The state induced by anesthesia looks a lot like a deep sleep, but it’s actually quite different. Doctors rely on a variety of chemicals to induce unconsciousness, and each works slightly differently in the brain. What all general anesthesia recipes have in common is that they induce unconsciousness while preserving the body’s automatic functions, such as breathing and digestion. Anesthesia also reduces sensitivity to pain, which is why people don’t typically have dreams of being in surgery or experiencing pain when they’re under the knife.
Because a wiggly patient can quickly be injured, anesthesia also limits or eliminates your ability to move. For the one to two people out of 1,000 who briefly awaken during surgery, this paralysis can be terrifying. Fortunately, people who awake during surgery don’t typically experience pain.
Doctors have traditionally theorized that, as anesthesia is eliminated from the body, the brain’s electrical activity steadily increases until the brain returns to normal. But new research at Rockefeller University has found that the process of waking up is much more complex.
Researchers knocked rats out using a popular anesthesia called Isoflurane. As the rats awakened from the anesthesia, researchers examined electrical activity in areas of the brain believed to be associated with wakefulness. In fully awake brains, the electrical activity in neurons oscillates, but in an anesthetized or sleeping brain, electrical activity is slower.
Instead of finding a gradual increase in oscillating neurons, researchers found that oscillations occurred suddenly. While every rat’s brain eventually had oscillations in the same “hubs,” the process through which neurons became more active in each hub varied from rat to rat. Researchers believe this indicates that there’s not a single path through which the brain awakens from anesthesia. Because every rat’s brain ultimately used the same hubs, though, the research suggests that certain brain activity is a necessary prerequisite to consciousness.
While research on rats isn’t always applicable to humans, rats and humans respond in similar ways to anesthesia. While anesthesia is extremely safe, a small number of people who undergo surgery don’t wake up. Among people over the age of 65, the risk is higher. By gaining a better understanding of how the brain wakes up from anesthesia, researchers may eventually find a way to reduce the risks of undergoing surgery.
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