Neuromuscular Flashcards
Amyotrophic Lateral Sclerosis (ALS)
Background
Considerations
Goals
Conflicts
Amyotrophic Lateral Sclerosis (ALS)
Background
Progressive degenerative disease of upper & lower motor neurons leading to denervation & atrophy of skeletal muscle with resultant weakness & eventual death
Considerations
Aspiration risk due to bulbar dysfunction
Perioperative respiratory failure due to weakness & aspiration
Autonomic dysfunction
Altered response to neuromuscular blockers:
Succinylcholine contraindicated due to hyperkalemia risk
NdMR (nondepolarizing muscle relaxant) sensitivity
Chronic pain (often girdle area)
Goals
Minimize aspiration risk (prophylaxis, consider RSI)
Maximize respiratory function (muscle strength, secretion & pain management)
Anticipate potential need for postop ventilation/ICU
Maintain stable hemodynamics
Conflicts
RSI vs. avoid succinylcholine/sensitive to NdMRs
RSI vs. maintain hemodynamic stability
Regional vs. existing neurologic deficits:
Epidural documented in case reports but be cautious of high block
Peripheral nerve blocks not documented because disease so rare but definitely a consideration given respiratory muscle weakness
Avoid interscalene so as to not compromise phrenic nerve
General anesthetic vs. respiratory depression (neuraxial is safe)
Guillain-Barre Syndrome (GBS)
Background
Considerations
Goals
Conflicts
Pregnancy Considerations
Guillain-Barre Syndrome (GBS)
Background
Acute inflammatory demyelinating peripheral polyneuropathy usually secondary to immunologic response to viral or bacterial infection
Ascending progressive muscle weakness, autonomic dysfunction & areflexia
Respiratory compromise:
25% will require mechanical ventilation
Forced vital capacity < 20 mL/kg, maximum inspiratory pressure < 30 cmH2O, or maximum expiratory pressure < 40 cmH2O → high risk of impending respiratory failure, urgent intubation & mechanical ventilation
Considerations
Aspiration risk due to to bulbar dysfunction
Perioperative respiratory insufficiency due to muscle weakness (anticipate need for postoperative ventilation)
Autonomic dysfunction with possible hemodynamic instability & autonomic hyperreflexia type reactions:
Arrhythmias, cardiac arrest
Physical stimulation can precipitate hypertension & tachycardia
Altered response to neuromuscular blocking drugs (NMBs):
Succinylcholine contraindicated due to hyperkalemia risk
NdMR (nondepolarizing muscle relaxant) sensitivity
↑ risk of venous thromboembolism
Neuropathic pain common (40-50%)
Treatment includes IVIG & plasma exchange, steroids NOT recommended
Goals
Minimize aspiration risk (consider prophylaxis, RSI)
Maximize respiratory function (avoid NMBs or reduced dose of NdMR & full reversal, secretions, pain management)
Maintain hemodynamic stability
Conflicts
RSI vs avoid succinylcholine, hemodynamic stability
Neurologic deficits & regional techniques
Pregnancy Considerations
Controversy regarding neuraxial but probabaly safe, document pre-existing deficits
If general anesthetic chosen: avoid succinylchonline & avoid or use minimal NdMR
Multiple Sclerosis
Background
Considerations
Goals
Conflicts
Pregnancy Considerations
Multiple Sclerosis
Background
Heterogenous disorder with variable clinical & pathologic features
Inflammation, demyelination & denervation are the major pathologic mechanisms that cause the clinical manifestations
Cause unknown, most widely accepted theory is of an inflammatory immune-mediated disorder (?EBV related- Kris)
