In March of 2020, New York City hospitals were crowded to capacity with individuals suffering from Covid-19. When their fluid-filled lungs could no longer provide oxygen, physicians often sedate and place patients on ventilators.
The recovering patients were removed from the machines and anaesthesia. Within a day or two, their physicians anticipated that they would regain consciousness.
Dr. Nicholas Schiff, a neurologist at Weill Cornell Medicine, began receiving calls around that time.
Dr. Schiff, who had spent 25 years treating consciousness issues, was baffled by the flood of Covid patients who were unconscious. It took many weeks or even months to awaken. Typically, though, patients recovered full awareness with no indication of brain injury.
Since then, Dr. Schiff and his colleagues have been attempting to make sense of this peculiar event. On Monday, he released a paper proposing a solution. The solution includes turtles.
Dr. Schiff and his coauthor, Dr. Emery Brown, a computational neuroscientist at M.I.T., suggested that the brains of unconscious Covid patients closely resemble those of turtles who spend the winter encased in ice. The turtles are able to live by placing their neurons into a state of remarkable silence that lasts for months. Drs. Schiff and Brown feel that the combination of Covid and sedatives has a comparable effect in humans.
If the idea holds true, it might suggest to novel approaches to prevent brain harm, such as placing individuals into this condition on purpose rather than by accident.
“If accurate, it may educate us how to better protect and maintain the brain,” stated Dr. Schiff.
Dr. Schiff learned that he was not alone in his experience. Numerous other neurologists saw Covid patients awakening quite slowly. Dr. Schiff, Dr. Brown, and his colleagues released a study of 795 severe Covid patients with delayed recovery at three hospitals in New York City and Boston in March of this year. A quarter of the patients required at least 10 days after being removed from a ventilator to respond to basic orders such as gripping the doctor’s finger. 10 percent of patients were remained unconscious after 23 days.
However, the study did not provide simple explanations for why they were suffering such a lengthy wait. The anaesthetic medicines were insufficient to explain the lengthy trek back to awareness. The time courses were ludicrous, said Dr. Schiff.
Damage to the brain may result in months of low awareness, however the majority of Covid patients had healthy brains. Dr. Schiff said, “There was no assumption that there would be an issue.”
Drs. Schiff and Brown have developed hypotheses for years on what occurs in the brain during comas, sleep, and anaesthesia. They shifted their focus to Covid. Unexpectedly, their quest for clues led them to studies of turtles.
In the northern hemisphere, freshwater turtles with a cold-blooded metabolic system must endure freezing winters. They do this by spending months scarcely breathing when buried in freezing mud. Turtles prepare their brains for winter by flooding them with the neurotransmitter GABA, according to laboratory-based turtle researchers. The chemical reduces neuronal activity so that neurons do not squander energy making electrical pulses.
“It’s as if they self-anesthetize,” said Dr. Brown.
During the winter, turtles exhibit different brain-wave patterns consisting of solitary bursts of electricity interrupted by extended periods of quiet. Similar to turtles, unconscious Covid patients have transient electrical activity bursts interspersed by lengthy periods of quiet. In addition, these patients were frequently given anaesthetics that resemble GABA.
In reaction to GABA-like sedatives and the stress of Covid, Drs. Schiff and Brown hypothesised that human neurons enter a phase in which they need less oxygen to live. Even after the effects of the sedatives have worn off, the brain may maintain this condition for months.
Amanda Bundgaard, a postdoctoral researcher at the University of Cologne in Germany who studies turtle brains, found the similarity fascinating. However, she advised against stretching the comparison too far since there is still so much to learn about turtles.
After months in a condition of suspended animation, turtles’ brains are flooded with oxygen to bring them back to life. The influx of oxygen should destroy their brains by initiating deadly chemical processes, which is remarkable.
Several studies show that turtles absorb the additional oxygen through a substance known as neuroglobin. However, it is probable that they employ a variety of different compounds to construct many lines of defence.
Martin Monti, a neuroscientist at UC-Los Angeles who was not involved in the research, said, “It’s wonderful to have a fresh idea to consider whether it helps us achieve better results for patients.”
In their report, Drs. Schiff and Brown recommend that neurologists examine cerebral fluid samples collected from Covid patients as they regained consciousness. They may secrete neuroglobin to protect their brains, similar to turtles.
Dr. Monti said, “That would be a fairly solid test of the idea.”
He noted that the concept might potentially lead to novel methods for preventing the death of brain tissue after strokes, heart attacks, or even severe brain injuries. A combination of sedatives and other therapies may drive neurons to form a turtle-like shell around themselves.
“This might become a new tool in the toolbox to help patients not only survive, but recover as much as possible,” stated Dr. Monti.