TETANIC STIMULATION,NEUROMUSCULAR MONITORING, TOF, STH, DBS, PTC

1. NEUROMUSCULAR
MONITORING
Dr. KAVITA KADYAN

2. What are we monitoring?
• Monitor – skeletal muscle contraction in response to a stimulus.
• Purpose – know the %age of Ach Nicotinic receptors blocked.
Use/objectives of NMM-
1. Onset of induction, dosage of nmbd for intubation
2. Determine level of block :
• Tracheal intubation response
• Surgical relaxation
• Reversal of patient from ms relaxants.

3. Why need NMM ?

4. ADVERSE EFFECTS OF RESIDUAL NEUROMUSCULAR
BLOCKADE
Physiological
changes
Clinical
implications
https://resources.wfsahq.org/atotw/residual-neuromuscular-blockade-anaesthesia

5. Muscle Paralysed state Implication
Pharyngeal:
Tongue
Tongue fall Upper airway obstruction
• (Desaturation,
• Need of re-intubation)
Palatal ms Closure of oral airway “
Larynx:
Vocal cords No phonation Patient cant tell
Laryngeal muscles No abduction of vocal cords Difficulty in breathing
No adduction of vocal cords Risk of aspiration,
Inadequate cough
Chest & Diaphragm • FRC, PEFR, VC ↓
• Impaired oxygenation-
ventilation
• Impaired lung functions
• Post op ventilator weaning
difficult,
• Atelectasis ↑
• Pneumonia↑
• Need of re-intubation
Rest of the body Weakness • Functional capacity to work ↓
Brain Hypoxic centre not activated • ↓sensitivity of chemoreceptors
to hypoxia

7. Conditions where NMM is “essential”
1. Patient :
• muscular disorder (myasthenia gravis, eaton lambert syndrome),
• liver or renal dysfunction (pharmacokinetics change),
• respiratory diseases, morbid obese
2. Surgery:
• prolonged duration,
• profound NM blockade (nmbd) ie neuro sx, ophthalmic sx, thoracic sx
3. Anesthesia:
• prolonged infusions of nmbd ,
• Reversal drugs may cause harm ( tachyyarythmias, cardiac failure)

8. Which muscles we monitor ?
• Aim:
Procedure Paralysis required
Intubation time Laryngeal, diaphragm, abdominal ms
Surgical maintenance time Abdominal ms, peripheral muscles
Extubation time No muscle paralysis required

9. • Q. Smooth, skeletal ???
• Q. central or peripheral muscles?
• Q. superficial or deep muscles?
Which muscles we monitor ?
Skeletal muscles.
Diaphragm, facial
muscles,
Thumb muscle,
Leg muscle
Peripheral
muscles(thumb,legs)
monitoring easy then
central muscles
(diaphragm, laryngeal
ms)

10. Can we measure central & deep muscles ?

11. Are all muscles equal in sensitivity to NMBD?
No ‼

12. Relative sensitivities of muscle groups to
muscle relaxants
Vocal cords: maximum resistant
Extra-ocular ms: least resistance

13. Differential
sensitivity of
muscle
groups to
NMBA
d/t variations in:
1. Ach-R density
2. Ach release
3. Ach esterase activity
4. Muscle fiber composition
5. Innervation ratio & no of NMJ
6. Blood flow
7. Muscle temparature

14. Relative sensitivities of muscle groups to
muscle relaxants
Vocal cords: maximum resistant
Extra-ocular ms: least resistance
Diaphragm & Laryngeal Ms:
• More AchR,
• More Ach ,
• [hence most resistant to both
NMBA]
• {1.4 to 2 times dose of muscle
relaxant as the adductor pollicis}
• More blood supply
{faster onset & offset of paralysis}
L
A
S
T
F
I
R
S
T
ONSET
for nmbd
drugs
RECOVERY
for nmbd
drugs
F
I
R
S
T
L
A
S
T
closely reflect the extent of paralysis of D & L ms.
Pharyngeal & upper oesophageal muscles are most sensitive to NDMR, so they recover very late &
TOF ratio ≥ 0.9 @ adductor pollicis is required for extubation

16. Clinical signs of
neuromuscular
recovery
Clinical criteria of extubation?

17. Clinical criteria of extubation?
• Eye opening
• Tongue protrude
• Head lift
• Hand grip
• Regular and adequate TV generate
But are these enough to prevent post operative
residual paralysis or recurarisation?

