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MONITORING OF NEUROMUSCULAR JUNCTION.pptx
- 1. MONITORING OF NEUROMUSCULAR JUNCTION MODERATOR: DR. S. Srinivas yadav (ASSISTANT PROFESSOR) SPEAKER : DR. C. Pooja (POST GRADUATE) Department of Anesthesiology & Critical care
- 2. Why NMJ monitoring? To ensure ideal intubating conditions have been met after administration of muscle relaxant. To ensure ideal surgical conditions have been met intraoperatively. To administer NMBA’s with appropriate dosing. Prevention of residual neuromuscular blockade. Surgical indications. Prolonged Anaesthesia. Presence of renal or hepatic diseases.
- 3. Methods of neuromuscularmonitoring Clinical methods Useful only towards the end of surgery for assessing recovery from NMB Peripheral nerve stimulator Subjective : visual / tactile Objective : Quantification with numerical values
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- 5. PERIPHERAL NERVE STIMULATOR Evoking the response of muscle by delivering an electrical stimulus to the nerve that innervates it. Simple Compact Light weight Stimulus – monophasic & rectangular wave form Length of pulse – should not exceed 0.2 to 0.3 ms Deliver constant current
- 6. PERIPHERAL NERVE STIMULATOR Stimulating electrodes Surface electrodes (30-70mA) Metal electrodes Needle electrodes (10mA) Current Supramaximal stimulus – 25 % of maximal stimulus Higher currents – oedema, diabetes Lower currents – needle electrodes are used
- 7. SITES OF PERIPHERALNERVE STIMULATION Ulnar nerve – adductor pollicis muscle Gold standard Lowest risk of direct muscle stimulation Easily accessible Posterior tibial nerve – flexor hallucis brevis muscle Facial nerve – orbicularis oculi Facial nerve – corrugator supercilii muscle
- 8. DIFFERENT MUSCLES GROUPSHAVE DIFFERENT SENSITIVITY TO NMBD’S Diaphragm & laryngeal adductors, corrugator supercili – resistant to NMBD’S Onset is late Recovery is fast Extrapolated by corrugator supercilii Peripheral muscles of limbs, orbicularis oculi, upper airway muscles – sensitive to NMBD’S Onset is fast Recovery is slow Extrapolated by adductor pollicis
- 9. Patterns of nervestimulation 1. Single twitch stimulation 2. Train of four stimulation(TOF) 3. Double burst stimulation(DBS) 4. Tetanic stimulation 5. Post tetanic stimulation(PTC)
- 10. Single twitch stimulation Earliest & simplest pattern Single electrical stimuli are applied to a peripheral motor nerve at frequencies ranging from 1.0Hz(once every second) to 0.1Hz(once every 10 seconds). Reference value before administration of NMBA is mandatory.
- 11. SINGLE TWITCH STIMULATION Application : Helps in establishing satisfactory intubating conditions Used in conjunction with tetanic stimulus to monitor deep levels of NMB Disadvantage : Insensitive : doesn’t decrease until 75- 80% receptors are blocked. Disappears completely when 90-98% receptors are blocked. cannot differentiate depolarizing & non depolarizing block
- 12. Train of fourstimulation Introduced by Ali & associates Most frequently used stimulation pattern Four supramaximal stimuli given every 0.5 sec (2Hz) Evaluated by TOF count & TOF ratio TOF count – onset of neuromuscular block, moderate blockade TOF ratio(T4/T1) – neuromuscular recovery from non depolarizing blockade
- 13. TRAIN OF FOUR Degree of fade is proportional to extent of neuromuscular block At unblocked NMJ, TOF ratio equals to 1.0 Phase 1 block of depolarizing muscle relaxants, twitch height is decreased in all four twitches, ( no fade and TOF ratio equals to 1.0) Phase 2 block of depolarizing muscle relaxants or block of NDMR T4 height starts to decrease when 70-75% receptors are blocked, while T1 remains same ( fade and TOF ratio equals to 0.7 80% receptors are blocked – 4th twitch disappears 85% receptors are blocked – 3rd twitch disappears 90% receptors are blocked – 2nd twitch disappears >90% receptors are blocked – 1st twitch disappears
- 14. TOF ADVANTAGES : Sensitive indicator of residual NMB than single twitch Control is not necessary. Can distinguish between depolarising & non depolarising block Help in detecting phase 2 block following succinylcholine administration LIMITATIONS : Poor performance at both extremes of NMB, deep relaxation or near complete recovery.
