Hyponatremia and Hypernatremia

Hyponatremia and Hypernatremia
By:Conor Gough, HO – III

Hyponatremia
* Defined as sodium concentration < 135 mEq/L * Generally considered a disorder of water as opposed to disorder of salt * Results from increased water retention * Normal physiologic measures allow a person to excrete up to 10 liters of water per day which protects against hyponatremia * Thus, in most cases, some impairment of renal excretion of water is present Causes * Normal ADH response to low sodium is to be suppressed to allow maximally dilute urine to be excreted thereby raising serum sodium level * Psuedohyponatremia – High blood sugar (DKA) or protein level (multiple myeloma) can cause falsely depressed sodium levels * Causes of Hyponatremia can be classified based on either volume status or ADH level o Hypovolemic, Euvolemic or Hypervolemic o ADH inappropriately elevated or appropriately suppressed ADH suppresion ADH elevation
First step in Assessment: Are symptoms present?
* Hyponatremia can be asymptomatic and found by routine lab testing
* It may present with mild symptoms such as nausea and malaise (earliest) or headache and lethargy
* Or it may present with more severe symptoms such as seizures, coma or respiratory arrest

Presentation determines if immediate action is needed
* If severe symptoms are present, hypertonic saline needs to be administered to prevent further decline
* If severe symptoms are not present, can start by initiating fluid restriction and determining cause of hyponatremia
* Oral fluid restriction is good first step as it will prevent further drop in sodium
* NOTE: This does not mean that you can’t give isotonic fluids to someone who is truly volume depleted

WHAT NEXT?
* With no severe symptoms and fluid restriction started, next step is to assess volume status to help determine cause
* Hypovolemic – urine output, dry mucous membranes, sunken eyes
* Euvolemic – normal appearing
* Hypervolemic – Edema, past medical history, Jaundice (cirrhosis), S3 (CHF)

Volume status helps predict cause
* Hypovolemia
o True Volume Depletion
o Adrenal insufficiency
o Thiazide overdose
o Exercised induced hyponatremia
* Euvolemia
o SIADH
o Primary Polydipsia
* Hypervolemia
o Cirrhosis and CHF

Workup for Hyponatremia
How to interpret the tests?
* Serum Osmolality
o Can differentiate between true hyponatremia, pseudohyponatremia and hypertonic hyponatremia
* Urine Osmolality
o Can differentiate between primary polydipsia and impaired free water excretion
* Urine Sodium concentration
o Can differentiate between hypovolemia hyponatremia and SIADH

Additional Tests
* TSH – high in hypothyroidism
* Cortisol – low in adrenal insufficiency, though may be inappropriately normal in infection/stressful state, therefore should get Corti-Stim test to confirm
* Head CT and Chest Xray – May see evidence of cerebral salt wasting or small cell carcinoma which can both cause hyponatremia
* Iatrogenic infusion of hypotonic fluids (“Surgeon sign”)
* Ecstasy use – increased water intake with inappropriate ADH secretion
* Underlying infections
* NSIAD – Nephrogenic syndrome of inappropriate antidiuresis – Hereditary disorder that presents with low sodium levels in newborn males with undetectable ADH levels
* Reset Osmostat – Occurs in elderly and pregnancy where regulated sodium set point is lowered

SIADH: Important concept to understand
Main diagnostic criteria for SIADH
Treatment is based on symptoms
Severe symptoms present
What if little to no symptoms are present?
Formulas that may help: How much sodium does the patient need?
* Sodium deficit = Total body water x (desired Na – actual Na)
* Total body water is estimated as lean body weight x 0.5 for women or 0.6 for men

How about an example:
What if the sodium increases too fast?
Risk Factors for demyelination
Treatment Options
Summary of Hyponatremia
Moving on to Hypernatremia
Causes of Hypernatremia
Symptoms of Hypernatremia
Diagnosis of Hypernatremia
Treatment of Hypernatremia
Summary of Hypernatremia

Hyponatremia and Hypernatremia.ppt