18. Things observed during NMM?
Ms. Contraction
after a
stimulus applied-
visual/tactile/
TOF %age
measure.
1.Count & %age
2.Fade
3.Potentiation

19. How to assess
muscle response?
Qualitative / subjective NMM
Muscle contraction is
subjectively assessed by
clinicians either
visually or tactically
Quantitative / objective NMM
Muscle response is objectively
measured with the help of
a sensor and displayed
on a screen

20. Fade ?
Fade = decrease in amplitude of muscle contraction in respective of
previous ms. contraction. i.e. T4/T1 or DBS2/DBS1 or ST1/ST control.
Or
Fade is progressive depression of height of subsequent response seen
with NDMR
No fade Fade is d/t blockade of
presynaptic AchR
which decrease Ach
release.

21. When we see fade ?
Fade can be seen at 2 times:
• a) when we administer NMBD i.e. at “INDUCTION”
• B)when we see weaning off NMBD, i.e. As the neuromuscular block
begins to wear off, the muscle will begin to respond to a stimulus, but
the twitch will be less than full strength i.e. at “EXTUBATION”
Induction extubation
Induction extubation

23. Ach Receptor occupancy and nmbd action ?

24. Mechanism of muscle contraction

25. Mechanism of muscle contraction

26. Brief mode of action of nondepolarizing
depolarizing drugs
Non- depolarizing
ATRACURIOUM & Ach compete,
More amount drug wins and attach to
receptor
Atracurium don’t open Na-K
NO AP
Depolarising /Sch/ non-
competitive
Phase I-
• Sch bind to AchR,
• Na-K open,
• AP generation, fasiculation,
• pseudocholinesterase takes time to act (blood),
• Sch don’t dissociate from Ach R ,
• hyperpolarisation
• Flaccid paralysis,
• Na-K closed
• pseudoE destroys Sch
• Receptor free from any drug
• Ach act on Ach R
• Normal muscle contract by opening Na-K
• { thus no reversal needed}
• Phase II=
• Repeated Sch dosage
• Sch never leaves this AchR { as Sch amount is more then Ach}
• Repolarisation has occurred
• AchR confrontational changes have occurred
• Na-K don’t open

27. Brief mode of action of nondepolarizing
depolarizing drugs
• Non- depolarising • Depolarising /Sch/ non-
competitive

28. Principles of Peripheral Nerve stimulation
Supramaximal stimulation
• Ohms law  V = I × R
• Current ( not voltage) is the determinant of
nerve stimulation
• All or none phenomenon
• Least amount of current required to begin
muscle contraction is called as threshold
current
• Muscle response ∝ Force of contraction∝ no.
of muscle fibres contracted ∝ Current
• Current required to produce the contraction of
all muscle fibres is called as maximal current

29. Supramaximal
current = 2.5 to 3
times Threshold
current = 15 to 20%
higher than
maximal current
This ensures the stimulus to be truly
maximal throughout the whole period of
monitoring irrespective of potential
changes in skin resistance
intraoperatively
A 30 mA current will usually produce
supramaximal stimulation in most of the
patients when Ulnar n is stimulated
Higher current may be needed with
posterior tibial nerve stimulation, in
patients with increased skin resistance
such as diabetes, oedema

30. • Frequency = no. of stimulus or electrical pulse per sec. (Hz)
• Waveform must be rectangular and monophasic
• The length of pulse should not exceed 0.2 to 0.3 ms

31. Safety range of
equipment
Neuromuscular block become
evident only after 70 to 80 % of
Ach® are occupied with nd-NMBD
For complete block 90 to 95% Ach®
has to be occupied
Currently available equipment
detect this 70 to 95% range of
receptor occupancy
i.e, during recovery from NMB, less
than 70 % of Ach_R occupancy is
not detectable by NMM

32. Calibration
To obtain accurate and
precise readings ,
equipment has to be
calibrated before use
• is within measurement window of the device
• & as close as possible to 100% control
response
Check whether
Muscle response to
supramaximal
stimulus

