U of U PA School Hypernatremia and Hyponatremia

What largely controls hyper/hyponatremia?

ADH

What are the levels of hyponatremia?

Hyponatremia - serum sodium <135

Mild - 125-135

Moderate - 120-125

Severe - <120

What types of tonicity can happen in hyponatremia? What is the most common?

Hypertonic

Isotonic

Hypotonic - most common

How should hyponatremia be assessed?

BMP

Osmolality

Volume assessment

What is pseudohyponatremia?

Isotonic hyponatremia

Low sodium, normal osmolality

-solutes cause decreased free water and sodium in plasma volume

Rare

What causes isotonic hyponatremia?

Increased plasma proteins or fats

-Severe hyperlipidemia or multiple myeloma

What causes hypertonic hyponatremia?

DKA

Mannitol

How does DKA cause hypertonic hyponatremia?

When glucose is elevated it draws water out of ICF into ECF diluting serum sodium

Exponentially increases in severity with increases in hyperglycemia

How does mannitol cause hypertonic hyponatremia? When is it used?

Sugar solute acts as an osmotic diuretic that draws water out of ICF into ECF

-Acts in lumen of nephron inhibiting water and solute reabsorption

Used in cerebral edema

What are the types of hypotonic hyponatremia?

Hypovolemic - decrease in water but larger decrease in salt

Euvolemic - increase in free water

Hypervolemic - increase in salt but larger increase in water

What causes hypovolemic hypotonic hyponatremia? (5)

Cerebral ssalt wasting

Diarrhea

Vomiting

Diuretics

Mineralocorticoid deficiency

What causes euvolemic hypotonic hyponatremia?

SIADH

Hypothyroidism

Beer potomania

What causes hypervolemic hypotonic hyponatremia? (4)

CHF

Cirrhosis

Nephrotic syndrome

Advanced renal failure

What can be checked for volume assessment? (5)

JVD

Edema

Dry mucous membranes

Tachycardia

Increased IVC collapse

What additional things can be used to assess the cause of hyponatremia?

Urine osmolarity and urine electrolytes

FEN(A)

1 L NS challenge

What does elevated urine osmolarity in the setting of hyponatremia indicate?

A problem with free excretion of water - process of turning down ADH is not happening

-SIADH

What is FEN(A)?

Fractional excretion of sodium

Measure of tubular reabsorption of sodium and can determine if sodium is lost by kidney or elsewhere

What do the results of a FEN(A) test reveal?

<0.1% - hypovolemic hyponatremia

>0.1% - hyper/euvolemic hyponatremia

What distorts FEN(A) results?

Diuretics

What is the 1 L NS challenge used for?

Differentiate SIADH from hypovolemia

Should decrease ADH and lower urine osmolarity

-Wont change in SIADH

How does EABV change in hypervolemic hyponatremia? What does this do?

Decreases activating RAAS causing ADH release increasing water reabsorption

What is cerebral salt wasting?

BNP/ANP interfere with sodium reabsorption

Similar appearance to SIADH

What causes cerebral salt wasting?

TBI

Brain infection

Subarachnoid hemorrhage

What causes SIADH? (4)

Adrenal dysfunction

Psychiatric meds

Small cell cancer

Surgery

How does urine appear in SIADH?

Increased urine osmolality

Urine very concentrated

What is tea and toast syndrome/beer potomania?

Long term ingestion of low electrolytes with little protein leads to euvolemic hypotonic hyponatremia

What determines hyponatremia symptoms?

Degree and abruptness of hyponatremia

What are the symptoms of hyponatremia? (6)

Headache

Nausea

AMS

Muscle cramping

Seizures

Coma

What is the goal of treatment for hyponatremia? What needs to be prevented?

Increase serum sodium slowly

Prevent ODS

How is hypovolemic hyponatremia treated?

NS if hyponatremic and hypotensive but without signs and symptoms of CHF or cirrhosis

Fludrocortisone if addisons

How is euvolemic hyponatremia treated? (4)

Fluid restriction with strict ins and outs

Increase solute intake

Loop diuretics

3% saline if severe

How is hypervolemic hyponatremia treated?

Water restriction

Loop diuretics

Vaptans

What causes hypernatremia?

Dehydration

DI

Sodium overload

-Salt poisoning

-Iatrogenic

What are the iatrogenic causes of hypernatremia?

Long term NS use

Long term GI content suctioning

Heavy loop diuretic use

What are the types of DI?

Central

Nephrogenic

Gestational

Psychiatric

What labs indicate central or nephrogenic DI?

Urine osmolality < serum osmolality

Urine sodium <25 often due to free water loss

If urine sodium is low, how can the type of DI be determined?

Water depravation

-If urine continues to be dilute DI confirmed

Central DI differentiated from nephrogenic via administration of desmopressin

-Desmopressin will restore homeostatic levels in central

How is hypernatremia treated?

If hypernatremic via extreme hypotonic loss

-Increase serum water levels via desmpressin, oral water, or IV D5W

If free water deficit

-Calculated to correct hypernatremia back to normal levels