Anesthesia p1 – Conscious Sedation, MAC, and Michael Jackson

Conscious sedation. It has a lot of names that people may know it as.
Monitored Anesthetic Care, or MAC, as anesthesiologists refer to it
Twilight (not the book, though that might cause it)

Basically, it’s when medication is administered to a patient to make a procedure tolerable, usually in conjunction with local anesthetics at the site of the procedure. Patients will likely have little remembrance of the procedure and may even lightly snooze during it. A patient can typically be aroused easily, answering questions or performing certain tasks.

Of course, there are levels to it. Light sedation is akin to having a drink, where it’s important for the patient to participate in the procedure. For example, the implantation of certain kinds of neurostimulators rely on the patient explaining what they’re feeling. Heavy sedation is used when the patient doesn’t really need to be with it for what’s going on. Sometimes patients in the Intensive Care Unit who are on a ventilator will receive heavy sedation; in the old days it was referred to as being ‘put into a coma’, which really doesn’t happen much anymore except in very isolated cases.

This is in contrast to general anesthesia, where the patient is at a much lower level of consciousness. Patients under general anesthesia receive either IV or inhaled anesthetics which render them completely unaware of what’s going on and unresponsive to stimulation. More on all that in another post. Just know that when you’re getting your gallbladder or appendix out, you’re under general anesthesia.

For a long time, it was believed that MAC anesthetics are safer than general anesthetics. However, studies have shown that bad things can still happen under sedation. While rare, it’s always possible for a patient to stop breathing if the sedation gets too deep. Yeah, that sounds pretty bad. However, when inducing a general anesthetic, patients stop breathing nearly 100% of the time. It’s part of our everyday job, and a patient not breathing under sedation is easily corrected without adverse complications to the patient. It does require, however, that the person pushing the medications pay attention.

And that’s what brings me to Michael Jackson, and his cardiologist.
There are certain standards involved in the administration of anesthesia. And make no mistake, MJ was receiving an anesthetic. But first, a few words on Propofol.

Propofol is an anesthetic, and when initially approved by the FDA it changed anesthesia. A lot. I use propofol every day, most days in every single case I’m involved in. Give a little, you get a reliable MAC drug that disappears within minutes of being turned off. It goes away quickly, independent of liver or kidney function. There’s no hangover effect afterwards, unlike with the drug it mostly replaced – sodium thiopental, also called Pentathal, long known as a ‘truth serum’.
More on that in a minute.

Anyway, there are standards that we follow in anesthesia. We use certain monitors on every case we do, and there are national guidelines for this. These guidelines are followed by all physicians as the golden rule for caring for patients under sedation. It includes, at a minimum, an EKG on the patient, a pulse oximeter measuring blood oxygenation, a blood pressure cuff going off every 5 minutes or less, an end tidal CO2 monitor, and – when shifts in temperature are expected – a method of measuring body temp.

So, what went wrong with MJ?

Well, to start with, the above listed monitors were sitting in the corner of the room, not on the patient. That’s pivotal. An end tidal CO2 monitor measures the amount of carbon dioxide in a patients exhalation. In a patient being sedated with propofol, it would’ve provided an early warning that Michael had stopped breathing. It would’ve alarmed if it hadn’t detected a breath for 30 seconds. The other important monitor is the pulse ox. When he went apneic, as his blood levels of oxygen declined, it would’ve been picked up by the pulse ox, which also would’ve alarmed. And finally, when his EKG started to change due to lack of oxygen and ischemia of the heart, the EKG monitor would’ve alarmed.

They don’t work if they aren’t on the patient. They also don’t work if they’re on the patient and you can’t hear them. We don’t leave our patients. One of the central tenets of our profession is vigilance.

Also, the physician should’ve explained to MJ about anesthesia better. We’ve really shot ourselves in the foot by calling anesthesia ‘sleep’ over the years. I understand why the practice was started, as it conveys a sense of something natural that we do every night and is perceived as safe. Before the monitors described above were required, anesthesia wasn’t that safe. Patients would stop breathing or not breath enough, and the only clue was when they turned blue. The widespread acceptance of pulse oximetry greatly changed the safety factor in anesthesia. These days, it’s safer to be anesthetized than to drive on the highway.

Still, anesthesia isn’t sleep, it’s unconsciousness. While that may sound like splitting hairs, the fact of the matter is that unconsciousness doesn’t provide the restful REM sleep that we all need to stay sane. By sedating MJ, his physician made his tired feeling worse. I’ve had plenty of patients emerge from anesthesia and tell me how tired they are. I’ve yet to have one wake up in ten years and feel refreshed. It’s more akin to running a 5k than taking a nap.

More next week!


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