33. Types of electrodes
1. silver or silver chloride gel
based surface electrodes
2. Metal ball electrodes (with no
cable)
3. Needle electrodes (s/c tissue
parallel to nerve)
(Thick skin, oedema, cold skin)

34. Modes of NMM ?

35. SINGLE TWITCH STIMULATION
• Single electrical stimuli at 1.0 Hz( 1
impulse in 1 sec) to 0.1 Hz(1 impulse
every 10 sec)
• We compare the strength of muscle
contraction to the control value
before the administration of the
muscle relaxant.
• The strength of response is expressed
as % of control (T1:Tc)
• Progressive decrease in response height
with both dMR & ndmr

36. SINGLE TWITCH STIMULATION
• The amplitude of muscle contraction decreases when about 75-
80% of the receptors are blocked, and
• It disappears when 90-95% of the receptors are blocked,

38. ED-95 value
PTC

40. Double burst stimulation
1st
burst
2nd
burst
• 2 short bursts of 50 Hz tetanic stimulation separated by 750 msec, with a 0.2 ms duration of each
square wave impulse in the burst
• In DBS (3,3) mode 3 impulses in each burst
• In DBS (3,2) mode1st burst has 3 impulses & 2nd burst has 2 impulse
Fade in the response to second burst compared to that of first burst is the basis for evaluation

41. Double burst stimulation
Fade seen by D2 burst/D1 burst
Comparison with TOF ratio ?
•It approximates the TOFR when comparing the second to the
first response.
•It may increase sensitivity of qualitative assessments since
fade can be detected at a TOFR around 0.6 with this method.
•Manual tactile detection of DBS Fade is much better
appreciated then TOF fade.

43. Double burst stimulation

44. TRAIN OF FOUR
STIMULATION
One set of stimulus = Four single pulses of equal intensity at intervals of 0.5 s (2Hz) & each set of
stimuli is repeated every 10 to 20 sec.
Findings
1. TOF Count = no.of evident
responses after TOF
stimulation
2. TOF Ratio = amplitude of
fourth response / amp.of
first response

45. TOF RESPONSE
DEPOLARISING BLOCK/Sch phase I
• No fade
• CONSTANT but DIMINSHED
Non-depolarizing block/Atra/Roc OR
Sch phase II
• Fade seen As block deepens , TOFR
decreases

46. TOF

47. TOF
T1 is last to go
T1 is 1st to appear
Application of TOF

48. TOF interpretation

51. Tetanic & Post Tetanic Count Stimulation
• Tetanic stimulation: High frequency electrical stimuli of 50 to 100 hz given for 5 sec. Or 200 Hz
stimulation for 1 sec ( should not be repeated more often than every 6 min.)
• PTC stimulation: Tetanic Stimulation  after 3 sec. 10-15 or 20 Single twitch stimuli @ 1 Hz

52. Tetanus fade
For muscle contraction, 2 things needed
1. Ach
2. free AchR at post synaptic membrane
Start of tetanic stimulation:
 large amounts of acetylcholine are released from immediately available stores in
the presynaptic nerve terminal.
Continued tetanic stimulation: { stores become depleted : equilibrium achieved}
 the rate of acetylcholine release decreases {mobilization} ≡ synthesis
 muscle response is maintained : acetylcholine released >the amount to evoke a
response.
Continued tetanic stimulation:
 postsynaptic event: free AchR at post-synaptic membrane ↓ {blocked by nmbd}
 Presynaptic event: impaired mobilization of acetylcholine within the nerve
terminal
 FADE seen: mainly a “presynaptic event”.
(Although the degree of fade depends primarily on the degree
of neuromuscular block, fade also depends on the frequency
(Hz), the length (seconds) of stimulation, and on how often
tetanic stimuli are applied)

53. Post Tetanic Count
Q. What are we counting ?
• MUSCLE CONTRACTION Response to PTC stimulus.
Q. When to use ?
• During deep block, when TOFC=0
Q. which surgeries should be monitored by PTC?
• Surgery where movement is to be avoided, e.g. Ophthalmic surgery, neuro-surgery.
Q. when PTC=0, do we need to repeat the NMBD dose during maintenance?
• No ‼ minimum PTC =1 needed to repeat the maintenance dosage.
Q. When we say that TOF twitch is imminent ( value of PTC)?
• 8-9 counts of PTC, TOF of 1 will be in 10 mins.
Q. To avoid diaphragmatic movement during sx, PTC ?
• ≤3 PTC responses is recommended (neuromuscular block of the peripheral muscles must be deep
so that the PTC is 1-3 at the thumb).

