The White Stuff: An informal look at propofol

In 2009 Michael Jackson passed away under tragic and unfortunate circumstances. The reason? It was an overdose of the anesthetic drug propofol. For over 20 years, propofol has been one of the most commonly used anesthetic drugs on earth, and if you had surgery during that time, it was more than likely used to put you to sleep. But until that June day two years ago, nobody outside of medicine had ever heard of it, and pundits were all over the TV in the days following Michael Jackson's death, speculating on how it might have killed him. That is a story for another blog entry. What I do want to do, however, is give a little insight into this mysterious drug, which even now I am asked about at least once a week. It is important because like I said, it is the single most common induction drug used today in anesthesia, and a little information goes a long way in reassuring anyone about to undergo anesthesia.

First of all, what is propofol? It is different from all of the other sedative drugs used in anesthesia today.  It is not a benzodiazepine, like the more familiar drugs Valium or Klonopin.  Nor is it a barbiturate, like sodium thiopental (Pentothal). Both of these drugs have known mechanisms of action; they make certain inhibitory substances in the nervous system more potent.  Propofol is in its own unique class of drugs; it is what is known as a "hindered phenol".

No, I don't really know what that means either.  Nor are people in general completely sure of how propofol works.  It is thought that like other sedatives, it potentiates the action of certain inhibitory substances, or neurotransmitters, in the central nervous system.

Enough about that.  Propofol is a relatively new drug, having just come along in the last twenty-five years or so.  Unlike most other drugs, which are mixed in saline or water, propofol is mixed in a lipid emulsion, with a substance, lecithin, that is similar to egg whites.  As such, propofol has a unique place in the pantheon of drugs because of its snow-white color.  It is often offhandedly referred to by non-anesthesiologist medical personnel as "milk of amnesia," a moniker I find annoying, albeit understandable.  Propofol does a few things that make it so valuable and useful for anesthesiologists:

It acts for a short time and is metabolized quickly.  Propofol is given in a large dose in the beginning of an anesthetic to put patients to sleep, and it causes almost immediate unconsciousness.  Within five to ten minutes, though, that large dose has completely worn off and the patient will awaken unless they are given more anesthetic.

It can cause that unconsciousness, yet can wear off quickly without lingering side effects.In fact, propofol, when used for sedation (or misused, like MIchael Jackson's physician did), needs to be given through a pump, continuously.  Shortly after the propofol stops, the patient wakes up and has little if any of the "hangover" feeling that characterized many sedative drugs before it.  That is a great, and very useful quality to have in a drug.

Propofol, however, has a couple of properties that can make it extremely dangerous if not used correctly.  First, it can cause blood pressure to drop significantly, especially in someone who is dehydrated - like a patient having surgery, who has been instructed not to eat or drink for at least 8 hours before their procedure.  If that drop in blood pressure isn't treated in some way and is allowed to continue for any period of time, it can cause significant damage to vital organs.  Elderly people are especially susceptible to this.

But the most significant - and now, the most notorious - property of propofol is that it decreases breathing, and can cause it to stop completely if given in large enough doses.  If that sounds alarming, it can be.  Propofol is a very safe drug in the hands of anesthesia providers who are trained in how to manage the airway and breathe for the patient who cannot do so on their own.  But for someone not trained in airway management, propofol can be an extremely dangerous drug indeed.  Almost all medical personnel are trained in basic or advanced life support, which does involve learning how to maintain an airway in a patient who is not breathing, but very few are trained with advanced airway management skills that are critical to know when such drugs as propofol are being given.

Doctors from specialties outside anesthesiology, like GI doctors and cardiologists, use mild sedation for a lot of their procedures, and have recently petitioned for the privilege of using propofol.  All have been turned down by the governing society of anesthesia, the American Society of Anesthesiologists.  They are certainly capable doctors in their area of expertise; they just don't necessarily have the skills in resuscitation and airway management to help a patient who stops breathing from an accidental overdose of propofol.  That's not their fault; their training focuses on their particular area of expertise.  Anesthesiologists do resuscitation and airway management for a living.

Again, it bears repeating that of the millions of surgeries performed in the United States each year under general anesthesia, propofol is used to put patients to sleep in, oh, 99.9% of them. Propofol is used, safely, in almost all of those as well, because it is given by an anesthesia provider who is vigilantly watching the patient with the help of multiple monitors, and has been trained for years in its proper use.