Neuroscience and awareness in the dying human brain: Implications for organ donation practices.
Consciousness has 2 components: wakefulness (arousal) and awareness (perception of the self and the external environment). Functional neuroimaging has identified 2 distinctive functional networks that mediate external awareness of the surrounding environment and internal awareness of the self. Recent studies suggest that awareness is not always associated with wakefulness. There is little clinical research that has specifically focused on determining awareness in the dying phase, after the cessation of systemic circulation. Pana et al (J Crit Care, http://dx.doi.org/10.1016/j.jcrc.2016.04.001) concluded from a retrospective analysis of published human and animal studies that the cessation of clinical brain function and spontaneous electroencephalography activity occurred within 30 seconds of circulatory arrest. They inferred from this that a 5-minute period of cessation of circulation constitutes a valid indicator that awareness has ceased. This aligns with the 5-minute no-touch time after the loss of arterial pulse, the current circulatory standard of death determination in non-heart-beating organ donation. We argue that the capacity for awareness may not be irreversibly lost after a relatively brief period of cessation of systemic circulation, and outline empirical data in support of the claim that awareness without wakefulness may be present. Obviously, if correct, this will have practical and ethical implications on organ donation practices.
Department of Critical Care, Mayo Clinic Hospital, Phoenix, AZ. Electronic address: rady.mohamed@mayo.edu.
Mohamed Y
MY
Rady
Department of Physical Medicine & Rehabilitation, Mayo Clinic, Scottsdale, AZ. Electronic address: jverheijde@mayo.edu.
Joseph L
JL
Verheijde
D001143:Arousal; D001364:Awareness; D001921:Brain; D001926:Brain Death; D003243:Consciousness; D003643:Death; D004569:Electroencephalography; D006323:Heart Arrest; D006801:Humans; D009488:Neurosciences; D009927:Tissue and Organ Procurement; D014851:Wakefulness