How it’s possible to sleep through surgery
Experiments using mice have revealed how our brain goes to sleep during general anaesthesia. Paradoxically, at a time when you would expect lower brain activity, the research showed increased activity after the anaesthetic was inhaled, but only in a select few neurons associated with sleep.
Despite being used for over 170 years, doctors still do not know exactly how general anaesthetics allow people to sleep through traumatic surgery.
In the latest research to cast new light on this mystery, mice were given two commonly used anaesthetic gases, isoflurane and halothane. Using imaging techniques, the researchers looked for altered brain activity immediately after the gases were inhaled. A small but very specific group of neurons in the hypothalamus region of the brain were activated, and only when sleep-inducing amounts of the gases were inhaled. The neurons are part of the so-called ventrolateral preoptic nucleus (VLPO), known to be highly active during natural sleep. Neighbouring neurons not associated with sleep were unaffected.
The results show that the anaesthetics are artificially activating parts of the brain that induce sleep, rather than shutting down the brain, as previously thought. Through understanding the true effects of medicines on the body, doctors and scientists can make them safer and more effective. The next step is to investigate why this induced artificial sleep is so much deeper than natural sleep, ensuring patients are not awoken by the first cut of the surgeon’s knife.