Hyponatremia

Definition

Evaluation: Order serum osmolality, urine sodium, urine osmolality, TSH, Lipid panel. 

Tips: Free water balance (Urine osmolality) is regulated by ADH. Sodium excretion (urine sodium) is regulated by aldosterone. If a patient has ESRD, the cause of hyponatremia is excess free water intake in the setting of impaired Kidney water excretion, and is not mediated by ADH. 

Step 1: Differentiate from true hyponatremia from pseudohyponatremia. 

Step 2: is ADH high or low? Compare serum osmolality to urine osmolality.

Step 3: If ADH is high, what is the volume status?

If ADH is activated, urine osmolality is usually >100. Urine Na can help to determine RAAS activation, which can narrow the differential in casese where volume status is not clear. A low urine Na (<20) suggests RAAS activation, as seen in hyper or hypovolemia; a high urine sodium may suggest SIADH. 

Hypervolemic: DDx: CHF, nephrotic syndrome, liver failure. 

Hypovolemic

Euvolemic:

Management: Repeat BMP q4hr. Goal to increase Na no more than 4 to 6 mEq/L in 24hrs to prevent osmotic demylination syndrome. Start treatment based on volume status

Evaluate and treat severe symptoms emergently in all patients

Select treatment approach based on volume status, severity, and etiology. 

Hypovolemia

SIADH: 

Hypervolemia:

If the serum sodium has been overcorrected:

Diagnosis and Management of disorders of body tonicity-Hyponatermia and Hypernatremia

Clinical practice guideline on diagnosis and treatment of hyponatremia


Revision #14
Created 25 February 2022 06:16:53 by Katarina Soewono
Updated 21 March 2022 04:17:48 by Katarina Soewono