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NEUROMUSCULAR MONITORING 
Dr.Malini Joshi 
Dr.Deepak Chavan
Objectives of NM Monitoring 
• Onset of NM Blockade. 
• To determine level of muscle relaxation during 
surgery. 
• Assess...
Why do we Monitor? 
Residual post-op NM Blockade 
– Functional impairment of pharyngeal and 
upper esophageal muscles 
• I...
Who should be Monitored ? 
• Patients with severe renal, liver disease 
• Neuromuscular disorders like myasthenia 
gravis,...
Various ways of nerve 
stimulation 
• Electrical: Most commonly used in 
clinical practice. 
• Magnetic: Less painful and ...
Principles of Peripheral Nerve 
Stimulation 
• Each muscle fiber to a stimulus follows an all-or- 
none pattern 
• Respons...
Essential features of PNS 
• Shape of stimulus should be monophasic and 
rectangular i.e Square-wave stimulus. 
• 0.2- 0.3...
• Current intensity : It is the amperage (mA) of 
the current delivered by the nerve 
stimulator(0-80 mA). The intensity r...
• Threshold current : It is the lowest current required 
to depolarize the most sensitive fibres in a given nerve 
bundle ...
Electrodes 
• Surface electrodes 
• Pregelled silver chloride surface electrodes for transmission 
of impulses to the nerv...
POLARITY 
• Stimulators produce a direct current by using 
one negative and one positive electrode 
• Should be indicated ...
VARIOUS SITE USED FOR NM MONITORING 
• Ulnar nerve: MOST COMMON 
SITE 
• place negative electrode 
(black) on wrist in lin...
• Facial nerve: place 
negative electrode 
(black) by ear lobe and 
the positive (red) 2cms 
from the eyebrow 
(along faci...
• Posterior tibial nerve: 
place the negative 
electrode (black) over 
inferolateral aspect of 
medial malleolus (palpate ...
Patterns of Stimulation 
• Single-Twitch Stimulation 
• Train-of-Four Stimulation 
• Tetanic Stimulation 
• Post-Tetanic C...
Single-Twitch Stimulation 
• Single supramaximal stimuli applied to a nerve 
at frequencies from 1.0Hz-0.1Hz 
• Height of ...
• Used to assess potency of drugs 
• Useful before induction to determine level at 
which supramaximal stimulus obtained 
...
Single-Twitch Stimulation
Train-of-Four Stimulation 
• Four supramaximal stimuli are given every 0.5 sec 
• “Fade” in the response provides the basi...
Train-of-Four Stimulation
Tetanic Stimulation 
• Tetanic Stimulation is 50-Hz stimulation given for 5 sec 
• During tetanus, progressive depletionof...
Tetanic Stimulation
Post-Tetanic Count Stimulation 
• Mobilization and enhanced synthesis of acetylcholine 
continue during and after cessatio...
Post-Tetanic Count Stimulation
Double-Burst Stimulation 
• DBS consist of two train of three impulses at 
50Hz tetanic stimulation separated by 750msec 
...
Double-Burst Stimulation
Non-depolarizing blockade 
• Intense NM Blockade 
• This phase is called “Period of no response” 
• Deep NM Blockade 
• De...
Contd… 
• Recovery 
• Return of 4th response to TOF heralds recovery phase 
• presence of spontaneous respiration is not a...
Depolarizing NM Blockade 
• Phase I block 
• Response to TOF or tetanic stimulation does not 
fade, and no post-tetanic fa...
Visual or tactile: 
Not sensitive enough to exclude 
possibility of residual neuromuscular 
blockade. Fade is usually unde...
Recording devices for measuring 
NM Function 
• Compound muscle action potential: It 
is the cumulative electrical signal ...
Electromyogram (EMG) 
• It records the compound MAP via recording electrodes placed 
near the mid portion or motor point o...
Mechanomyographic device 
(isometric) 
(Adductor pollicis force translation monitor) 
• Quantifies the force of isometric ...
Accelerography 
(non isometric) 
• This technique uses a miniature piezoelectric transducer to 
determine the rate of angu...
Clinical tests of Postoperative 
Neuromuscular Recovery 
Reliable Unreliable 
Sustained head lift for 5 sec Sustained eye ...
