The brain is not dead when the cortex is dead.

To the Editor: In a recent issue of Critical Care Medicine, with interest we read the article by Dhanani et al (1), concerning vital signs after circulatory arrest following withdrawal of lifesustaining therapy. The article has timely given the persistent controversy regarding criteria of death in circulatory death organ donors. How many minutes after circulatory arrest can we consider the patient dead respecting the dead donor rule? As brain activity is a crucial determinant in the concept and determination of death. The authors state that, based on their limited observation that neurologic function could permanently ceases prior to the 5-minute wait period, required for circulatory death organ donation. They came to this conclusion on electroencephalographic (EEG) recordings in four patients, among which in one patient delta-waveform activity persisted following cessation of the electrocardiogram and arterial pressure. We think that this conclusion is to easily reached. With surface EEG recording, only the outer layer of the cerebral cortex can be reached. It is incorrect to state that based on this clinical observation, neurologic function had permanently ceased. It is recently recognized that the cerebral cortex and hypothalamus share massive bidirectional connections. Pessoa (2) concluded that “the hypothalamus is involved in a host of basis control functions. It is part of an extensive bidirectional connective system with cortex and many subcortical structures, in a manner that allows for extensive integration of cognitive and emotional information.” As the deeper structures of the brain are more resistant to hypoxia than the cortex (3), we should be very careful stating that “neurologic function permanently has ceased” prior to the 5-minute waiting time after only recoding surface cortical activity. Dr. Kompanje has disclosed employment, lectures, and royalties. Dr. Bakker has disclosed that he does not have any potential conflicts of interest.