neuromuscular disease - dr. fjotland

neuromuscular disease - dr. fjotland

Transcript

1. NEUROMUSCULAR DISEASE & ANESTHETIC CONCERNS CHRISTOPHER W. FJOTLAND, MD
2. OUTLINE • MYASTHENIA GRAVIS • PARANEOPLASTIC NEUROMUSCULAR SYNDROMES • MUSCULAR DYSTROPHIES • MYOTONIC DYSTROPHY
3. GOALS • Understand and differentiate each disease • Understand anesthetic concerns and possible complications • Improve patient care & patient safety • Improve board scores by getting these questions right
4. MYASTHENIA GRAVIS
5. MYASTHENIA GRAVIS • Autoimmune - post-synaptic AChR at neuromuscular junction (IgG) • Loss of AChR 3 ways • Competitive blockade • Complement-mediated lysis of receptors • Increasing degradation of the receptor • Hallmark: skeletal muscle weakness w/ exercise & improvement with rest • Incidence: highest in women in 3rd decade; Men w/ 2 peaks in 3rd & 6th decades • Associated w/ other autoimmune dz (hypothyroid, RA, lupus) • Course: exacerbations & remissions • Clinical features • Muscles innervated by CN most frequently involved • Pharyngeal & ocular weakness - ptosis, diplopia, dysphasia • Severe • proximal muscle weakness - resp failure, aspiration (bulbar) • Cardiomyopathy ➡️ cardiac failure
6. MG CLINICAL CLASSIFICATION
7. WORK UP • Tensilon test • Distinguish between myasthenic & cholinergic crisis • 10mg edrophonium (cholinergic agent) • MG = strength will improve • Chol = ACh will worsen symptoms (Rx w/ atropine)
8. TREATMENT • Pyridostigmine (most common) - anticholinesterase - increase ACh • Excessive administration - Cholinergic crisis • Steroids • Immunosuppressives - azathioprine, cyclophosphamide • Plasmapheresis (dysphasia, resp failure or normal & under going a surgical procedure) • Thymectomy
9. ANESTHETIC CONCERNS • More sensitive to resp depressant effects of narcotics & anxiolytics • Resistant to depolarizing agents; Require 2-3x SCh dose • Sensitive to non-depolarizing NMB (avoid if possible) • Profound muscle relaxation with volatile agents • Avoid ester LA (metabolized by cholinesterase, pt often taking antichol) • MG crisis can be precipitated by inadequate pyridostigmine, non- depolarizing NMB, excessive neostigmine, intubating dose of SCh • Post op vent risk: Dz >6 yrs, concomitant pulm dz, VC <4ml/kg, pyridostigmine dose >750 mg/d • Medical management must be optimized • Bulbar involvement - pre-op IV IG or plasmapheresis • Adjustments in antichol, immunosupp or steroid Tx may be necessary
10. MYASTHENIA GRAVIS VS MYASTHENIC SYNDROME MS (Lambert-Eaton) MG Path Pre-synaptic Post synaptic Clinical Prox muscle weakness Improved w/ exercise Muscle pain common Reflexes decreased or absent Extraoccular, bulbar, facial m. Worsens w/ exercise Muscle pain uncommon Reflexes not effected Gender M>F F>M Co-existing Small cell lung ca Thymoma NMB SCh sensitive Non-depol sensitive Antichol- poor response SCh resistant Non-depol sensitive Antichol - good response
11. PARANEOPLASTIC NEUROMUSCULAR SYNDROMES
12. PARANEOPLASTIC NEUROMUSCULAR SYNDROMES • Immune- mediated diseases assoc w/ underlying cancer • Lambert-Eaton (Myasthenic syndrome) • Limbic Encephalitis • Neuromyotonia • Stiff Person syndrome • Myotonic dystrophy • Polymyositis
13. LAMBERT-EATON (MYOTONIC SYNDROME) • See Chart (Slide 9) • Proximal muscle weakness typically begins in the LEs - can spread to UE, bulbar & respiratory muscles • Auto-immune - presynaptic voltage gated Ca channels (nerve terminal) - reduce the release of ACh • Weakness improves with exercise, worsened with rest • Rx: Guanidine hydrochloride & 3,4-diaminopyridine (DAP) - increase presynaptic release of ACh • Steroids and other immunosuppressive meds, plasmapheresis
14. LIMBIC ENCEPHALITIS • Degenerative CNS d/o - personality changes, hallucinations, seizures, autonomic dysfunction, dementia & asymmetric loss of sensation in extremities • Strong assoc w/ small cell lung ca (neurological dysf often precedes cancer diagnosis) • Tx: Tx cancer, immunosuppressive meds
15. NEUROMYOTONIA • Peripheral nerve hyperexcitability • Assoc. w/ underlying cancer, also may be inherited or associated w/ diabetic, drug- or toxin-induced, or other acquired neuropathies • Features: myokymia (continuous undulating movement of muscles described as a bag of worms), stiffness, impaired muscle relaxation, painful muscle cramping, hyperhidrosis and muscle hypertrophy • Treatment: immunoglobulin therapy, plasma exchange, admin of anticonvulsants