54. Post Tetanic Count
facilitation or potentiation
• As the deep block weakens, more and more
responses to post-tetanic twitch stimulation
appear.
Fade in the tetanic stimulus response is the
least sensitive subjective measure of
strength and is not reliably detected until the
TOFR falls below 0.4.

55. Post Tetanic Count
Q. After tetanic stimulation we observe any increase / decrease in the amplitude of
ms. contraction?
• Post tetanic facilitation or potentiation is observed (INCREASE in ms. contraction)
• Post Tetanic facilitation is the phenomenon of exaggerated response to
stimulation (which is seen max around 3 sec & last for 2 min) following a tetanic
stimulus.
• It is d/t exxagarated release of Ach leading to high levels of Ach w.r.t receptor
blocking drugs at motor endplate
• With dMR, response to TS will decrease in amplitude but sustained & no PTF
• With NDMB, response to TS will decrease in amplitude ass. with fade + PTF
• Note: Fade is due to Presynaptic Ach R block

56. Which mode when to
use?
• INTUBATION
• MAINTENANCE
• RECOVERY
• PACU

57. Which mode when to use?

58. Choice of Nerve-muscle unit ?
• Q. Sensory or Motor or Mixed nerve ?
• Q. Superficial or Deep nerves?

59. Choice of Nerve-muscle unit ?
• Q. Central or peripheral muscles?
• Q. Which among these muscles is the central acting muscle, which
corresponds to the onset of action of laryngeal ms. and diaphragm?
corrugator supercili
muscle

60. POLARITY ?
• 1 negative(distal) and 1positive(proximal)electrode (colour coded, red & black)

61. Ulnar nerve
• Most commonly used
• Easily accessible if arm in outstretched & hand in
supine position
• Lowest risk of direct muscle stimulation due to good
topographic separation

62. Posterior tibial nerve
• Can be used when hands are inaccessible
Q.Flexor hallucis brevis is similar to what
muscle for nerve stimulation?
• The onset & recovery of NMB at flexor hallucis brevis is
almost consistent with that of adductor pollicis muscle

63. 1.Facial nerve (zygomatic br)-orbicularis oculi
2.Facial nerve (temporal br)-corrugator supercili muscle
• High risk of direct muscle
stimulation due to close
proximity of nerve &
muscles
Facial nerve

64. Facial nerve
1. Which facial muscle behaves similarly to the
Adductor pollicis ms muscle for nerve
stimulation?
Ans. orbicularis oculi
2. What facial muscle is similar to the diaphragm
and laryngeal muscles?
Ans. corrugator supercili muscle

65. Assessment of response

68. How to assess
muscle response?
Qualitative / subjective NMM
Muscle contraction is
subjectively assessed by
clinicians either
visually or tactically
Quantitative / objective NMM
Muscle response is objectively
measured with the help of
a sensor and displayed
on a screen

69. Quantitative / objective NMM

70. Mechanomyography
• measures the isometric contraction of a muscle
• Preload of 200 to 300 g is applied to thumb
• The arm and hand should be rigidly fixed, and care
should be taken to prevent overloading of the
transducer
• A transducer converts Force of contraction generated at
adductor pollicis to electrical signal which is recorded,
amplified & displayed on screen
• MMG is gold stantard of NMM
• But not commercially available d/t bulky equipment &
used for research purpose only

71. Acceleromyography
• Is based on Newton’s 3rd law, F=ma
• It measures isotonic acceleration of
stimulated muscle by using a piezoelectric
transducers
• M/c commercially available monitor &
therefore become standard for qualitative
NMM today

72. Electromyography
• Measures compound muscle action potential
generated by stimulation of a peripheral nerve
• 3 electrodes
1. Active electrode (over muscle belly)
2. Reference electrode ( over tendon
insertion)
3. Ground electrode( between both) (neutral
site distant to the muscle)

