Mythbusters: Does Mixing Local Anesthetics Help Onset & Duration?

In this Mythbusters episode, we dig into the controversy around mixing two local anesthetics of differing pharmacodynamics in order to leverage the best qualities of both. Does this actually work? Watch this video to find out...

[@streen2000]

Thanks for the great video. However, I feel there's also a false dichotomy here. The mixing of 2 LAs within same perineural space (I agree that with ultrasound, we can get really close nowadays) can actually lead to dilution of the 2. The studies you quoted describe using x volume of mepi/lidocaine 1/1.5% with x volume of bupi 0.5%. If you poured these into a container in equal volumes, for instance, instead of injecting into a patient, you would get a 0.25% bupi mixture etc. Have there been any studies investigating mixing to achieve an effective volume of 1.5% lidocaine, for instance? I.e. 10 mls of 2% lidocaine with 10 mls 0.5% bupivacaine.

[@jam04pro]

Love regional anesthesia and love this Chanel:)

[@drcliff1983]

Great video as always! Thanks

[@yohaisteinberg4102]

Thank you very much for this video, truly eye opening.
I would like to know if anyone knows a way to comper equitoxic doses of different LA's?

[@MrLaurichu]

yes i am intersted to know the calculation of toxic dose of a mixture of LA

[@user-sb8zr7xk3t]

Thanks so much

[@intestinomedicino]

I´ve tried this with USG supraclavicular block and it holds true, using bupivacaine alone has way more duration that mixing it with lidocaine and have not seen too much onset difference, my mixture used to be 10cc of 2% lidocaine with 10cc of 0.5% bupivacaine, nowadays I use 20cc of 0.25 bupivacaine with a better duration of post operative analgesia.

[@quro86]

And the very same onset time? Full concentration of two LA vs 1 Local half concentration and same onset? that is against pharmacological mechanisms, local anesthetic mass has something to do in penetrating the nerve.
If you are talking about analgesia in a mixed anesthesia (GA plus block) that holds true, but for surgical anesthesia it sounds counterintuitive.

[@intestinomedicino]

@@quro86 onset is slightly longer by around 5 mins using 10cc of normal saline with 10cc of 0.5 bupivacaine (which makes the same concentration as 10cc of 2% lidocaine and 10cc of 0.5% bupivacaine) and 3 or my patients were discharge the next day with pain managed with paracetamol only, surgeries were performed around 8 to 9 PM, and were 2 distal radius fractures and 1 olecranon ages around 70 yo and sedation with fentanyl plus midazolam only, tbh I was a little nervous at first but everything worked .

[@quro86]

@@intestinomedicino arithmetically speaking it is the same concentration, but in one mixture you are diluting with water, and in other mixture you are diluting with another substance with biological activity. It’s not the same.
I’ll try it out.

[@sergioalbertodiazramirez1131]

So, it's better to use either Bupivacaine with epinefrin or lidocaine with epinefrin rather than the combination of these. isn't it?

[@uramalakia]

How about mixing ropivacaine with dexamethasone and dexmedetomidine? ;)

[@harounism]

FINALLY.

[@mikhailswartz]

👏🏾👏🏾👏🏾👏🏾👏🏾

[@JustPeaceLoveAndKindness]

Make it even more simpler, all your examples on slide at 6:56 don’t need or should move a great deal post-op. So, just use 0.5% Bupiv in all the blocks….unless there’s a shortage, then save the Bupiv for big procedures with higher pain potential post-op.

[@Radoblenc]

Yes, I'm going to stop mixing LA hereafter. Just 0.75% Ropivacaine 20cc with dexmeditomidine 25 mcg gives a good 12 -14 hours of LA but at the expense of delayed awakening in GA + brachial plexus block. Has anyone else observed this?

[@quro86]

What if you want a large volume of LA for regional anesthesia and you want to decrease de volume of the more toxic/longer action LA? i.e. Lidocaine to reduce the amount of bupivcaine/ropivacaine.