Lesson of the week: Hyponatraemic seizures and excessive intake of hypotonic fluids in young children

Publisher Website
Google Scholar
Abstract
Afebrile seizures in young children may be caused by hyponatraemia—take a dietary history and measure serum electrolytes The differential diagnosis of afebrile seizures in children with normal development includes epilepsy and metabolic disorders. Children admitted to hospital with seizures (febrile or afebrile) of unknown cause are often treated with antibiotics and antiviral agents for suspected infection of the central nervous system while investigations are undertaken. Afebrile seizures caused by hyponatraemia associated with excessive intake of hypotonic fluids was first reported in 1967.1 This is a common problem in the United States,2–8 but it has rarely been reported in the United Kingdom.9 10 We describe four cases (table). ### Case 1 A 20 month old girl presented with a short history of vomiting, cough, and anorexia. She had attended the accident and emergency department on four occasions—with a viral illness, urinary tract infection, pertussis, and breath holding. She was admitted for observation, and a provisional diagnosis of viral illness was made. The girl refused solid food but took fluids well over the next 48 hours. At this time she had a tonic seizure associated with apnoea but responded to treatment with rectal diazepam. Biochemical investigations showed serum sodium concentration 116 mmol/l, chloride 84 mmol/l, potassium 2.8 mmol/l, urea 2.8 mmol/l, and creatinine 35 mmol/l. The patient's fluid intake was restricted to 60% of the maintenance requirement, but four hours later she had a further tonic seizure associated with decerebrate posturing. She was intubated and ventilated and given intravenous mannitol and phenytoin. Computed tomograms of the brain showed diffuse cerebral oedema (figure). Her urine output over the next 12 hours was approximately 12 ml/kg per hour, and with fluid restriction her serum electrolyte values returned to normal. Repeat computed tomography 24 hours later showed appreciable improvement, with normal basal cisterns …