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Neuromuscular Emergencies Hanni Bouma R3 Neurology Outline Approach to neuromuscular respiratory failure Signs & Symptoms Investigations Knowing when (to ask someone else) to intubate Overview of: Myasthenic crisis GBS Botulism True or false? Regarding GBS… ~10% of pts will require intubation. All cases of suspected GBS should be treated with either IVIG or PLEX. Normal CSF protein precludes the diagnosis. Hypertension is the most common autonomic complication. Case 1 A 32-yo M with MG since age 20, on stable dose of pred 40, Imuran, and Mestinon, is admitted to hospital for elective bowel surgery (complications of diverticulitis) Pt. has persistent diplopia and mild fatigable weakness at the deltoids The surgery team calls you the morning of his scheduled surgery to ask if they should do anything for his myasthenia. Case 1 You should: A) Suggest switching to equivalent dosage of IV steroids while NPO B) Review med list & advise re: drugs that might trigger a crisis (ie. Antibiotics!!) C) Kindly recommend postponing the surgery for pre-op IVIG or PLEX D) All of the above Case 2 A 10-month-old infant presents with constipation and poor feeding followed by progressive hypotonia, descending weakness, dilated pupils, and bilateral ptosis. What is the likely diagnosis? How was it likely acquired? How would you treat him? Case 3 You are called to see a patient in ICU with known diagnosis of MG, recurrent crises leading to ICU admissions, on stable dose of pred 60 mg qd and Imuran. Admitted with MG crisis, intubated then trach’ed. Now, 2 weeks later, “doing better” as per ICU. They want to start tapering his prednisone. What do you advise them to do? Case 3 1) Agree with their plan to begin a slow tapering course by 10 mg qweek initially. 2) Discuss the patient with their treating neurologist. 3) Advise them to avoid rapid tapering of steroids given the risk of recurrent crisis. 4) Both 2 & 3. Part 1: Neuromuscular Respiratory Failure Respiratory Failure Basics Type I: Hypoxia without hypercapnia Usually associated with ↑ WOB V/Q mismatch most common Vascular disease/shunts (PE, Pulm. HTN, R->L shunts) Interstitial lung disease (ARDS, cardiogenic pulmonary edema, pneumonia) Pneumothorax, atelectasis Type II: Hypercapnia with or w/o hypoxia A.k.a. hypoventilation Neuromuscular conditions Deformities (kyphoscoliosis) Reduced breathing effort (extreme obesity, drug effects, brainstem lesion affecting respiratory drive) Increased airway resistance (asthma, COPD) Neuromuscular Causes 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 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 > distal (MG & GBS) Ascending in GBS Sensory Sx.? Distal paresthesias common in GBS No sensory inv’t in MG History +FH? 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 Exam Long, thin face? (myotonic dystrophy? Congenital?) Skin rash (dermatomyositis? CNs Pupils: Reactivity may be lost in botulism or Miller-Fisher variant of GBS EOM: Opthalmoparesis or ptosis (MG? mitochondrial D/O? MFS?) Presence or absence of bulbar weakness? Motor exam: Fasciculations? (ALS, organophosphate poisoning); tone; power (fatigable weakness? Distribution proximal vs. distal?) Exam Sensory: Normal in MG Distal sensory loss in GBS, esp vib/prop Sensory level at C-spine level w/ quadriparesis = Cspine lesion Coordination: Ataxia in MF variant of GBS Reflexes: Areflexia in GBS; preserved in MG Mechanisms 1) Bulbar dysfunction: Facial, oropharyngeal, laryngeal weakness upper airway obstruction in supine position Impaired swallowing aspiration 2) Inspiratory muscle weakness/diaphragmatic paralysis atelectasis V/Q mismatch hypoxia 3) Expiratory muscle weakness hypoventilation AND weak cough/poor secretion clearance aspiration, pneumonia 4) Acute complications PE Symptoms If subacute (ie. GBS): dyspnoea and orthopnoea If gradual onset, inadequate