hypoadrenocorticism pt 2 Flashcards
type of azotemia related to hypoadrenocorticism? causes? treatment?
- Pre-renal
- USG < 1.030 (unable to concentrate)
> in 50-75% of patients
> Despite marked dehydration & hypotension
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Causes - Decreased medullary blood flow
- Medullary washout
- Decreased response to ADH
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Treatment - Adequate fluid replacement
hyperkalemia DDx
- Hypoadrenocorticism ‘Addisonian crisis’
- Acute Kidney Injury
- 3rd space losses
> i.e. Abdominal effusion - Tissue trauma
> Crush injury, thromboembolus, tumour lysis - Gastrointestinal disorders
> i.e. Whipworm infection
ECG - when would we perform / based on what symptoms? relationship to addison’s?
- what might we see related to addison’s?
- Perform in all dogs with bradycardia or K+ > 6.5 mEq/L
- ECG changes often correlate poorly with K+ levels in dogs with Addison’s disease
- Abnormal rhythms associated w/ Addison’s disease
> Sinoatrial standstill (Hyperkalemia)
> Ventricular premature contractions
> Atrial fibrillation
possible radiograph findings for addison’s
Volume depletion
* Microcardia
* Narrowed vena cava
* Hypoperfused (black) lung fields
* Megaesophagus
> Very rare (< 1% cases)
Addison’s disease has been implicated / is screened for when the following conditions are encountered:
- Vomiting / Diarrh- non-specific GI Signs
- Hypoglycemia
- Hypercalcemia
- PU/PD
- Megaesophagus
- Lymphopenia
> Inappropriate lymphocyte count in a sick dog - Eosinophilia
diagnostic testing for addison’s - screening and definitive testing
Screening test
* Basal serum cortisol
> Cortisol concentration > 55 nmol/L (> 2ug/dL)
=> Rule – OUT Addison’s disease
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Definitive diagnosis
> ACTH stimulation test
ACTH stimulation test
- what samples do we take?
- how do we interpret?
- Baseline (pre, 0 hour) blood sample taken
- ACTH injected
- Post injection blood sample taken
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Interpretation of ACTH stimulation test: - Pre:
> Plasma cortisol < 30 nmol/L
=> (Ref range 30-300 nmol/L) - 1 hour post ACTH:
> Plasma cortisol < 30 nmol/L
=> (Ref range 30-300 nmol/L) - Confirms Addison’s disease
Dexamethasone and the ACTH stimulation test - does it impact? use?
- Does NOT interfere with cortisol determination
- Used in the initial treatment of acute adrenocortical insufficiency without interfering with ACTH-response testing
what drugs can interfere with the ACTH stimulation test? what can we do about this?
Cross reaction with serum cortisol assays:
* Prednisone
* Prednisolone
* Hydrocortisone
* Cortisone
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* Withhold until completion of ACTH stimulation test
* If any of the above are inadvertently administered, glucocorticoid therapy must be switched to dexamethasone for at least 24 hours prior to performing ACTH stimulation test
treatment for acute addisonian crisis
- goals? how/ when do we make our definitive diagnosis and why?
Acute Addisonian Crisis:
1. Correct hypovolemia
2. Correct hypoglycemia (if present)
3. Correct electrolyte abnormalities (K+)
4. Correct acid-base abnormalities
5. Supplement with glucocorticoid
6. Supplement with mineralocorticoid
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Definitive diagnosis performed while resuscitative measures are in progress, or once animal more stable
lPoor absorption of ACTH gel from IM site in severe dehydration
fluid treatment - administration technique / schedule for addisonian crisis
Intravenous fluids
* Aggressive fluid resuscitation
* Shock rate 90 ml/kg (dog)
> With frequent reassessments q 10-15 minutes
* May require 60-80 ml/kg/hr for first 1-2 hours
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Thereafter:
* Fluids decreased to keep up with urinary losses
* Tapered to maintenance rate & discontinued over a few days
what type of fluids to use in an addisonian crisis? effect of any IV fluid selected?
Fluid selection
* LRS / PLA
> K+ 4-5 mEq/L
> Alkalinizing solution
* 0.9% NaCl
> K+ free
> Acidifying solution
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Effect of any IV fluid selected
* Dilutional effect on K+
* Improved renal perfusion & excretion of K+
what to give to correct hypoglycemia in an addisonian crisis? other effects of this treatment?
- Correct hypoglycemia (glucose ≤ 3.0 mmol/L)
- 50% dextrose
> 0.5 - 1.0 ml/kg IV bolus
> Dilute to 25% or less, with IV fluids, to avoid thrombophlebitis - Maintain on glucose supplementation as needed
> 2.5-5% dextrose CRI at maintenance fluid rates
> Consider high fluid rate - Dextrose supplementation will also improve increased K+
how to administer glucocorticoids in an addisonian crisis, schedule
Intravenous glucocorticoids
* Rapid-acting formulation
> Dexamethasone sodium phosphate
> 0.1 mg/kg IV initially
> Previously much higher doses recommended
* Continue daily dexamethasone (0.1 mg/kg IV q 24 hours) until patient able to take oral prednisone
how / when should we correct acidosis in addisonian crisis? another outcome of this therapy?
- Reserved for life-threatening acidosis
> pH < 7.2 - Treatment: Conservative sodium bicarbonate IV
- Bicarbonate therapy will also improve K+
