Principles of Management of Severe Hyponatremia

H yponatremia represents a serious health hazard. 1 Hospitalized patients, nursing home residents, women, and children exhibit high frequency and/or severity of hyponatremia. Hyponatremia developing during the course of other morbid conditions increases their severity. Estimates of direct costs for treating hyponatremia in the United States ranged between $1.61 and $3.6 billion. Clinical manifestations of hyponatremia are universal and range from subtle (disturbances of balance, problems in cognition detected only during specific testing) to lifethreatening manifestations of increased intracranial pressure with life-threatening hypoxia and noncardiac pulmonary edema. Although the treating physicians must make an accurate diagnosis based on well-established and described clinical criteria, treatment is also guided by the severity of these manifestations. The magnitude and rate of increase in serum sodium concentration ([Na]) during treatment are critical. Overcorrection of chronic hyponatremia may lead to osmotic myelinolysis, whereas undercorrection may fail to prevent life-threatening manifestations. The mainstays of treatment are restricted free water intake and saline infusion, with or without furosemide. There are 2 indications for saline infusion in hyponatremia. Overt manifestations of hyponatremia are treated with hypertonic saline, whereas symptomatic hypovolemia associated with hyponatremia without overt symptoms is usually treated with isotonic saline. In both situations, the infusion of saline results in rising [Na]. This rise can be slower or faster than desired, with potentially dire clinical consequences. To achieve the desired rise in [Na], several formulas, most often the Adrogue–Madias formula, are used to calculate volume, rate, and strength of saline infusion. The predictive accuracy of the Adrogue–Madias formula is, in general, good. However, the rise in [Na] exceeds the value predicted by this formula in some instances, particularly in patients with hypovolemic hyponatremia. This report presents the principles of management of hyponatremia with saline infusion. We analyzed factors that cause deviations in the change of [Na] from the predicted values. We present a clinical protocol for managing hyponatremia with saline infusion based on this analysis.