Limitations of NM Monitoring 
• Neuromuscular responses may appear normal 
despite persistence of receptor occupancy by 
N...
THANK YOU !
NEUROMUSCULAR MONITORING
NEUROMUSCULAR MONITORING
NEUROMUSCULAR MONITORING
NEUROMUSCULAR MONITORING
NEUROMUSCULAR MONITORING
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NEUROMUSCULAR MONITORING

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NEUROMUSCULSR MONITORING

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NEUROMUSCULAR MONITORING

  1. 1. NEUROMUSCULAR MONITORING Dr.Malini Joshi Dr.Deepak Chavan
  2. 2. Objectives of NM Monitoring • Onset of NM Blockade. • To determine level of muscle relaxation during surgery. • Assessing patients recovery from blockade to minimize risk of residual paralysis.
  3. 3. Why do we Monitor? Residual post-op NM Blockade – Functional impairment of pharyngeal and upper esophageal muscles • Impaired ability to maintain the airway • Increased risk for post-op pulmonary complications • Difficult to exclude clinically significant residual curarization by clinical evaluation
  4. 4. Who should be Monitored ? • Patients with severe renal, liver disease • Neuromuscular disorders like myasthenia gravis, myopathies, UMN and LMN lesions • Patients with severe pulmonary disease or marked obesity • Continuous infusion of NMBs or long acting NMBs • Long surgeries or surgeries requiring elimination of sudden movement • Surgeries requiring profound NM blockade
  5. 5. Various ways of nerve stimulation • Electrical: Most commonly used in clinical practice. • Magnetic: Less painful and does not require physical contact with body.
  6. 6. Principles of Peripheral Nerve Stimulation • Each muscle fiber to a stimulus follows an all-or- none pattern • Response of the whole muscle depends on the number of muscle fibers activated • Response of the muscle decreases in parallel with the numbers of fibers blocked • Reduction in response during constant stimulation reflects degree of NM Blockade • For this reason stimulus is supramaximal
  7. 7. Essential features of PNS • Shape of stimulus should be monophasic and rectangular i.e Square-wave stimulus. • 0.2- 0.3 msec duration so it falls within absolute refractory period of motor unit in the nerve. • Constant current variable voltage • Battery powered. • Digital display of delivered current. • Audible signal on delivery of stimulus. • Audible alarm for poor electrode contact. • Multiple patterns of stimulation (single twitch,train-of-four, double-burst, post-tetanic count).
  8. 8. • Current intensity : It is the amperage (mA) of the current delivered by the nerve stimulator(0-80 mA). The intensity reaching the nerve is determined by the voltage generated by the stimulator and resistance and impedance of the electrodes, skin and underlying tissues. • Nerve stimulators are constant current and variable voltage delivery devices. • Reduction of temperature increases the tissue resistance (increased impedance) and may cause reduction in the current delivered to fall below the supramaximal level
  9. 9. • Threshold current : It is the lowest current required to depolarize the most sensitive fibres in a given nerve bundle to elicit a detectable muscle response. • Maximal current:current which generate response in all muscle fibre • Supramaximal current : • It is approximately 25% higher intensity than the current required to depolarize all fibres in a particular nerve bundle. This is generally attained at current intensity 2-3 times higher than threshold current. • Submaximal current : A current intensity that induces firing of only a fraction fibres in a given nerve bundle. A potential advantage of submaximal current is that it is less painful than supramaximal current. • Stimulus frequency : The rate (Hz) at which each impulse is repeated in cycles per second (Hz).