Considerations
Multisystem effects of demyelination:
Aspiration risk (bulbar dysfunction)
Respiratory failure/insufficiency (central hypoventilation & neuromuscular weakness)
Autonomic dysfunction with possible hemodynamic instability
Altered response to NMBs (neuromuscular blocking drugs):
Succinylcholine contraindicated due to hyperkalemia risk (denervation, misuse myopathy)
Sensitive to NdMRs (nondepolarizing muscle relaxants), but can also be resistant
Potential perioperative exacerbation of disease:
Neuraxial technique (spinal > epidural) but very controversial & some sources suggest regional/neuraxial acceptable
Hyperthermia
Immunosuppressive medications (steroids, interferon, methotrexate)
Goals
Minimize aspiration risk (consider prophylaxis, RSI)
Maximize respiratory function (avoid paralysis, full NMB reversal, secretions, pain management)
Maintain hemodynamic stability
Prevent postoperative exacerbations by avoiding triggers (hyperthermia, stress, +/- neuraxial)
Inform patient of potential perioperative aggravation of symptoms
Conflicts
Neuraxial technique vs. disease exacerbation:
Spinal traditionally considered contraindicated, but controversial
Low dose epidural most likely safe, have discussion with patient
Peripheral nerve block is safe, as those nerves are not involved
RSI vs. hemodynamic stability
RSI vs. avoid succinylcholine
Pregnancy Considerations
Neuraxial (both epidural/spinal) NOT contraindicated
Discuss risk with patient that there may be post-operative/post-delivery relapse, regardless of anesthetic technique
Myasthenic (Eaton-Lambert) Syndrome
Background
Considerations
Optimization
Goals
Myasthenic (Eaton-Lambert) Syndrome
Background
Autoantibodies are directed against presynaptic voltage-gated calcium channels
↓ release of acetylcholine
Frequently associated with cancers (paraneoplastic syndrome)
Considerations
Muscle weakness predisposing to respiratory failure after anesthesia; potential need for post-op PPV
Associated with lung carcinoma
Extremely sensitive to both succinylcholine & NdMRs (nondepolarizing muscle relaxants)
Autonomic dysfunction present in 30%
Optimization
Counsel & prepare for postop PPV/ICU
IVIG prep may help ↑ muscle strength
Goals
Minimize use of neuromuscular blockers, optimize postoperative ventilation status
Regional anesthesia preferred to general anesthesia if possible
Myotonic Dystrophy
Background
Considerations
Goals/Optimization
Conflicts
Pregnancy
Myotonic Dystrophy
Background
Clinically & genetically heterogeneous disorder with two major forms: type 1 (DM1) & type 2 (DM2)
Multisystem disorder characterized by skeletal muscle weakness & myotonia, cardiac conduction abnormalities, cataracts, testicular failure, hypogammaglobulinemia, & insulin resistance
Considerations
Multisystem disease:
Airway
Bulbar dysfunction & risk of aspiration
Central sleep apnea
Respiratory:
Restrictive lung disease (weak respiratory muscles)
Possible pulmonary hypertension
↓ ventilatory response to hypoxia/hypercarbia
Cardiac:
Cardiomyopathy
Dysrhythmias & heart blocks
GI:
Delayed gastric motility
Endocrine:
Hypothyroid, diabetes mellitus, adrenal insufficiency
Altered sensitivity to anesthetic agents:
Succinylcholine contraindicated due to risks of hyperkalemia & myotonic contractures
Sensitivity to CNS depessants (propofol, opioids, benzodiazepines, barbiturates)
Cholinesterase inhibitors may trigger myotonic contracture, don’t use neostigmine!
