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Neuromuscular Disorders: disorders of neuromuscular junction, motor neuron, and muscle

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Title: Neuromuscular Disorders: disorders of neuromuscular junction, motor neuron, and muscle


1
Neuromuscular Disorders disorders of
neuromuscular junction, motor neuron, and muscle
  • Kasia Petelenz
  • Greg Gordon (and others)
  • November 15, 2005

2
Myasthenia Gravis
  • Incidence 110,000 to 130,000
  • Women 20 30 years of age are most often
    affected men older than 60 display symptoms
  • Acquired chronic autoimmune disorder
  • Hallmarks are weakness and rapid exhaustion of
    voluntary skeletal muscles

3
Myasthenia Gravis
  • Muscle strength characteristically improves with
    rest, deteriorates rapidly with exertion
  • Skeletal muscle atrophy is unlikely
  • Laryngeal and pharyngeal muscle weakness may lead
    to aspiration, problems clearing secretions,
    difficulty chewing.

4
Myasthenia Gravis Presentations
  • Clinical Classification
  • Class 1 ocular symptoms only
  • Class 1A ocular symptoms with EMG evidence of
    peripheral muscle involvement
  • Class 2A mild generalized symptoms
  • Class 2B more severe and rapidly progressive
    symptoms
  • Class 3 acute and presenting in weeks to months
    with severe bulbar symptoms
  • Class 4 late in the course of disease with
    severe bulbar symptoms and marked generalized
    weakness

5
Myasthenia Gravis
  • Disease course marked by exacerbations and
    remissions
  • Infection, stress, surgery, pregnancy have
    unpredictable effects, but often cause
    exacerbations
  • Antibiotics can aggravate weakness
  • Diseases considered AI in origin often coexist
  • Decreased thyroid function
  • RA
  • SLE
  • Pernicious Anemia

6
Mechanism - MG
  • Decrease in functional Acetylcholine receptors at
    the nicotinic neuromuscular junction
  • 70 - 90 have circulating antibodies to AChRs
  • Neonatal
  • Transient born to mothers with MG Abs cross
    placenta
  • Only 12 symptomatic

7
(No Transcript)
8
Therapy - Myasthenia Gravis
  • Immunosuppressants
  • Steroids - Commonly cause dose dependent weakness
  • Azathioprine,Cyclosporine
  • Plasmapheresis, iv immunoglobulin
  • Acute exacerbations, i.e. in immediate
    post-operative period if anticholinesterases have
    been withheld and symptoms are severe
  • Plasmapheresis IVIG for 5 days -gt rapid
    improvement, may last for weeks
  • Thymectomy

9
Important part of Rx
  • Anticholinesterase drugs
  • Pyridostigmine, po duration of 2-4 hours
  • Excessive administration -gt Cholinergic Crisis
  • SLUDGE Salivation, lacrimation, urination,
    defecation, miosis bradycardia bronchospasm
  • Profound weakness due to excess Ach at NMJ -gt
    persistent depolarization
  • Treatment of Cholinergic Crisis Atropine,
    Mechanical Ventilation if needed

10
Anesthetic Concerns - MG
  • Pre-op Predictors of Need for Post-Operative
    Ventilatory Support
  • Disease duration gt 6 years
  • Concomitant pulmonary disease
  • Maximum inspiratory force (MIF) lt-25cm H2O
  • VC lt 4 mL/kg
  • Pyridostigmine dose gt750 mg/day

11
Anesthetic Considerations
  • Old School Recommended to d/c anticholinesterase
    if pt has only mild weakness
  • Theory Potentiates Sux, inhibit effect of NDMRs
  • Pts more susceptible to vagal arrhythmias
  • Slows metabolism of ester LAs, Sux, Mivacron
  • New School No experimental evidence to suggest
    that altering a pts anticholinesterase regimen
    has any clinically significant effect on NMB or
    duration of mechanical ventilation post-op.

