I had shoulder surgery yesterday. Prior to the procedure an anesthetist performed a nerve block. It’s been 16 hours and I still cannot feel or move my arm. I am just now starting to be able to wiggle my fingers.
I don’t understand how the anesthesia can last so long. I saw the needle with the medication and there really wasn’t much of it. How is the medication not quickly carried away from the injection site?
Thank you in advance!
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How anaesthesia works is actually somewhat of a mystery. We know it does work, but in a lot of cases, we are just guessing at the correct amount to give based on previous successes and failures. So, the anesthesiologist has to use knowledge of your body mass, like metabolic rate, and other factors to hopefully hit the sweet spot. I haven’t read any current research on this for a while, though, so maybe depending on the anaesthesia you were given more can be said
They used a kind of medication called a Sodium Channel Blocker. These work by stopping the nerves from being able to send signals back to the nervous system. You only need a really small amount in the right spot to block these signals.
You can think of it like freezing a water pipe. You don’t need to freeze all of the pipe to stop the flow, just a small section. As time goes on, the ice melts and the flow returns.
Much like freezing water, how long it will last can vary from person to person. Some people are more sensitive to these medications and take a longer time to clear them out of their system. The amount of circulation to the area, amount of medication used and specific nerve can also be factors in the duration of action.
For surgeries like this, it is better to overshoot duration than have it wear off early, so a long-acting medication like bupivacaine or ropivacaine will be used. When you inject these directly into and around the nerve, they “hang out” there for quite a while. The areas around nerves can create little pockets of medication that slowly works it’s way into the nerve.
We pick our spots carefully as well. Knowing just where to inject a local anaesthetic is really important. The best places are easy to access and away from any major blood vessels.
The specific answer depends on which medicine you received.
Different medicines last longer than others.
Longer lasting medicines are ones like bupivicaine, which lasts from 8-18 hours. The specific time depends on the amount you got and the rate at which you break it down.
There is another version of bupivicaine which is bound to fat membranes (liposomes). This one lasts up to 72 hours.
Can’t move it? Hmm… that’s a little funky, but could be the swelling.
I had shoulder surgery in April (Bicep Tenodesis and AC joint decompression) and they loaded me up with the nerve block; lasted like 24-36 hours, it was awesome until it wore off. I could move everything though, well as much as you want to right after surgery.
Sounds like yours is starting to wear off; have the pain meds ready. Probably by the end of today/tomorrow it’ll be worn off and you’ll be wishing it was still there.
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