Febrile seizures caused by hyperventilation, not illness severity

October 13, 2011

Pediatricians commonly get the panicked call or visit from parents who have witnessed a febrile seizure and are convinced their child’s illness has taken a turn for the worse. Here’s something that can help calm them down: Febrile seizures appear to have more to do with hyperventilation than the severity of the illness. Why do researchers believe that, and what illnesses are more and less likely to set off seizures in young children?

Pediatricians commonly get the panicked call or visit from parents who have witnessed a febrile seizure (FS) and are convinced their child’s illness has taken a turn for the worse.

Here’s something that can help calm them down: FS appear to have more to do with hyperventilation than the severity of the illness.

According to a recent study, FS may be associated with the elevated blood pH and low carbon dioxide levels of respiratory alkalosis caused by hyperventilation. “Our findings reveal that febrile seizures are associated with respiratory alkalosis and unrelated to the severity of the underlying infection or fever level,” said lead researcher Sebastian Schuchmann, MD, PhD.

Febrile seizures affect about 4% of children and usually occur between the ages of 6 months and 5 years, according to the National Institute of Neurological Disorders and Stroke. In some populations, certain genetic and environmental factors double the incidence of FS to 8%. Although frightening to parents, febrile seizures typically have no long-term effect.

Researchers enrolled 433 age-matched children with similar levels of fever from 2 groups presenting to an emergency department. One group of 213 was admitted for FS, mostly from respiratory tract infection, and the other group of 220 had gastroenteritis (GE). All patients had their capillary pH and carbon dioxide levels measured immediately on admission to the hospital.

The children with FS had respiratory alkalosis, with a pH in the range of 7.46, whereas those with GE had metabolic acidosis, with a pH in the range of 7.31, according to researchers who found that FS did not occur in children with GE except in a subgroup of 15 patients who had an alkaline blood pH level. For 8 patients who were admitted for FS and GE, blood pH was elevated with FS with a more acidotic pH found in the children presenting with GE.

Researchers concluded that FS is associated with a systemic respiratory alkalosis, independent of the severity of the underlying infection as indicated by the level of fever. Additionally, the low pH associated with GE may be protective against FS, and even children with a genetic susceptibility to FS tend not to have seizures when GE induces their fever.

“Further investigation of methods that control the body’s acid-base status may lead to the development of novel therapies for treating febrile seizures,” said Schuchmann. The authors suggested one possible treatment: an application of 5% carbon dioxide in the breathing air of a patient with FS.

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