12
Anesthetic Considerations
  • Increased risk for aspiration
  • Premed with Reglan/Ranitidine
  • Reduced respiratory reserve
  • Avoid premeds with opioids, benzos
  • Pts are very sensitive to respiratory depressant
    effects

13
Anesthetic Considerations - MG
  • Response to Sux is unpredictable
  • Relative resistance usually seen
  • ED95 approximately 2.6 x normal
  • Exquisitely sensitive to NDMRs!!
  • All NDMRs have been used successfully and
    uneventfully if twitches are monitored
  • Should be titrated in 1/10 to 1/20 normal dose
  • Sensitivity to NMDRs is increased during
    co-administration of potent inhaled anesthetic
  • Reverse with standard doses of anticholinesterase
    and anti-cholinergic

14
Post-Op Considerations MG
  • Case Scenario Pt extubated in OR, 40 minutes
    later c/o feeling weak and unable to breathe
  • Myasthenic crisis decreased response to
    anticholinesterases
  • Cholinergic crisis overdose of
    anticholinesterases
  • Both increases in muscle weakness, salivation,
    and sweat occur

15
Post-Op Anesthetic Considerations Myasthenia
Gravis
  • Differentiate with response to 10mg iv
    Edrophonium
  • Myasthenic crisis shows some improvement in
    muscle strength
  • Cholinergic crisis shows no increase in muscle
    strength and worsening of respiratory distress.

16
MG upstairs
  • Epidural Analgesia preferred
  • Maintains SV and LA dose can be easily titrated
  • No evidence that MG pts are more sensitive to LA
    used for conduction anesthesia, but MG
    predisposes to increased weakness
  • Amide LAs probably better
  • Hepatic Metabolism
  • Not hydrolyzed by serum cholinesterases
  • Emergent C/S
  • Sux to allow rapid control and protection of
    airway

17
Lambert-Eaton Syndrome
  • Mimics Myasthenia Gravis
  • Most often affects older males
  • Usually associated with Small Cell CA (lung)
  • Voltage increment to repeated stimulation and a
    poor response to anticholinesterases
  • Sensitive to NMDRs, normal/increased response to
    Sux
  • Antibodies to Ca channel associated protein
    synaptogamin present

18
Motor Neuron Diseases
  • Degeneration of upper and/or lower motor neurons
  • i.e. Amyotrophic Lateral Sclerosis
  • Muscular weakness and atrophy
  • Steady, asymmetric progression
  • Sensory systems, voluntary eye movements, and
    urinary sphincters are spared

19
Amyotrophic Lateral Sclerosis
  • Progressive neuromuscular disorder
  • Characterized by degeneration of spinal motor
    neurons, leading to
  • Denervation
  • Muscle wasting
  • Paralysis
  • Eventually death, most often secondary to
    respiratory failure

20
ALS Anesthetic Concerns
  • Increased Sensitivity to NDMRs
  • Reduction in choline acetyltransferase (involved
    in synthesis of ACh) occurs secondary to
    degeneration of anterior horn cells
  • Avoid Sux
  • Hyperkalemic response in degenerating muscles

21
ALS Anesthetic Concerns
  • GA documented to cause ventilatory depression
    post-operatively, even without use of muscle
    relaxants
  • Respiratory complications are common and a major
    cause for concern
  • Regional relatively contraindicated in pts with
    motor neuron disease, including ALS, for the fear
    of exacerbating the disease

22
ALS Case Description
  • 76 y/o with rapidly progressing ALS, s/p femoral
    head fx
  • PE siallorrhea, dysarthria, dysphonia, cachexia
  • Recent PFTs reveal 20 nL lung function
  • Refused to withdraw Do not intubate orders for
    the intra and post-op time frames

23
Intra-Op Course
  • Intrathecal Catheter placed at L3/4
  • 0.25 mL of Bupivicaine 0.75 (1.9 mg) injected
    through catheter
  • T8 level
  • Catheter was discontinued upon completion of case
  • POD 1 minor desats, resolved with O2 therapy
  • No c/o HA during post-op course

24
Choice of most minimally invasive anesthetic
method
  • Case reports have documented successful use of
    epidural anesthesia
  • Gradual onset of block
  • Less hemodynamic instability
  • But inadequate epidural anesthesia may result
  • Incremental Intrathecal technique allowed
    adequate anesthesia without adverse hemodynamic
    consequences, and enabled extension of block as
    needed