Risk of perioperative myotonic crisis:
Triggers:
Drugs (e.g., succinylcholine, neostigmine)
Surgical manipulation, electrocautery, nerve stimulator
Hypothermia/shivering
Treatment:
Phenytoin, procainamide, quinine, IM lidocaine, ↑ volatile anesthetic
Phenytoin/procainamide: 18mg/kg over 20 min
Quinine 300-600mg IV
Muscle relaxants & IV anesthetics do NOT work
Goals/Optimization
If elective, multidisciplinary discussion regarding plans for surgery
Prevent aspiration, administer aspiration prophylaxis
Avoid hemodynamic instability
Avoid precipitants of myotonic crisis & treat if required
Arrange appropriate disposition (need for post-operative monitoring, ventilation)
Conflicts
Need to prevent aspiration (RSI) vs contraindication to succinylcholine & high dose rocuronium (as reversal with neostigmine contraindicated)
Pregnancy
High risk pregnant patient: ↑ muscle weakness/myotonia, heart failure, uterine atony, postpartum hemorrhage
Neuraxial anesthesia is preferred for labor & vaginal or cesarean delivery
Parkinson’s Disease
Background
Considerations
Goals
Conflicts
Medications and Parkinson’s
Parkinson’s Disease
Background
Central dopamine deficiency leading to rigidity, tremors & late dementia
Considerations
Elderly with associated co-morbidities
Potential difficult airway (temporomandibular joint & cervical spine rigidity)
↑ risk of peri-operative complications:
Airway: airway obstruction
Pulmonary: aspiration (secondary to bulbar dysfunction, esophageal dysfunction & gastroparesis) & restrictive lung disease (secondary to chest wall rigidity)
Cardiac: autonomic instability
Neurologic: worsening of neurologic symptoms & risk of postoperative delerium
Management of medications (see paragraph below for further details):
Ensure perioperative use of anti-parkinson’s medications
Avoid medications which exacerbate/precipitate parkinsonism
Avoid meperidine in patients on selegiline
Goals
Safe airway management:
Aspiration prophylaxis
Modified RSI
Avoid clinical exacerbation:
Continue anti-parkinson medications perioperatively
Avoid anti-dopaminergic medications: droperidol, metoclopramide, methotrimeprazine
Maximize respiratory function
Prevent delirium
Conflicts
Aspiration risk vs autonomic instability/difficult airway
Regional anesthesia with tremulous patient vs risks of GA
Medications & Parkinson’s
Avoid drugs that precipitate or exacerbate Parkinson’s disease (ie. dopamine antagonists):
Metoclopramide
Butyrophenones (droperidol, haloperidol)
Phenothiazines (chlorpromazine, methotrimeprazine)
Selegiline (type B MAO inhibitor):
Used to prevent central breakdown of dopamine to improve parkinson’s symptoms
Usually safe as is not a type A MAO inhibitor
Avoid meperidine in patients taking selegiline (case reports of hyperthermia, agitation, muscle rigidity & seizures)
Opioids:
May have ↑ muscle rigidity with fentanyl & morphine
Dystonic reactions associated with use of alfentanil & fentanyl
Polymyositis & Dermatomyositis
Background
Considerations
Conflicts
Pregnancy considerations
Polymyositis & Dermatomyositis
Background
Idiopathic inflammatory myopathies characterized by proximal skeletal muscle weakness & evidence of muscle inflammation
Dermatomyositis but not polymyositis is associated with a variety of characteristic skin manifestations
Considerations
Potential difficult airway (restricted temporomandubular joint & cervical spine mobility)
Aspiration risk (esophageal dysfunction)
Respiratory:
Interstitial lung disease, pulmonary fibrosis
Potential postoperative respiratory muscle failure & need for ventilation
Cardiovascular:
Myocardial fibrosis, myocarditis, conduction defects, arrhythmias
Altered response to succinylcholine (theorectical hyperkalemia) & possible sensitivity to NdMRs (nondepolarizing muscle relaxants):
Avoid succinylcholine, consider ↓ rocuronium dose
Treatment: steroids, immunosuppressants, IVIG, monoclonal antibodies
Conflicts
RSI for aspiration risk vs. difficult intubation
RSI for aspiration risk vs. avoid succinylcholine
RSI for aspiration risk vs. cardiac induction
Pregnancy Considerations
Avoid succinylcholine if RSI for general anesthesia
Caution with neuraxial if already compromised respiratory muscles
Myasthenia Gravis
Background
Considerations
Goals
Conflicts
Pregnancy considerations
