Covid patients to regain consciousness

It can take weeks for Covid patients to regain consciousness after being taken off ventilators.

According to a new study, the combination of the virus and anaesthesia causes the brain to go into a prolonged state of silence, similar to that of a freshwater turtle in the winter.

 STUDY ABOUT RECOVERY FROM COVID

In March 2020, New York City's hospitals were overrun with Covid-19 patients. When their fluid-filled lungs could no longer provide oxygen, doctors sedated them and placed them on ventilators.Patients who were able to recover were taken off the machines and anaesthesia. Their doctors expected them to wake up within a day or so.But that's when Dr. Nicholas Schiff's phone, a neurologist at Weill Cornell Medicine, began to ring.

"We're getting all these strange consults," Dr. Schiff recalled. "After surviving Covid, people have been released from anaesthesia, but they are not waking up."

Dr. Schiff, who had spent the previous 25 years treating consciousness disorders, was perplexed by the influx of unconscious Covid patients. It took them weeks, if not months, to wake up. However, they usually recovered full consciousness with no evidence of brain damage.

Since then, Dr. Schiff and his colleagues have been attempting to make sense of this strange phenomenon. He published a paper proposing an answer on Monday. And the solution involves turtles.

According to Dr. Schiff and his collaborator, Dr. Emery Brown, a computational neuroscientist at M.I.T., the brains of unconscious Covid patients resemble those of turtles that spend the winter encased in ice. Turtles survive by putting their neurons into a strangely quiet state that lasts for months. Dr. Schiff and Brown believe that combining Covid with sedatives causes a similar response in people.

If the theory holds up, it could point to new ways to save people from brain damage: deliberately putting them in this state rather than by accident.

"If it works, it can teach us how to better protect and preserve the brain," Dr. Schiff said.

Dr. Schiff discovered that his experience was not out of the ordinary. Many other neurologists had observed Covid patients taking an unusually long time to awaken. Dr. Schiff, Dr. Brown, and their colleagues published a study of 795 severe Covid patients with delayed recovery in three hospitals in New York City and Boston in March of this year. One-quarter of the patients required 10 days or more after being taken off a ventilator to perform simple commands such as squeezing a finger the doctor's finger After 23 days, 10% were still unconscious.

However, the analysis did not provide any simple explanations for why they were experiencing such a long delay. The long journey back to consciousness could not be attributed solely to the anaesthetic drugs. "The time courses were absurd," said Dr. Schiff.

WHAT EXPERT SAYS

Although brain damage can cause months of unconsciousness, many of the Covid patients had healthy brains. "There was no expectation of a problem," Dr. Schiff explained.

Dr. Schiff and Dr. Brown have been researching what happens in the brain during comas, sleep, and anaesthesia for many years. They now concentrated their efforts on Covid. Their search for clues led them unexpectedly to turtle research.

Coldblooded freshwater turtles must survive cold temperatures all over the northern world winters. They accomplish this by spending months buried in frozen mud and barely breathing. Turtle researchers have discovered that the animal prepares its brain for winter by flooding it with a chemical called GABA. The compound reduces neuron activity so that they do not waste energy producing electrical pulses.

"It's as if they anaesthetize themselves," Dr. Brown explained.

During the winter, the turtles' brain-wave patterns are distinct, with isolated bursts of electricity separated by long stretches of silence. Unconscious Covid patients, like turtles, produce brief bursts of electrical activity between long silences. And these patients were usually given anaesthetics that mimic GABA.

Dr. Schiff and Dr. Brown proposed that in response to GABA-like sedatives and Covid's stress, human neurons shift to a quiet mode where they don't require much oxygen to survive. The brain can remain in this state for months after the sedatives wear off.

"I think it's an intriguing analogy, definitely," said Amanda Bundgaard, a postdoctoral researcher who studies turtle brains at the University of Cologne in Germany. However, she cautioned against stretching the analogy too far at this point because there is still so much to learn about turtles.

"One thing that may be a little problematic is that we don't know how turtles recover from this," she explained.

Turtles return to normal after months of suspended animation by flooding their brains with oxygen. That's remarkable, because the increase in oxygen should have killed their neurons by causing toxic chemical reactions.

According to some research, turtles absorb extra oxygen via a chemical called neuroglobin. However, it is possible that they use aa variety of other chemicals to create numerous lines of defence

"It's exciting to have a new hypothesis to think about if it helps us create better outcomes for patients," said Martin Monti, a neuroscientist at the University of California, Los Angeles who was not involved in the study.

CONCLUSION FROM DOCTORS

Dr. Schiff and Dr. Brown propose in their paper that neurologists should examine samples of cerebrospinal fluid taken from Covid patients as they regained consciousness. To protect their brains, they may release a surge of neuroglobin, similar to turtles.

"That would be a pretty good hypothesis test," Dr. Monti said.

He went on to say that the hypothesis could lead to new ways to keep brain tissue alive after strokes, heart attacks, or even traumatic brain injuries. Sedatives in combination and other treatments may cause neurons to form a turtle-like shell around themselves.

"This could eventually become a new tool in the toolbox to help patients not only survive, but recover as well as possible," said Dr. Monti.

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