respiration usually occurs first during sleep Symptoms of nocturnal hypoventilation: Easy to overlook a broken sleep pattern, nightmares, nocturnal confusion, morning headache, daytime fatigue, mental clouding and somnolence. SOBOE less common in NMDs than in those with other Cardioresp D/O (reduced mobility) Dyspnoea when lying flat or immersed in water suggests weakness of the diaphragm Warning signs Rapid, shallow breathing Stridor Bulbar weakness weak cough, nasal voice, pooling of saliva Orthopnea Staccato speech Abdominal paradox http://www.youtube.com/watch?v=RFGzdNFu XIM Weakness of neck & trapezius muscles Single-breath count Mehta, S. “Neuromuscular disease causing acute respiratory failure.” Respiratory Care, 2006. 51 (9): 1016-1023. 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 < 20 ml/kg (or 1 L) means intubation Max inspiratory pressure. Index of ability to avoid atelectasis. Normal = > 80 cm H2O (male), >70 cm H2O (female). MIP >-30 means intubation Max expiratory pressure. Index of ability to cough/clear secretions. Mean MEP = 140 cm H2O (male), 95 cm H20 (female). MEP <40 means intubation Investigations ABG: Hypercarbia (PCO2 > 45 mmHg) • PCO2 often normal or low until late in NM resp failure • • Established resp failure from NMDs: low pO2, normal pH, elevated bicarb & pCO2 Elevations of bicarb & pH with normal pO2 & pCO2 suggest nocturnal hypoventilation Hypoxia (PO2 < 75 mmHg) = usually atelectasis or pneumonia in acute setting Basic labs (CBC, SMA-10, LFTs, CK) CXR Predictors of need for MV 20/30/40 rule or reduction in VC, MIP, MEP by >30% PO2 <70 mmHg on RA or PCO2 >50 mmHg w/ acidosis Dysarthria, dysphagia, impaired gag reflex Intubation: things to think about Code status? Call ICU if signs of imminent resp failure Identify early to avoid emergency intubation…elective intubation always preferred Minimizes atelectasis/pneumonia Minimizes complications of intubation specific to NMDs Avoid depolarizing NM blockers NPPV? Few studies on its use in GBS & MG Inappropriate if upper airway function severely impaired More often used in chronic NMDs (ALS, muscular dystrophies) for chronic hypoventilation General care Serial PFTs (MIP/MEP/FVC) bid to qid Electrolytes: low potassium, high magnesium & low phosphate exacerbate muscle weakness Chest physio, suctioning & incentive spirometry DVT prophylaxis HOB elevation NPO if bulbar weakness; NG or Dobhoff feeding Part 2: MG GBS Botulism 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 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) Sensory: normal Reflexes: preserved Thymic abnormalities: Malignant thymoma in 10-15% (more severe disease) Thymic hyperplasia in 50-70% Investigations Ach receptor Abs Anti-MuSK Abs Edrophonium (Tensilon) test: obsolete EMG: Repetitive nerve stimulation: >10% decrement in amplitude betw 1st & 5th CMAP Single-fiber: “jitter” Sens >95% for MG but not specific Management: general Symptomatic therapy (mild-moderate weakness): Short-term disease suppression: Cholinesterase inhibitors (Mestinon) To hasten clinical improvement in hospitalized pts w/ crisis or impending crisis; pre-operatively; chronic refractory disease PLEX or IVIG Long-term immunosuppression: When weakness is inadequately controlled by Mestinon Prednisone Azathioprine (if steroid failure or excessive SE) Cyclosporine, Mycophenolate mofetil… Myasthenic Crisis Defined by resp failure requiring ventilatory assistance Occurs in 20-30%; mortality 5% Common precipitants: Infection in 40% (esp respiratory) Medications Surgery Pregnancy Aspiration Drugs that exacerbate MG Antibiotics: (**Penicillins like Tazocin are OK!) Aminoglycosides (genta, tobra) Fluroquinolones (cipro) Macrolides (erythromycin, azithro, tetracycline, doxycycline) Cardiac: All beta-blockers Calcium channel blockers Anticonvulsants: Phenytoin, CBZ Antipsychotics, lithium Thyroid hormones Magnesium toxicity Iodinated contrast agents