Understanding Anesthesiology - The Global Regional Anesthesia ...

Peripheral nerve stimulator
A peripheral nerve stimulator is used to assess neuromuscular transmission when neuromuscular
blocking agents (NMBA) are used. The careful assessment of the depth of neuromuscular
blockade allows the anesthesiologist to provide appropriate relaxation to facilitate surgery
(when required) and to time the deliver of NMBA and their reversal agents to ensure
the adequate return of muscle strength on emergence.
Typically, the peripheral nerve stimulator is used to deliver 4 successive electrical stimuli (2
per second) to a superficial peripheral nerve such as the median or facial nerve. The anesthesiologist
will observe the number of twitches that the muscle produces and whether there is
“fade” associated with those twitches. Fade is the successive decrease in amplitude of each
twitch. The presence of less than four twitches or the presence of four twitches with fade provide
evidence of residual neuromuscular blockade.
A patient could have 70% of his acetylcholine (Ach) receptors blocked and still register four
equal twitches! It is for this reason that the limits of the peripheral nerve stimulator must be
understood: it is specific but not sensitive for the presence of neuromuscular blockade. The
most reliable indicators of the return of muscle strength are clinical ones: grip strength, head
lift, ability to generate an adequate tidal volume and strong cough.
Related Glossary Terms
Anticholinesterase, Neuromuscular junction, Non-depolarizing muscle relaxants, Residual
block
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Chapter 2 - Anesthetic Equipment and Monitoring
Chapter 3 - General Anesthesia
Chapter 3 - General Anesthesia