25
Disorders of Muscle
  • Congenital Muscular Dystrophies
  • Myotonic
  • Duchenne, Becker
  • Acquired Myopathies
  • Cushings Syndrome
  • Dermatomyositis
  • Polymyositis

26
Myotonic Dystrophy
  • Characterized by persistent contractures of
    skeletal muscles after voluntary contraction or
    following electrical stimulation
  • Peripheral nerves and NMJ are not affected.
  • Abnormality in the intracellular ATP system that
    fails to return calcium to the sarcoplasmic
    reticulum
  • Contractures are not relieved by NDMRs, regional
    or deep anesthesia
  • Infiltration of LA into skeletal muscle may
    induce relaxation
  • Depression of rapid sodium flux into muscle cells
    by phenytoin, procainamide, quinidine, may
    alleviate contracture by delaying membrane
    excitability

27
Characteristic Appearance - MD
28
Coexisting Organ Dysfunction - MD
  • Cardiac Involvement
  • Mitral valve prolapse 20 of individuals
  • Deterioration of the His-Purkinje system lead to
    arrhythmias
  • 1st degree AV block very common
  • Pulmonary Pathology
  • Restrictive lung disease
  • Impaired responses to hypoxia and hypercarbia

29
Coexisting Organ Dysfunction - MD
  • Cataracts very common
  • GI abnormalities
  • Gastric atony
  • Intestinal hyper-motility
  • Pharyngeal muscle weakness with impaired airway
    protection
  • Cholelithiasis

30
Anesthetic Pre-Op Concerns
  • Eventually develop extremely compromised
    respiratory function
  • Pulmonary Aspiration, Pneumonia
  • Chronic Alveolar hypoventilation because of
    impaired neuromuscular function -gt chronic
    hypercapnea
  • Decreased FRC, VC, MIP
  • Avoid premeds very sensitive to respiratory
    depressant effects of narcotics and benzos

31
Anesthetic Concerns MD
  • Avoid Etomidate
  • May cause myoclonus and precipitate contractures
  • Avoid Sux
  • Produces an exaggerated contracture
  • Susceptible to MH
  • Avoid Anticholinesterases may precipitate
    contracture by increasing ACh available at NMJ
  • Keep room warm shivering may lead to
    contractures

32
Anesthetic Concerns MD
  • Exaggerated effects of myocardial depression from
    inhaled agents- even Asymptomatic pts have some
    degree of cardiomyopathy
  • Anesthesia and surgery could theoretically
    aggravate co-existing cardiac conduction blockade
    by increasing vagal tone or causing transient
    hypoxia of the conduction system
  • Pregnancy
  • Exacerbation of symptoms is likely
  • Uterine atony and retained placental often
    complicate vaginal delivery

33
Guillaume Benjamin Amand Duchenne
  • The French neurologist, who studied and defined
    many neuromuscular diseases, in the mid 1900s,
    including the one named for him

34
Completely irrelevant side note
  • Duchenne investigated facial expression in a
    crude but effective manner of shocking the
    facial muscles using galvanic current defined
    facial expressions

35
Duchenne Muscular Dystrophy
  • Most common muscular dystrophy encountered by
    anesthesiology
  • Incidence 13,500 live male births
  • Characterized by painless degeneration and
    atrophy of skeletal muscles
  • X-linked disorder
  • DMD gene isolated to short arm of the X
    chromosome at position 21
  • Estimated mutation rate is one of the highest for
    any human disease

36
Duchenne Muscular Dystrophy
  • DMD gene product dystrophin
  • Absent or nonfunctional in DMD patients
  • Associated with muscle cell membranes
  • In its absence, a sequence of events occurs that
    leads to calcium influx into the muscle cells -gt
    cell degeneration and death
  • Affects Skeletal, Cardiac, and Smooth muscle