73. Advantages over MMG:
• The equipment is not as bulky and is easier to assemble.
• The arm and hand do not need to be fixed as rigidly.
• new sites for recording the EMG : the larynx and the diaphragm.
Disadvantages:
• It is prone to interference: diathermy, Hand temperature, hand
movement, direct muscle stimulation.
Electromyography

74. Laryngeal EMG:
• Laryngeal electrode attached to the
tracheal tube and placed between the
vocal cords.
• Monitor: the onset of neuromuscular block
in the laryngeal muscles.
Electromyography (non-invasive)

75. Normal М-wave from the diaphragm during stimulation of the phrenic
nerve in a child aged 12
Diaphragmatic EMG :
• In paravertebral surface, the
recording electrodes are placed
on the right of vertebrae T12/L1
or L1/L2 for monitoring the
response of the right
diaphragmatic crux to
transcutaneous stimulation of the
right phrenic nerve at the neck
Electromyography (non-invasive)

76. Kinemyography
• A bending sensor with a piezoelectric
core is placed b/w thumb & forefinger.
• Muscle contraction causes bending of
sensor which is converted to electrical
signal by piezoelectric transducer.

77. PHONOMYOGRAPHY
• PMG measures: low-frequency sounds of
muscle contraction with special microphones
following nerve stimulation.
Advantage:
• adductor pollicis muscle, diaphragm, larynx,
and eye muscles.
• In addition, the ease of application is
attractive.
Disadv.: PMG-based monitors are not currently
commercially available

78. CUFF PRESSURE MODALITY
• Detects: changes in cuff pressure due to
muscle contraction.
Method:
• Electrodes integrated into a BP cuff
stimulate the brachial plexus at the
humeral level.
• The subsequent bulk contraction of the
upper arm generates pressure change in
the blood pressure cuff which is
analyzed and displayed at the monitor

79. COMPRESSOMYOGRAPHY
• Measures: pressure changes in a
hand-held balloon.
• Method: Following ulnar nerve
stimulation, the force of muscle
contraction of the hand muscles is
transmitted to a balloon secured in
the patient’s hand.

80. •
4 levels of NMB with NDMR are
1. Intense NMB
2. Deep NMB
3. Moderate NMB, also called
as surgical block, TOFC 1 or 2
is sufficient relaxation for
most surgical procedures
4. Recovery phase

81. Level of NMBD

83. DEEP AND INTENSE BLOCK disadvantage
1. Patient are completely paralyzed and cannot signal awareness with
voluntary or involuntary movements.
2. Another is that deep or intense block cannot readily be reversed by
neostigmine. Only sugammadex can reverse a deep or intense
neuromuscular block (if caused by rocuronium or vecuronium)

84. ASSESSMENT

85. •Tests including sustained head or leg lift, eye or mouth opening, and
hand grip can be performed at TOF ratios between 0.4-0.9.6
Qualitative Assessment of Strength: Clinical Tests

86. 4. Recovery
from NMB
• Return of the fourth response in the TOF marks the recovery
phase
• TOFR is used to asses the extend of NMB recovery
• TOFR ≤ 0.4 unable to lift head or arm, TV may be normal
but Inspiratory force & vital capacity is reduced
• TOFR 0.5 to 0.6  most pts can lift head for 3 s, open eyes
widely, protrude tongue but vital capacity & Insp. force is still
reduced.
• TOFR 0.7 to 0.75 most pt can cough sufficiently, lift head for
5 s but hand grip strength is still low
• TOFR ≥ 0.8 VC & IF become normal, however, pt may still
have diplopia, blurred vision & facial weakness
• To exclude clinically significant residual NMB with certainty
TOFR recorded with MMG or EMG must be ≥ 0.9 or with AMG
must be atleast 1.0

88. Unreliable signs

89. Reliable signs
“SUSTAINED”
a) Head lift
b) Leg lift
c) Hand grip
≥5 sec

90. Clinical signs of
neuromuscular
recovery
Clinical criteria of extubation?

91. Reversal- neostigmine or suggamadex?

92. Level of NMB with subsequent doses of NDMR is
monitored using PTC, TOFC & TOFR
Reversal with Neostigmine should not be attempted
until at least 2 responses to TOFC is present
For extubation, residual NMB has to be ruled out by
TOFR ≥ 0.9 with MMG/EMG or at least 1 with AMG