CEEG began within six hours of the patient returning to the cardiac intensive care unit after surgery. Monitoring continued for 48 hours if no seizures were detected and for 24 hours after the last seizure if a seizure occurred. EEG technologists were present for EEG monitoring and interpretation at all times.

The neonates had a range of cardiac defects, with 42% class I (two ventricles with no aortic arch obstruction), 22% class II (two ventricles with aortic arch obstruction), 9% class III (single ventricle with no aortic arch obstruction), and 27% class IV (single ventricle with aortic arch obstruction). A variety of repairs were performed, including stage I Norwood (27%) and arterial switch operations (16%).


Bedside clinicians identified events such as abnormal body movements, hypertension, or tachycardia in 32 neonates - but none of these events had associated abnormal EEG activity. However, 13 of the 161 neonates (8%) had EEG seizures. Of these, 85% (11) were not detected clinically. "This indicates that bedside clinical assessment for seizures without CEEG is unreliable," explained lead investigator Maryam Y. Naim, MD, Division of Cardiac Critical Care, Departments of Anesthesiology and Critical Care Medicine and Pediatrics, The Children's Hospital of Philadelphia, and Assistant Professor, Perelman School of Medicine at the University of Pennsylvania.

When seizures occurred, they were severe. Sixty-two percent of the neonates with seizures experienced status epilepticus, a dangerous condition in which either a single seizure lasts more than 30 minutes or recurrent seizures together last for more than 30 minutes within a one-hour block.

Dr. Naim and colleagues found that the occurrence of seizures in this patient group was "ominous because 38% (5/13) of neonates with postoperative seizures died" (compared to 3% of those who did not have seizures). Indeed, seizures appear to be a marker of brain injury, since many of those with seizures had diffuse or multifocal lesions apparent on MRI or ultrasound. In the editorial, Dr. Backer and Dr. Marino commented, "Although this may have been a result of increased severity of disease and comorbidities, the prevention of postoperative seizures is still an important goal, which can only be achieved if we monitor for seizures and then use assessment of various surgical and postoperative management strategies to eliminate the development of seizures."

The investigators looked for predictors of seizure occurrence. They found that surgical factors such as delayed sternal closure and longer deep hypothermic circulatory arrest duration were associated with an increased seizure risk. Seizures were also more frequent in neonates who subsequently required extracorporeal membrane oxygenation or experienced cardiac arrest.

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