SIADH

Question 1

____ cardinal finding of the symptomatic syndrome of inappropriate antidiuretic hormone (SIADH)

SIADH can be caused by:

Hyponatremia of SIADH is characterized by ____smolality and ____ concentrated urine and ____urine ____excretion

Renal, adrenal, and thyroid functions are normal, and neither & NOT dehydrated

Answer 1

Hyponatremia

cerebral disorders
pulmonary disease
adverse effects of medications

hypoosmolality
inappropriately > USG
inappropriate urine sodium excretion.

neither edema, dehydration, nor azotemia is typically present in animals with SIADH.

Question 2

excess of ADH called:
aka:
excessive release of ADH from:
C/S: 
3 causes:

Answer 2

SIADH
Schwartz-Bartter's syndrome
neurohypophysis or ectopically source
CNS
CNS, pulmonary disease, drugs

Question 3

failure to recognize the true incidence of SIADH may be caused by lack of clinical suspicion, transient nature of some forms of SIADH, or rapid demise

Answer 3

incidence likely more common than DI
recognition of SIADH is important bc causes can be remedied by drug withdrawal and patient death that can be iatrogenic if SIADH is treated too aggressively

Question 4

SIADH is defined as an excess of ADH in the absence of

Answer 4

hypovolemia or hyperosmolality

Question 5

Causes:
CNS:
Pulmonary:
Neoplasia:
Drugs:

Answer 5

Central Nervous System Disorders
Head trauma
Hydrocephalus
Cerebrovascular accidents
Brain tumor
Meningitis/Encephalitis
Pain
Nausea
Psychologic stress

Pulmonary Lesions
Bacterial pneumonia
Aspergillosis
Lung tumors
Positive pressure ventilation
Dirofilariasis

Malignancies
Pancreatic carcinoma
Prostatic carcinoma
Thymoma
Osteosarcoma

Drugs
Antidepressants
Neuroleptics
Antineoplastics cyclophosphamide and vinca alkaloids
Nonsteroidal antiinflammatory drugs
Opioids

Question 6

CNS and MoA:
Pulmonary and MoA:
Neoplasia MoA:
Drugs and MoA:

Answer 6

CNS -direct stimuation of supraoptic and paraventricular nuclei

Pulmonary -tumor produce ectopic ADH
-interrupt inhibitory impulses in vagal afferents from stretch receptors in the atria and great veins
PPV - inhibit low-pressure baroreceptors and stimulate the release of ADH

Neoplasia - ectopic ADH and rare
Drugs - >ADH secretion unknow MoA

Question 7

C/S - ___ level___:

Answer 7

<120mEq/L Na and CNS C/S

Question 8

Lab findings:
hyponatremia secondary to:

secretion of renin and aldosterone is inhibited by:

serum osmolality is less than _____
urine osmolality is more than _____
urine sodium usually more than _____

ANP secreted in response to ____
further inhibits renin and aldosterone and promotes___

Answer 8

ADH - renal retention of free water
inhib Aldost. b/c normovolemia
= ongoing urinary Na losses

normovolemia with expanding ECF

<280 mOsm/kg
>150 mOsm/kg
>20 mEq/L

strech
naturesis

Question 9

Hypochloridemia may be severe enough to cause metabolic ____

Blood urea nitrogen (BUN) and uric acid concentrations are decreased by:

increased BUN concentration typically ___ dx of SIADH.

Answer 9

alkalosis

dilution and increased GFR

Excludes

Question 10

Dx

Answer 10

CXR, MRI, drugs

Question 11

Dx:

measure plasma ADH?

ddx most easily confused:
how to ddx:

other ddx (5):

Answer 11

charac. clinical features + exclusion of other hypoNa

unreliable and unnecessary for diagnosis

Addison’s - primary hypoadrenocorticism
azotemia and hyperkalemia +/- volume status if crisis

CHF
nephrosis
severe liver disease
hyperglycemia
hyperlipidemia

Question 12

Tx:
correct underlying cause - remove drugs

emergent:
1. fluids:

2. acute severe cases:
   1’
   Why not isotonic saline infusion:

hyponatremia > 24 to 48 hours:
prevent ____

initial goal:

2’

Answer 12

discontinued fluid administration
restricted access to water

hypertonic (3%) saline
slowly over 2 to 4 hours if CNS C/S
2 to acute hyponatremia and cerebral edema

unsuitable low sodium will be excreted in the urine while the water will be retained, worsening the hyponatremia

central pontine myelinolysis
<12 mEq/L/day (0.5 mEq/L/hr)

concentration to 125 to 130 mEq/L

furosemide - beneficial to inhibit resorption of water in the renal tubules and reduce the risk of volume overload

Question 13

Demeclocycline

Lithium

Answer 13

tetracycline antibiotic, inhibits the action of ADH on the renal tubules
potentially nephrotoxic and renal function must be monitored closely
improvement may take 1 to 2 weeks
safe and effective dosage in dogs not established

Lithium will also inhibit the action of ADH on the renal tubules
precluded by its toxicity

Question 14

Px:
depends on the cause
If caused by a malignant tumor:

Answer 14

SIADH usually is incurable

can be controlled w water restriction and Na suppl