Extracellular-Fluid andIntracellular-Fluid Compartmentsunder Normal Conditions andduring States of Hyponatremia.
Effects of Hyponatremia onthe Brain and AdaptiveResponses.
Clinical Signs of Hyponatrema Nausea, vomiting, anorexia, muscle cramps, confusion, and lethargy, and culminate ultimately in seizures and coma. Seizures are quite likely at [Na+] of 113 mEq/L or less.
Diagnostic Criteria for Syndromeof Inappropriate Secretion of ADH Hypotonic hyponatremia Inappropriately elevated urine osmolality (usually >200 mOsm/kg) Elevated urine [Na+] (typically > 20 mEq/L) Clinical euvolemia Normal adrenal, renal, cardiac, hepatic, and thyroid function Correctable with water restriction
Total Body [Na+] Deficit= (desired plasma [Na+]－measured plasma [Na+]) ×TBW
Emergency Treatment of SevereHyponatremia Although specific or general treatment of hyponatremia for the condition discussed may be initiated in the ED, there is generally little urgency to address the hyponatremia immediately when [Na+] is 120 mEq/L. If hyponatremia is severe (<115 mEq/L or when the patient is symptomatic), treatment should be initiated.
Emergency Treatment of SevereHyponatremia Situations that warrant consideration of emergent treatment are hypovolemic patients and patients in extremis, (e.g., mental status changes or coma). In hypovolemic patients, the [Na+] deficit should be calculated and replaced with normal saline solution. Urine electrolytes are useful only before beginning treatment and therefore should be collected in the ED. The rise in [Na+] should be no greater than 0.5 to 1.0 mEq/L per hour.