Ketamine and Trismus

[DartmouthDave]

Hello,

I know that Ketamine sometimes causes non-purposeful movements and hyperreflexia. But, I have seen two burn patients (one electrocution and the other was spilled gas on a fire) that have had prolonged trismus when Ketamine was used as an induction agent. Needless to say, it cause some moments of anxiety.

I have looked at Micromedex (a pharm database at work), spoke with a Pharmacist and checked a few other sources but nothing conclusive.

However, it is odd that it happened so profoundly, twice, with two different burn patients.

Has anybody had issues with trismus and Ketamine?

Thank you,

David

[chbare]

David:

There is probably not going to be a satisfactory answer. First, I'd ask what paralytic was used and were any adjunctive substances such as fentanyl used. There are some reasonably well defined mechanisms for trismus with these agents.

Looking at ketamine in a vacuum, the honest answer is we do not have a completely well developed mechanism of action for this agent. The consensus revolves around NMDA (type of glutamate receptor) receptor interaction. However, there are reports of movement disorders and muscle tone alteration (dystonic reactions). This is likely due to some dopaminergic effect. So, a dopaminergic hypothesis is a good starting point. Also remember, people can have a variety of genetic polymorphisms that can increase the risk of uncommon reactions.

Start with the "mundane" considerations first however.

[J306]

I've heard of Ketamine causing an idiosyncratic reaction similar to the one you described. I believe Ketamine was used as the primary inducting agent causing a trismus type reaction. I believe Midazolam 5 mg completely reversed the reaction with no complications.

[island emt]

we don't have ketamine used for humans in this area.

It was a favorite of the RAVE crowd a few years back. " Special K" was the street name.

They were stealing it from veterinary clinics and break ins were high in the 2000 - 2004 time frame. ]

We did see the tonic clonic muscle activity , posturing and trismus events from party goers that were treated.

good time to practice nasal intubations.

[croaker260]

We currently use Ketamine in my area, and I do not recall seeing anything like trismus, other than the brief fasciculations you occasionally see with succs. That said I routinely use a little Midazolam pre-intubation in my "cocktail" as well (2.5-5 mg). I started using this back when we used etomidate instead at the recomendation of a local doc, as we were seeing myoclonic fasciculation /trismus with Etomidate. Since I aded a little versed, havent seen it since.

So that would be my recomendation. I know some medics think that using ketamine removes the need of Midazolam altogether, but I think they work well together. With a paralytic too , of course.

[J306]

In Saskatchewan we unfortunately do not have the scope of practice yet to use paralytics.. Our options include Ketamine, Midazolam, Etomidate, and Fentanyl. Protocol is only a couple years old and has had mixed reviews so far.

[firemedic37]

I remember back five years ago that we used only Valium and Etomidate for sedation to "knock" down the pt so we could intubate them. We soon realized that this was not working very well and decided to go full pledge RSI and the result speak for themselves.

My "cocktail" varies depending where I am at. In the hospital it is Versed, Fentanyl and Succs and continued with Propofol and Fentanyl. In the field it is Versed, Fentanyl and Vec since we don't carry Succs on the trucks and continued with Versed and Fentanyl. A few years ago I would tell you to keep them paralyzed but if they are properly sedated the need for paralytics decreases. I think a lot of people over look the combination of Fentanyl and Versed, it is very potent and will do a very good job together.

Now back to the original questions, the only time we used Ketamine is in the hospital for pediatric sedation and for pt's with severe asthma. Otherwise we use different medications as mentioned above.

There are numerous "cocktails" that work and t is important to find one that will work for you and your situation. The first thing I would do is ask your training officer or Medical Director about it and see what their recommendations are.