37
  • Progressive disease course

38
DMD Disease Progression
  • Under 2 yrs old
  • Behave like healthy toddlers
  • 2-5 yrs old
  • First outward signs of muscular weakness
  • Clumsiness, frequent falling, waddling gait,
    difficulty climbing stairs
  • Calf muscles begin to look enlarged
  • 6-12 yrs old
  • Child walks on toes secondary to Achilles tendon
    tightening and to compensate for weak quads
  • Weakening pelvic and shoulder girdles -gt
    compensatory lordosis

39
Gowers Maneuver
40
DMD Disease Progression
  • 8-14 yrs old
  • Lose ability to walk
  • Decrease in caloric requirements -gt even normal
    diet leads to obesity
  • 95 develop scoliosis
  • Adult phase
  • Scoliosis weakened respiratory muscles,
    inactivity, obesity -gt compromised lung expansion
    and function
  • Vital capacity decreased approximately 50
  • Weak cough -gt vulnerable to pneumonia
  • Late 20s
  • 90 die of respiratory complications, 10 cardiac

41
Cardiopulmonary Dysfunction
  • Degeneration of cardiac muscle inevitable
  • Tall R waves in V1 deep Q waves in limb leads
    short PR intervals sinus tach
  • MR due to papillary muscle dysfunction
  • Decreased cardiac contractility
  • Pulmonary difficulties
  • Chronic weakness predisposes to decreased ability
    to cough, leads to accumulation of secretions -gt
    pneumonia
  • Sleep apnea common -gt pulmonary hypertension

42
Case Report DMD, PEG, and LMA
  • 20 yr old with DMD
  • Chronic Respiratory Failure
  • Vital Capacity 450 mL (9 predicted)
  • Maximum inspiratory and expiratory pressures -20
    and 5 cm H2O
  • To generate effective cough MEP gt60
  • Cough peak flow of 40 L/min
  • Cough lt160 L/min associated with ineffective
    airway clearance
  • On 24 hr nasal BiPAP, settings 20/7, rate 16

43
Case Report DMD, PEG, and LMA
  • CHF
  • LVEF 20
  • Physical Exam
  • hypertrophied tongue
  • MP III
  • muscle strength 1-2/5 upper and lower extremities

44
Case Report DMD, PEG, and LMA
  • Procedure performed in PACU
  • Standard monitors
  • Premed 1mg Midazolam, just prior to induction
  • Induction
  • 300mcg/kg/min Propofol, adj for maintenance as
    needed
  • 30 mg Ketamine
  • SV with NPPV until eyelash reflex abolished

45
Case Report DMD, PEG, and LMA
  • Appropriate LMA inserted
  • Well lubricated gastroscope passed through the
    mouth, behind LMA
  • LMA deflated as necessary to allow better scope
    navigation
  • Ventilation assisted as needed to maintain PaCO2
    35-40
  • LMA removed after procedure under deep sedation
    with spontaneous ventilation, and NPPV replaced
  • PICU monitoring overnight, d/c home lt 24 hours

46
(No Transcript)
47
Why this type of anesthetic?
48
Anesthesia Concerns with DMD
  • Lingular hypertrophy difficult intubation
  • Association with MH has been suggested but not
    validated
  • But, avoid volatile agents if possible, and keep
    Dantrolene available

49
Anesthesia Concerns with DMD
  • NDMRs ok, but action is prolonged
  • SUX IS CONTRAINDICATED
  • Regenerating muscle fibers, common in DMD until
    at least 8 years of age, are considered to be
    more vulnerable to the effects of SUX
  • Difficult Extubation
  • Endotracheal edema
  • Mucosal congestion
  • Inability to clear retained secretions
  • Acute respiratory failure

50
Review Questions (Hall)
  • 173. Which of the following diseases is
    associated with increased resistance to
    neuromuscular blockade?
  • A. Myasthenia Gravis
  • B. Myasthenic Syndrome
  • C. Huntingtons chorea
  • D. Duchenne muscular dystrophy

51
Answer A
  • Myasthenia Gravis
  • Fewer AChRs.
  • Resistant to Sux.
  • Sensitive to NMDRs.
  • Myasthenic Syndrome (Eaton Lambert)
  • Decreased release of Ach but normal number of
    AChRs
  • Sensitive to Sux and NMDRs
  • Huntingtons chorea
  • Decreased plasma cholinesterase activity
  • Prolonged response to Sux
  • Duchenne Muscular Dystrophy
  • Sux is relatively contraindicated
  • NMDRs have a normal response, although patients
    have prominent skeletal muscle weakness.

