Abstracts

Rationale: Dysregulation of cardiopulmonary function often accompanies focal and generalized seizures. Seizures may induce a cerebral hypermetabolic state reflected in increases in cerebral oxygen use and glucose metabolism that, in turn, lead to compensatory increases in cerebral blood flow and cerebral pO2 levels. We observed systemic blood oxygen saturation levels in a term neonate who was intubated and ventilated during treatment for seizures to determine systemic effects unconfounded by motor activity or central respiratory control changes.

Methods: A term infant was delivered via vaginal delivery complicated by shoulder dystonia. Several hours after birth, the patient had 3 apneas severe enough to require ventilation. Further apneas led to intubation and positive pressure ventilation (Figure A). The patient was treated with phenobarbital after which seizures occurred at about 8 (Sz2), 10 hours (Sz3), and 18 hours (Sz4) after monitoring. Electroclinical autonomic neonatal seizures arose from the left temporal region. Seizures ceased after 18 hours of monitoring. The patient remained ventilated through the monitoring session with synchronized intermittent mandatory ventilation with pressure-support. Brain MRI showed left temporal subarachnoid hemorrhage with additional multifocal small intracranial hemorrhages. Oximetry, heart rate, and minute ventilation are plotted for each seizure in a focused timeline (Figure B-E).

Results: Each seizure demonstrated a period of desaturation, most impressive in Sz1 in which preictal saturations ranged from 95-96% and dropped to a nadir of 85.2%. Relative desaturation persisted after cessation of seizure activity for ~10 minutes before returning to baseline. Subsequent seizures lead to desaturations of 2-3% from baseline. Seizure-associated heart rate changes varied. During Sz1, the preictal heart rate of 140 BPM dipped 10 BPM after onset, returned to baseline, and fell again to remain 10 BPM lower than the preictal baseline. Heart rate did not change during Sz2. Minute volumes rose with ongoing seizure activity during Sz1-3, indicating self-regulated, increased tidal volumes. Noise prevented complete interpretation of EKG during Sz3/4 and the minute volume of Sz4.

Conclusions: Nonmotor, neonatal seizures, when amplified by neonatal physiology, appear sufficient to cause systemic oxygen desaturation. If we consider the case as a “black box” model, inputs of respiration (mechanical ventilation), cardiac function (heart rate), and muscle activity did not directly increase oxygen use. We infer that the output function of systemic oxygen saturation can only respond to the remaining input variable of nonmotor seizure activity driving cerebral hypermetabolism. The case emphasizes the potentially large metabolic burden of neonatal seizures.

Funding: Please list any funding that was received in support of this abstract.: None.