Continuous Adductor Canal Nerve Blocks: Relative Effects of a Basal Infusion v. Hourly Bolus Doses
Status:
Completed
Trial end date:
2014-12-01
Target enrollment:
Participant gender:
Summary
Patients usually experience moderate-to-severe pain following the knee replacement that is
often treated with a femoral nerve block (injection of numbing medicine placed around the
main nerve of the knee joint). To make the nerve block last longer, a tiny tube is often
placed next to the nerve and numbing medicine is infused for multiple days. However, while
the numbing medicine takes away pain, it also decreases sensations, muscle strength, and
proprioception (knowing where the leg is in space without looking at it) which greatly
increases the risk of falling. Since falling can be catastrophic following major surgery, a
femoral nerve blocks are being phased out by surgeons and anesthesiologists. The
most-promising replacement is called an adductor canal nerve block. For this new type of
block, a perineural catheter is inserted into a small canal in the middle of the upper leg.
This canal contains the sensory nerve fibers leading to the knee, and only a single nerve
that serves a relatively small muscle. Multiple studies have demonstrated a dramatic increase
in muscle strength using the new adductor canal block compared with the traditional femoral
block. However, practitioners perceptions of the new block is that it provides insufficient
pain control following knee arthroplasty, even though all of the sensory nerves affected with
the femoral block are also-theoretically-affected with the adductor canal block. One reason
for this difference may be the small canal of the latter which is a relatively tight area in
which the numbing medicine might not spread particularly well (due to pressure from
surrounding tissues). One way to possibly counter this issue is by providing repeated boluses
of the numbing medicine that will improve the medicine's spread relative to a
more-traditional slow, continuous ("basal") infusion. This study seeks to compare these two
techniques of medication administration through perineural adductor canal catheters:
Our primary aim is to test the hypothesis that, for continuous adductor canal blocks,
providing local anesthetic as repeated, hourly bolus doses results in an increased sensory
block compared with providing local anesthetic as a continuous basal infusion at an
equivalent hourly dose.
As a secondary aim, we hypothesize that, for continuous adductor canal blocks, providing
local anesthetic as repeated, hourly bolus doses results in either equivalent or less motor
block compared with providing local anesthetic as a continuous basal infusion at an
equivalent hourly dose.