Week #13 as a CRNA Student- I’m Going to Cut You- Don’t Move!

by admin

Introduction to Neuromuscular Blockers

NMB= Neuromuscular Blocker= Paralytics= Muscle Relaxants= Your Patient Isn’t Going to Move (Hopefully!)

When do you use them?

Apparently, we use NMB’s more now than we used to.  We used to use them for cases where the patient’s breathing would interfere with the operation, like in the open chest cardiac & lung cases.  I can imagine it’s pretty hard to operate on a moving target!  Now we use them more frequently because we want most of our patients to be immobile.  A patient can be completely unconscious and still move limbs in response to noxious stimuli.  One of our professors jokes that you wouldn’t want the patient to reach up and hand you a retractor.  Ahh…Anesthesia humor!

What are they called?

If you’ve been an ICU RN, you might be familiar with some of the drugs.  The most commonly used relaxants are Rocuronium (Zemuron), Vecuronium (Norcuron), Cisatracurium (Nimbex), and Succinylcholine (Anectine).  The shortest acting drug we use is Succinylcholine and it is most commonly used during induction for intubation purposes.  Roc, Vec, and Nimbex are titrated for muscle relaxation during the procedure.

How do you give NMB’s?

NMB’s are given IV and are titrated to peripheral nerve stimulator (PNS) response.  The PNS is usually placed over the ulnar nerve or the facial nerve.  If you remember the next two sentences I write- you will inevitably earn exam points and board points at some point in your career.

The facial nerve is a more accurate determinate of diaphragm paralysis during induction and when placed properly it stimulates the orbicularis oculi muscle.  The ulnar nerve is a more accurate determinate of muscle relaxant reversal during emergence and it stimulates the adductor pollicis muscle.  There you go- 2 points.

The reason why one is better for induction and one is better for emergence has to do with the distribution of blood flow and also the sequence of paralysis.  When you give IV paralytic it works from the head down; Face, extremities, torso, abdominal muscles and lastly the diaphragm.  The eyelids are the easiest muscle to paralyze and the diaphragm is the hardest.

What’s the goal?

The ultimate goal is to the keep the patient 95% paralyzed.  This will keep the patient immobile for any type of surgery.  However, since we are able to reverse the paralytics with Neostigmine, we can get a patient 100% paralyzed and still have some extra drug floating around in the blood stream.  If you aren’t familiar with receptors, by the time you graduate CRNA school you will be!  There are ALOT of different receptors in our body.  The paralytics work in the neuromuscular junction and block Acetylcholine (ACh) from attaching to the muscle receptor which would result in a contraction (and hence, a moving unconscious patient).  So when a drug like Rocuronium is given in an appropriate dose, it blocks all of the receptors and whatever is left floats around in the blood.  Obviously, we want as little EXTRA drug floating around because at the end of the case we need the patient to breathe spontaneously and protect their airway so they can be extubated.

Quick note on Non-Depolarizers vs Depolarizers

Succinylcholine is the only depolarizing muscle relaxant that we use.  It is called depolarizing because when it binds to the ACh receptor, it does exactly what ACh does and makes the muscle depolarize (contract).  BUT, it doesn’t get metabolized as quickly as ACh so the muscle only contracts once and then remains blocked.  This initial depolarization is referred to as a fasiculation.  You will see your patient start to twitch from head to toe because each muscle contracts once on the way down the body.  Non-depolarizers work by blocking ACh from activating the receptor so you will not see the initial fasiculation.  *Fasiculations are more apparent in muscular individuals.  I’m only tell you that so I have an excuse to put this next photo in.

 That wraps it up for Week 13!  Do you have experience using NMB’s in clinicals or any advice for us learners while we explore using the peripheral nerve stimulator?  We’d love to read your questions and comments below!




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