Patients often tell me after they have awakened from anesthesia, particularly propofol sedation, that it was the best sleep they ever had. They feel totally refreshed and often jokingly ask for some of the good stuff to take home with them. I always wondered what it is about propofol that makes patients feel so relaxed and carefree after its use.
Now in a fascinating Sunday Review article in the New York Times, researchers at the University of Rochester have identified a crucial neural cleansing function of the cerebral spinal fluid. It appears that the flow of CSF around the brain is significantly increased when the brain is in the sleep state. This is important because it is speculated that the byproducts of brain metabolism, like beta amyloids, if not removed from the nerve tissues and allowed to accumulate, can lead to long term dementia and Alzheimer's disease.
The researchers measured the CSF movement in mice using fluorescent markers. They then measured the flow of the fluids in sleeping mice. It turns out that when the mice were awake, the circulation was only five percent that of the sleep state. The amount of interstitial space between brain cells increased dramatically, allowing the CSF to penetrate deeper into brain tissue and extract the neuronal waste. The increased flow allowed the sleeping brain to be cleared out twice as quickly as the awake brain.
The interesting part is that this clearing mechanism also works when the mice are under anesthesia. The article doesn't specify the type of anesthetic used or how long the mice were anesthetized. But this should be a subject that the ASA and anesthesia researchers all over the world should be swarming over.
Imagine the implications this research could have if it pans out in humans. Dementia in the elderly is becoming an ever increasing burden in our society. Right now there is no treatment. The only things we can do to help these patients are to make sure they don't fall and break something or prevent them from aspirating. All that is a consequence of their worsening mental status which we are helpless to intervene. If anesthesia could lessen or eliminate the neural toxic waste that is thought to be the source of dementia, this would be a huge boon to mankind and a prestigious notch in the belt for anesthesiology, ranking right up there with Morton's first demonstration at MGH.
Imagine an office where patients with dementia would come to get anesthesia to help their brains get rid of its toxic waste. It would be similar to a dialysis clinic but staffed with anesthesiologists or anesthesia assistants. Patients would come a few times a week to get their scheduled anesthetic to prevent their Alzheimer's from deteriorating. The treatments would be expensive, but still cheaper than taking care of millions of debilitated patients that are currently draining our healthcare system. It would truly mark another golden age of anesthesia. I can't wait to see how this line of research works out.