Naim, M. J Thorac Cardiovasc Surg. 2015 Jul;150(1):169-78.
Journal link: Subclinical seizures identified by postoperative electroencephalographic monitoring are common after neonatal cardiac surgery
- Neonates undergoing cardiac surgery for repair of congenital heart disease are at risk for seizures in the postoperative period
- Clinically evident seizures reported in 5-20% of neonates following surgery
- Studies using continuous electroencephalograms (EEG) report that EEG-only seizures may be even more common
- Postoperative seizures are associated with worse neurodevelopmental outcomes, abnormal neurologic examination results, and abnormal neuroimaging
- The American Clinical Neurophysiology Society (ACNS) recommends continuous EEG monitoring after neonatal cardiac surgery
Purpose of Study: To determine the incidence of postoperative EEG seizures in neonates following cardiac surgery with cardiopulmonary bypass (CPB) at a single center and to identify the risk factors for seizures
- Continuous EEG was recommended for all neonates ≤ 30 days of age with corrected gestational age ≤ 44 weeks after cardiac surgery with CPB
- Continuous full-array EEG was implemented within 6 hours of returning to the cardiac intensive care unit (CICU) after surgery
- Abnormal movements or vital sign fluctuations noted by the clinical team were marked on the recording as push-button events
- The CICU team was alerted by the EEG technologist or encephalographer if an electrographic seizure occurred
- Anti-seizure medications were administered at the discretion of the on-call neurologist and cardiac intensivist
- Postoperative EEG was obtained in 161 of 172 eligible neonates (94%)
- The median age at surgery was 5 days (IQR 3-7)
- The 5 most common operations were: Stage 1 Norwood- 43 (27%); arterial switch operation- 25 (16%); systemic to pulmonary artery shunt- 17 (11%); complete repair of tetralogy of Fallot- 14 (9%); truncus arteriosus repair- 12 (8%).
- The median duration of CPB was 46 minutes (IQR 38-62). Deep hypothermic circulatory arrest (DHCA) was used in 96 neonates (60%) with a median duration of 41 minutes (IQR 32-50).
- Bedside clinicians identified events concerning for clinical seizures in 32 neonates, but none of these episodes correlated with an EEG seizure.
- EEG seizures occurred in 13 of 161 neonates (8%)(Clinical and subclinical).
- The median seizure onset was 20 hours (IQR 15-34) after return to the CICU postoperatively.
- In 11 neonates, seizures were only evident on EEG (85%)
- Seizures were more common in:
- Younger neonates with longer CPB and DHCA times
- Single ventricle defects with arch obstruction
- Patients requiring delayed sternal closure
- Patients with postoperative cardiac arrest
- Patients on ECMO.
- With a multi-variate logistic model evaluating variables known to the clinician at time of admission to the CICU, only delayed sternal closure (odds ratio [OR] 3.99; 95% confidence interval [CI] 1.04-15.29; p = 0.04) and DHCA duration (OR 1.04; 95% CI 1.00-1.08; p = 0.04) were significantly associated with seizures.
- EEG background category did not predict seizure occurrence (p = 0.85).
- Mortality was higher among neonates with seizures (38% vs. 3%; p <0.01).
Neurodevelopmental outcomes were not evaluated in this study, so an association between seizure occurrence and adverse neurodevelopmental outcomes cannot be determined.
A single center implemented routine continuous EEG monitoring in all neonates undergoing cardiac surgery with CPB and identified an 8% incidence of postoperative EEG seizures, most of which were EEG-only. Bedside clinical assessment for seizures without continuous EEG was unreliable. The only risk factors for EEG seizures known at the time of CICU admission following surgical repair were delayed sternal closure and longer DHCA duration. Seizures were associated with higher mortality. Further study is needed to determine whether identification and management of seizures improve neurodevelopmental outcomes.