1.24 Myasthenia Gravis Flashcards
Define Myasthenia Gravis
Autoimmune disease
Younger women + Older Men
IgG abod attack AChR
@ Post synaptic membrane of NMJ
Prevent binding of ACh to rec
↑ rate AChR degradation
Stimulate complement related damage
to Post synaptic membrane
Margin of safety lost in NM transmission
Assoc thymus hyperplasia in majority patients
Signs and Symptoms
Demonstrable weakness skeletal muscle
- worse post exercise + evening
- improves w/ rest
- Prox > Distal
Partial + Unilateral ptosis
diplopia
blurred vision -
solitary signs in 15% ocular myasthenia gravis
Bulbar involvement
Resp muscle involvement
20-30%
especially intercost / diaphragm
Sparing sensory and reflex abnormality
Effects of LT steroids
Cushingoid
Anaesthetic Mx
Preop
Assess bulbar and resp fxn
Serial FVC
- poor <2.9L (indicative need post op ventilation)
PreOp physio
Optimisation anticholinesterase +
Immunosuppression therapy
Consider PLEX / IV IgG if poor control
Omit anticholesterase on morning srugery
ensure steroid cover @ induction if approp
Premed in patients w/ good reserve
Aware other autoimmune disease
- thyroid DM Rheumatoid
Intraop
Intubation advisable
- high risk aspiration (bulbar)
Avoid Sux relative resistance (↓AChR) Prolong action and propensity phase 2 block
NDMB quicker onset + prolong action - consider ETT without NDMB - Reduce dose trac prob safest - metab and avoidance of reversal agents
Intubation facilitated exacerbated
NMB properties of volatile agents
Post op
Extubate if uncomplicated
Low threshold CCM postop
If ↓preop FVC/Bulbar involvement / co existing resp disedase
- elective post op IPPV in ICU
- Restart antichol tx and titrate to effect
↓requirements in 48h post op
