#Tweetorial! Continuing with the #NeuroBootCamp my co-chiefs and I are leading @EmoryNeurology on #NeuroEmergencies, today’s #MedEd topic will be:
“Myasthenic Crisis”
Keep in mind I’m approaching this with my #NeuroCritCare hat on @MedTweetorials
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“Myasthenic Crisis”
Keep in mind I’m approaching this with my #NeuroCritCare hat on @MedTweetorials
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Some basic background info: Myasthenia Gravis is an autoimmune disorder causing faulty neuromuscular junction transmission. Typically due to one of the following antibodies:
-AchR
-MuSK
-LRP4
-Can be seronegative
20% have crisis within 1st yr of diagnosis!
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-AchR
-MuSK
-LRP4
-Can be seronegative
20% have crisis within 1st yr of diagnosis!
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Clinically Myasthenia manifests itself with ptosis, fatigable weakness, eye movement abnormalities, and in the case of crisis- respiratory compromise.
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Myasthenic crisis respiratory compromise is result of weakness of intercostal/accessory muscles and eventually diaphragmatic weakness.
Can also affect bulbar muscles causing difficulty with secretion control.
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Can also affect bulbar muscles causing difficulty with secretion control.
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What causes a crisis?
Infection is most common but a whole list of medications can trigger as well including numerous antibiotics, gabapentin, and calcium channel agonists.
myasthenia.org/Portals/0/Caut…
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Infection is most common but a whole list of medications can trigger as well including numerous antibiotics, gabapentin, and calcium channel agonists.
myasthenia.org/Portals/0/Caut…
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How do you know if your patient is impending respiratory failure due to myasthenia?
Start with your exam!
-Assess for strength of cough/sniff
-Count to >20 in single breath
-Any change to voice or short staccato speech?
-Bulbar/neck flexion weakness?
-Accessory muscle use?
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Start with your exam!
-Assess for strength of cough/sniff
-Count to >20 in single breath
-Any change to voice or short staccato speech?
-Bulbar/neck flexion weakness?
-Accessory muscle use?
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Don’t forget to get help from the #RespiratoryTherapist who can perform bedside PFTs. You are looking at 3 main things:
1- vital capacity (<20ml/kg is bad)
2- Max Inspiratory Force/NIF (>-30cmH2O is bad)
3- Positive Expiratory Force (<40cmH2O is bad)
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1- vital capacity (<20ml/kg is bad)
2- Max Inspiratory Force/NIF (>-30cmH2O is bad)
3- Positive Expiratory Force (<40cmH2O is bad)
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So those respiratory mechanics give an easy rule to remember:
20/30/40 rule- if any of these are true your patient is impending respiratory failure and you need to consider intubation
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20/30/40 rule- if any of these are true your patient is impending respiratory failure and you need to consider intubation
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You can avoid intubation by bridging with bipap.
Bipap decreases length of ICU stay and time on ventilator in myasthenic crisis.
Hypercapnia is predictive of Bipap failure.
But you really shouldn’t rely on ABG to triage (evaluate clinically).
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Bipap decreases length of ICU stay and time on ventilator in myasthenic crisis.
Hypercapnia is predictive of Bipap failure.
But you really shouldn’t rely on ABG to triage (evaluate clinically).
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If you must intubate- elective is preferred over emergent. Keep in mind these patients can crash quickly.
Avoid depolorizing agents and typically use a slightly lower dose of nondepolarizing agent such as rocuronium.
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Avoid depolorizing agents and typically use a slightly lower dose of nondepolarizing agent such as rocuronium.
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Your initial ventilator settings should favor an assist control setting with pressure support and a goal to wean to a spontaneous pressure support setting as patient improves with treatment.
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Speaking of treatment what should we treat with??
In acute crisis stop pyridostigmine. It is a symptomatic treatment and will not speed their recovery. (And can worsen secretions)
Can start treatment with IVIG (0.4gm/kg/d x5days) or PLEX (5 sessions over 7-10 days)
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In acute crisis stop pyridostigmine. It is a symptomatic treatment and will not speed their recovery. (And can worsen secretions)
Can start treatment with IVIG (0.4gm/kg/d x5days) or PLEX (5 sessions over 7-10 days)
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No definitive evidence to say if PLEX or IVIG is better. PLEX works a little faster but is also more invasive/comes with more complications related to large bore central access.
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Once IVIG or PLEX has started you should also add 1mg/kg steroids. Use caution in non intubated patients however cause steroids can acutely worsen respiratory status. Their effect kicks in at 2-6wks (around when IVIG/PLEX effect is wearing off)
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But when can you extubate? Back to your #RespiratoryMechanics!
Vital capacity >15ml/kg
MIP/NIF>-30
Satisfactory oxygenation
Can also assess for improvement in exam with improving neck flexion and bulbar strength
Some may require reintubation or trach (>20% in some studies)
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Vital capacity >15ml/kg
MIP/NIF>-30
Satisfactory oxygenation
Can also assess for improvement in exam with improving neck flexion and bulbar strength
Some may require reintubation or trach (>20% in some studies)
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Definitive steroid sparing therapy includes:
-Azathioprine 2-3mg/kg with steroids
-Rituximab- for MuSK specifically
-Thymectomy (not an acute treatment)
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-Azathioprine 2-3mg/kg with steroids
-Rituximab- for MuSK specifically
-Thymectomy (not an acute treatment)
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Appreciate everyone reading. Welcome all questions/corrections/teaching points! #Neuromuscular #NeuroCritCare #NeuroTwitter @VJeanneretl @andresdeleonb @neurocritical @aartisarwal @SitaraKoneru @carogsantibanez @Tracey1milligan @MedTweetorials @AaronLBerkowitz @gradydoctor
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All of this is meant for educational purposes/board review only and you should consult a neurocritical care or neuromuscular specialist to help with your management of this illness!
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@threadreaderapp please unroll
@VizcarraJA @NMatch2021 @SitaraKoneru @MonicaDhakar @katskript @ShaerQasem @sallywilliamsmd @SharashidzeVera @DeniseFChen @EmmGeezee join in on the teaching!