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- 16. Double burst stimulation Developed by viby – mogensen & associates Two short bursts of 50Hz tetanic stimulation separated by 750ms, with 0.2ms duration of each square impulse in each burst. Number of impulses in each burst may vary Response to DBS is 2 short muscle contractions Evaluated by fade in second burst compared to first burst.(D2/D1) Developed with specific aim of improving manual (tactile or visual) detection of residual non depolarizing block.
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- 18. Tetanic stimulation Proposedby Tassonyi 50-100Hz stimulation given for 5 sec Evaluated by one strong sustained muscle contraction In non depolarizing block - fade Painful – limits its use in unanaesthetised patients
- 19. Post tetanic stimulation Developed by viby – mogensen Composite stimulation pattern – tetanic stimulation followed by 10 to 15 single twitches given at 1Hz starting 3 seconds after end of tetanic stimulation. Evaluated by enhancement effect(facilitation) – occurs in phase 2 block of depolarizing & block of non depolarizing muscle relaxants. Post tetanic count – inversely proportional to degree of blockade
- 20. Tetanic & posttetanic stimulation
- 21. Intense block Deepblock Moderate/surgical Recovery Response to nerve stimulation Period of no response Absence of response to TOF , but with presence of atleast one response to PTC Stimulation Gradual return of four responses to TOF stimulation Return of fourth response to TOF stimulation Anatgonism with cholinesterase inhibitor( neostigim ine) impossible impossible Should not be attempted - inadequate TOF ratio >0.9 Antagonism with sugammadex (block caused by vec or roc) 16mg/kg 4mg/kg 2mg/kg EVALUATION OF RECORDED EVOKED RESPONSES NON DEPOLARIZING NEUROMUSCULAR BLOCK
- 24. DEPOLARIZING NEUROMUSCULARBLOCK Phase 1 block : response to TOF or tetanic stimulation does not fade, no posttetanic facilitation Phase 2 block : fade in response to TOF & tetanic stimulation & post tetanic facilitation
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- 27. Objective monitors 1. Mechanomyography(MMG) 2. Electromyography (EMG) 3. Acceleromyography (AMG) 4. Kinemyography (KMG) 5. Cuff pressure modality (CPM) 6. Compressomyography (CMG) 7. Phonomyography (PMG)
- 28. Mechanomyography Measuresthe isometric contraction of muscle after stimulation of corresponding nerve. Electromyography Records the compound muscle action potentials produced by stimulation of peripheral nerve. Acceleromyography Records the isotonic acceleration of stimulated muscle
- 29. Kinemyography Stretching/bending of flexible piezoelectric film in response to nerve stimulation generates a voltage that is proportional to amount of stretching or bending. Cuff pressure modality (CPM) Detects changes in cuff pressure due to muscle contractions. Compressomyography Measures pressure changes in a hand held balloon, Phonomyography Measures intrinsic low frequency sounds of muscle contractions with special microphones following nerve stimulation
- 31. Role of neuromuscularmonitoring in neuromuscular diseases Myasthenia gravis – Down regulation of Ach receptors Resistant to succinyl choline – requires more dose Sensitive to NDMR – 50 -75% decrease in dose Before giving NDMR – TOF ratio <0.9 – more sensitive to NMDR Hemiplegia Upregulation of AchRs Increased dosage of NDMR
- 32. REFERENCES MILLER’S ANESTHESIA– 9th edition UNDERSTANDING ANESTHESIA EQUIPMENT – A.DORSCH & E.DORSCH STOELTING’S PHYSIOLOGY & PHARMACOLOGY IN ANESTHESTIC PRACTICE
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