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Myotonic Dystrophy - Anaesthetic Considerations
- 2. Outline • Case • Background • Signs and symptoms • Treatment • Considerations for anaesthetic • Summary
- 3. Case • 46 year old male • Known myotonic dystrophy • Right open ankle fusion & osteotomy • WHAT ARE THE ANAESTHETIC CONSIDERATIONS?
- 4. Background (1) • LOTS OF NAMES – Myotonic Dystrophy – Steinert’s Disease – Dystrophica Myotonica – Myotonica Atrophica – Batten-Curschmann’s – Hoffman’s
- 5. Background (2) • Chronic, slowly progressing, highly variable, multisystem disease • M=F • 1 per 7000/8000 people • Autosomal dominant – DMPK gene, nucleotide repeat disorder, anticipation • 2 types: – Type 1 – Type 2 - Proximal Myotonic Myopathy (PROMM)
- 6. Signs and symptoms (1) • Neuro: – Wasting/weakness of muscles – Myotonia – Cognitive impairment – Behavioural problems – Excessive sleepiness • CVS: – Heart conduction defects; arrhythmias – Cardiomyopathy • Resp: – Regular chest infections – Aspiration – Hypoventilation, OSA
- 7. Signs and symptoms (2) • Endocrine: – Insulin resistance, hypothyroidism – Male infertility – Premature frontal balding • Opthalmology: – Cataracts – Ptosis • GI – Swallowing problems – Gallstones – Constipation/diarrhoe a • Skeletal – Scoliosis – Talipes
- 9. Useful clinical clue for diagnosis: Failure of spontaneous letting go of the hands following strong handshakes due to myotonia
- 10. Definitive diagnosis by: • DNA analysis • EMG • Slit lamp exam of lens • Serum CK • Serum FSH, testosterone • ECG • Muscle biopsy
- 11. Treatment • No cure or treatment • Manage complications – orthotics, pacemakers, physio, mobility aids
- 12. Myotonic Dystrophy & Anaesthesia
- 13. Anaesthetic related problems • Diagnosis • Getting correct history • Cardio-respiratory complications • Aspiration risk • ? Difficult airway • Analgesic/anaesthetic drugs • Neuromuscular blocking drugs • Myotonia triggers • Pregnancy
- 14. Pre-assessment • Precise diagnosis • Full discussion with patient & family re: potential risks/benefits • Assessment of function & co-morbidities • Investigations • Anaesthetic plan • Planning post-op care
- 15. Cardiac investigations • Routine ECG – Abnormality may not be apparent on ECG • If symptomatic – 24 hr ECG tape – Invasive electrophysiological studies – ECHO • If asymptomatic – annual ECG, 24hr tape every 2 years, TTE every 5 years
- 16. Respiratory investigations • CXR – Subclinical aspiration common • Pulmonary function tests – Spirometry – ABG
- 17. Airway problems • ? RSI – Aspiration risk – Avoid suxamethonium • ? Intubation difficulty
- 18. Peri-operative management • Sensitivity to sedative, analgesic, anaesthetic drugs • Neuromuscular blockade – NDMR in reduced doses (10 - 20%); avoid suxamethonium • Close temperature control • Use of regional anaesthesia if possible
- 19. Peri-operative complications • OSA, aspiration • Dysrrythmias, cardiac failure • Autonomic dysfunction • Myotonia • Rhabdomyolysis
- 20. Myotonia • Can be precipitated by: – suxamethonium – anticholinesterases – opioids – alterations in temperature/shivering – acidosis
- 21. Post-operatively • Timing of extubation • Avoid hypothermia • Monitor electrolytes • May need higher level of care post op (HDU, ITU) • High index of suspicion for respiratory complications • Opioids with caution for post op analgesia
- 22. Pregnancy in MD • Increase in myotonic symptoms • Atonic uterus • PPH common • Mother can pass on congenital form to baby
- 23. Case • Spinal sited with 2.2ml 0.5% heavy marcain and 0.3mg diamorphine • No sedation required • Oxygen via simple hudson facemask • Uneventful anaesthetic
- 24. Summary • Large spectrum of signs & symptoms • Often misdiagnosed or underdiagnosed condition • Knowledge & awareness of condition means the avoidable & expected complications can be minimised
