Prolonged postictal hypercapnia is associated with delayed recovery of consciousness after generalized convulsive...

Postictal impairment of breathing and arousal is a significant contributor in many SUDEP cases. Central CO₂ chemoreception, which mediates ventilatory response, is often blunted after generalized convulsive seizures (GCS). It is plausible that the central chemoreceptors that mediate arousal in response to hypercapnia are similarly impaired after GCS, thereby contributing to delayed recovery of consciousness (ROC). Therefore, we hypothesized that greater severity of postictal hypercapnia is associated with longer latency to early signs of ROC following GCS.

Epilepsy patients were monitored with video-EEG, respiratory effort and airflow, transcutaneous (Tc) CO₂, and pulse oximetry. Primary outcomes were latency to early signs of ROC and duration of postictal immobility (PI). The interictal hypercapnic ventilatory response (HCVR) was measured in a subset of patients. Univariable and multivariable generalized linear models were created.

A total of 149 GCS were recorded from 86 of 351 participants. Evaluable peri-ictal TcCO₂ and video-EEG data were available in 47 GCS in 38 participants (Female = 50%). In multivariable models, duration of postictal hypercapnia and temporal lobe seizures were significantly associated with prolonged latency to early signs of ROC, while preictal TcCO₂ level and postictal generalized EEG suppression (PGES) duration were significantly associated with PI duration. Interictal HCVR slope was negatively associated with postictal hypercapnia.

Interictal HCVR is negatively associated with postictal hypercapnia, and the latter is associated with delayed ROC. In addition, preictal TcCO₂ and PGES duration are associated with PI duration. The significance of these findings should be examined in future studies as potential risk markers for SUDEP.