The many important causes of hypernatremia (Fig 1) include nasogastric hyperalimentation, diabetic coma, acute renal failure, improper mixture of dialysis fluid, dehydration secondary to either fever or elevated ambient temperature, and diabetes insipidus ( S,n.y.d,e.LeLal 1987; E§l,e.v§ky,et,a/ 1996). In the elderly, hypernatremia is often associated with infirmity and inability to obtain water, leading to gradual desiccation ( SD,yder,et,a/ 1987). Diabetes insipidus is associated with hypernatremia only when the patient has impaired thirst or is unable to obtain water. A subgroup of patients often develop hypernatremia secondary to excessive administration of hypertonic NaCl or NaHCO3. Such patients are generally critically ill, and intravenous bicarbonate leads to a dangerously elevated plasma osmolality with infrequent survival. A similar outcome may be observed after inadvertent intravenous hypertonic NaCl for therapeutic abortion.
Fig. 1 The major causes of hypernatremia in a geriatric hospital population. About two-thirds of all cases are due to surgery, infirmity, febrile illness, or diabetes mellitus. (Data from Snyde_ref_a/ (1987).)
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