hypoadrenocortism Flashcards
what is hypoadrenocortism
immune mediated destruction of the adrenal cortex leading to cortisol and aldosetrone deficiency
What are the fuctions of cortisol and aldosterone as they relate to the clibical signs of addisons.
- Cortisol: many but mainly maintanence of GI mucosal health and regulating vasomotor tone.
- Aldosterone: Renal retention of water and sodium and potassium excretion.
Is there a typical signalment for addisons?
Young to middle aged female dogs
Poodle, soft coated wheaten terriers and nova scotia duck tolling retrievers overrepresented
What are the clinical signs of addisons
- Crisis with collapse and haemorrhagic GIT
- Can be vague with general malasie, weakness, tremouring, GI signs and PUPD
How is hypoadrenocortism definitely diagnosed
By an ACTH stimulation test
- cortisol <55mmol/l 1 hour after exogenous ACTH administration.
What is the significance og the sodium potassium ratio
- aldosterone responsive for renal retention of sodim and excretion of potassium.
- therefore sodium potassium ratio typically low.
- Less than 26 very suggestive though not diagnostic as other conditions eg AKI, pyometra, may also cause
What is the significance of the stress leukogram?
Dogs that present similary collapsed from other conditions would be expected to have a stress leukogram (lymphopeania). This may be unexpectedly absent if the patient has addisons.
How could addisons be ruled out on intial bloodwork
a resting cortisol >55mmol/l
The main bloodwork abnormalities in an addisionian patient are lack of ACTH stimulation, Absent stress leukogram and a low Na:K ratio. What other abnormalities maybe seen?
- Azotaemia. (inappropriately low USG as hyponatraemia impairs concentrating ability)
- Anaemia, lack of bone marrow stimulation by cortisol.
- Hypoglycaemia (cortisol stimulates gluconeogenesis and glycogenolysis)
- Hypercalcaemia
What are the main elements of treatment for hypoadrenocortism
- Fluid therapy
- Correct electrolyte disturbances
- Glucocorticoid replacement
- Mineralocorticoid replacement
- Supportive/GI care
- Supplement hypoglycaemia
What is an appropriate fluid choice for hypoadrenocortism
- Isotonic crystaloid.
- Aimig to restore perfudion and GFR, replace losses and help correct electrolytes.
- Give boluses as needed initially then to support losses and continue until able to eat unaided.
What is the most life threatening consequence of an addisonian crisis
Hyperkalaemia.
-assess ECG on triage, beging IVFT and administer calcium gluconate if needed
What causes clinical signs in hyponatraemia and how does it effect fluid resus in addisons
Cell swelling of the CNS caused by water moving from the now realitively hypo-osmolar extracellular space into cells. if <130mmol/l should custom make fluid similar to patient NA levels for bolusing (as risk of myelinolysis wth fast correction).
What is typically used for initial glucocorticoid replacement?
- 0.1mg/kg dexamethason IV SID.
- Will not interfere with cortisol assays bt should have definative diagnosis before giving.
When is prednisolone initiated and how is the dose altered.
- Started at 0.5mg/kg SID when patient is eating.
- Taper to 0.05 - 0.25mg/kg, aimimg for lowest dose with no GI signs or lethargy.
- If phyical or mental stress is anticipated the dose is temporialy increased to cope with increased cortisol demand.
What is the potential advantage of using dexamethasone over a hydrocortisone CRI
- Dont have the cost or complications associated with CRI use.
- Hydrocortisone has mineralocorticoid activity and if used early could cause faster changes in sodium concentration.
How are mineralocorticoids supplemented.
- DOCP injection onve the diagnosis is confirmed.
- start at 2.2mg/kg and check electrolytes 10 days later.
- Dose can be reduced each time until the lowest maintanence dose is found.
- Could check electrolytes from 25 days onward to try and extend the dosing interval but it may be more practical to stick to monthy with a lower dose.
What supportive care might an addisonian patient revieve
- Antiemetics
- Antiacid (only if GI bleeding is evident)
- opioid analgesia if needed
- pressors if needed to maintane BP (rare, check volume status)
What are some possible complications in a patient hospitalised for hypoadrenocortism
- Persistent hypotension needing pressors (rare)
- Acute kidney injury
- Aspiration pneumonia
- Bacterial translocation from intestinal mucosa
How does hypoadrenocortism present differently in cats than in dogs
- Cats respond more slowly
- Cats are more cardiovascularly compromised and more likely to be dependant on pressors
