Hypernatremia

Hypernatremia:

–      Produced by either administration of hypertonic fluids or much more frequently, loss of thirst mechanism or failure of ADH mechanisms

–      Water moves from ICF → ECF

                                            &Cells dehydrate Because of extremely efficient

•        regulatory

mechanisms such as ADH and thirst, hypernatremia generally occurs only in people with prolonged lack of thirst mechanism

•        Patients with loss of ADH (Diabetes Insipidus) usually can compensate with increased fluid intake.

Causes of Hypernatremia:

•        Excessive loss  of maily water in prolonged fever ,. Insufficient intake of water (hypodipsia)

•        GI losses

•        Diabetes Insipidus (both central and nephrogenic)

•        Osmotic Diuresis – DKA

•        Hypothalamic lesions which affect thirst center like tumors, granulomatous diseases or vascular disease

•       

 Sodium Overload – Infusion of Hypertonic sodium bicarbonate for metabolic acidosis.

Symptoms of Hypernatremia:

•        Initial symptoms include lethargy, weakness and irritability

•        Can progress to twitching, seizures, obtundation or coma

•        Resulting decrease in brain volume can lead to rupture of cerebral veins leading to hemorrhage

•        Severe symptoms usually occur with rapid increase to sodium concentration                                                

•        Sodium concentration greater than 180 mEq are associated with high mortality.

Diagnosis of Hypernatremia:

•        Same labs as workup for hyponatremia: Serum osmolality, urine osmolality and urine sodium

•        If urine osmolality is lower than serum osmolality then DI is suspecte

•        Administration of DDAVP will differentiate types of DI

    Urine osmolality will increase in central DI, no response in nephrogenic DI.

Treatment of  hypernatremia:

Typical fluids given in form of Dextrose 5%

•        Same as hyponatremia, sodium should not be lowered by more than 12 mEq/L in 24 hours

Overcorrection can lead to cerebral edema which can lead to encephalopathy, seizures or death.