Mg

[Jeff05]

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43 year old female with a history of MG for 10 years presents for a thymectomy. She is obese and has a history of severe GERD c/o of a hiatal hernia. She did not take her pyridostigmine today - "they told me not to take any meds."

She is with her family in the holding area. Daughter asks "will i be able to talk to my mom later today?"

What's your anesthetic plan? Why?
What if she brought you a piece of paper that said her dibucaine number was 20?
What do you tell the daughter?

 

[Noyac]

Nice, a clinical post, finally.

I'll reserve my response so that the residents can have a chance.

 

[Licoricestick]

43 year old female with a history of MG for 10 years presents for a thymectomy. She is obese and has a history of severe GERD c/o of a hiatal hernia. She did not take her pyridostigmine today - "they told me not to take any meds."

She is with her family in the holding area. Daughter asks "will i be able to talk to my mom later today?"

What's your anesthetic plan? Why?
What if she brought you a piece of paper that said her dibucaine number was 20?
What do you tell the daughter?

Alright - I'll bite - with the caveat that I haven't had a myasthenic patient yet so this is all as yet unapplied (and probably not very well thought through) theory.

Pre op evaluation
Airway - I'd want to know if there was anything other than the obesity that was likely to make her difficult to ventilate and/or intubate.
??OSA/mouth opening/jaw protrusion/MP
GORD - is this controlled at all? I assume she didn't take her usual meds for it this morning. Depending on timing of procedure I'd give oral ranitidine plus what I assume would be her usual PPI (if procedure >1hr away) or IV access and IV ranitidine and pantoprazole
MG- how severe? PFTs available (specifically FVC)? Other meds other than pyridostigmine (specifically immunosuppressants)? Doses of other meds and pyridostigmine? Exercise tolerance? Does anything OTHER than muscle fatigability limit her exercise tolerance?
Any cardiac history?
Anything else other than MG influencing respiratory function? Any recent infection?
Size/location of thymus - review scans re possibility of intrathoracic airway obstruction
Convert pyridostigmine dose to IM/SC neostigmine and give dose in substitution for regular morning dose
Group and match
Post op disposition - needs ICU bed booked


Daughter gets told "maybe" with exactly what I would tell her altered by what I would learn about preop risks for post op ventilation. I understand most patients don't require prolonged postoperative ventilation post thymectomy for MG, but some do. Regardless her mother will be in ICU etc

Induction
If satisfied with airway assessment (and assuming that this isn't the scenario with sux apnoea) RSI with propofol, sux (at 1.5-2mg/kg) after good preox and optimal positioning (ramping).

Maintenance
volatile - desflurane or sevo (and maybe remi? - I read conflicting things about remi elimination in MG),
option 1: no further NMBAs.
Option 2: low doses (~10%) of non depolarising agent (I'd pick vec)
monitor neuromuscular function (including post sux wearing off and pre first dose of vec)
IPPV
steroid cover if on pre op steroids

Emergence
Reversal of NMBA if used (preferred reversal agent - sugammadex if available, otherwise neostigmine/glycopyrrolate)
Ensure adequate return of neuromsucular function prior to extubation - maintenance of adequate tidal volume + sustained headlift.
Extubate awake
If unable to extubate then sedate (short acting agent - propofol would be my preference although I think dexmedetomidate would also be good)and transfer to ICU for ongoing ventilation

Other
Remeber possibility of myasthenic or anticholinergic crises - esp prior to extubation

Post op
pain management: epidural or PCA + regular paracetamol
recommence pyridostigmine ASAP, use parenteral neostigmine or NGT if unable to take orals
continue steroid cover if required
May go to ward day 1 post op if no respiratory compromise
deep breathing and coughing

If dibucaine number is 20 - awake FOI with subsequent management as above.
for AFOI - Firstly tell surgeons to go and have a coffee in the tea room. Avoid anticholinergic premed (suction is your friend), good topicalisation with amide LAs only, careful sedation (I'd probably use some midazolam - 1mg to start with then 0.5mg increments).
Once CO2 confirmed - propofol induction cont as above.


OK - open for criticism!

 

[lvspro]

Alright - I'll bite - with the caveat that I haven't had a myasthenic patient yet so this is all as yet unapplied (and probably not very well thought through) theory.

