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Neuromuscular Emergencies

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Neuromuscular Emergencies Hanni Bouma Drugs that exacerbate MG Antibiotics: Aminoglycosides (genta, tobra) Fluroquinolones (cipro) Macrolides (erythromycin, azithro ... – PowerPoint PPT presentation

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Title: Neuromuscular Emergencies


1
Neuromuscular Emergencies
  • Hanni Bouma

2
Objectives
  • Discuss the approach to neuromuscular respiratory
    failure
  • Signs Symptoms
  • Differential diagnosis
  • When to intubate
  • Brief overview of GBS MG

3
Case 1
  • 26 yo previously healthy F p/w tingling in feet
    since 1 week ago. Two days later noticed
    difficulty climbing stairs, followed by weakness
    of her arms. She is areflexic.
  • What percentage of patients with her disease
    develop resp failure?

4
Case 1
  • A) 5
  • B) 10 to 20
  • C) 25 to 50
  • D) 70 to 85

5
Case 2
  • 73 yo M adm w/ 3-month history of progressive
    proximal weakness
  • 1 day after muscle biopsy, noticed on rounds to
    be breathless
  • What are we likely to see if this patient is in
    resp failure?

6
Case 2
  • A) Significant accessory muscle use
  • B) Pt complaining that I cant breathe!
  • C) Shallow breaths weak cough neck flexor
    weakness
  • D) Able to count to 40 in a single breath

7
Case 3
  • 63 yo M with limb-onset ALS since 2007 p/w
    choking sensation, difficulty getting air in
  • Not on home BiPAP
  • No prior aspiration pneumonias no fever, no
    leukocytosis

8
Case 3
9
Case 3
10
Case 3
  • Which of the following are you LEAST likely to
    find in this patient?
  • A) FVC 1.1 L, MIP -20, MEP 30
  • B) MEP 40, MIP unable to complete
  • C) pH 7.35, pCO2 60, bicarb 36
  • D) FVC 4 L, MIP -90, MEP 100

11
What can cause generalized weakness leading to
resp failure?
  • Spinal cord lesion
  • Cervical cord compression, transverse myelitis
  • Motor neuron lesion
  • ALS
  • Peripheral nerve lesion
  • GBS, CIDP, critical illness polyneuropathy, Lyme
    disease, tick paralysis, toxic
  • NMJ disorder
  • MG, LEMS, botulism, organophosphate poisoning
  • Muscle lesion
  • Polymyositis, dermatomyositis, critical illness
    myopathy, hyperthyroidism, congenital myopathy
    (muscular dystrophy), mitochrondrial myopathy

12
Mechanisms of NM resp failure
  • 1) Upper airway obstruction
  • Facial, oropharyngeal, laryngeal weakness ?
    mechanical obstruction in supine position
  • impaired swallowing/secretion clearance ?
    aspiration
  • 2) Inspiratory muscle weakness? atelectasis ? V/Q
    mismatch ? hypoxia
  • 3) Expiratory muscle weakness ? weak cough/poor
    secretion clearance ? aspiration pneumonia
  • 4) Acute complications ? PE, pneumonia, etc.

13
History
  • Time course?
  • progressive weakness over hours to days ? GBS
  • fluctuating weakness (on an hourly basis) present
    for weeks/months ? MG
  • Distribution of weakness?
  • Proximal gt distal (MG GBS)
  • Ascending in GBS
  • Initally EOM/oropharyngeal muscle weakness, then
    generalizes in botulism
  • Sensory Sx.?
  • Distal paresthesias common in GBS
  • No sensory invt in MG

14
History
  • Pain?
  • Low backache frequently in GBS neck pain
    C-spine lesion?
  • Antecedent illness?
  • 60 of GBS triggered by viral URT illness or
    C.jejuni gastro
  • 40 of myasthenic crises triggered by infection
  • Medications
  • Exposure to fertilizers pesticides?
  • Organophosphate poisoning
  • Recent diet
  • Botulism from home-canned goods

15
Exam Signs of resp failure
  • Tachycardia
  • Rapid, shallow breathing
  • Stridor
  • Weak cough, nasal voice, pooling of saliva (signs
    of bulbar dysfunction)
  • Orthopnea (abnormal if VC drops gt10 supine)
  • Staccato speech the need to pause between words
  • Abdominal paradox diaphragm weakness
  • weakness of neck trapezius muscles (parallels
    diaphragm weakness)
  • Single-breath count ask them to inhale fully
    count from 1 to 50. If lt25, sign of severe
    impairment of VC

