1. SZ Fan 2002 Muscle Relaxants & Monitoring 台大麻醉部 范守仁醫師 fan@dr.com http://an.mc.ntu.edu.tw

2. SZ Fan 2002 1958, Christie & Churchill- Davidson described assessment of neuromuscular blockade during anesthesia by the use of a nerve stimulator 1932 used purified fractions of curare in patients with tetanus & spastic disorders 1940 as an adjuvant to shock therapy (Bennett) 1942: 1st muscle relaxation in anesthesia (Griffith and Johnson)

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4. Nicotinic Acetylcholine Receptor Consists of 5 glycoprotein subunits to form an ion channel. 2 alpha, 1 beta,1 delta1 gamma Ach binds to the 2 alpha subunits opening the channel 1-10 million receptors across cell membrane

5. SZ Fan 2002 Pharmacokinetic profile will be abnormal Severe renal disease Liver disease Severe illness Extremes of age

6. SZ Fan 2002 Pharmacodynamic profile will be abnormal Neuromuscular disease Drug interactions Burns Neonates

7. SZ Fan 2002 Spontaneous offset of blockade is undesirable Ophthalmologic procedures Neurosurgery Microsurgical procedure

8. SZ Fan 2002 Maximal postoperative muscle power is required Severe pulmonary disease Myopathic & neuromuscular disorders Marked obesity Risk of aspiration

9. SZ Fan 2002 Reversal of blockade is contraindicated Severe heart disease Severe bronchial asthma Prolonged procedures neuromuscular blockade is produced by continuous infusion

10. SZ Fan 2002 Monitoring Methods Clinical assessment Force transducer Acceleration transducer Compound-evoked electromyographic potential Acoustic myography

11. SZ Fan 2002 Supramaximal Stimulation Electrical stimulus ~ 20-25% > maximal response The impulse is monophasic & rectangular The optimal pulse duration ~ 0.2-0.3 ms 25-50 mA, with a skin resistance ~ 2.5 k  cooling the skin resistance may increase up to 5 k 

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13. Single-Twitch Stimulation ST single stimuli are applied at rates from 0.1 to 1.0 Hz muscle response to single twitch stimulation depends upon the frequency of stimulation at rates > 0.15 Hz, the evoked response will gradually decrease and settle at a lower level therefore rates of 0.1-0.15 Hz are generally used accuracy is generally poor, as clinical assessment of twitch strength is usually employed and notoriously unreliable

14. SZ Fan 2002 Train of Four Stimulation TOF introduced by Ali et al. in 1970 four supramaximal stimuli are delivered at 2 Hz (1 per 0.5 sec) each train is separated by 12-20 seconds a TOF normally shows little difference between the four responses the degree of competitive neuromuscular blockade may be assessed by, a. the ratio of the 4th to the 1st response b. the number, or TOF count

15. SZ Fan 2002 Train of Four Stimulation TOF assessment of transmission in the absence of baseline data a. normal ® 4:1 ratio ~ 1.0 b. partial competitive blockade ® the ratio decreases, or "fades", in relation to the degree of blockade c. partial non-competitive blockade the ratio remains ~ constant, twitch height uniformly reduced TOF fade after the use of succinylcholine signifies the onset of phase II blockade it is difficult even for experienced observers to estimate the TOF ratio above ~ 0.4 accordingly, TOF is not useful for exclusion of residual neuromuscular paralysis

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17. Tetanic StimulationTS tetanic stimulation rates vary from 30, 50, 100 to 200 Hz the usual pattern is 50 Hz for a period of 5 seconds some recommend using high frequencies (100, 200 Hz) for 1 second the patterns of response are, i. normal ® no tetanic fade ii. partial competitive blockade ® tetanic fade iii. partial non-competitive blockade ® no tetanic fade

18. SZ Fan 2002 Tetanic StimulationTS fade is due to depletion of readily available stores of Ach at equilibrium, the rate of release is equal to the rate of mobilization when this safety margin is reduced by competitive postsynaptic blockade, does fade in the muscle response begin in addition to blocking postsynaptic receptors, the nondepolarizing neuromuscular blocking drugs also impair mobilization of ACh within the nerve terminal

19. SZ Fan 2002 Tetanic StimulationTS post-tetanic facilitation : increased mobilization of ACh within the nerve continues for some time after tetanic stimulation PTF usually disappearing within 60 seconds of tetanic stimulation tetanic stimulation has a number of disadvantages, a. it is very painful b. in the late phase of recovery it may prolonged blockade in the muscle group tested however, it offers no additional information to a TOF, unless combined with a post-tetanic count if a 100Hz @ 5 sec tetanus is used there is an improvement in clinical assessment when compared to a TOF ? painful

20. SZ Fan 2002 Post-Tetanic Count PTC

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22. Post-Tetanic Count PTC PTC 1. single twitch, 1 Hz, for 1 minute 2. tetanus, 5 seconds @ 50 Hz 3. 3 seconds latency period 4. single twitch count, 1 Hz, for 1 minute ® count = ?/60

23. SZ Fan 2002 Post-Tetanic Count PTC Clinical Data a. pancuronium ~ 35 mins b. atracurium ~ 7-8 mins c. vecuronium ~ 7-8 mins application: 1. when no response to ST or TOF 2. movement must be eliminated, such as in ophthalmic surgery… the response to PTC depends upon, a. the level of neuromuscular blockade b. the frequency & duration of tetanus c. the interval between the tetanus and stimulation d. the frequency of stimulation possible antagonism of neuromuscular blockade, localised to the tested muscle; PTC should not be performed > 6 minutes

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25. Double Burst StimulationDBS manual, or tactile, assessment of small amounts of residual neuromuscular blockade Manual assessment of TOF is insufficient to exclude shallow degrees of residual blockade with DBS it is easier to "feel" fade in the response DBS consists of two short bursts of 50 Hz, separated by 750 ms the duration of each square wave in the burst is 0.2 ms initial studies were with 3 pulses @ 50 Hz in each burst, DBS3,3

26. SZ Fan 2002 Double Burst StimulationDBS the normal response to DBS is two short muscle contractions of equal force in partially paralysed patients the second contraction is weaker measured mechanically, DBS correlates closely with the TOF response when measured manually, the assessment of DBS correlates more closely than manual TOF with the mechanical TOF response Absence of fade on DBS usually means significant residual neuromuscular blockade is absent

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30. Diaphragm :faster onset and faster recovery? the source of these differences may include, Different safety margins for different groups Fibre composition Innervation ratio Blood flow Muscle temperature

31. SZ Fan 2002 Surface laryngeal Electromyography Electrode attached to the tracheal tube and placed between the vocal cords at intubation The laryngeal recurrent nerve was transcutaneously stimulated with an external nerve stimulator. Hemmerling et al.

32. SZ Fan 2002 Acceleromyography in the face Orbicularis oculi Corrugator supercilii

33. SZ Fan 2002 Surface diaphragmal electromyography 1986, Donati et al. introduced monitoring of the diaphragmatic response using surface skin electrodes Electrodes have to be placed within the surgical Field or, as in laparoscopic surgery

34. SZ Fan 2002 Phase II or Dual Block

35. SZ Fan 2002  Evidence-based practice dictates more attention should be paid to monitoring neuromuscular function  Residual block remains a threat to the patient with the intermediate-acting neuromuscular blocking drugs

36. SZ Fan 2002 AS/3 Monitor Vaporizer Control NoteBook Graseby 3500 Aspect 1050

37. SZ Fan 2002 Thank you for Your Attention

38. SZ Fan 2002