Hypernatremia resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Definition

Hypernatremia is an electrolyte disturbance consisting of an elevated sodium level in the blood. It is defined as a serum sodium concentration exceeding 145 mEq/L.

Causes

Life Threatening Causes

Conditions that may cause death or permanent disability within the next 24 hours

Common Causes

The most common cause of hypernatremia is not an excess of sodium, but a relative deficit of free water in the body. Hypernatremia can be caused by many disease processes and drugs.

• Free water loss in form of diarrhea, diabetes insipidus, diuretics, osmotic agents, insensible losses or impaired thirst response due to any disease process affecting the hypothalamus are common causes.

• Primary sodium excess is a rare cause of hypernatremia and ca be due to sodium salt ingestion or minaralocorticoid excess.

Management

Serum sodium > 145

Urine output

Low

High

High urine osmolality

Urine osmolality

Hypotonic fluid loss GI losses nausea, vomiting, renal losses, diuretics

Low

High

Calculate free water deficit (see below) Replace both free water deficit and maintenance fluid Rate of correction no more than 1mEq/L/h Hypotensive - Normal saline, Stable D5W Replace 1/2 fluid in 24 hrs Other half in 24-48 hrs

References

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