Partially Revived Dead Pig Heads Prove We Still Don’t Fully Understand Brain Death

Everybody knows you’ve got five minutes, tops, to prevent brain damage once the flow of oxygen is disrupted to the brain. Past the five-minute mark, the brain is believed to suffer a cascade of failures causing permanent injury and the eventual inability to sustain life, even if oxygen is restored.

The science behind that five-minute cut-off has been repeatedly affirmed over the decades. It’s been charted in the long-term recovery and prognosis of hundreds of thousands of patients over the last 50 years who suffered varying degrees of oxygen deprivation but did not die as a result. We know, factually, that brain damage begins quickly when cells are deprived of oxygen, and nothing we’re about to discuss in this story challenges that basic finding. But if a new team of researchers is right, the question of when we’re actually dead — and how long activity might be preserved for — just got a lot more complicated.

In Which I Summarize the Plot of Porkenstein

There are two ways to tear this particular Band-Aid off. I’m going for the fast-but-accurate version:

Researchers collected 32 pig heads immediately after they were slaughtered. Four hours after the pigs had died, they hooked them up to a machine (dubbed BrainEx). BrainEx infused the pork pates with a secret sauce the team whipped up to protect brain cells and restore other aspects of homeostatic operation. This solution was pumped in for six hours, after which the control brains were no longer in any condition for comparison, having already badly decayed. The team then compared the treated brains with the control brains that weren’t modified in any way, as well as brains that had been perfused with a control fluid.

The result:

[W]e observed attenuation of cell death and preservation of anatomical and neural cell integrity. We also found that specific cellular functions were restored, as indicated by vascular and glial responsiveness to pharmacological and immunogenic interventions,  spontaneous synaptic activity, and active cerebral metabolism in the absence of global brain activity.

These findings show that, with appropriate interventions, the large mammalian brain retains an underappreciated capacity for normothermic restoration of microcirculation and certain molecular and cellular functions multiple hours after circulatory arrest.

It is important to stress that these brains were not conscious, even if cells within the brain showed responsiveness to pharmacological or immunological stimuli. The researchers specifically checked for cross-neuron communication and found none. “Spontaneous global activity,” they write, “did not reemerge.” Translation: The pigs did not “wake up.”

Significance

These findings seem similar, at least in principle, to the attempt to recover functional DNA from a woolly mammoth that we wrote about earlier this year. In that case, the most intact mammoth nuclei — nuclei that are 25,000 years old — attempted to replicate when injected into a mouse egg. In this situation, introducing a protective and supportive chemical solution back into brain tissue demonstrated that some functionality can continue to persist (or be restarted) long after such actions were thought to be impossible. In both cases, what we observed is a machine attempting to restart its own internal processes once a method was provided for doing so. In both cases, the degree of damage was severe enough to prevent this from fully occurring.

Bioethicists are concerned about the implications for our understanding of brain death and when that process occurs. I’m less certain of this. There’s tremendous potential for these findings to be misunderstood, but they don’t demonstrate that a pig came “back to life” in any fashion. The idea that a larger degree of individual cell function may be preservable over longer periods of time than we realized doesn’t change the fact that brain damage from oxygen loss sets in very quickly in critical brain areas. This discovery doesn’t appear to point the way towards any treatments for that problem, even if it does demonstrate that the brain’s decay post-mortem occurs in stepwise fashion over a longer period of time than previously realized.

Absent the kind of global activity that would indicate a conscious mind, I’m not sure we’ve found an ethical minefield, so much as we’ve discovered that brains rot more slowly than we thought they did.

Feature image by Ben Salter/CC by SA 2.0

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