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The Ultra-short & ultra-safe procedural block:  

3% 2-Chloroprocaine

maximum dose = 800-1000 mg (20-30mL of the 3% solution)

3% 2-Chloroprocaine for ultra-short blocks in the 60-90 minute range.  This is perfect for reductions or procedures where you would like a brief block.  As an ester rapidly metabolized in the blood ( <60 second half-life), the risk of toxicity is very very low.  This low toxicity allows safe use of a high concentration ( 3%) that likely contributes to the very fast onset of the block.

Use this med when you as the ED provider are in control of your time and the procedure.  It really does wash out quick, which is great if you completed the procedure, not so great if it wears off before you even get started!!!

 Example:  20ml interscalene brachial plexus block for shoulder reduction

Procedural block where 2-3 hours of surgical anesthesia is needed

1.5% Mepivacaine

Maximum dose = 5-6mg / kg (20mL 1.5% solution)

Intermediate potency amide perfect for those intermediate blocks when  a several hour window of surgical level anesthesia is needed.  Fast onset with 2-3 hours of dense surgical anesthesia.  Consultants can be unexpectedly delayed and it is very very disappointing to have a block wear off just as the procedure is starting.  Mepivacaine gives dense block and a nice window for this scenario.  Mepivacaine does not have a strong vasodilatory affect and is typically used without epinephrine.

Example: 20mL 1.5% Mepivacaine infraclavicular brachial plexus block for distal radius fracture reduction and splinting.

The safer alternative for a long block.  Hip fractures etc...
0.5% Ropivacaine (This means you need to dilute the 1% solution 1:1 with normal saline)

Maximum dose = 3mg / kg  ( no more than 300 mg total ~ 1 and 1/2 of the 1% 20mL bottles)

Ropivacaine is lipophilic amide structurally similar to bupivacaine with reduce cns and cardiovascular toxicity and some degree of preferential sensory blockade. It will produce a very long 6-8hours+ block.

It remains a powerful local anesthetic that should be used with caution.  You should have a sound understanding of the recognition and treatment of LAST with intralipid at hand.

Example: 40ml of 0.5% ropivacaine for hip fracture analgesia.

Remember, whenever doing blocks and especially if using bupivacaine or ropivacaine, Intralipid is your friend :)