Neuromuscular Monitoring in the Perioperative Period



  • Neuromuscular monitoring devices were introduced into clinical practice in the 1970s
  • Qualitative neuromuscular monitors, or peripheral nerve stimulators, provide an electrical stimulus to a motor nerve and the response of corresponding muscle subjectively evaluated
  • MC (nerve + muscle) monitored: Ulnar nerve + Adductor pollicis.

Train of four (TOF):


  • When train of four monitoring is used continuously, each set of stimuli is normally repeated every 10th to 20th second
  • These sets are called trains because their shape bears the resemblance of a train
  • Each stimulus in the train causes the muscle to contract, and ‘fade’ in the response provides the basis for evaluation.

Normal monitoring:

  • Frequency of stimuli: 2 Hz = 2 stimuli/ sec
  • Time gap between 2 stimuli = ½ = 0.5 sec
  • Time gap between 2 TOF = 10-20 sec.

Application of Non-Depolarizing Muscle Relaxants (NDMR):

  • Characterized by ‘fade‘ response

Application of Depolarizing Muscle Relaxants (NDMR):

  • Fade response is absent
  • T4/T1 ~ 1.

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