drug class used in medically induced coma

[fever5]

I'm currently a med I student in a pr session about head trauma. dicussion came to drugs used in medically induced comas. An initial search of UptoDate and Pub med didn't turn up anything useful.

Does anyone know if they use long acting benzo or a barbiturate or another class for a medically induced coma?

Thanks,

fever

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[2ndyear]

Barbiturarates, most commonly Pentobarb. In theory you could use Propofol as well. It has about the same actions as barbiturates yet is metabolized very quickly, requiring constant infusion, yet when you turn it off the patient wakes up very quickly with no hangover effect. Here's a link:
http://www.trauma.org/anaesthesia/barbcoma.html

 

[sdn1977]

Actually, when I worked in the ICU pharmacy, we used IV Versed. We used to use diazepam, but it is more difficult to titrate off. Versed has a shorter half life, so starting about the 3rd day, it would be titrated off in time for the neurologist to come in to assess the patient then it would get turned back up again. This also allowed easy EEG's without too much prior notice too. I've used propofol too, but that is VERY expensive (however, it has recently become generic, so that is less an issue - same idea as Versed though). I haven't used barbiturates in years and years unless seizures were an issue (altho diazepam is better for this too.) The problem with barbiturates is that they are not very water soluble, so not really good for IV infusion (this can be an issue with diazepam, but there are reasonable concentrations that we can provide nursing to acheive the goal). IM injections are too long acting for these situations, IMO. When you do your search, try looking for continuous IV sedation - that might yield better results than drug induced coma.

 

[fever5]

thanks for both of your comments. very helpful; thanks.

 

[sdn1977]

sorry...when I thought about it later I realized I should have added that if the sedation is to go on longer than a few days, we often switched to lorazepam...it is a bit longer acting, has no active metabolites & is less expensive than Versed. With propofol, because of its high lipid solubility, it has a very high volume of distribution which means that during long infusions (days...) the rate to maintain sedation is about half that required for induction & the terminal half life of the drug is 1-3 days after a 10 day infusion. Finally, for propofol, it is a lipid emulsion, so you must consider the fat content and adjust TPN or tube feedings appropriately (1.1kcal/1ml). Also, some patients cannot tolerate continuous lipid emulsions (their triglycerides will rise & stay elevated indicating difficulty clearing the lipid from the liver). Probably more than you wanted to know, but all considerations used in the choice of drug to maintain sedation in the ICU.

 

[bigdan]

Great answers, guys (or gals).

First, to 2nd year, really good look on the link to trauma.org.

Second, sdn1977, you impressed the **** outta me, especially if that knowledge is off the dome and not 'cause you have a book open. Nice work.

Keep the info coming!

dc

 

[DropkickMurphy]

It also depends on the allergies of the patients- if a person is allergic to eggs or shellfish you can't use propofol (or at least this is what I was taught; I'm just an RT so correct me if I'm wrong) due to the makeup of the emulsion propofol comes in.

BTW most of the experience I have had with prolonged sedation for neurological insult has been with barbiturates or propofol.

 

[sdn1977]

Great answers, guys (or gals).

First, to 2nd year, really good look on the link to trauma.org.

Second, sdn1977, you impressed the **** outta me, especially if that knowledge is off the dome and not 'cause you have a book open. Nice work.

Keep the info coming!

dc

Thanks! and yeah..it is off the dome (funny saying!). I spent 20+ years working hospital pharmacy & about 10 of that in the ICU pharmacy & since drugs are my thing....I had to get good at knowing what other disciplines needed drug-wise to manage the pt. In my setting, the pharmacists managed the intravenous nutritional support, so that's where that stuff comes from. Funny - my daughter is an MSI and just learning about pharmacokinetics - I think its all a bit confusing right now for her...so I can understand where you all are coming from. But...when you get time...ask your pharmacist - we'll give you more drug info than you probably ever wanted!

 

[sdn1977]

It also depends on the allergies of the patients- if a person is allergic to eggs or shellfish you can't use propofol (or at least this is what I was taught; I'm just an RT so correct me if I'm wrong) due to the makeup of the emulsion propofol comes in.

BTW most of the experience I have had with prolonged sedation for neurological insult has been with barbiturates or propofol.

Yes! - you're right about the eggs - it has egg lecithin which is an emulsifier (helps to keep all the components of the emulsion from separating). Not shellfish - that is usually a form of a iodine allergy & sometimes other components of shellfish and not an issue with propofol.

Sorry if I conveyed that there was only one way of providing continuous sedation - it was not my intent! Many, many articles support the use of barbiturates & propofol, in addition to other agents. So much depends upon the physician's own experience and comfort with dosing, training of the nursing staff, what kind of involvement each department had in developing the protocols, economics of the hospital drug purchasing agreements, etc.....So, again...I meant no disrespect to any other institution's choice of agent(s) - sorry!

 

[DropkickMurphy]

Actually I thought it was phosphatide from eggs that made up the emulsion? Also I believe there is soybean oil in it, but I'm not 100% on that, so perhaps a soy allergy would also be a contraindication?

 

[DropkickMurphy]

Addendum to previous post: I looked it up, the emulsion is made of "Propofol emulsion contains soybean oil, egg phosphatide, and glycerol" (SOURCE: http://www.musc.edu/pharmacyservices/Drugs/P/Propofol.doc )

 

[Skialta]

Don't forget the paralytic for the head trauma, vecuronium or pancuronium.

 

[sdn1977]

Ok...now this is really, reallly more than you want...this is a subject called pharmaceutics (how to get this chemical into a form which would be a good, practical drug). Yes, propofol has soybean oil - the active chemical is not water soluble so a lipid product is used to keep it soluble & in this situation, soybean oil is used. I've never seen a soy allergy which affected drug choice, but it could happen. But, to keep it isotonic, isoosmotic, etc...we have water soluble phase also. The combination of these two phases - water insoluble & water soluble (also caled immiscible liquid phases) is called an emulsion. Because of the thermodynamics of these two unstable phases which can result in a "breakage" of the emulsion (in which the two phases separate), you have to add an emulsifier to stabilize it. One of the most common emulsifiers used for intravenous medications is phospholipids (another interchangeable term is phosphatides). Phospholipids are esters (remember that from organic???) consisting of glycerol in combination with fatty acids, phosphoric acid & some nitrogenous products. Pharmaceutically, the most important member of this group of phospholipids are lecithins. So...the meaning of what you actually read was exactly the same - just the chemistry words used are a bit different. It is the soybean oil which is the caloric source, but, IMO...it is the egg protein which is the potential allergy source. See....it really is more than you wanted to know! (& yes, I did actually look up that phosopholipids were esters...that was way too long ago for me to have it "off the dome" - I love that saying!).

 

[sdn1977]

Don't forget the paralytic for the head trauma, vecuronium or pancuronium.

Yeah these and other neuromuscular blockers to facilitate intubation. Also often used for head trauma...diazoxide - to reduce edema in the head, narcotics - to facilitate anesthesia & pain, lots of anticonvulsants if seizures are an issue....plus all the other stuff associated with trauma in general - antibiotics, nutritional support, antihypertensives or pressors if BP becomes out of control...I've seen pretty much everything used on these pts except maybe contraceptives.