Role of Inappropriate Antidiuretic Hormone Secretion in Hyponatremia associated with Febrile Convulsions

ABSTRACT

PURPOSE: Febrile convulsion is a common clinical problem in young children. In spite of their frequent occurrence, there is little information available about the value of investigation with febrile convulsion. Recent studies found a correlation between low serum sodium levels and risk of febrile convulsions. We carried out a study to evaluate the role of inappropriate ADH secretion in hyponatremia in relation to febrile convulsions. METHODS: This study used seventy cases(46 boys, 24 girls) with febrile convulsion, that were treated at the pediatric department of Korea University Medical Center Ansan hospital from Jan. 1998 to Aug. 1999. During the same period, thirty one cases(19 boys, 12 girls) with fever but without convulsion(control group I) and twenty four cases(16 boys, 8 girls) with convulsion but without fever(control group II) were evaluated in comparison with febrile convulsion group. Serum sodium, osmolality, vasopressin and urine osmolality of each group were measured on admission and analyzed by ANOVA. RESULTS: The mean serum sodium concentration of febrile convulsion group, control group I and control group II were 134.3+/-2.4mmol/L, 136.4+/-2.0mmol/L, and 136.0+/-2.2 mmol/L respectively. The serum sodium level of patient group was significantly lower than those of control group I and II(P<0.05). The case of the serum levels less than 135mmol/L was 54.3%(38/70) in patient group, 16.1%(5/31) in control group I and 12.5% (3/24) in control group II. Serum osmolality, uine osmolality of patients group were not significantly different from those of each control group. Vasopressin level of febrile convulsion group was higher than that of each control group. The risk of recurrent convulsion approaches 60%(15/25) of cases with hyponatremia less than 135mmol/L. CONCLUSION: We conclude that febrile convulsions are not mediated by hyponatremia but induce the changes in serum vasopressin and sodium level.