Electromyographic Monitoring and Postoperative Recovery



Status:Recruiting
Healthy:No
Age Range:18 - 90
Updated:3/30/2019
Start Date:March 26, 2019
End Date:February 28, 2021
Contact:Glenn S Murphy, MD
Email:dgmurphy2@yahoo.com
Phone:847-570-2760

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Residual neuromuscular blockade (weakness) is a common occurrence in the postanesthesia care
unit when muscle relaxant drugs have been used in the operating room. The only method of
reliably detecting residual neuromuscular blockade is through the use of quantitative
neuromuscular monitors. These devices measure and quantify the degree of muscle weakness and
display the results on a screen. When using train-of-four (TOF) nerve stimulation, the ratio
of the fourth muscle contraction (twitch) to the first twitch will be displayed; when this
ratio is 90% (or 0.9) or greater, full recovery of muscle strength is present, and the
endotracheal tube can be safely removed. At the present time, there is only one commercially
available quantitative monitor produced in the United States -the TOF-Watch. The TOF-Watch is
not used by many clinicians because it requires experience to obtain accurate results, is
expensive, and is subject to interference by factors in the operating room. The aim of this
investigation is to examine a new quantitative monitor (the TetraGraph, an electromyography
(EMG) device) in the clinical setting. Patients will be randomized to receive either
electromyography monitoring (EMG group-using the TetraGraph) or qualitative peripheral nerve
stimulator monitoring (PNS group-the standard type of neuromuscular monitoring used at
NorthShore University HealthSystem). The primary endpoint of the investigation is the
incidence of postoperative residual blockade (defined as a TOF ratio < 0.9 with TOF-Watch,
the current "gold standard quantitative monitor). Secondary endpoints include a variety of
standard clinical recovery variables.

Although anesthesiologists recognize that residual neuromuscular block can adversely affect
postoperative recovery, a high percentage of patients continue to arrive in the PACU with TOF
ratios < 0.9. An important reason this problem occurs is that anesthesiologists rarely use
quantitative neuromuscular monitoring in the operating room. In current anesthesia practices,
clinicians typically use standard peripheral nerve stimulators (qualitative neuromuscular
monitors) and / or clinical tests of muscle strength to detect residual muscle weakness at
the end of surgical procedures. Qualitative nerve stimulators/monitors are routinely used in
the operating rooms; TOF electrical stimuli are applied to a peripheral nerve, and the
contractions of the innervated muscle observed. However, visual or tactile assessment of TOF
stimulation using these monitors is only effective in detecting profound levels of muscle
weakness (TOF ratios < 0.4) Therefore, qualitative nerve stimulators are unable to reliably
detect clinically relevant neuromuscular block (TOF ratios of 0.5-0.9). Clinical assessment
of patients for signs of muscle weakness (head-lift, hand squeeze) is also an insensitive
method of detecting residual neuromuscular block, since many patients can perform these tests
with TOF ratios as low as 0.5.

In order for clinicians to reliably exclude residual neuromuscular blockade, quantitative
neuromuscular monitoring should be used. At the present time, only one stand-alone
quantitative monitor has been produced for clinical use, the TOF-Watch (Blue Star
Enterprises, Chanhassen, Minnesota-no longer manufactured). This technology
(acceleromyography (AMG)) uses a piezoelectric crystal to sense the acceleration of muscle
contractions, and converts this data into a displayed TOF ratio (0-100%). Although the use of
the TOF-Watch has been demonstrated to reduce the risk of residual blockade, the routine
application of this monitor by clinicians has been limited by a number of factors, related to
complexity of use in the operating room.. There is an urgent need for an easy-to-use and
accurate quantitative neuromuscular monitor in the clinical setting. Recently, a new device
has been developed that uses electromyography (EMG) technology to assess recovery of muscle
function in the clinical setting (the TetraGraph). This EMG device measures electrical
activity (compound muscle action potentials) following nerve stimulation (usually at the
thenar eminence after ulnar or median nerve stimulation). When TOF stimuli are provided, this
data is then converted to a measurable TOF ratio (from 0-1.0 or 0-100%). In a study completed
at NorthShore University HealthSystem, the investigators compared the applicability (ease of
use, equipment need, etc.), repeatability (precision or internal consistency), and
performance (agreement with established standard, bias) of this EMG technology to the
TOF-Watch (the current clinical "gold standard" quantitative neuromuscular monitor). The
subsequent analysis suggested that EMG monitoring accurately measures onset and recovery of
neuromuscular function in the operating room.

The use of quantitative neuromuscular monitoring in the operating room should allow for more
rational management of dosing and reversal of NMBAs. Furthermore, if incomplete neuromuscular
recovery is detected at the end of a surgical procedure, tracheal extubation can be delayed
until full recovery of muscle strength has occurred. Therefore, fewer patients should leave
the operating room with muscle weakness, and the risks/complications of residual blockade in
the PACU reduced. The aim of this clinical investigation is to determine whether EMG
monitoring in the operating room reduces the incidence of postoperative residual blockade
(measured at the time of tracheal extubation and on arrival to the PACU). During the PACU
admission, patients will also be assessed for potential complications related to incomplete
neuromuscular recovery (signs and symptoms of muscle weakness, episodes of hypoxemia and
airway obstruction, prolonged PACU length of stay). Patients will be randomized to receive
either electromyography monitoring (EMG group-TetraGraph) or qualitative peripheral nerve
stimulator monitoring (PNS group) in the operating room. The primary endpoint is the
incidence of postoperative residual block (defined as a TOF ratio < 0.9 with the TOF-Watch
monitor). Secondary endpoints include a variety of clinical recovery variables listed below.

Inclusion Criteria: American Society of Anesthesiologists Status I - III patients
undergoing surgery requiring neuromuscular blockade

Exclusion Criteria:

presence of an underlying neuromuscular disease; use of drugs known to interfere with
neuromuscular transmission (antiseizure medications, anticholinesterases, magnesium
sulfate); renal insufficiency (serum creatinine > 1.8 mg/dL) or renal failure.
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Phone: 847-570-2760
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