Donation After Brain-stem Death
Whilst death is popularly associated with loss of circulatory function, the accepted professional definition of death is that of a simultaneous and irreversible loss of both the capacity for consciousness and the capacity to breathe. This state can be arrived at in various ways, and different circumstances may require different diagnostic criteria to be used (Figure 1). For instance, the criteria required to confirm death that follows failed cardio-pulmonary resuscitation differ from those used in cases of advanced decomposition.
Death and its diagnosis
Whilst loss of cardiac activity is frequently the cause of loss of respiration and consciousness, it is not an essential pre-requisite. The neurological standard for the diagnosis and confirmation of death applies in circumstances where brain injury is suspected to have caused irreversible loss of consciousness and respiration before terminal apnoea has resulted in hypoxic cardiac arrest and circulatory standstill. The diagnostic criteria for so-called brain death were first described by the Harvard Medical School in 1968, whilst the original Code of Practice for the diagnosis of brain-stem death in the UK was published in 1976. The brain-stem is the neuroanatomical focus for the capacity for both respiration and consciousness , and the UK standard for the neurological determination of death is based upon
- the principle that complete loss of brain-stem function is of itself sufficient to allow the diagnosis of death to be confirmed and
- the belief that such a state can be recognised clinically in most cases.
Functions of the brain-stem
- control of respiration
- integrative control of the cardiovascular system
- conduit for almost all ascending and descending neuronal pathways
- maintenance of the capacity for consciousness.
In contrast, the neurological standard used in North America and Australia seeks to identify a state of whole brain death. Despite this rather fundamental distinction, the clinical elements of the various diagnostic schedules for the neurological determination of death around the world are very similar, with differences emerging only when the need for confirmatory or ancillary investigations are considered.Next section: Donation After Circulatory Death