Extracellular-Fluid andIntracellular-FluidCompartments underNormal Conditionsand during States ofHypernatremia.
Effects of Hypernatremiaon the Brain and AdaptiveResponses.
Clinical Signs of HypernatremicStates Related to Serum OsmolalityOsmolality (mOsm/kg) Manifestations350–375 Restlessness, irritability375–400 Tremulousness, ataxia400–430 Hyperreflexia, twitching, spasticity>430 Seizures and death
Causes of Hypernatremia *Likely or important ED diagnostic considerations.Inadequate water intake* GI loss* Inability to obtain or swallow water Vomiting, diarrhea, intestinal fistula Renal loss Impaired thirst drive Central diabetes insipidus Increased insensible loss Impaired renal concentrating abilityExcessive sodium Osmotic diuresis (multiple causes)* Iatrogenic sodium administration – Hypercalcemia – Sodium bicarbonate – Decreased protein intake – Hypertonic saline – Prolonged, excessive water intake – Sickle cell disease Accidental/deliberate ingestion of large – Multiple myeloma quantities of sodium – Amyloidosis – Substitution of salt for sugar in infant – Sarcoidosis formula or tube feedings – Sjögren syndrome – Salt water ingestion or drowning – Nephrogenic diabetes insipidus Mineralocorticoid or glucocorticoid – Congenital excess* Drugs/medications – Primary aldosteronism Alcohol, lithium, phenytoin, propoxyphene, sulfonylureas, amphotericin, colchicine – Cushing syndrome Skin loss – Ectopic ACTH production Burns, sweating Peritoneal dialysis Essential hypernatremia – Loss of water in excess of sodium
Most hypernatremia encountered in theED is related to severe volume loss.In otherwise healthy patients, hypovolemialeads to conservation of free water by thekidneys that results in low urine output(<20 mL/h) with high osmolality (usually>1000 mOsm/kg water).
Diabetes Insipidus Diabetes insipidus is characterized by the failure of central or peripheral ADH response. Urine osmolality is low (200 to 300 mOsm/kg, with urinary [Na+] of 60 to 100 mEq/kg)
Treatment The cornerstone of treatment is volume repletion. Volume should be replaced first with NS or lactated Ringers solution. Some practitioners inappropriately fear using NS solution from concern that an [Na+] of 154 mEq/L exceeds normal serum [Na+]. However, in most hypernatremic states, there is a total body [Na+] deficit, and the use of NS allows a more gradual decrease in serum [Na+]. Once perfusion has been established, the solution should be converted to 0.45% saline or another hypotonic solution until the urine output is at least 0.5 mL/kg/h. The reduction in [Na+] should not exceed 10~15 mEq/L per day.
Calculation of Free Water Deficit measured[Na ] TBW 0.6 1 desired[Na ]Replacement Volume = TBW deficit × 1/(1－X)X= [Na+] of resuscitation fluid / [Na+] of isotonic saline