Purpose: Autonomic effects of seizures, including cardiorespiratory abnormalities, may be involved in sudden unexpected death in epilepsy (SUDEP). The purpose of this study was to determine the prevalence and risk factors for ictal hypoxemia (oxygen saturation <90%) and ictal bradycardia (heart rate < second percentile for age) in children during recorded seizures.
Methods: The medical records of children admitted to our Epilepsy Monitoring Unit (EMU) between November 1, 2007 and March 13, 2009 were reviewed. Children selected for this study had at least one partial complex or generalized convulsive seizure with recorded oximetry and/or heart rate data.
Results: Forty-nine children were identified and 225 seizures were analyzed. Ictal hypoxemia was observed in 48.9% of children and 26.8% of seizures. Ictal hypoxemia was significantly more likely to occur during generalized versus nongeneralized seizures (43.9% vs. 18.9%) and when tapering antiepileptic drugs (AEDs) (75% vs. 35.5%). For partial complex seizures, there was an association between ictal hypoxemia and prolonged seizure duration. There was no correlation between ictal hypoxemia and partial seizure onset localization or lateralization. Ictal bradycardia occurred in 8.2% of children and 3.7% of seizures. Ictal bradycardia was observed solely with partial complex seizures of extratemporal onset. Due to the low prevalence of ictal bradycardia, these findings were not statistically significant.
Discussion: Ictal hypoxemia is common, particularly in the setting of generalized tonic-clonic seizures, prolonged partial complex seizures, and when AEDs are tapered. In contrast to previous ictal bradycardia studies, ictal bradycardia occurred exclusively in extratemporal partial complex seizures in this cohort.