16. STIFF PERSON SYNDROME • Progressive d/o characterized by axial stiffness and rigidity that my subsequently involve the proximal limb muscles • Advance: paraspinal rigidity may cause spin deformities which may cause difficulties with ambulating and a history of frequent falls • Treatment: Tx underlying cancer, immunoglobulin, benzodiazepines
17. MYOTONIC DYSTROPHY • (Will discuss w/ muscular dystrophies)
18. POLYMYOSITIS • Inflammatory myopathy of skeletal muscle (especially proximal) • Characterized: weakness and fatiguability • Prone to aspiration and frequent pneumonia’s • Cardiac dysrhythmias (conduction defects) • Therapy: Tx underlying neoplasm, IG, steroids, immunomodulators (methotrexate)
19. ANESTHETIC CONSIDERATIONS NEUROMUSCULAR PARANEOPLASTIC SYNDROMES • Very sensitive to BOTH depolarizing & non-depolarizing NMB • Volatile agents alone are often sufficient to provide muscle relaxation for intubation and most procedures • NMBs should be given only in small increments with careful monitoring • Pt’s often exhib marked debility - benzos, opioids and other medications w/ sedative effects should be used cautiously
20. MUSCULAR DYSTROPHIES
21. MUSCULAR DYSTROPHIES • Group of diseases characterized by delayed muscle relaxation after stimulation (muscle fiber necrosis and regeneration ➡️ degeneration and progressive weakness) • Autosomal dominant, variable penetrance • Contractures not relieved by non-depolarizing NMB or regional anesthesia • Difficulty clearing secretions, increased risk of respiratory failure and aspiration • Duchenne’s is most common
22. DUCHENNE’S MUSCULAR DYSTROPHY • X-linked recessive • Abnormal production of dystrophin (protein on sarcolemma of muscle fibers) • Creatine Kinase (CK) elevated (10-100x normal) • Dx confirmed by muscle Bx
23. DUCHENNE’S MUSCULAR DYSTROPHY • MCC death = Aspiration pneumonia or heart failure • Pulm - Resp muscle degeneration + kyphoscoliosis • Weak cough (diff clearing secretions) + restrictive pattern • Frequent pulmonary infections + pulm HTN • Cardiac - Cardiac muscle degeneration +papillary muscle dysfunction • Dilated or hypertrophic cardiomyopathy + mitral regurg • CHF • Arrhythmias secondary to fibrinolysis of conducting system and cardiomyopathies • GI - delayed emptying + hypomotility • Regurgitation + aspiration
24. BECKER’S MUSCULAR DYSTROPHY • X-linked recessive • Mutation of dystrophin gene • Similar to Duchenne’s but presents later in life & progresses more slowly • MCC death = pulmonary complications
25. DUCHENNE’S & BECKER’S ANESTHETIC CONSIDERATIONS • Complicated by muscle weakness & cardio/pulmonary manifestations • Pre-op sedatives should be avoided (resp depression & aspiration) • Intra-op positioning may be difficult (kyphoscoliosis & contractures) • SCh should be avoided - massive rhabdomyolysis, hyper K & death • Hyper K can widen QRS ➡️ vfib • Volatile agents can also cause rhabdo • Halothane - exaggerated myocardial depressant effect, arrhythmias • NO INCREASED RISK OF MH • Titrate non-depol NMB slowly, some are very sensitive
26. MYOTONIC DYSTROPHY • Multisystem d/o MCC of myotonia (slowing of relaxation after muscle contraction in response to stimuli) • Autosomal dominant, clinically appear in 2nd-3rd decade, can be paraneoplastic • Clinically: muscle weakness, atrophy (usually of cranial muscles - in contrast to most myopathies which effect more distal muscles) • Rx/prevent crisis - Phenytoin, quinine, procanimide • Decrease Na influx into skeletal myocytes, delaying return of membrane excitability following an action potential
27. MYOTONIC DYSTROPHY • Pulm - Decrease VC + chronic hypoxemia • Cor pulmonale • Cardiac - conduction abnormality + cardiomyopathy • Arrhythmias + heart block (often presents prior to muscular sx) • GI - hypomotility • Aspiration • Endocrine - pancreatic, adrenal, thyroid, gonadal insufficiency • Metabolic - Hyper K & hyperglycemia
28. MYOTONIC DYSTROPHY ANESTHETIC CONSIDERATIONS • Increase risk of cardio/pulmonary complications (esp when under going surgery prior to Dx - prolonged apnea follow GA) • Prolonged hypoventilation, atelectasis, aspiration, pneumonia & arrhythmias/arrest • AVOID - SCh, Neostigmine, K containing IVF, Hypothermia • SCh - intense myotonic contractions (chest wall, masseter , laryngeal spasm) + hyper K • If needing NMB, use small doses of short acting • Neostigmine - exacerbate myotonia • Avoid pre-medication, very sensitive to opioid and sedative medication (prolong apnea)
29. THANK YOU