Musculoskeletal Disease Flashcards
Describe pathophysiology of Myasthenia Gravis
autoimmune dz. IgG mediated destruction of post junctional nicotinic receptors.
does myasthenia gravis get worse or better throughout the day or with exercise?
gets worse throughout the day and gets worse with exercise
how do periods of rest affect myasthenia gravis symptoms?
they improve. period of rest allows for the recovery of skeletal muscle function
which organ plays a key role in myasthemia gravis?
thymus
list the symptoms of myasthenia gravis
diplopia
ptosis
bulbar m. weakens (dysphagia, dysarthria, and difficulty handling secretions)
dyspnea with exertion
proximal muscle weakness
what is the earliest symptom of myasthenia gravis?
ptosis
list situations that exacerbate symptoms of myasthenia gravis
pregnancy
infection
electrolyte abnormalites
surgical and psychological stress
aminoglycoside abx
how does pregnancy affect myasthenia gravis and the neonate.
pregnancy intensifies symptoms in 1/3 of women.
anti-Ach R antibodies cross the placenta and cause weakness in up to 15-20% of neonates.
neonate may need airway mgmt
what percentage of neonates are affected by muscle weakness when mom has myasthenia gravis?
up to 15-20%
how long does neonatal muscle weakness persist when mom has myasthenia gravis? why does it last this long?
up to 2-4 weeks. this is the half life of anti-ach R antibodies.
what are the 4 treatment options for myasthenia gravis?
anticholinesterase
immunosupression
surgery
plasmapheresis
which immunosupressive meds can be used for myasthenia gravis
corticosteroids
cyclosporine
azithroprime
mycophenolate
what surgery is used to tx myasthenia gravis
thymectomy
when is plasmapheresis used to tx myasthenia gravis?
used for temp relief during myasthenia crisis or before thymectomy
what is the first line tx for myasthenia gravis
oral pyridostigmine
what is the tensilon test?
when edrophonium 1-2mg IV is given
this is to determine is patient is having cholinergic crisis or myasthenic crisis
if symptoms get worse: cholinergic crisis
if symptoms get better it is myasthenic crisis
how do you treat cholinergic crisis?
anti-cholinergic
how is sensitivity to NMBs affected by myasthenia gravis? What are the implications?
increased sensitivity to NDNMB, so decrease dose by 1/2 to 2/3
decreased sensitivity to Sux, if you need to RSI increase dose to 1.5-2mg/kg
what is another consideration with sux use in pt with myasthenia gravis?
if patient is taking oral pyridostigmine this an prolong DOA of sux.
do you really need to use NMBs in patients with myasthenia gravis?
May not need to, because VA cause muscle relaxation in the ventral horn
what are the main post op concerns for patients with myasthenia gravis?
higher risk of residual neuromuscular blockage if NMBs are used
bulbar m. weakness (difficulty with oral secretions > ^ risk of pul aspiration)
pt should be told about risk of post op ventilation
what increases risk of pop-op ventilation in patients with myasthenia gravis
dz duration > 6yrs
daily pyridostigmine > 750mg / day
vital capacity <2.9L
COPD
surgical approach: mediain sternotomy > transcervical thymectomy
what are two other names for Eaton-Lambert Syndrome?
myasthenic syndrome
lambert eaton myasthenic syndrome (LEMS)
describe pathophys of eaton lambert syndrome
IgG mediated destruction to pre-synaptic voltage-gated Ca++ channels at the presynaptic nerve terminal
This limits the ammount of Ca++ that can enter cell with depolarization > decreased ammount of Ach release into synaptic cleft
are post-synaptic nicotinic Receptors affected in eaton-lambert syndrome?
no
explain clinical presentation of eaton lambert syndrome
proximal muscles are most affected
worse in the morning and gets better throughout the day
resp. muscles and diaphragm become weak
autonomic nervous system dysfunction > orthostatic hypotension, slowed gastric motility, urinary retention
how is eaton lambert syndrome treated?
3,4-Diaminopyridine (DAP) increases Ach release from the pre-synaptic neuron and ^ strength of contraction
how are NDNMBs and sux affected by eaton lambert syndrome?
patient is sensitive to both, so decrease dose of both
do you really need paralytics with eaton lambert syndrome?
probably not, VAs provide enough muscle relaxation for most surgical procdures
how is reversal of NMBs affected in eaton lambert?
reversal with anticholinesterases may be inadequete despite proper dosing
post op considerations for eaton lambert syndrome?
high risk of post op ventilatory failure
eaton lambert syndrome is associated with what other major disease?
small cell carcinoma of the lung (oat cell carcinoma)
consider possibility of eaton lambert syndrome in what patients?
any patient with suspected lung cancer undergoing mediastinoscopy, bronchoscopy, or throacoscopy
what is the most common cause of acute generalized paralysis? what did it used to be?
