train of four

I work on a Trauma/Surgical ICU and generally it's the head injuries that are on Vecuronium that require checking the TOF. The vec keeps them from moving around and increasing their ICP. The electrodes are placed along the ulnar nerve near the wrist and you're trying to maintain 1-2 twitches. They are also usually on versed and morphine for pain and sedation management. the black terminal is closest to the wrist with the red terminal closest to the body. Eye care is important, we use lacrilube. Sorry not real technical explanation but I like to keep it simple.

Do you check for a reflex response, or what?

What is the four in the term train of four?

Well before you start the med (vec in this case) you establish a baseline of how much mA (milliamps) it takes to elicit a response from the patient. By response I mean that the stimulator applies 4 electical impulses in rapid succession and normally this would cause the thumb to abduct and your little fingers to flex with each impulse. Your goal is to titrate the vec so that you are only getting 1-2 twitches. hope that makes sense.

Does anyone know of a website that has a picture of the train of four?

Thank you for the reply. I really appreciate the response.

Yep, makes sense, thank you.

Hey!!!

Well, as mentioned--'train of four' is used to evalute how deeply paralysed your Pt is. How's it do that?

The curare type meds work by blocking the synapse that occurs at the junction of nerve cells and muscle cells. (Which is why we also give pain meds and anxiety-amnesia meds like fentanyl and versed--because the Pt is not unconscious. Their neurons are communicating with other neurons just fine.)

Now the more of the curare-type drugs you give--the more completely you block the synapses, OK? So you might be giving too little--and the ICP will be higher that you want or the Pt will be fighting the Vent. Or you might be giving too much and the Pt is like yesterday's noodles--which is not what we're aiming at.

So we put the T-O-F machine onto their ulnar nerve like Monkeyman said and push the START button and the machine gives a set of 4 (duh!) small shocks into the nerve. The first shock is tiny; the second a little bigger; the third bigger still--and you guessed the fourth is the biggest. (I googled around a bit but didn't find how many milli-amps are involved--but it doesn't matter. They're small little shocks.)

You will gently hold your Pt's hand and feel his thumb and the number of twitches that the T-O-F produces is the result of the procedure. If it's four twitches--increase the paralytic a bit, then recheck in a couple of minutes. If no twitch occurs--decrease the paralytic, then recheck in a couple of minutes. Your goal is two or three responses.

Different units have different ways to chart this and different intervals that it has to be done in. I'm accustomed to doing a TOF q1h on paralysed Pts.

Hope that helps

Papaw John

Thank you for the information. Does anyone know why steroids are contraindicated with paralytics? How do steroids and paralytics interact to cause a adverse reaction? I really appreciate all this information. It is very helpful.

papawjohn, thanks for the reply. I enjoy reading your posts as well as those of the other more experienced nurses on this forum, it really helps me at work. I used to work in Jacksonville, fl with a john that I think used to go by your moniker, wondered if you might be one and the same.

papawjohn, thanks for the reply. I enjoy reading your posts as well as those of the other more experienced nurses on this forum, it really helps me at work. I used to work in Jacksonville, fl with a john that I think used to go by your moniker, wondered if you might be one and the same.

OOPs, hit the button twice

Hey Y'all!!!

Thank you so much for the kind words. Here's my 'thing'--lots of nurses feel dumb. But they aren't--they just haven't had an explanation that make sense to them. I have a 'visual' sort of learning, myself--and if once I can get a 'picture' of a procedure or physiological event, then I've got it forever. I think many of us are the same way.

I've never lived in Jacksonville. Spent a couple of weeks there fixing my sailboat once--a long story for another time. (The telling of if is improved if we can have a couple of cold beers as the saga progresses.) And 'Papaw' is Appalachian for 'Grandpa'--my grandson named me.

But back to business--are paralytics and steroids contraindicated? I didn't remember that. My memory doesn't extend to specifically recalling that I've given (say) q6h Solumedrol and Norcuron at the same time but I know I never heard it was specifically wrong. Hum. I give up on that---will pay attention to any response from someone more current.

Papaw John

If you use paralytics and TOF to assess the effectiveness of these drugs, you should have a policy in your unit. I know myself, we don't use them that often, so I would have to look it up before I started a paralytic with TOF. As others have mentioned, you titrate your paralytic based on the number of twitches you see when the patient's nerve is stimulated. The number of twitches corresponds to the percentage of nerves blocked. I can't remember the exact percentages, but for a rough estimate, if you get 4 twitches, then you have 0% blocked (not enough paralytic), with zero twitches you would have 100% blockage (way too much paralytic), with three twitches I think it is around 25% blocked. I think most facilities want 2 or 3 twitches.

As PapawJohn mentioned, always, always make sure your patient has something for sedation and pain administered. It is cruel to use a paralytic and not sedate or give analgesics. The patient is aware and conscious of their surroundings, they just can't move anything, imagine how helpless and scary that would be. When I was a new nurse on orientation, we took report from a nurse who had taken care of the patient on norcuron gtt and didn't sedate or give anything for pain. When my preceptor asked her why not, her response was "well, he didn't squeeze my hand that he was hurting". Duh, because he is paralyzed. When we stopped the gtt early that morning after extubation, he was freaking out because he thought he had a car wreck and was paralyzed! Always communicate with your patient what is going on. Don't assume they can't understand you or they've already been told.

Thank you for the information. Does anyone know why steroids are contraindicated with paralytics? How do steroids and paralytics interact to cause a adverse reaction? I really appreciate all this information. It is very helpful.

I just learned this yesterday from a coworker. She said there is a risk of peripheral demyelination when paralytics and steroids are used together.