Triple-blind randomized clinical trial of time until sensory change using 1.5%
mepivacaine with epinephrine, 0.5% bupivacaine, or an equal mixture of both for
infraclavicular block.
Author(s): Laur JJ, Bayman EO, Foldes PJ, Rosenquist RW.
Affiliation(s): Department of Anesthesia, University of Iowa, Roy J. and Lucille A. Carver
College of Medicine, Iowa City, IA 52242, USA. john-laur@uiowa.edu
Publication date & source: 2012, Reg Anesth Pain Med. , 37(1):28-33
BACKGROUND AND OBJECTIVES: Practitioners mix faster-onset, intermediate-duration
local anesthetics (LAs) with slower-onset, long-duration LAs to get fast
peripheral nerve block (PNB) onset and long duration. We hypothesized that 1.5%
mepivacaine (with epinephrine) (mepivacaine) or 1.5% mepivacaine (with
epinephrine) mixed with 0.5% bupivacaine (mixed) would reduce PNB sensory onset
by 20% or more versus 0.5% bupivacaine alone (bupivacaine).
METHODS: Patients (n = 93) having arm surgery were randomized to 1 of the 3 LA
groups. Infraclavicular PNB was administered using 1 of 3 LAs; afterward, PNB
sensory (motor) onset, duration, and other outcomes were assessed. Subjects,
physicians, and the biostatistician were blinded until study completion.
RESULTS: Median (interquartile range) PNB sensory onset (in minutes) was as
follows: mepivacaine, 3 (3-6); mixed, 6 (3-6); and bupivacaine, 6 (3-12) (P =
0.0085). Mepivacaine PNB sensory onset was not faster than mixed (P = 0.57), but
mixed was faster than bupivacaine (P = 0.0035). More mixed group patients
achieved PNB sensory onset (0.81) versus the bupivacaine group (0.54) at 6 mins.
Median (interquartile range) PNB motor onset (in minutes) was as follows:
mepivacaine, 15 (12-18); mixed, 17 (12-21); and bupivacaine, 21 (12-24) (P <
0.0001). Median sensory and motor PNB duration (in minutes) was as follows:
mepivacaine, 281 and 320; mixed, 439 and 556; and bupivacaine, 850 and 1109.
Sensory (motor) PNB duration was shorter with mepivacaine versus mixed (P <
0.0001, P = 0.034), and mixed was shorter versus bupivacaine (P = 0.0243, P =
0.034).
CONCLUSIONS: Mixing 1.5% mepivacaine (with epinephrine) with 0.5% bupivacaine
speeds up PNB sensory (motor) onset compared with 0.5% bupivacaine alone.
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