Brain Death: Tests & Secondary Reactions

[nomadreid]

TL;DR

If brain death is definitely determined by a lack of brain activity, then why are secondary reactions the primary basis of a diagnosis; wouldn't the lack of activity from an EEG be sufficient?

Looking at the site
https://emcrit.org/ibcc/brain-death/
and similar sites, I see that there are a series of tests of secondary reactions for brain death. Isn't the lack of brain activity sufficient?

 

[pinball1970]

Summary: If brain death is definitely determined by a lack of brain activity, then why are secondary reactions the primary basis of a diagnosis; wouldn't the lack of activity from an EEG be sufficient?

Looking at the site
https://emcrit.org/ibcc/brain-death/
and similar sites, I see that there are a series of tests of secondary reactions for brain death. Isn't the lack of brain activity sufficient?

I have been thinking about this recently due to a case in the UK last week.

What the criteria is? sliding scale? necrosis? I will check your link and have a look around.
A few life sciences guys on here as you know.

 

[256bits]

Summary: If brain death is definitely determined by a lack of brain activity, then why are secondary reactions the primary basis of a diagnosis; wouldn't the lack of activity from an EEG be sufficient?

I see that there are a series of tests of secondary reactions for brain death. Isn't the lack of brain activity sufficient?

Could parts of the brain be' dead' and not others - the cerebrum, the brain stem,,..
An active brain stem can support breathing, in which case a 'normal' person would consider the individual to be still 'alive'.
Lack of brain activity due to other causes such as anaethseia, or hypothermia, for example may be indistinguishable for an EEG scan, so a time period would be set so that the flat line is consistent, and not just a one off symptom of a recoverable patient.

 

[pinball1970]

Could parts of the brain be' dead' and not others - the cerebrum, the brain stem,,..
An active brain stem can support breathing, in which case a 'normal' person would consider the individual to be still 'alive'.
Lack of brain activity due to other causes such as anaethseia, or hypothermia, for example may be indistinguishable for an EEG scan, so a time period would be set so that the flat line is consistent, and not just a one off symptom of a recoverable patient.

I don't know is the short answer but slightly longer answer is that the brain Stem itself is important. It gets injured you die.
Need @jim mcnamara

I could Google but you can do that.

Scatter gun best @berkeman @BillTre and @atyy

That should cover it. A view on the UK case would be interesting. Archie B

 

[Astronuc]

Summary: If brain death is definitely determined by a lack of brain activity, then why are secondary reactions the primary basis of a diagnosis; wouldn't the lack of activity from an EEG be sufficient?

Looking at the site
https://emcrit.org/ibcc/brain-death/
and similar sites, I see that there are a series of tests of secondary reactions for brain death. Isn't the lack of brain activity sufficient?

Going a step further - https://emcrit.org/ibcc/brain-death/#brain_death_basics

• Defined as irreversible cessation of all cerebral and brainstem functioning.
• Brain death is legally recognized as equivalent to cardiopulmonary death in the United States.
• Brain death is defined by a strict set of criteria that, once met, confers zero likelihood of awakening from coma.

If it is just the cerebrum, one could still live, but mostly likely not communicate or think, or have self awareness, depending on how much or what regions in the cerebrum would be affected. The brain stem controls activities like breathing, and when damaged or nonfunctional, one cannot live without extraordinary measures of care such as artificial respirator, feeding tubes, and probably a catheter and rectal tube. That is apparently the situation with Archie B.

Assessing brain death is complicated: https://emcrit.org/ibcc/brain-death/#diagnosis_of_brain_death

 

[jim mcnamara]

Involuntary controls are the domain of the autonomic nervous system -
https://www.ncbi.nlm.nih.gov/books/NBK539845/

This system provides "wiring" between the central nervous system and somatic tissues. The easiest to understand is regulation of heartbeat - via the vagus nerve. All of the wiring uses connection to the brain stem.

The brain stem contains:
cardiac,
respiratory,
vomiting,
and vasomotor centers.

It is the communication point for autonomic functions input & output:
breathing,
heart rate,
blood pressure, and sleep wake cycle.

Anatomy
https://en.wikipedia.org/wiki/Medulla_oblongata

The loss of anyone of the three parts of the brain stem:
medulla oblongata,
pons, or
midbrain

is ultimately fatal.

Article on possible consciousness for short period after beheading:
https://theconversation.com/did-anne-boleyn-really-try-to-speak-after-being-beheaded-106650

 

[256bits]

It is not apparent that an EEG would pickup signals that a ECG could, due to the attenuation trough the tissue surrounding the brain.

There is this, where a 'dead' mammalian brain was shown to observe activity, that even the ECG could not globally pickup.
https://pubmed.ncbi.nlm.nih.gov/30996318/

With this system, we observed preservation of cytoarchitecture; attenuation of cell death; and restoration of vascular dilatory and glial inflammatory responses, spontaneous synaptic activity, and active cerebral metabolism in the absence of global electrocorticographic activity. These findings demonstrate that under appropriate conditions the isolated, intact large mammalian brain possesses an underappreciated capacity for restoration of microcirculation and molecular and cellular activity after a prolonged post-mortem interval.

 

[Oldman too]

There is this, where a 'dead' mammalian brain was shown to observe activity, that even the ECG could not globally pickup.
https://pubmed.ncbi.nlm.nih.gov/30996318/

It appears that brains aren't the only pig organs that have this ability.
https://www.nature.com/articles/d41586-022-02112-0

 

[256bits]

It appears that brains aren't the only pig organs that have this ability.
https://www.nature.com/articles/d41586-022-02112-0

I saw that too.
OrganX compound

 

[Fra]

Summary: If brain death is definitely determined by a lack of brain activity, then why are secondary reactions the primary basis of a diagnosis; wouldn't the lack of activity from an EEG be sufficient?

as EEG is the projection of the brains electrical fields on the scalp, it is dominated by the cortex as deep brain sources such as the brain stem would be more attenuated at the scalp.
https://www.pnas.org/doi/10.1073/pnas.1705414114

"EEG may be insensitive to detect brain activity in certain areas of the brain: it does not register the electrical activity of the lower brainstem, and may be flat in patients with preserved subcortical function.
...
EEG is very susceptible to false positives: it is sensitive to drug effects [9], and to a greater or lesser degree unreliable in the setting of sedation, hypothermia, toxic or metabolic factors, and artifacts [68]. EEG also is prone to interference, such as with electromagnetic fields in the intensive care unit [9], or as interference between EEG and EMG, especially in brain-dead patients in whom EMG activity may be enhanced. Often, administration of muscle relaxants is necessary to achieve isoelectric EEG readings [69, 70]."
-- https://link.springer.com/article/10.1007/s12028-009-9231-y

/Fredrik

 

[Laroxe]

Actually EEG recordings are not a good indicator of brain death and its such an important decision that most countries in the west have established criteria / codes of practice that should be followed.
In the UK a series of tests must be conducted by two senior Drs, usually not the ones directly responsible for the persons care. The tests have to be repeated on two separate occasions and are usually supported by the results of a wide range of other clinical indicators, the EEG could be one of these. This document covers the issues but regardless, it is often a difficult and emotional decision for everyone involved.

https://www.aomrc.org.uk/wp-content...ctice_Confirmation_Diagnosis_Death_1008-4.pdf