Pre op evaluation
Airway - I'd want to know if there was anything other than the obesity that was likely to make her difficult to ventilate and/or intubate.
??OSA/mouth opening/jaw protrusion/MP
GORD - is this controlled at all? I assume she didn't take her usual meds for it this morning. Depending on timing of procedure I'd give oral ranitidine plus what I assume would be her usual PPI (if procedure >1hr away) or IV access and IV ranitidine and pantoprazole
MG- how severe? PFTs available (specifically FVC)? Other meds other than pyridostigmine (specifically immunosuppressants)? Doses of other meds and pyridostigmine? Exercise tolerance? Does anything OTHER than muscle fatigability limit her exercise tolerance?
Any cardiac history?
Anything else other than MG influencing respiratory function? Any recent infection?
Size/location of thymus - review scans re possibility of intrathoracic airway obstruction
Convert pyridostigmine dose to IM/SC neostigmine and give dose in substitution for regular morning dose
Group and match
Post op disposition - needs ICU bed booked


Daughter gets told "maybe" with exactly what I would tell her altered by what I would learn about preop risks for post op ventilation. I understand most patients don't require prolonged postoperative ventilation post thymectomy for MG, but some do. Regardless her mother will be in ICU etc

Induction
If satisfied with airway assessment (and assuming that this isn't the scenario with sux apnoea) RSI with propofol, sux (at 1.5-2mg/kg) after good preox and optimal positioning (ramping).

Maintenance
volatile - desflurane or sevo (and maybe remi? - I read conflicting things about remi elimination in MG),
option 1: no further NMBAs.
Option 2: low doses (~10%) of non depolarising agent (I'd pick vec)
monitor neuromuscular function (including post sux wearing off and pre first dose of vec)
IPPV
steroid cover if on pre op steroids

Emergence
Reversal of NMBA if used (preferred reversal agent - sugammadex if available, otherwise neostigmine/glycopyrrolate)
Ensure adequate return of neuromsucular function prior to extubation - maintenance of adequate tidal volume + sustained headlift.
Extubate awake
If unable to extubate then sedate (short acting agent - propofol would be my preference although I think dexmedetomidate would also be good)and transfer to ICU for ongoing ventilation

Other
Remeber possibility of myasthenic or anticholinergic crises - esp prior to extubation

Post op
pain management: epidural or PCA + regular paracetamol
recommence pyridostigmine ASAP, use parenteral neostigmine or NGT if unable to take orals
continue steroid cover if required
May go to ward day 1 post op if no respiratory compromise
deep breathing and coughing

If dibucaine number is 20 - awake FOI with subsequent management as above.
for AFOI - Firstly tell surgeons to go and have a coffee in the tea room. Avoid anticholinergic premed (suction is your friend), good topicalisation with amide LAs only, careful sedation (I'd probably use some midazolam - 1mg to start with then 0.5mg increments).
Once CO2 confirmed - propofol induction cont as above.


OK - open for criticism!

Good answer! I didn't even think of the dibucaine number dood, that's pretty heavy.

Just to add some bits n pieces to the MG Dx b/c itz the biggie here in terms of boards. Not to belittle the GERD, but I think everyone knows all about it. We see it so often, and take care of so many pts with it on a daily basis, that it's almost second nature.

Pre-op: Evaluate the pt in terms of bulbar symptoms. See if they have any impairment of the facial muscles, neck flexion, issues with speech or swallowing b/c besides PFT's, those are the things that best predict the need for post-op ventilation. Issue of pt on steroids is adressed above, but MG-ers on steroids w/i 3 mo need coverage, and those currently on them are at an increased risk of needing post-op vent. Pt should have taken her Pyrido, but itz kewl cuz u can give IV, but adjust the dose (forgot this # if anyone cares to fill it in). May need IVIG, or plasmapheresis pre-op if pt is looking lousy, but case is emergent (this really isn't emergent, but it is Tx so risk:benefit analysis of going now).

Intra-op: TIVA using propofol and remi is recommended by longnecker. If NDMB used, 1/5 dose is to be used. Otherwise, above iz a good way to go.