Mehta, S. Neuromuscular disease causing acute
respiratory failure. Respiratory Care, 2006. 51
(9) 1016-1023.
16
Focused exam
  • HEENT
  • look for pooled secretions
  • Swallow test
  • Dysphonia (nasal voice from palatal paralysis)
  • Dysarthria
  • Lungs
  • Diaphragm observe/palpate for normal, outward
    abdominal movement with inspiration
  • Cough strength
  • Count test (1 to 50)

17
Neuro exam
  • CNs
  • Pupils
  • Reactivity may be lost in botulism or
    Miller-Fisher variant of GBS
  • EOM
  • weakness ptosis characteristic of MG, but also
    seen in MF, botulism, etc.
  • Face, palate, tongue, neck strength
  • Motor exam
  • Fasciculations? (ALS, organophosphate poisoning)
    tone power (distribution of weakness? Fatigable
    weakness?)
  • Sensory
  • Distal sensory loss in GBS
  • Sensory level at C-spine level w/ quadriparesis
    C-spine lesion
  • Coordination
  • Ataxia in MF variant of GBS
  • Reflexes
  • Areflexia in GBS usually preserved reflexes in
    MG

18
Investigations
  • Bedside PFTs 20/30/40 rule
  • Vital capacity (max exhaled volume after full
    inspiration). Normal 60 ml/kg (4 L in 70 kg
    person). VC lt 20 ml/kg (or 1 L) means intubation
  • Max inspiratory pressure. Index of ability to
    avoid atelectasis. Normal lt-50 cm H2O. MIP gt-30
    means intubation
  • Max expiratory pressure. Index of ability to
    cough/clear secretions. Normal gt60 cm H2O. MEP
    lt40 means intubation
  • PFTs may be low if inadequate mouth closure from
    facial palsy, and may fluctuate in MG

19
Investigations
  • ABG
  • Hypercarbia (PCO2 gt 45 mmHg) hypoventilation
  • PCO2 often normal or low until late in NM resp
    failure
  • Hypoxia (PO2 lt 75 mmHg) V/Q mismatch ? usually
    atelectasis or pneumonia in this setting

20
Investigations
  • Basic labs (CBC, SMA-10, LFTs, CK)
  • CXR
  • EKG (electrolyte D/O GBS assd w/ dysautonomia ?
    arrhythmias)

21
General care
  • Electrolytes low potassium, high magnesium low
    phosphate ? exacerbate muscle weakness
  • Serial PFTs (MIP/MEP/FVC) bid to qid
  • Chest physio, suctioning incentive spirometry
  • DVT prophylaxis
  • HOB elevation
  • NPO if bulbar weakness NG or Dobhoff feeding
  • Bowel/bladder paralysis predisposes to
    constipation GBS pts may have urinary retention

22
Determine
  • If resp failure is imminent
  • If ICU should be involved
  • What is the localization?

23
Predictors of need for MV
  • 20/30/40 rule
  • or a reduction in VC, MIP, MEP by gt30
  • PO2 lt70 mmHg on RA or PCO2 gt50 mmHg w/ acidosis
  • Dysarthria, dysphagia, impaired gag reflex
  • In GBS
  • Time from onset to admission lt 7 days
  • Inability to cough
  • Inability to stand
  • Inability to lift elbows or head
  • LFT increases
  • Presence of autonomic dysfxn

Sharshar T, Chevret S, Bourdain F, Raphael JC.
Early predictors of mechanical ventilation in
Guillain-Barre syndrome. Crit Care Med
200331(1)278283.
24
Intubation things to think about
  • Code status?
  • Identify imminent resp failure early to avoid
    emergency intubation
  • Minimizes atelectasis/pneumonia
  • Minimizes complications of intubation specific to
    GBS MG
  • Dysautonomia can cause severe bradycardia, BP
    shifts, profound hypotension w/ sedatives
  • Denervated muscle can cause fatal hyperkalemia
    with use of succinylcholine
  • Avoid depolarizing NM blockers
  • Small doses of benzos

25
NPPV?
  • Few studies on its use in GBS MG
  • Inappropriate if upper airway function severely
    impaired or hypercapnic resp failure

26
GBS
  • Most common cause of acute or subacute gend
    paralysis
  • Monophasic AIDP autoimmune attack against
    surface antigens on peripheral nerves
  • Develops 5 days to 3 weeks after resp/GI
    infection in 60
  • Campylobacter jejuni (26)
  • Viral URTI, influenza
  • EBV, CMV, VZV, HIV, hep A B, coxsackie
  • Other precipitants immunization, pregnancy,
    surgery, Hodgkins disease

27
Presentation
  • Sensory
  • distal paresthesias/numbness (earliest Sx.)
  • Reduced vibration/proprioception
  • Motor
  • Symmetric evolves over days to 1-2 wks
  • Ascending LE before UE proximalgt distal
  • May progress to involve trunk, intercostals,
    neck, bulbar, B/L FNs
  • Median duration from onset to max weakness 12
    days
  • Reflexes reduced, then absent
  • Autonomic instability
  • Sinus tachy/brady, arrhythmias, labile BP (esp
    hypertension), urinary retention, anhydrosis
  • Other low backache very common, myalgias