- 25. References • http://www.myotonicdystrophysupportgroup.org • FRCA “Neuromuscular disorders and anaesthesia” (2009)http://www.frca.co.uk/Documents/126%20Neur omuscular%20disorders%20and%20anaesthesia.pdf • AAGBI Video Platform “Neuromuscular Disease”http://videoplatform.aagbi.org/videoPlayer/?v id=100 • http://mda.org/disease/myotonic-muscular- dystrophy/signs-and-symptoms/adult-onset-MMD • http://myotonic.org/sites/default/files/pages/files/Ane sthesia%20Guidelines.pdf
Editor's Notes
- First described by Steinert in 1909 in Germany – 9 cases. Described later that year in UK about 5 cases including 3 family members (siblings) with the characteristic faces. Certain areas of DNA have repeated sequences of two or three nucleotides.; number of repeats is proportional to severity of disease On average 50% chance passed onto child - Normally the symptoms of the disease become more severe and the age at onset becomes earlier in successive generations of a family – i.e. ANTICIPATION Type 2: Distinct features – proximal muscles, muscle pain, no facial weakness, no congenital form. Different genetic abnormality (chromosome 3 not 19); 4 amino acid repeat rather than 3 amino acid repeat Similarities – autosomal dominant, muscle weakness, myotonia, cataracts, cardiac conduction defects, gonadal atrophy
- Weakness is very variable and may range from mild to severe. It particularly involves the face and eyelids (ptosis), jaw, neck (SCM), distal limbs (forearms and hands, lower legs and feet). Diaphragm and intercostals. It can affect speech and result in a lack of facial expression Myotonia is difficulty in relaxing a muscle after it has been contracted, for example it may be difficult to let go after gripping something. Myotonia tends to affect grip more than other muscles, but can affect the tongue Chest and Breathing problems- Chest infections may result from weakness of breathing muscles or from food entering the lungs as a result of poor swallowing. Inadequate breathing during the night may lead to disturbed sleep, difficulty waking, morning headaches, loss of appetite and daytime sleepiness. Cause of death in 40%
- (DM same incidence as general population) Swallowing problems due to oesophageal dysfunction
- Myotonia = delayed relaxation of muscles after contraction
- DNA analysis - Can see on chromosome and how many repeats have got
- Precise diagnosis not always possible as occasionally anaesthesia is required for diagnosis
- 24 hr tape - if lots of ventricular arrhythmias then consider IED)
- Restrictive picture on pulm func tests due to the scoliosis
- Sensitivity to sedatives or painkillers – hence less likely to be able to cough and clear their secretions as prolonged apnoea and respiratory depression; also inhalational drugs like isoflurane can prolong QT Atracurium is a popular choice due to its spontaneous Hoffman degradation but the key to muscular blockade is careful titration and close monitoring with a peripheral nerve stimulator (PNS) Suxamethonium causes prolonged myotonia so avoid In those with cardiovascular complications and autonomic dysfunction, severe hypotension may result from neuroaxial blockade
- Suxamethonium gives prolonged myotonia, and not able to reverse so AVOID NDMR reversal with neostigmine can precipitate myotonia Consequences of hypothermia can include triggering of muscle spasms, increased sensitivity to muscle relaxants and aggravation of rhabdomyolysis
- Not to extubate until patient able to maintain adequate tidal volumes and airway reflexes returned (as resp failure and aspiration too high risk) – mandatory physio Avoid shivering as triggers myotonia Particularly K+ in light of high rhabdomyolysis risk (could urine dip for myoglobin or serum CK) Opioids can depress respiration as well as slow gastric transit and thus increase aspiration risk