ABSTRACT
OBJECTIVE: Severe hyponatremia is rare but constitute a true medical emergency since it has deleterious effects on the central nervous system. The etiology and clinical presentation of severe hyponatremia are diverse and nonspecific, furthermore, the optimal therapeutic approach is debatable at the present time. Therefore, the purpose of this study is to analyze the clinical manifestations of severe hyponatremic patients and to assess the outcomes with special reference to the rate of its correction. METHODS: This retrospective study analyzed the clinical course of 27 consecutive patients(pts) at a single medical center who presented with neurologic hyponatremic symptoms as well as a serum sodium (Na) concentration less than 125mEq/L. RESULTS: Of 27 hyponatremic patients, male to female ratio was almost equal, 13 to 14, and mean age was 67.1 years. The most common cause of hyponatremia was SIADH(11 pts, 40.7%), followed by hypovolemia(11 pts, 37.1%), and edema(4 pts, 14.8%). Hyponatremic neurologic symptoms included lethargy(33.3%), confusion with drowsy mentality (33.3%), dizziness(18.6%), and semicoma(7.4%), respectively. The rate of increase to a serum Na concentration to 125mEq/L during correction of hyponatremic averaged 0.56+/-0.49mEq/L/hr while the maximum increase in serum Na concentration during any period of the hospital course, mostly initial phase, averaged 0.69+/-0.63mEq/L/hr in all 27 pts, of whom 18 pts(66.7%) was less than 0.5mEq/L/hr, 3 pts from 0.5 to 1.0mEq/L/hr(11.1%), and 6 pts more than 1.0mEq/L/hr(22.2%). All 27 pts but one recovered from neurologic symptoms due to hyponatremia without neurologic sequale. Extrapontine myelinolysis with locked in condition was developed during the course of treating hyponatremia in a pts, of whom serum Na concentration before treatment was the lowest(92mEq/L) with the rate of correction to 125mEq/L by 1.26mEq/L/hr and the initial rate of correction within the first 6 hour by 3.17mEq/L/hr. No one died of hyponatremia itself during the course of its treatment but 3 deaths of 27 pts were attributed to the pts' severe underlying diseases. CONCLUSION: Surprisingly, these data revealed the relatively benign course of severe symptomatic hyponatremia. However, in assessing the outcome of severe symptomatic hyponatremia, the initial degree of hyponatremia as well as the rate of correction during its treatment, particularly the initial rate of correction within the first 6 hour, would be considered.