Not Understanding Train-of-Four Use

[Pachinko]

I cannot find a clear description of how to use train of four and am unclear on the concept.

Everything I read says that you should block a pt so that 1/4 or 2/4 twitches are noted. However, that goal doesn't mean anything because you can raise the voltage as needed to increase the number of twitches. Also, presumably, most people have different thresholds for stimulation to begin with, so no single voltage serves as a baseline for everyone.

Does this even make sense?

[CNL2B]

Some of the TOFs at my facility do not have adjustable voltage. Of the ones that do, we turn the voltage all the way up (to 10 mA) and adjust based on the twitches from that. I have played with these a little bit and adjustment in the voltage from low to high still generates a twitch no matter where the voltage is at -- you get a stronger twitch (so it is easier to see) if you turn up the voltage, but if you are checking in the right location, the twitch is still there if the voltage is lower. At my facility, checking at 10 mA is the policy. Your facility should have a TOF policy that identifies exactly how you do it with your equipment.

If you can locate the ulnar nerve appropriately and place the device or electrodes correctly, I have not seen a big variation in stimulation thresholds between individuals -- 10 mA (or whatever the other brand that is not adjustable generates) typically works fine. Sometimes with extreme arm edema or diaphoresis you can have trouble, but otherwise if you know how to use your equipment, you are in good shape.

[detroitdano]

Hopefully whoever paralyzed the patient at the start of things did the TOF right, you get a baseline capture with a certain voltage and continue to use that voltage from there on out.

Increasing edema makes it tough, and most people who need paralysis are hit up bad so it's tough to get right.

From what I've read, Nimbex get dialyzed out so when you've got someone on CVVH it complicates things even more. Good times.

[baweRN]

At my facility, we have a protocol that requires the RN that initiates the TOF to locate and isolate two sites and record the voltage used to get the required number of twitches to use as a baseline. All the RNs after use the same voltage to assess whether the pt is adequately paralyzed or not.

[Nurse J in OH]

Definitely try to find the policy for your unit but I agree with the above... I was taught to chart the baseline placement and voltage to get 4/4 before initiating the treatment so that you can compare. You are correct that in theory you could ramp up the voltage and still get the twitches, but you should be testing at a consistent voltage (based on the unblocked response) so that the results are not artificial.

[marty6001, EdD, EMT-P, APRN]

You have to remember to get a baseline train of four before paralyzing the patient. If you don't get a baseline, the test is useless. And yes, it is a 4/4 TOF baseline. That way, when your drip is running, you use the same voltage and get your 1-2/4 twitches.