Hypernatremia – colloquially called excess sodium – (synonyms: hypertonic dehydration; hypovolemic hypernatremia; salt edema; ICD-10-GM E87.0: hyperosmolality and hypernatremia) occurs when the concentration of serum sodium in an adult rises above a value of 145 mmol/l.
Physiological serum osmolarity depends almost exclusively on sodium concentration. Thus, hypernatremia is accompanied by hyperosmolality (hyperosmolarity).Osmolality is the sum of the molar concentration of all osmotically acting particles per kilogram of solvent. In the case of hyperosmolality (hyperosmolal), there is a greater number of dissolved particles per kilogram of liquid than in the reference liquid.
The following forms of hypernatremia are distinguished:
- Hypovolemic hypernatremia (= hypertonic dehydration/”dehydration”): excessive sodium concentration with simultaneously decreased intravascular volume (“in the vessels”); this results from increased fluid excretion (urine, sweat) or due to illness or medication
- Hypervolemic hypernatremia (= hypertonic hyperhydration/”overhydration”): too high sodium concentration with simultaneously increased intravascular volume; this arises from too high saline intake; alimentary: seawater intoxication (drinking salt water) or iatrogenic (e.g., infusion of hypertonic saline or sodium bicarbonate solution or sodium-containing penicillin salts)
The prevalence (disease frequency) is about 5%.In the intensive care unit, sodium balance disorders are among the most common electrolyte disorders (disturbance of electrolytes (blood salts)), with a prevalence of about 25%, and are associated with poor patient outcome (therapeutic outcome).
Course and prognosis: Hypernatremia results in fluid shifts between the extracellular and intracellular spaces (extracellular space (ECR) = intravascular space (located inside the vessels) + extravascular space (located outside the vessels); intracellular space (IZR) = fluid located inside the body cells). In this process, fluid is withdrawn from the brain, i.e. the brain cells become dehydrated (“dehydrated”). This results first in non-specific symptoms (severe thirst, feeling of weakness, fatigue, fever, restlessness and difficulty concentrating) and later in cerebral symptoms (clinical appearance of brain disorders) such as cephalgia (headache), seizures, confusion and disturbances of consciousness (somnolence/drowsiness with abnormal sleepiness up to coma/severe deep unconsciousness characterized by the absence of reactions to response). Treatment of hypernatremia, if the cause is disease, must be causal (“causative”). Otherwise, treatment is symptomatic, i.e., oral or intravenous fluid administration (e.g., 5% glucose solution and one-third of the fluid deficit with isotonic electrolyte solution; see “Drug Therapy” for details).