  10. 10. Electrodes • Surface electrodes • Pregelled silver chloride surface electrodes for transmission of impulses to the nerves through the skin • Transcutaneous impedance reduced by rubbing • Conducting area should be small(7-11mm) • Needle electrodes • Subcutaneous needles deliver impulse near the nerve • Require less current
  11. 11. POLARITY • Stimulators produce a direct current by using one negative and one positive electrode • Should be indicated on the stimulator • Maximal effect is achieved when the negative electrode is placed directly over the most superficial part of the nerve being stimulated • The positive electrode should be placed along the course of the nerve, usually proximally to avoid direct muscle stimulation
  12. 12. VARIOUS SITE USED FOR NM MONITORING • Ulnar nerve: MOST COMMON SITE • place negative electrode (black) on wrist in line with the smallest digit 1-2cm below skin crease • positive electrode (red) 2- 3cms proximal to the negative electrode • • Response: Adductor pollicis muscle – thumb adduction
  13. 13. • Facial nerve: place negative electrode (black) by ear lobe and the positive (red) 2cms from the eyebrow (along facial nerve inferior and lateral to eye) • • Response: Orbicularis occuli muscle – eyelid twitching
  14. 14. • Posterior tibial nerve: place the negative electrode (black) over inferolateral aspect of medial malleolus (palpate posterior tibial pulse and place electrode there) and positive electrode (red) 2- 3cm proximal to the negative electrode • • Response: Flexor hallucis brevis muscle – plantar flexion of big toe
  15. 15. Patterns of Stimulation • Single-Twitch Stimulation • Train-of-Four Stimulation • Tetanic Stimulation • Post-Tetanic Count Stimulation • Double-Burst Stimulation
  16. 16. Single-Twitch Stimulation • Single supramaximal stimuli applied to a nerve at frequencies from 1.0Hz-0.1Hz • Height of response depends on the number of unblocked junctions • Prerelaxant control response is noted & compared with subsequent responses • Response will only be depressed when NM blocker occupies 75% receptor
  17. 17. • Used to assess potency of drugs • Useful before induction to determine level at which supramaximal stimulus obtained • Useful to determine onset of NM block • In both depolarising & non depolarising blocks there is progressive decrease in twitch height • So can not differentiate between depolarising & non depolarising NM blocker • Major limitation is need to measure control twitch before NM blocker i.e. prerelaxant control response is necessary
  18. 18. Single-Twitch Stimulation
  19. 19. Train-of-Four Stimulation • Four supramaximal stimuli are given every 0.5 sec • “Fade” in the response provides the basis for evaluation • The ratio of the height of the 4th response(T4) to the 1st response(T1) is TOF ratio • In partial non- depolarizing block T4/T1 ratio is inversely proportional to degree of blockade • In Depolarizing block, no fade occurs in TOF ratio so equal depression in twitch height • Fade, in depolarizing block signifies the development of phase II block
  20. 20. Train-of-Four Stimulation
  21. 21. Tetanic Stimulation • Tetanic Stimulation is 50-Hz stimulation given for 5 sec • During tetanus, progressive depletionof acetylcholine output is balanced by increased synthesis and transfer of transmitter from it’s mobilization stores. • NDMR reduces the margin of safety by reducing the number of free cholinergic receptors and also by impairing the mobilization of acetylcholine within the nerve terminal there by contributing to the fade in the response to tetanic and TOF stimulation. • A frequency of 50Hz is physiological as it is similar to that generated during maximal voluntary effort. • During normal NM transmission and pure depolarizing block the response is sustained • During non- depolarizing block & phase II block the response fades • During partial non- depolarizing block, tetanic stimulation is followed by post-tetanic facilitation
  22. 22. Tetanic Stimulation
  23. 23. Post-Tetanic Count Stimulation • Mobilization and enhanced synthesis of acetylcholine continue during and after cessation of tetanic stimulation. • Used to assess degree of NM Blockade when there is no reaction single-twitch or TOF • Number of post-tetanic twitch correlates inversely with time for spontaneous recovery • Tetanic stimulation(50Hz for 5sec.) and observing post-tetanic response to single twitch stimulation at 1Hz,3sec after end of tetanic stimulation • Used during surgery where sudden movement must be eliminated(e.g., ophthalmic surgery) • Return of 1st response to TOF related to PTC
  24. 24. Post-Tetanic Count Stimulation
  25. 25. Double-Burst Stimulation • DBS consist of two train of three impulses at 50Hz tetanic stimulation separated by 750msec • Duration of each impulse is 0.2msec • DBS allow manual detection of residual blockade under clinical conditions • Tactile evaluation of fade in DBS 3,3 is superior to TOF as human senses DBS fade better. • However, absence of fade by tactile evaluation to DBS does not exclude residual NM Blockade
  26. 26. Double-Burst Stimulation
  27. 27. Non-depolarizing blockade • Intense NM Blockade • This phase is called “Period of no response” • Deep NM Blockade • Deep block characterized by absence of TOF response but presence of post-tetanic twitches • Surgical blockade • Begins when the 1st response to TOF stimulation appears • Presence of 1 or 2 responses to TOF indicates sufficient relaxation
  28. 28. Contd… • Recovery • Return of 4th response to TOF heralds recovery phase • presence of spontaneous respiration is not a sign of • adequate neuromuscular recovery. • T4/T1 ratio > 0.9 exclude clinically important residual NM Blockade • Antagonism of NM Blockade should not be initiated before at least two TOF responses are observed
  29. 29. Depolarizing NM Blockade • Phase I block • Response to TOF or tetanic stimulation does not fade, and no post-tetanic facilitation • Phase II block • “Fade” in response to TOF in depolarizing NM Blockade indicates phase II block • Occurs in pts with abnormal cholinesterase activity and prolonged infusion of succinylcholine
  30. 30. Visual or tactile: Not sensitive enough to exclude possibility of residual neuromuscular blockade. Fade is usually undetected until TOF ratio values are <0.5.
