hyponatremia in children 03.19.2010
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Differential Diagnosis of
Hyponatremia in Children
Eric Spiegel
3/19/2010
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Hyponatremia
Usually found on screening labs, because its
usually asymptomatic unless really severe
Indicates a failure to maintain the correctquantity of water in the body with regards to
the solute in different body water spaces
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ADH
Two major stimuli for the release ofADH
Rise in serum osmolality to >295 mOsm/L
Decrease in effective blood volume A good rule of thumb for evaluation of
hyposmolar states (hyponatremic) :
When osmol receptors and volume receptors for
control ofADH receive opposing stimuli, the
volume receptors generally win
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ADH
For example, under ordinary circumstances.
There will be no release ofADH and no water
conservation if serum osmolality is below 270
However, if, despite a low osmolality, ADH will be
released if there is a state of volume depletion
(And the urine will NOT be maximally dilute.)
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SIADH
Also, even though the USUAL stimuli for ADH
release are blood volume and osmolality,
there are times when neither are present and
ADH is being released
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FE Na
Next, measure the conservation of sodium
with FeNa
(U/P Na / U/P Cr ) x 100 The most effective way to differentiate
prerenal and renal Azotemia
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Hyponatremic states in pediatrics
State of
Body Water
Specific
Gravity
Uri
ne
Na
Fena BUN Disease states
Dehydrated >1.020 2 Up Renal failure , adrenal insufficiency, diuretic
use
Edematous >1.020 2 Up Renal failure
Normal
hydration
>1.004 >20 >2 Low SIADH, (drugs?, CNS disease?, pulmonary
disease?)
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Dehydration?
The first branch point in you diagnosis
Reduced body Na AND body water (Na > H20)
Decreased sodium intake, conservation orboth that exceeds those of water
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Gastroenteritis
Usually stimulates sodium conservation in the
proximal and distal tubule decreased urine
sodium
Decreased extracellular volume -> ADH
release, conserving water
If water intake > sodium intake, hyponatremia
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ARF complicating diarrhea
Severe dehydration that causes blood volume
collapse severe enough to decrease renal
blood flow
Administration of small amounts of water to
these children with severe oliguria can cause
hyponatremia
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Hyponatremic states in pediatrics
State of
Body Water
Specific
Gravity
Uri
ne
Na
Fena BUN Disease states
Dehydrated >1.020 2 Up Renal failure , adrenal insufficiency, diuretic
use
Edematous >1.020 2 Up Renal failure
Normal
hydration
>1.004 >20 >2 Low SIADH, (drugs?, CNS disease?, pulmonary
disease?)
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Hyponatremic states in pediatrics
State of
Body Water
Specific
Gravity
Uri
ne
Na
Fena BUN Disease states
Dehydrated >1.020 2 Up Renal failure , adrenal insufficiency, diuretic
use
Edematous >1.020 2 Up Renal failure
Normal
hydration
>1.004 >20 >2 Low SIADH, (drugs?, CNS disease?, pulmonary
disease?)
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Adrenal Insufficiency
Due to congenital abnormalities of adrenal
hormone synthesis, or due to idiopathic
adrenal insufficiency
Could be iatrogenic, due withdrawl of steroids
Usually has associated hyperkalemia
But High K can be in ARF, as well
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A word about Aldosterone
increases the reabsorption of sodium and water and
the release (secretion) of potassium in the kidneys
a steroid hormone produced by the adrenal cortex in
the adrenals, and acts on the distal tubules and
collecting ducts of the kidney to cause the
conservation of Na, secretion of K, & increased water
retention
Addisons disease has severely decreased activity of
aldosterone (due to autoimmune destruction)
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Treatment of hyponatremia with
dehydration Hydrate!
Isotonic solution (usually with bicarb, ie LR)
Measure the urine volume during this periodcarefully if concerned for renal railure
Treat the underlying condition
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Hyponatremia with gross edema
CHF, Severe liver disease, or Nephrotic
syndrome
The reduction ofeffective blood volumeinitiates conservation of sodium and water
This only causes a pathologic excess of sodium
and water
Diuretics cause naturesis, but proportionally moreso than of water, leading to hyponatremia
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Hyponatremia with gross edema
Could also be due to a patient with renal
failure who had large quantities of water
without appropriate salt intake
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Hyponatremic states in pediatrics
State of
Body Water
Specific
Gravity
Uri
ne
Na
Fena BUN Disease states
Dehydrated >1.020 2 Up Renal failure , adrenal insufficiency, diuretic
use
Edematous >1.020 2 Up Renal failure
Normal
hydration
>1.004 >20 >2 Low SIADH, (drugs?, CNS disease?, pulmonary
disease?)
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Hyponatremia with normal hydration
SIADH
Urine is less than maximally dilute
when hyposmolality is present
and there is no volume stimulus to release the ADH
Increased effective volume results in normal
glomerular filtration rate and no tendency to
conserve sodium
Thus, urinary sodium losses in the presence of
hyponatremia
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SIADH
Can be caused by:
CNS : meningitis and encephalitis
Pulm : pneumothorax, pneumonia, atelectasis Drugs: tylenol, barbiturates, indomethacin,
morphine
Water restriction is the most effective
treatment (and again, the underlyingcondition)
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