hyponatremia in children 03.19.2010

8/9/2019 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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State of

Body Water

Specific

Gravity

Uri

ne

Na



use


Normal

hydration


disease?)


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State of

Body Water

Specific

Gravity

Uri

ne

Na



use


Normal

hydration


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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State of

Body Water

Specific

Gravity

Uri

ne

Na



use


Normal

hydration


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)

hyponatremia in children 03.19.2010

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