One of the qualities of sedatives usually considered valuable for medical procedures is anterograde amnesia (temporarily blocking the ability to form new memories) - which is what you experienced, Russell. There are some sedatives which produce this effect at doses where you still remain somewhat conscious - which enables the patient to follow simple instructions like "turn on your side". Some members of the benzodiazepine family (same family as diazepam/Valium and alprazolam/Xanax) do this well (e.g. midazolam aka Versed). Ethanol can also do this sometimes (often called a blackout). I think their thinking is that if you do experience something unpleasant at least you won't be traumatized by it. It can be rather mind-twisting to consider what happens if you are able to feel pain but don't remember it later. Anesthetists are concerned mostly with anesthesia recall (ability to remember painful events) since that is the most directly observable event in terms of what the patient can report afterwards, but they do concern themselves with preventing the conscious or even unconscious experience of pain to begin with. Modern anesthesia practice uses a layered approach - they sometimes use local anesthetic to reduce or eliminate pain at the operation site. They also sometimes use an opioid analgesic to reduce the sensation of pain. On top of these is the general anesthetic (usually inhaled for major surgery but sometimes could be purely IV-delivered). The patient is also usually sedated prior to receiving the general anesthetic (as I already mentioned) and sometimes a muscle relaxant is given to prevent involuntary movement or airway reflexes (like gagging/coughing/larynx spasm) while the patient is intubated. Since sedation and muscle paralysis do not produce unconsciousness or pain relief, great care is used to ensure proper pain relief and depth of anesthesia (lack of consciousness) - especially if muscle relaxants are used. Without muscle relaxants, painful stimulus will sometimes cause jerking or twitching of limbs by the patient which is thought to be reflex-based and not conscious action. If you induce profound general anesthesia, this doesn't usually happen but it's considered safer to maintain a slightly lighter depth (still sufficient to prevent consciousness but not deep enough to suppress all reflexes) and use other means of pain relief (like local anesthetic or opioids). Anesthetists can use these reflexive reactions to painful stimuli as a guide to achieving the proper depth of anesthesia and pain relief. Secondarily, and especially if muscle relaxants have been used, they use respiration rate, heart rate, blood pressure, and brain waves to determine proper depth, pain relief, and whether the patient might be aware or in pain. Someone who is experiencing great stress will have an elevated respiration, heart rate, and blood pressure even if skeletal muscles cannot move. They are supposed to watch for this and provide more pain relief/deeper anesthesia if it happens. (Even though they make every effort to prevent it from happening in the first place and it usually doesn't). There are also various algorithms which produce an anesthesia depth "score" or figure-of-merit from analysis of brain waves. Bispectral Index is one. I'm not a doctor or a nurse but medicine is one of my interests and I've read quite a bit about anesthesia. I've had "conscious sedation" several times for endoscopy procedures. My amnesia was not as profound as Russell's - I do remember a bit of each instance but definitely less than if I were fully awake. Meperidine/Demerol or fentanyl were used for pain relief. I've only had general anesthesia once - propofol - and beforehand I was a bit worried about the philosophical question I mentioned above (What if I feel pain but don't remember it afterwards?). I suppose that question is not possible for me to answer, still, of course, but my experience was very good and perhaps as close to answering that question as possible: about 20 seconds after being given the injection, I became very dizzy (I was of course already lying down) and then suddenly blacked out. The memory of that moment of going out is quite vivid and strong. I do have memories then from before waking but they are memories of a dream - just like normal sleep. They are very vague but it was definitely not a nightmare - it was a dream about the procedure I was having but it was neither super pleasant nor horrible, just like waiting for something to be finished. Then I also remember the moment of waking up at the end - just like normal sleep. Sean On Tue, Aug 20, 2019 at 8:10 AM RussellMc wrote: > On Tue, 20 Aug 2019 at 19:31, Sean Breheny wrote: > > > My $0.02 on a few quick items: > > > this is why they typically sedate you with some other > agent first (usually intravenous although it could be nitrous oxide) and > then begin administering the inhaled anesthetic. They'd have to be pretty > sophisticated to make this work right by feeding N2O first through a pipe > and then some other anesthetic (N2O doesn't render you completely > unconscious and you recover very quickly when exposed to clean air). Larg= e > quantities of these expensive agents would be needed and there would be a > lingering smell. > > My experience of pre-meds was stunning. > C4-5 spinal fusion. > As we were about to enter the operating room. > "I'll just give you a shot of premeds ..." > I have no recollection of anything from that moment until waking up in > intensive care. > He was very proud latterly. I was annoyed. I value (no doubt strangely) t= he > rigmarole of preparation for operation (not that I've had overly many). > To (presumably) experience that, but to lose it entirely from memory, was > disturbing. > > > Russell > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .