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
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
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
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