Post-op: Classic post-op vent predictors that we r usually asked on boards
1. Time of disease> 6 years
2. Preoperative respiratory symptoms
3. Pyridostigmine dosage greater than 750 mg/day
4. Vital capacity <40 mL/kg


Daughter: I would stress the very real possibility that mom is going to end up on a vent b/c she has had it for so many years. I would also discuss that the reason is not b/c she is really sick, but that she just takes longer to recover from anesthesia than everyone else b/c of her MG. That way, at worse case scenario, you're right n baby-girlz been warned, and at best you were wrong, but thats ok cuz pt is doing well.

Dibucaine#: So pt is on pyrido which means the cholinesterase activity is lowered, pt ability to break down dibucaine is depressed, and hence a lower number. Besides the AFOI, it also indicates that you have to be careful with SCH. Most of the sch you give to a nl pt is broken down b/4 it has a chance to do anything (on the order of 90% i believe). So in a pt that can't break it down, a nl or larger dose of sch may produce a P2 block. If you give NDMB and then reverse at the end, you've effectively remove pt ability to remove SCH, and have a dual path of NMB (dep/and Non-dep) in a lower number of ach receptors!. So, that being said, in an MG pt, on lg doses of cholinesterase inhib you have to be careful with SCH.

Anything else we need to cover here?

Ok, back to reading ICU crap 🙁

 

[Noyac]

I agree with all the above. But I would just avoid sux all together in this pt. She may have increased or decreased sensitivity to sux being a myasthenic. A dibucaine # of 20 tells me No sux. I'd either do an RSI without any NMBA or with a small dose of roc maybe 20-30mg given early enough to work (b/4 the propofol but with some versed). If airway looks questionable, AFOI. If npo and GERd well controlled you could also do an inhalational induction and topicalize the airway. This all depends on the severity of the disease.


With this technique, her daughter should be able to speak with her post-op.

If her pyridostigmine dose is high and/or she is currently on steroids would any of you start her on a neostigmine infusion post-op for 24hrs?

 

[lvspro]

I agree with all the above. But I would just avoid sux all together in this pt. She may have increased or decreased sensitivity to sux being a myasthenic. A dibucaine # of 20 tells me No sux. I'd either do an RSI without any NMBA or with a small dose of roc maybe 20-30mg given early enough to work (b/4 the propofol but with some versed). If airway looks questionable, AFOI. If npo and GERd well controlled you could also do an inhalational induction and topicalize the airway. This all depends on the severity of the disease.


With this technique, her daughter should be able to speak with her post-op.

If her pyridostigmine dose is high and/or she is currently on steroids would any of you start her on a neostigmine infusion post-op for 24hrs?

On second look, I'd agree with noy and not use SCH because it's too thin of a tightrope to walk. You don't really know what the right dose is, so why mess w/it.

About the pyrido/steroid thing. I mentioned it before, but now that u r making it clear that she is on high dose, as well as steroid, it may be a good idea to seriously consider plasmapheresis. Those two indicate a greater number of antibodies as well as a lower number of receptors, so a double whammy in MG needs to be optimized, and pheresis considered. I may consider neo gtt post op, but then I'm exposing her to all the crap that goes along w/it (MS changes, cardiac condxn issues, arrhythmias, etc...), and despite being young and otherwise healthy, she may be better served with my recc. What say u?

 

[dhb]

I would avoid any kind of muscle relaxant: intubate with remifentanil or with 10% topical lido.
Plasmapheresis should only be a second line therapy if you can't get her of the vent the next day.
She definitely should have took her medications in the morning and this should be addressed per-op: steroids + cholinesterase inhib.
If the surgeon plans on doing a mini sternotomy i would highly suggest some form of regional anesthesia bilat paravertebral? intercostal block?
Tiva with remi is acceptable but i wouldn't be afraid of any other opiate since there's no effect on muscular function.

 

[Noyac]

i wouldn't be afraid of any other opiate since there's no effect on muscular function.

That's were people get burned. Opiates (except for remi) are something to be careful with in these pts. Their respiratory status/effort is the one thing we worry most about and opiates can suppress this significantly in MG.

 

[Arch Guillotti]

I also would avoid sux altogether. Personally I would avoid any NMB. Remi for the case with some judicious morphine at the end. Someone with a sternotomy is going to need some sort of pain control, though they don't seem to hurt as bad as I would imagine.