28
Investigations
  • EMG
  • Reduced conduction velocities
  • Loss of F waves
  • Conduction block in motor nerves
  • Reduced motor amplitudes 2 axonal damage ?
    worse Px.
  • CSF
  • High protein (may be normal in first 2 days)
  • No cells or few lymphs
  • 10 have 10-50 lymphs

29
Management
  • Admit for observation (potential for
    deterioration)
  • Determine if resp failure imminent
  • Dysautonomia most frequently sustained HTN
    tachycardia
  • Esp in older pts w/ CAD, consider Labetolol
  • Hypotension in 10 ? fluids, pressors
  • PLEX (4-6 Rx. q1-2d) IVIG (0.4g/kg/d x 5 d)
  • Equally effective
  • PLEX useful in first 2 weeks benefit less clear
    after that
  • Steroids no proven benefit

30
Course
  • Progression over 1-4 weeks
  • Plateau 2-4 months
  • Recovery few wks to months
  • Mortality 3-5
  • Poor prognosis
  • Resp failure requiring intubation
  • Advanced age
  • Very low distal motor amplitudes (axonal damage)
  • Rapidly progressive weakness over 1 week

31
MG
  • Ab-mediated attack on nicotinic Ach rec ?
    defective transmission across NMJ
  • Bimodal F 20-30 yo M 50-60 yo
  • 2 autoimmune forms
  • Ach receptor Ab 80 with generalized MG 50
    with ocular MG
  • Anti-MuSK Ab 50 of patients who are Ach rec Ab
    negative typically female with prominent bulbar
    weakness

32
Presentation
  • Motor
  • Fluctuating, fatigable weakness involving eyes
    (90), face/neck/oropharynx (80), limbs (60)
  • Limbs rarely affected in isolation
  • Rest restores strength (at least partially)
  • Usually insidious onset
  • Sensory normal
  • Reflexes preserved
  • Thymic abnormalities
  • Malignant thymoma in 10-15 (more severe disease)
  • Thymic hyperplasia in 50-70

33
Myasthenic Crisis
  • Defined by resp failure requiring ventilatory
    assistance
  • Occurs in 20-30 mortality 5
  • Common precipitants
  • Infection in 40 (esp respiratory)
  • Pregnancy
  • Medications
  • Aspiration
  • Surgery
  • Emotional upset, hot environment

34
Drugs that exacerbate MG
  • Antibiotics
  • Aminoglycosides (genta, tobra)
  • Fluroquinolones (cipro)
  • Macrolides (erythromycin, azithro, tetracycline,
    doxycycline)
  • Cardiac
  • All beta-blockers
  • Calcium channel blockers
  • Class I anti-arrhythmics (quinidine,
    procainamide)
  • Anticonvulsants
  • Phenytoin, CBZ
  • Antipsychotics, lithium
  • Thyroid hormones
  • Magnesium toxicity
  • Iodinated contrast agents
  • Muscle relaxants
  • Baclofen
  • Long-acting benzos
  • Too much anticholinesterase

35
Investigations
  • Ach receptor Abs
  • Anti-MuSK Abs
  • EMG
  • Repetitive nerve stimulation gt10 decrement in
    amplitude betw 1st 5th CMAP
  • Sens/spec 90 when weak, proximal muscles
    stimulated lt50 sens in pts w/o limb weakness
  • Single-fiber jitter (variation in time
    interval betw firing of muscle fibers in same
    motor unit)
  • Sens gt95 for MG but not specific
  • Edrophonium (Tensilon) test
  • Not recommended in suspected crisis

36
Management
  • Determine if resp failure imminent
  • Stop exacerbating meds
  • Treat infection
  • Symptomatic therapy (mild-moderate weakness)
  • Cholinesterase inhibitors (Mestinon)
  • Short-term disease suppression
  • To hasten clinical improvement in hospitalized
    pts w/ crisis or impending crisis
    pre-operatively chronic refractory disease
  • PLEX improvement w/i days, but lasts only 2-4
    wks
  • IVIG benefit may last up to 30 days
  • Comparable benefits
  • Long-term immunosuppression
  • When weakness is inadequately controlled by
    Mestinon
  • Prednisone
  • Azathioprine (if steroid failure or excessive SE)

37
Key points
  • 20/30/40 rule
  • Identify pts at risk for resp failure EARLY to
    avoid emergency intubation
  • Dont wait for pts to complain of SOB before
    doing bedside PFTs
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