There is a small amount of similarity in terms of electrical activity, but the two processes are chemically distinct. The electrical activity is only similiar in that it comes from the brain and therefore is recognisable as waveforms – you lose all REM sleep while under anaesthesia. Sleep is a complex state that is not simply just reduced activity. Sleep includes complex processing by various areas of the brain, possibly enhancing memory storage and “cleaning” junk, other parts are periods of reduced activity.
The real difference however comes from the surgical procedure you are likely receiving, the stress, cortisol, sympathetic activation produce a vastly different physiological state to natural sleep.
It should be noted that during minor procedures (i.e dental surgery, etc) you are not actually “knocked out”. Usually you’re put under what’s called “twilight sedation” in which you are mostly conscious and responsive, but your memory is suppressed. This enables you to be responsive and cooperative with the surgeon, such as moving or opening your mouth when needed. Generally you’re not fully awake, but sort of sleepy/extremely relaxed. Pain killers are administered separately so you’re not being tortured.
Do people Snore while Anesthetized?
Snoring is just partial airway collapse due to reduced tone of the muscles holding up the soft tissue in the area. Whether that reduced tone is due to sleep or anesthetics, the end outcome (noises and obstruction) will be the same. Snoring with an airway in is probably a bad sign, and I would be thinking about changing the airway.
Consider that if somebody got drunk and starts snoring – that doesn’t mean they’re sleeping, they could also be passed out from alcohol. They should be placed on their side in recovery position, monitored, and drawn on with permanent marker. That’s just basic triage 😉
More Detail about Sleep:
Sleep is divided up into Rapid Eye Movement (REM) & Non-REM sleep. we spend 80% of sleep in NREM & 20% in REM. Different phases of sleep can be identified on electroencephalogram (EEG) which when awake displays high frequency, low amplitude beta & gamma waves.
REM sleep is characterised by a disorganised EEG similar to the waking state, rapid jerking eye movements, increased blood pressure & heart rate, nonsensical dreams (“I went down a water slide with Santa”) & loss of muscle tone, presumably so we don’t act out our dreams.
NREM sleep has four phases:
EEG waves become progressively slower and larger (alpha, theta, then delta waves). We spend 50% of sleep in phase 2 NREM. Phase 4 is characterised by difficult rousing and organised dreams (“I have a meeting to get to tomorrow morning”). Deep NREM sleep is also the phase associated with parasomnias (e.g. sleepwalking, sleep talking), night terrors and bed wetting in children. The EEG of anaesthesia varies depending on the agents used but most resembles the synchronised low frequency, high amplitude wave of phase 3/4 NREM.
Bonus: Can We Sneeze When We Sleep?
The trigeminal motoneuron pools that mediate the sneeze reflex are inhibited during NREM sleep and are actively suppressed during REM sleep as part of atonia. Which means it is much more difficult to sneeze during NREM sleep and nearly impossible in REM (without also causing waking).