Consciousness, conscious sedation, awareness

Started by George Miklos, December 29, 2004, 01:32:58 AM

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George Miklos

The topic of BIS and Entropy monitors triggered me to ask my pet question that I pose to residsents:

1. When does sedation become anesthesia?

2.When does conscious sedation become awareness?

My answer to question 1 is that the sedation ---> general anesthetic spectrum has no sharp demarcation line. A GA occurs when some intervention needs to be taken to support a patient's airway. I know others have a different definition, but for me, this is a useful one because at this point of sedation, a degree of expertise (namely somebody trained in anesthesiology) is required to continue in a safe manner. Non-experts should NOT venture beyond this point!

For question 2, I do not have an answer. Sedation is tricky. It is a constant battle to balance the degree of sedation with the level of surgical stimulus while maintaining a patent airway and adequate ventilation. This degree of sedation is NOT always acheivable. Either the airway is lost, and an intervention is required (which by my answer to question 1 becomes a GA!) or the sedation is inadequate and the patient becomes aware!

Is awareness without recall (or memory or the event) true awareness? Do these insults lie buries deep in our unconscious to disturb us in the future (or revealed by hypnosis)?

I make sure that when I consent a patient for "sedation" that they understand that there MAY BE bits of the surgery that they may recall post-operatively. To do otherwise is negligent. I also reassure them that they are in charge - if they want more sedation or more local, the surgery will stop until this happens. The only way I can guarantee a lack of awareness is with a GA (and even then I cannot guarantee it!).


Sandy Hancock

Sedation means just that. It does not even suggest, let alone guarantee, lack of awareness.

I never promise patients having sedation they will have no recall, but unfotunately the surgeon or nurses have usually got in first. I promise they will be relaxed and comfortable - if they are not, they will let me know somehow and I will give them more stuff.

Like George, if patients insist they do not want to know anything about the procedure, I tell them they are getting a GA.

Defining anaesthesia as loss of airway control is clearly not good enough. Some patients never lose their airway, some do it when clearly quite rousable. I would suggest lack of reponse to a noxious stimulus is more precise, but actually question the usefulness of any such definitions. As was stated earlier, it's all a continuum, and the boundaries are blurred.

Therese Huntly

Sure, consciousness, sedation, GA is all a spectrum.

I find Georges's definition useful in at least one respect: when non-anesthetists are giving sedation, including in some cases propofol (eg the Emergency Room, Gastro Suite, Radiology etc) and they give so much that the patient's airway needs support, it is a satisfying thing to ask teh sedationist if they are comfortable to have given a GA.

I mention this because we are currently having a review of sedationin outlying areas of our hospitals, where inexperienced doctors and nurses are using drugs far beyond their abilities. Often without adequate monitoring and often (esp in ER) in non-fasted patients!