Chapter 39
- Neuromuscular Monitoring
- Jørgen Viby-Mogensen
Traditionally, the degree of neuromuscular block during and after
anesthesia is evaluated with clinical criteria alone. However, many studies have
documented that routine clinical evaluation of recovery of neuromuscular function
does not exclude clinically significant residual curarization.[1]
[2]
[3]
[4]
Therefore, there is a growing understanding that more attention should be paid to
objective monitoring of the degree of neuromuscular block during and after anesthesia
and to the problems of residual curarization.[5]
[6]
In awake patients, muscle power can be evaluated through tests
of voluntary muscle strength, but during anesthesia and recovery from anesthesia
this is not possible. Instead, the clinician uses clinical tests to assess muscle
power directly and to estimate neuromuscular function indirectly (muscle tone, the
feel of the anesthesia bag as an indirect measure of pulmonary compliance, tidal
volume, and inspiratory force). All of these tests, however, are influenced by factors
other than the degree of neuromuscular blockade. Therefore, whenever more precise
information regarding the status of neuromuscular functioning is desired, the response
of muscle to nerve stimulation should be assessed. This procedure also takes into
account the considerable variation in individual response to muscle relaxants.
This chapter reviews the basic principles of peripheral nerve
stimulation and the requirements for effective use of nerve stimulators. It also
describes the response to nerve stimulation during depolarizing (phase I and phase
II) and nondepolarizing neuromuscular blocks. Finally, this chapter discusses methods
of evaluating evoked neuromuscular responses both with and without the availability
of recording equipment.
