October 26, 2012
Anesthesia More Similar To Sleep Than Originally Understood
Connie K. Ho for redOrbit.com — Your Universe Online
Close your eyes, inhale slowly, and then exhale. Lie back and feel your body slowly relax as you melt into the cushion. Everything fades away as darkness slowly takes over and a feeling of peace passes over.
For those who love sleep, the aforementioned sentiments might seem familiar. They might even seem familiar to those who have been anesthetized for surgery, where the brain turns off and tunes into sleep mode.
In particular, a new study published in the current edition of Current Biology, a Cell Press publication, discovered that drugs not only switch wakefulness “off” but push all sleep circuits to be turned “on.”
Max Kelz, an anesthesiologist, was interested in finding out about the state of sleep for patients who are put under anesthesia.
"Despite more than 160 years of continuous use in humans, we still do not understand how anesthetic drugs work to produce the state of general anesthesia," explained Kelz, a researcher at the University of Pennsylvania, in a press release. "We show that a commonly used inhaled anesthetic drug directly causes sleep-promoting neurons to fire. We believe that this result is not simply a coincidence. Rather, our view is that many general anesthetics work to cause unconsciousness in part by recruiting the brain's natural sleep circuitry, which initiates our nightly journey into unconsciousness."
With anesthesia, there is a difference between natural sleep and unconsciousness. As such, those who are in deep sleep any regular night can be aroused but those who receive anesthesia will maintain deep sleep through any intensive surgery.
“General anesthetics have been used to manipulate consciousness in patients for nearly 170 years, but it is still not known how these drugs impart hypnosis. At the molecular level, the number of possible effector sites is staggering: dozens of molecules are known to be sensitive to anesthetic agents,” wrote the researchers in the introduction of the article.
The researchers studied the region of the brain located deep inside the hypothalamus, which can increase activity when an individual falls asleep. They discovered that isoflurane, a type of anesthetic drug, was able to increase activity in the sleep-promoting brain area of mice. They used a mix of direct electrical recording and other methods to determine that animals who lacked function of those specific neurons in the brain eventually became more resistant to falling into a state of sleep with anesthesia.
“This work demonstrates that anesthetics are capable of directly activating endogenous sleep-promoting networks and that such actions contribute to their hypnotic properties,” noted the researchers in the article.
Based on the findings, researchers believe that more aspects of anesthesia are understood and the researchers intend to study the topic further in the future.
"The development of anesthetic drugs has been hailed as one of humankind's greatest discoveries in the last thousand years," concluded Kelz in the statement. "Anesthetics are annually given to over 230 million patients worldwide. Yet as a society, and even within the anesthesia community, we seem to have lost our curiosity for how and why they work."