There's no local anesthetic with a short onset and a long duration.
And mixing doesn't work.
If you need a fast onset, I'd do the block with 2% lidocaine or 1.5% mepivacaine.
If you also need a long duration, you can either then put in a catheter and bolus it with long acting LA later, or, just wait the 20-30 mins for onset. Or, have your surgeon supplement at the beginning.
Once worked with a dumb hand surgeon who wanted quickly-performed and long acting blocks but also to be able to cut 8-10 minutes after block completion. This dummy literally deemed every block a failure because, surprise, he had to supplement at incision. No matter how many times you explained the above concepts, he persisted. Not fun.
Anesth Analg. 2011 Feb;112(2):471-6. doi: 10.1213/ANE.0b013e3182042f7f. Epub 2010 Dec 14.
The effect of mixing 1.5% mepivacaine and 0.5% bupivacaine on duration of analgesia and latency of block onset in ultrasound-guided interscalene block.
Gadsden J1, Hadzic A, Gandhi K, Shariat A, Xu D, Maliakal T, Patel V.
Author information
Abstract
BACKGROUND:
Short- and long-acting local anesthetics are commonly mixed to achieve nerve blocks with short onset and long duration. However, there is a paucity of data on advantages of such mixtures. We hypothesized that a mixture of mepivacaine and bupivacaine results in a faster onset than does bupivacaine and in a longer duration of blockade than does mepivacaine.
METHODS:
Sixty-four patients undergoing arthroscopic shoulder surgery (ages 18 to 65 years; ASA physical status I-II) with ultrasound-guided interscalene brachial plexus block as the sole anesthetic were studied. The subjects were randomized to receive 1 of 3 study solutions: 30 mL of mepivacaine 1.5%, 30 mL of bupivacaine 0.5%, or a mixture of 15 mL each of bupivacaine 0.5% and mepivacaine 1.5%. The block onset time and duration of motor and sensory block were assessed.
RESULTS:
Onset of sensory block in the axillary nerve distribution (superior trunk) was similar among the 3 groups (8.7 ± 4.3 minutes for mepivacaine, 10.0 ± 5.1 minutes for bupivacaine, and 11.3 ± 5.3 minutes for the combination group; P = 0.21 between all groups). The duration of motor block for the combination group (11.5 ± 4.7 hours) was between that of the bupivacaine (16.4 ± 9.4 hours) and mepivacaine (6.0 ± 4.2 hours) groups (P = 0.03 between bupivacaine and combination groups; P = 0.01 between mepivacaine and combination groups). Duration of analgesia was the shortest with mepivacaine (4.9 ± 2.4 hours), longest with bupivacaine (14.0 ± 6.2 hours), and intermediate with the combination group (10.3 ± 4.9 hours) (P < 0.001 for mepivacaine vs. combination group; P = 0.01 for bupivacaine vs. combination group).
CONCLUSIONS:
For ultrasound-guided interscalene block, a combination of mepivacaine 1.5% and bupivacaine 0.5% results in a block onset similar to either local anesthetic alone. The mean duration of blockade with a mepivacaine-bupivacaine mixture was significantly longer than block with mepivacaine 1.5% alone but significantly shorter than the block with bupivacaine 0.5% alone.
