Serum sodium levels and probability of recurrent febrile convulsions

In a prospective study of 69 children with febrile convulsions, serum sodium levels were often lower than normal (52% had levels <135 mmol/l). The mean level (134.4±0.4 mmol/l) was significantly lower as compared to a group of children without fever (140.6±0.4 mmol/l,n=23) and as compared to a group with fever but without convulsions (137.6±0.6 mmol/l,n=31). The probability of a repeat convulsion within the same febrile period appeared to be significantly related to the serum sodium level.Conclusion Measurement of the serum sodium is a valuable investigation in the child with a febrile convulsion. The lower the serum sodium level, the higher the probability of a repeat convulsion. This knowledge may be of practical value in deciding whether to admit the child or allow it to return home and in advising parents or carers of the risk of a repeat convulsion.