52
Review Questions (Hall)
  • 489. 37 y/o male with myasthenia gravis, to ED,
    confused, agitated, 2 day h/o weakness, SOB. RR
    30 breaths/min, TV 4mL/kg.
  • ABG PaO2 60 PaCO2 51 HCO3 -25 pH 7.3
    SaO2 90
  • Edrophonium 5mg iv -gt TV 2mL/kg
  • A. Tracheal Intubation and Mechanical Ventilation
  • B. Repeat Edrophonium
  • C. Neostigmine 1 mg IV
  • D. Emergency Trach
  • E. Atropine 0.4 mg IV

53
Answer A
  • Cholinergic crisis vs. myasthenic crisis
  • Cholinergic crisis worsens with administration of
    anticholinesterase
  • Pt should be electively intubated until strength
    returns.

54
Review Questions (Hall)
  • 669. A lumbar epidural is placed in a 24 y/o G1P0
    with myasthenia gravis. Select the true
    statement regarding neonatal MG.
  • A. The newborn is usually affected.
  • B. The newborn is affected by maternal IgM
  • C. The newborn may require anticholinesterase
    therapy for up to 3 weeks
  • D. The newborn will need lifelong treatment
  • E. Only female newborns are affected

55
Answer C
  • IgG antibodies are directed against AChRs
  • IgG can cross placenta
  • Neonatal MG is characterized by muscle weakness
    (hypotonia, respiratory difficulty)
  • Presents within the first 4 days of life (80
    within first 24 hours)
  • Anticholinesterase therapy may be required until
    the maternal IgG is metabolized

56
References
  • Bach JR, Ishikawa Y, Kim H. Prevention of
    Pulmonary Morbidity for patients with Duchenne
    Muscular Dystrophy. Chest 19971121024-28
  • Benumoff JL, ed. Anesthesia Uncommon Diseases,
    4th Ed. Philadelphia WB Saunders. 9, 373-4
  • Brimacombe J, Newell S, Bergin A, et al. The
    Laryngeal Mask for Percuatneous Endoscopic
    Gastrostomy. Anesth Analg 200091635-6
  • Dillon FX. Anesthesia issues in the perioperative
    management of myasthenia gravis. Semin Neurol.
    2004 Mar24(1)83-94.
  • Faust RJ, ed. Anesthesiology Review, 3rd Ed.
    Philadelphia Churchill Livingstone. 490-494
  • Hara K, Sakura S, Saito Y, et al. Epidural
    Anesthesia and Pulmonary Function in a Patient
    with Amyotrophic Lateral Sclerosis. Anesth Analg
    199683878-9

57
References
  • Morris P. Duchenne Muscular Dystrophy a
    challenge for the anaesthetist. Paediatric
    Anaesthesia 199761-4
  • Moser B, Lirk P, Lechner M, et al. General
    anaesthesia in a patient with motor neuron
    disease. Eur J Anesthes 200421921-922
  • Otsuka N, Igarashi M, Shmiodate, et al.
    Anesthetic management of two patients with
    amyotrophic lateral sclerosis. Masui. 2004
    Nov53(11)1279-81
  • Pope JF, BirnKrant DJ, et al. Noninvasive
    Ventilation during percuatneous gastrostomy
    placement in Duchenne Muscular Dystrophy. Pediatr
    Pulmonol 199723468-471
  • Stoelting RK, Dierdor SF, ed. Anesthesia and
    Co-Existing Disease, 4th Ed. Philadelphia
    Churchill Livingstone. 217,517-519,522-528
  • Yao FS, ed. Anesthesiology Problem-Oriented
    Patient Management, 5th Ed. Philadelphia
    Lippincott Williams Wilkins.1019-1032
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