Weakness in PACU
Myasthenic Crisis vs Cholinergic Crisis
Myasthenia Gravis
Background
Autoimmune disorder characterized by weakness & fatigability of skeletal muscles
Weakness results from an antibody-mediated immunological attack directed at acetylcholine receptors (or receptor-associated proteins) in the postsynaptic membrane of the neuromuscular junction
Considerations
Bulbar/skeletal muscle weakness resulting in ↑ risk of:
Aspiration
Perioperative respiratory failure
Potential systemic complications:
Thymoma & possible anterior mediastinal mass
Myocarditis causing cardiomyopathy, atrial fibrillation, heart block
Altered response to NMB (neuromuscular blocking) medications:
Very sensitive to NdMR (nondepolarizing muscle relaxants): avoid or use 1/10 normal dose with continuous monitoring
Resistant to succinylcholine (ED95 2.6X normal)
Treatment: steroids, immunosuppressants, anticholinesterases
Risk of perioperative myasthenic or cholinergic crises
Goals
Minimize risk of aspiration (prophylaxis, RSI)
Minimize risk of perioperative respiratory failure (judicious NMBs & opioids) & anticipate need for post-op ventilation
Minimize risk of myasthenic or cholinergic crisis
Optimize neuromuscular function
Conflicts
RSI vs altered response to neuromuscular blockers
RSI vs cardiac involvement
RSI vs anterior mediastinal mass
Magnesium for pre-eclampsia in pregnancy vs contraindicated due to muscle weakness
Pregnancy Considerations
1/3 improve, 1/3 stay the same, 1/3 get worse
Exacerbations usually in 1st trimester with improvement in 2nd & 3rd
~ 30% experience relapse postpartum
↑ abortion, preterm labor, maternal morbidity & mortality
Cholinesterase inhibitors: minimal placental transfer but have uterotonic effects
Monitor for fatigue/weakness during labour (consider measuring vital capacity)
Magnesium is relatively contraindicated due to muscle weakness
Generally, neuraxial anaesthesia preferred (for labour & vaginal or cesarian delivery) unless severe bulbar or respiratory involvement, then consider general anesthetic for cesarian delivery:
Ester local anaesthetics may have prolonged half-life in patients taking cholinesterase inhibitors → increased risk of toxicity, use amide local anesthetics
In patients with moderate respiratory compromise, the use of BiPAP may improve the safety of neuraxial anesthesia
Be prepared for transfer to ICU for postpartum ventilation if severe disease
Neonatal myasthenia in 16% due to transfer of maternal IgG antibodies across the placenta, resolves in 3 to 4 weeks
Weakness in PACU
Management
Attend to patient: rule out airway obstruction, life-threatening hypoventilation, hypoxemia, hypercarbia, or anything requiring immediate airway management & PPV
Examine:
Vitals
? aspiration, sepsis, surgical complication
? myasthenic crisis (weakness improves with tensilon test)
? cholinergic crisis (salivation, lacrimation, urination, diarrhea, GI symptoms, emesis, bradycardia, bronchoconstriction, bronchorrhea)
Review medications given in OR, PACU
Send ABG, electrolytes
Myasthenic Crisis vs Cholinergic Crisis
Myasthenic Crisis:
Weakness exacerbated by infections, electrolyte abnormalities, pregnancy, surgery, emotional stress, drugs (aminoglycosides), or interruption of immunosuppressants
Improvement with edrophonium (tensilon test):
Tensilon test: 1.5 mg increments of edrophonium to 10 mg total (should get better in about 2 minutes)
Consider elective intubation if vital capacity < 20cc/kg or maximum inspiratory force worse than -30 cmH2O
Consider PO or IV dose of pyridostigmine:
PO: 30-120 mg/day, onset 15-30 min, peak 2 hrs, duration 4 hrs
IV dose is 1/30 of PO dose
Alternative treatment is neostigmine 0.5-2.5 mg IV/SC q1-3 hours titrated to response (max = 10mg/24hours)
Neurology consult for management (plex, IVIG, steroids)
Cholinergic Crisis:
Due to excessive cholinesterase inhibitors
Symptoms of acetylcholine excess (SLUDGE BBB): salivation, lacrimation, urination, diarrhea, GI symptoms, emesis, bradycardia, bronchorrhea, bronchospasm
Distinguish by giving edrophonium (tensilon test) which improves symptoms if myasthenic crisis & worsens symptoms if cholinergic crisis
Treatment includes endotracheal intubation, atropine & cessation of cholinesterase inhibitors until the crisis is over
