Introduction: Neonates with critical congenital heart disease (cCHD) that undergo cardiac surgery are at risk of perioperative brain injury and its early identification can help set familial expectations and guide postoperative care. We report preoperative EEG as a proxy measure of pre-existing brain injury in neonates undergoing cardiac surgery including aortic arch repair and their postoperative and long-term outcomes.

Methods: This prospective observational cohort study acquired preoperative EEG from 17 scalp electrodes (full 10:20 minus Fp1, Fp2). Background EEG patterns, sleep-wake cycling, dysmaturity, encephalopathy grade, and seizures were interpreted using recommended guidelines. We collected duration of paediatric intensive care unit (PICU) admission, 3-month mortality, and neurodevelopmental outcome (2-year postoperative Bayley-III composite scores).

Results: Between September 2020 – February 2023, 36 full-term neonates were recruited (median age 8 days old; IQR: 6-11; 64% male); 14 (39%) underwent Norwood surgery and 22 (61%) aortic arch repair. The median duration of preoperative EEG was 154 minutes (IQR: 99-205). Background EEG was abnormal in 14 (39%), sleep-wake cycling was absent in 1 (3%), and dysmaturity seen in 10 (28%). Mild and moderate encephalopathy were seen in 10 (28%) and 4 (11%) respectively; 2 (6%) had subclinical seizures. Median PICU stay in those with encephalopathy/any background EEG abnormality was 10 days (IQR: 5-32) and 7 days (IQR:2-20) in those without. Bayley-III scores in 4/5 domains were lower in those with EEG abnormalities or encephalopathy. By 3-months postoperatively, eight (22%) had died of whom 6 (75%) had preoperative encephalopathy. EEG abnormalities, encephalopathy, and lower Bayley-III scores were more frequently seen in those undergoing Norwood.

Conclusion: Preoperative EEG identified pre-existing neurological abnormalities in more than a third of neonates with cCHD. We have observed that PICU admission may be longer in the presence of encephalopathy and long-term neurodevelopmental outcome may be worse. A large-scale prospective study is on-going and will address the significance of these preliminary findings.