  31. 31. Recording devices for measuring NM Function • Compound muscle action potential: It is the cumulative electrical signal generated by the individual action potentials of the individual muscle fibres.
  32. 32. Electromyogram (EMG) • It records the compound MAP via recording electrodes placed near the mid portion or motor point of the muscle and a slightly remote indifferent side. • The latency of the compound MAP is the interval between stimulus artifact and evolved muscle response. • The amplitude of the compound MAP is proportional to the number of muscle units that generate a MAP within the designated time interval (epoch) and this correlates with the evoked mechanical responses. • For experimental studies  The best signal is usually obtained by placing the active receiving electrode over the belly of the muscle with the reference electrode over the tendon insertion site  The ground electrode is placed between the stimulating and recording electrodes.
  33. 33. Mechanomyographic device (isometric) (Adductor pollicis force translation monitor) • Quantifies the force of isometric contraction • The force  electrical signal  pressure monitor and recorded. • Key features : a. Alignment of the direction of thumb movement with that of the pressure transducer. b. Application of consistent amount of baseline muscle tension (preload 200-300 gms) c. Transducer and monitor with adequate monitoring range and zeroing of the monitor before stimulation. DISADV:  These devices are difficult to set up for stable and accurate measurements  Proper transducer orientation, isometric conditions, and application of a stable preload are required  Maintenance of muscle temperature within limits is important
  34. 34. Accelerography (non isometric) • This technique uses a miniature piezoelectric transducer to determine the rate of angular acceleration. • Newton’s second law, F=m*a • Muscle must be able to move freely. • The piezoelectric crystal is distorted by the movement of the crystal inlaid transducer which is applied to the finger and an electric current is produced with an output voltage proportional to the deformation of the crystal. • This is a non-isometric measurement and there are less stringent requirements for immobilization of arm, fingers and thumb and also no preload is necessary. • TOFguard, • TOF–watch (Organon Teknika), • Para Graph Neuromuscular Blockade Monitor (Vital signs), • Part of Datex AS/3 monitoring system (M-NMT)
  35. 35. Clinical tests of Postoperative Neuromuscular Recovery Reliable Unreliable Sustained head lift for 5 sec Sustained eye opening Sustained leg lift for 5 sec Protrusion of tongue Sustained handgrip for 5 sec Arm lifted to the opposite shoulder Sustained “tongue depressor test” Normal tidal volume Maximum inspiratory pressure 40 to 50 cm H2O or greater Normal or nearly normal vital capacity Maximum inspiratory pressure less than 40 to 50 cm H2O
  36. 36. Limitations of NM Monitoring • Neuromuscular responses may appear normal despite persistence of receptor occupancy by NMBs. • T4:T1 ratios is one even when 40-50% receptors are occupied • Patients may have weakness even at TOF ratio as high as 0.8 to 0.9 • Adequate recovery do not guarantee ventilatory function or airway protection • Hypothermia limits interpretation of responses
  37. 37. THANK YOU !

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