Fourrier analysis demonstrate EEG slowing after circulatory arrest at 20 degrees C

The electroencephalographic (EEG) monitoring in infants and children submitted to cardiac surgery under circulatory arrest (CA) and deep hypothermia (20 degrees C) (DH) is usually performed by display or record without analysis. These data disclose the reappearance of EEG activity but give no qualitative analysis of EEG recovery after CA. The electrical activity of the brain was monitored in these conditions by spectral analysis (fast Fourrier transformation with on-line processing). Spectral analysis of the EEG signal recorded during open heart surgery in nine infants and children operated under DH with, in five cases, CA is presented and discussed. The Fourrier analysis demonstrate in all patients with long CA (more than 30 min.) a spectral abnormality, namely the absence of fast activity (8-24 Hz) at least for the remainder of the operation. This abnormality was not present in operations without CA and was only transient after CA of shorter duration.