Anesthesia for Colonoscopy

[URGettingSleepy]

Hi all.

Posts from laypeople probably aren't all that common in these forums, but Googling for anesthesia-related message boards didn't yield all that many results, and as this one seems to be the most active, I thought I'd take my chances Actually, I'm schooled and work in the engineering field, but there are many aspects of scientific and medical fields that I find fascinating (including anesthesiology) which I research out of curiosity on my own time, thus prompting my question.

A couple of days ago, I went in for a colonoscopy. A couple of years ago, I accompanied my dad for a colonoscopy as the "designated driver", and I learned that for his procedure, the primary sedative was Versed. As such, he was in a state of what I believe is referred to as "conscious sedation", as he did recall a good portion of his procedure. My procedure, on the other hand, was a little more involved in terms of anesthesia. The ambulatory center at which my procedure was performed had a couple of staff anesthesiologists, and from my conversation with the anesthesiologist prior to the procedure, I learned that I would be put under general during the procedure and would be administered Versed, Fentanyl, and Propofol. Having never been under any type of sedation previously (let alone general anesthesia!) I was a little nervous, but in a strange way also a little curious and interested as this would be my first time ever going under.

In any event, shortly before being wheeled back to the procedure room, the anesthesiologist came over and administered some medication through my IV. I'm guessing that this was the Versed, as he mentioned that it would make me feel a little relaxed. I was expecting to feel a little light headed or sleepy, but honestly, I didn't really notice any effect at all from this medication. Shortly thereafter, I was moved into the procedure room. After hooking up the oxygen and connecting me to the meters, the anesthesiologist mentioned that he was going to start administering additional medication. Now I was under the impression that I would notice myself becoming relaxed and drifting off to sleep, but all I recall is being fully awake while equipment was being connected to me, and the next thing I know, I'm waking up in recovery, fairly coherent, and with absolutely no recollection of the procedure whatsoever. Having watched a number of videos on YouTube and the like, it always looks like patients drift off to sleep after being administered Propofol, so I found it interesting that I never experienced a "getting sleepy" stage, as it was a seemingly instant transition from being fully awake to being asleep for me. That said, do some of the more physical signs of going under (like closing one's eyes) commonly occur shortly after one is already asleep?

Secondly, I'm curious as to what point in the procedure the anesthesiologist would have administered the Fentanyl. Would this have likely been done after administering the Propofol? Unfortunately, as I was positioned on my side, I couldn't see the IV line, so I wasn't able to see whether the milky Propofol or something else was being injected immediately before I fell asleep. Is there a chance that the Fentanyl could have been administered first and is actually what knocked me out so quickly? If not, what's the basic purpose for administering Fentanyl during a colonoscopy?

On a somewhat unrelated note, the anesthesiologist did inform me that I would be breathing on my own throughout the procedure, although I've seen that in a number of surgical procedures, patients are intubated shortly after going under anesthesia. That said, what are the determining factors for whether or not a patient will be intubated? Does it depend on strength / amount of anesthetic used, or is it only required when strong muscular relaxants will be administered?

By the way, thankfully the results of my colonoscopy were just fine. I had been experiencing some rectal discomfort, and through previous tests my colorectal specialist had pretty much narrowed the cause down to muscle spasms, but on account of my family history, he recommended a colonoscopy just to err on the side of caution. As I mentioned previously, I've always found anesthesiology fascinating, and having now experienced it first-hand for the first time, it's truly amazing how easy anesthesiology can be on patients.

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[2ndyear]

I'm glad you had a positive anesthesia experience for your colonoscopy, and I'm happy that this was provided by an anesthesiologist. Some GI doctors are pushing for full use of general anesthetics such as propofol (or a new pro-drug formulation) administered by an RN with no anesthesia provider present.

Propofol and midazolam (versed) have amnestic and sedative properties, but no effect on pain. As colonoscopy can be a bit painful, a small amount of a drug that decreases pain is helpful.

As for breathing on your own, drugs and doses determine how much and if you will breathe on your own, as well as the type of procedure. Propofol in a large enough dose causes apnea every single time its administered. This dose is awfully close to the 'just getting off to sleep' dose in many patients (hence the need for a dedicated anesthesia provider when its given, not the same person driving the scope in your colon). For many superficial or extremity procedures, we can maintain spontaneous ventilation easily. Inhaled anesthetics are commonly used (sevoflurane, desflurane, isoflurane) either by face mask or LMA (laryngeal mask airway). If the surgery requires relaxation of muscles, or if the patient is inappropriate for spontaneous venitilation, we administer a neuromuscular blocker and intubate the trachea.

 

[cchoukal]

Your experience is sort of what I would hope for for a patient undergoing colonoscopy, and how I would approach the case in a normal healthy person who, for whatever reason, had the benefit of an anesthesiologist for the procedure. The anesthesiologist likely administered midazolam (Versed) in the pre-op area, wheeled you back to the procedure room, and started a continuous infusion of propofol while attaching the monitors (BP cuff, pulse oximiter, etc.). As the target concentration of propofol approached steady state at a reasonable concentration, you lost consciousness. You might have experienced a period of sleepiness or impending sleep at the time but have no memory of that period as a normal consequence of the drug. Unconsciousness does not necessarily mean you would stop breathing and in a healthy patient in the lateral position with your face easily accessible by the anesthesiologist, it would not be unusual or (dare I say) unsafe to have you unconsious and breathing on your own. As someone pointed out above, it was probably during this time that the anesthesiologist gave fentanyl. It is possible/likely that, even with the described level of sedation, you might have moved or squirmed a little either when the scope was inserted or advanced, and yet have no memory of this.