Muscle relaxants Baclofen Long-acting benzos **Too much anticholinesterase Myasthenic crisis: management General Determine if resp failure is imminent!! Stop any meds that may be contributing Mestinon usually stopped as well May contribute to increased airway secretions in intubated patients Treat any infection Myasthenic Crisis: management Specific PLEX or IVIG: start one or the other, quickly Comparable efficacy Evidence somewhat limited…TBD later Earlier response seen with PLEX, but more adverse events Preference somewhat individualized… Myasthenic crisis: management PLEX Removal of anti AChR and antiMuSK Abs 1 session/day x 5 Rapid onset of action (3-10 days) Need central line with associated complications No superiority of PLEX qd x 5 vs qod x 5 PTX, hemorrhage, line sepsis Caution in pts with sepsis, hypotension; may lead to increased bleeding and cardiac arrhythmias Myasthenic crisis: management IVIG 0.4g/kg/day x 5 days Easily administered and widely available Long duration of action May last as long as 30 days Side effects Anaphylaxis in IgA deficiency Renal failure, pulmonary edema Aseptic meningitis Thrombotic complications and stroke Myasthenic crisis: management Therapeutic effect of PLEX & IVIG is shortlived…lasts weeks Therefore, glucocorticoids started at high dose (60 to 80 mg qd) as well Onset of benefit at 2-3 wks, peaks at 5.5 mos Initiation ass’d with transient worsening of weakness, serious in up to 50% Occurs 5-10 days after initiation & lasts 5-6 days Resp failure requiring MV in up to 10% Concomitant use of PLEX or IVIG helps to prevent this transient worsening GBS Most common cause of acute or subacute gen’d 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, Hodgkin’s disease Presentation Sensory: distal paresthesias/numbness (earliest Sx.) Reduced vibration/proprioception Motor: Symmetric; evolves over days to 1-2 wks Ascending: LE before UE; proximal> distal Reflexes: reduced, then absent Autonomic instability Other: low backache very common, myalgias Investigations NCS/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 Management Admit for observation (potential for deterioration) Determine if resp failure imminent IVIG (0.4g/kg/d x 5 d) or PLEX (4-6 Rx. q1-2d) Equally effective (2012 AAN guideline) PLEX useful in first 2 weeks; benefit less clear after that…also more adverse effects Steroids no proven benefit Predictors of need for MV in GBS Time from onset to admission < 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 2003;31(1):278–283. Course Progression over 1-4 weeks 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 Botulism Toxin is a presynaptic blocker of Ach release Onset of Sx. 12-36 hours after ingestion Prodrome: N/V, abdo pain, diarrhea, dry mouth Symmetric neurologic deficits First develop acute cranial neuropathies (opthalmoplegia, can be total; B/L ptosis, dysphagia, dysarthria, facial weakness) Blurred vision secondary to pupillary dilatation Descending muscle weakness No sensory deficits apart from blurred vision Urinary retention/constipation (smooth muscle paralysis) Respiratory failure is primary cause of death “Dozen Ds” of Botulism dry mouth diplopia dilated pupils droopy eyes droopy face diminished gag reflex dysphagia dysarthria dysphonia difficulty lifting head descending paralysis diaphragmatic paralysis Botulism Investigation: Foodborne: serum analysis for toxin by bioassay in mice Analysis of stool, vomitus, and suspected food items may also reveal toxin Infantile: isolation of C.botulinum spores & toxin detection in stool EMG Treatment: Equine serum heptavalent botulism antitoxin Children older than 1 year of age and adults Human derived botulism immune globulin (BIG-IV or BabyBIG) Infants less than 1 year of age Key points 20/30/40 rule Identify pts at risk for resp failure EARLY to avoid emergency intubation Don’t wait for pts to complain of dyspnea before doing bedside PFTs