 

[Jeff05]

excellent responses.

just a note
Dibucaine#: So pt is on pyrido which means the cholinesterase activity is lowered, pt ability to break down dibucaine is depressed, and hence a lower number.

this is incorrect. the dibucaine number provides a qualitative (atypical vs. normal enzyme) and NOT a quantitative assessment. therefore, someone with a normal pseudocholinesterase taking inhibitors (pyrido, etc) would have a NORMAL dibucaine number - ie 80.

this patient's 20 signifies homozygous for the atypical enzyme.

 

[Jeff05]

this patient was very functional, but due to long h/o dz and high dose of pyrido the daughter was told that postoperative ventilation is a real possibility.

IV in holding 45 min before induction. oral pyrido with a sip of h20.
Famotidine, metoclopramide, bicitra rolling back into room.

"stress dose" steroids (patient on sig prednisone dose).

T4 epidural

RSI with propofol/lidocaine/remi.

maintain with des/remi/dex

epidural activated towards the end with 0.1% bupiv 5mL. awake and comfy on dex. 5 second head lift.
PSV 5 - patient taking tidal volumes of 450mL. tube out.

 

[lvspro]

The dibucaine thing sounds about right. I was reasoning thru it, but was flawed in not thinking quant vs qual -itative. Tnx for correcting me.

Great case man. Covers MG which is a 2-3 board q topic, and pseudocholinesterase deficiency in one case.

 

[Licoricestick]

Good case - thanks!

Question about remi in these patients - I thought that remi metabolism by the nonspecific esterases could be inhibited by pyridostigmine? Is this a clinical concern or just theoretical?

 

[dhb]

That's were people get burned. Opiates (except for remi) are something to be careful with in these pts. Their respiratory status/effort is the one thing we worry most about and opiates can suppress this significantly in MG.

I agree i was talking intra-op that's why i stated that some kind of regional would be optimal for post-op pain control to avoid opiates outside of the very controled setting of the OR/PACU.

 

[dhb]

T4 epidural

epidural activated towards the end with 0.1% bupiv 5mL. awake and comfy on dex. 5 second head lift.
PSV 5 - patient taking tidal volumes of 450mL. tube out.

I was thinking about the epidural but this could effect ventilatory muscles: intercostal + diaphragm. The margin is quite tight between pain relief at the t1-t4 area and affecting your C3-C5 zone.
It would require tight post-op monitoring i wouldn't send her on the floor with an epidural.

 

[Noyac]

I was thinking about the epidural but this could effect ventilatory muscles: intercostal + diaphragm. The margin is quite tight between pain relief at the t1-t4 area and affecting your C3-C5 zone.
It would require tight post-op monitoring i wouldn't send her on the floor with an epidural.

Low concentration Ropivicaine wouldn't knock out the resp muscle function too bad. Just a thought.

I think she would need a monitored bed the first night and therefore, I wouldn't worry about an epidural on the floor. Obviously the nursing care would need to be up to par.

However, having done many CABG's on pts with long standing MG I don't find the epidural to be all that necessary. It would just be a nice touch.

 

[dfk]

I would avoid any kind of muscle relaxant: intubate with remifentanil or with 10% topical lido.
Plasmapheresis should only be a second line therapy if you can't get her of the vent the next day.
She definitely should have took her medications in the morning and this should be addressed per-op: steroids + cholinesterase inhib.
If the surgeon plans on doing a mini sternotomy i would highly suggest some form of regional anesthesia bilat paravertebral? intercostal block?
Tiva with remi is acceptable but i wouldn't be afraid of any other opiate since there's no effect on muscular function.

the problem i see with this (at my facility anyway) is that NPs are the ones doing the pre-admission testing, and i've seen many pre-ops have orders to take too few 'right' meds or too many 'unnecessary' meds. not pinpointing level of provider, but more so of lack of education on what actually matters.

 

[Noyac]

the problem i see with this (at my facility anyway) is that NPs are the ones doing the pre-admission testing, and i've seen many pre-ops have orders to take too few 'right' meds or too many 'unnecessary' meds. not pinpointing level of provider, but more so of lack of education on what actually matters.

Welcome to the future of US healthcare were midlevels are used more and more. We have all seen the cookie cutter approach of midlevels and how they feel they are doing the job but don't understand enough to think outside the box much less use reason and education to make the right decision.