgical procedures
true
lack of __________ in addisonian patients will cause the most dramatic clinical signs such as weakness, severe dehydration, bradycardia (inappropriate in a dehydrated patient - should be tachycardic), abdominal pain, & hypothermia
aldosterone
T/F: addison’s should make your differential list if you have a sick dog with > 500 eosinophils/ul
true
what lab abnormalities are commonly seen on cbc from an addison’s patient?
anemia is common - gi bleeding from cortisol deficiency, decreased production from cortisol deficiency
polycythemia - from dehydration
lack of a stress leukogram!!!!! eosinophilia is a classic marker
why are your serum electrolytes all over the place in addisonian patients? what changes may you see first?
they are profoundly affected by the lack of aldosterone!!!!
hyponatremia may precede hyperkalemia
what ratio of sodium:potassium may clue you into a diagnosis of addison’s?
<1:27 very suggestive
what electrolyte abnormalities are commonly seen on biochemistry panel from an addison’s patient?
sodium - low due to aldosterone deficiency
potassium - high due to aldosterone deficiency
phosphate - high due to decreased renal blood flow
chloride - low due to gi & urinary losses
calcium - elevated total calcium due to decreased renal blood flow & hyponatremia
what changes are seen on a chemistry panel due to lack of cortisol in addisonian patients?
hypoglycemia, hypocholesterolemia, hypoalbuminemia, changes in liver enzymes (ALT, AST mildly increased), ALP may be strangely low, & increased BUN due to gi hemorrhage
what abnormalities are commonly seen on biochemistry panel from an addison’s patient?
BUN - elevated due to dehydrated and/or gi hemorrhage
creatinine - elevated due to dehydration
albumin - elevated due to dehydration or decreased due to gi blood loss
glucose - +/- low due to impaired gluconeogenesis
cholesterol - +/- low due to impaired hepatic & gi function
what would you expect to see on urine analysis for an addisonian patient? why?
urine specific gravity < 1.020 - lack of aldosterone impacts urine concentrating ability
casts may be noted if severe dehydration has caused tubular damage
what may be seen on thoracic radiographs of an addisonian patient?
microcardia
pulmonary hypoperfusion
megaesophagus
what may be seen on abdominal ultrasound of an addisonian patient?
small adrenal glands in most cases (left cranial pole < 3.7 mm)
very rare, but may see infiltrated & enlarged glands
what are six examples of when you should list hypoadrenocorticism as a differential for a sick dog?
- patient has waxing/waning non-specific illness with anorexia & lethargy, with eosinophilia noted, if they improve with fluids, or if they improve with steroids
- episodes of diseases that seem to be triggered by stressful events
- any patient with gi disease - may be acute, chronic, severe, or signs of substantial gi hemorrhage
- any patient with azotemia
- any patient with hyponatremia/hyperkalemia
- any patient with hypoglycemia
how is baseline cortisol used to establish a diagnosis of addison’s?
baseline cortisol < 2 ug/dl is highly suggestive - in house assays are fast but not all options are reliable, so use a send out test to verify
why do you need to be careful if using a baseline cortisol measurement to diagnose addison’s in a patient that has recently been on prednisone?
cortisol assays cross react with prednisone! may not get correct results
how is an ACTH stimulation test used to diagnose addison’s disease?
ideally performed prior to giving any steroids, but dexamethasone is okay because it’s not detected by cortisol assays
same procedure as covered for cushings
how is an ACTH stim test interpreted for diagnosing addison’s?
flat line result confirms it - cortisol is usually below detection limit both pre & post
post <3 ug/dl is diagnostic for HOC, 3-5 ug/dl is suspicious
T/F: a single baseline cortisol concentration > 2 ug/dl rules out addison’s disease
what test is required to differentiate between primary & secondary hypoadrenocorticism in dogs with normal electrolytes?
endogenous acth levels
will a cortisol to acth ratio identify a dog with secondary hypoadrenocorticism? how is it used?
nope!
in house platforms used to measure acth patient side - dogs with primary HOC have very low cortisol & very high acth
T/F: a patient in an addisonian crisis may die of hyperkalemia within minutes of presentation
true
what is the purpose of using fluid therapy for a patient in an addisonian crisis?
used to improve renal perfusion & will dilute serum potassium
T/F: in an addisonian crisis, any replacement crystalloid is okay to use
true
what is the ideal fluid choice to use for a patient in an addisonian crisis? what other electrolyte are you watching when you start this therapy?
0.9% NaCl (potassium free) unless sodium is <130 mmol/L - if so, need to use LRS or create a fluid with [Na] within 10 mmol/l of the patient
chloride - can rise with NaCl
what is the purpose of adding dextrose to fluid therapy for a patient in addisonian crisis? how is this achieved?
addresses hypoglycemia & facilitates the shift of potassium into the cells
add 50 ml of 50% dextrose to 1 liter of fluid to get a 2.5% solution
how can dextrose be used to manage hyperkalemia in a patient in an addisonian crisis?
0.25 ml/kg of 50% dextrose IV - dilute if not going fast with fluids & then supply dextrose in fluid bag at 2.5%
how can beta agonists be used to manage hyperkalemia in a patient in an addisonian crisis?
terbutaline at 0.01 mg/kg IV/IM/SQ
albuterol by inhaler
how can calcium gluconate be used to manage hyperkalemia in a patient in an addisonian crisis?
stabilizes the heart muscle, but does not decrease serum potassium levels!!!
0.4-1.0 ml/kg over 20 minutes
how can regular insulin be used to manage hyperkalemia in a patient in an addisonian crisis?
moves potassium into cells, but you must provide dextrose in fluids to prevent hypoglycemia
risk of hypoglycemia without careful monitoring - regular insulin is your last choice to use!!!!
0.05 U/kg IV
what is fludocortisone? what is its purpose?
oral drug that works as an aldosterone replacement - works faster than DOCP but is less reliable
we use it as a bridge before giving DOCP as we wait for confirmation of diagnosis
what is DOCP?
desoxycorticosterone pivalate (percorten-v, zycortal)
potent mineralocorticoid - need to decrease book dose by 25% in larger dogs
T/F: after an addisonian crisis, most patients are better within 12-24 hours & can generally be switched to oral medication and be weaned off fluids within 24 hours
true
how is glucocorticoid replacement therapy done for addisonian patients after a crisis?
start prednisone at a supra-physiologic dose (0.5-1.0 mg/kg/day) because they are under tremendous stress from their illness
taper them down to the lowest effective dose over 4 weeks - approximately physiologic dose (0.1 mg/kg/day)
may need to increase if a stressful event is anticipated or occurs
need to decrease dose if pu/pd occurs
T/F: if you ever have an addisonian cat, you need to use prednisolone at a higher physiologic dose (0.3 mg/kg/day)
true
when do you need to start mineralocorticoid replacement in an addisonian patient?
only necessary if serum electrolytes are abnormal!!! DOCP is drug of choice
how is DOCP given to patients with addison’s? what is the recheck schedule used? why?
SQ every 25 days, 2.2 mg/kg, but lower in giant breeds (1.1 mg/kg)
check electrolytes day 12 & 25 - verifies adequate dose (day 12) & duration (day 25)
check lab work every 3-6 months when stable
what client information is necessary for owners with addison’s dogs?
life long therapy is required
normal life span is expected
need to increase prednisone at times of stress
