Quantitative Electroencephalography Alpha:Delta Ratio and Suppression Ratio Monitoring During Infant Aortic Arch Reconstruction

Background: During infant aortic arch reconstruction, traditional electroencephalography (EEG) provides only qualitative data limiting neuromonitoring efficacy. Interhemispheric differences in the alpha:delta ratio (ADR) and suppression ratio (SR) measured using quantitative EEG generate numerical trends that may suggest cerebral ischemia. We hypothesized that the ADR and SR during cardiopulmonary bypass (CPB) would correlate with hemodynamics, and that ADR and SR interhemispheric differences would precede neurological injury from infants requiring aortic arch reconstruction.

Methods: During aortic arch reconstruction, bilateral hemispheric ADRs and SRs were recorded every five minutes in conjunction with mean arterial pressure, temperature, CPB flow, and cerebral oximetry. Data were grouped into the cooling, antegrade cerebral perfusion (ACP), and rewarming periods of CPB. Correlation analysis determined relationships between the ADR, SR, and hemodynamic data. The cumulative interhemispheric ADR and SR differences were calculated during CPB. Neurological injury was defined as clinical/subclinical seizure or stroke.

Results: Among 79 infants, the ADRs decreased significantly during rewarming, whereas SRs were significantly greatest during ACP. There was a direct correlation between the ADR and cerebral oximetry (R² = 0.734; P < 0.001) and an inverse correlation between the SR and temperature (R² = 0.882; P < 0.001). Eight infants developed neurological injury that was more often preceded by an interhemispheric ADR difference >0.1 (50% vs 7.8%; P = 0.01) or SR difference >18% (41.7% vs 4.8%; P = 0.008).

Conclusions: The ADR and SR correlate with cerebral oximetry and temperature, respectively, and significant interhemispheric differences often preceded neurological injury, suggesting the importance of quantitative EEG monitoring during infant aortic arch reconstruction.