Guiliian-Barre
used to be Polio though
what is another name for Gullian-Barre Syndrome?
acute idopathic polyneuritis
describe pathopys of Guillian-Barre
immunologic assault on myelin in the peripheral nervous system. action potential cant be conducted so motor end plate never gets the incoming signal
Guillian-Barre is usually preceded by what and for how long?
flu like illness 1-3 weeks before paralysis
how long does Guillian-Barre usually last?
usually persists for 2 weeks with full recovery in about 4 weeks
what are the most common etiologies of Gullian-Barre?
campylobacter jejuni gacteria
epstein barr virus
CMV
vaccinations
surgery
lymphomatas dz
what percent of Guillian-Barre cases develop chronic inflammatory demyelinating poly neuropathy?
about 2%
what are common s/s of Guillian-Barre?
flaccid paralysis begining in distal extremities and ascending bilaterally towards proximal extremities, tunk, and face
intercostal muscle weakness impairs ventilation
sensory deficits cause paresthesia, numbness, and pain
autonomic dysfunction is common: tachycardia or bradycardia, HTN of HoTN, diaphoresis or anhidrosis
orthostatic hypotension
what is the treatment for Gullian-Barre?
plasmapheresis and IV IgG
what are the main anesthetic considerations for Gullian-Barre?
skeletal muscle denervation, impaired ventilation, autonomic dysfunction
can you use sux with gullian -barre?
no avoid because of the risk of extra junctional receptors
how is response to NDNMB affected in Guillian-Barre?
increased sensitivity
how does Guillian-Barre affect facial and pharyngeal muscles?
impaired swallowing and increaesd risk of aspiration
post op consideration for Guillian-Barre
may need post op ventilation
can you get autonomic dysfunction from Guillian-Barre? what does this put the patinet at risk for and what do they need?
yes.
risk for hemodynamic instabilitity from anesthesia, position changes, PPV, and blood loss.
so they need an a-line
what is the risk of indirect sympathomimetics in Guillian-Barre?
risk of an exaggerated response because of up regulation of post-junctional adrenergic receptors
can you use regional anesthesia in Guillian-Barre?
it is controversial, the dada in inconclusive
are steroids useful for Guillian-Barre?
no
Guillian-Barre causes imobbility which increases risk for?
DVT
What is familial periodic paralysis?
acute episodes of skeletal m. weakness accompanied by changes in serum potassium concentration
what are the two variants of familial periodic paralysis?
Hypokalemic - occurs when serum K decreases
Hyperkalemic - occurs when serum k increases
explain pathophys of familial periodic paralysis
disorder of the skeletal m. membrane which causes reduced excitability
hypokalemic periodid paralysis is associated with what channelopathy?
calcium channelopathy
hyperkalemic periodic paralysis is associated with what channelopathy?
sodium channelopathy
what is the treatment for hypokalemic periodic paralysis and hyperkalemic periodic paralysis?
acetazolamide is for both.
It creates a non-ion gap acidosis which protects against hypokalemia
it also facilitates renal potassium excretion which guards against hyperkalemia.
blank must be avoided at all costs with familial periodic paralysis? In what clinical situation would this cause you do do something different from the norm?
hypothermia
even on cardiac bypass must maintain normothermia
what drugs must be avoided in hypokalemic periodic paralysis?
anything that decreases K
anything that has glucose (will also decrease K)
Sux
what drugs must be avoided in hyperkalemic periodic paralysis?
anything that will raise K
why must you avoid sux in hypokalemic periodic paralysis?
possible link to MH. so best to just avoid it. Doesn’t have anything to do with K release or glucose.
how is the response to NDNMB affected in patietns with familial periodic paralysis?
both hypokalmeic and hyperkalemic variatns are MORE sensitive to NDNMBs
describe pathophys of malignant hyperthermia
- T-tuble depolarized
- extracellular Ca enters via dihydropyridine receptor
3.defective ryanaodine receptor (RYR1) activated
- sacroplasmic reticulum releases way too much Ca++
- More Ca++ causes more muscle contraction and cell tries to return excess Ca++ via SERCA2 pump
- substantial ATP consumption, O2 consumption, and CO2 production
- breakdown of sarcolema allows pottasium, myoglobin to enter systemic circulation
how often does MH occur
1:5,000 to 1:50,000
in MH RYRI can be thought of as what?
basically a Ca++ faucet that can’t be turned off
what factors increase risk of MH?
male sex
youth
midwest geography
what conditions are associated with MH?
Only 3 conditions are definitively associated with MH.
- King-Denborough Syndrome
- Central Core Disease
- Multicore disease
some texts list evan myopathy but not naglehout or MHAUS website
describe pathophys of duchene muscular dystrophy
there is no dystrophin (a structural protein) this leads to destabalization of the sarcolema during muscle contraction and increased membrane permeability.
the increased membrane permeability leads to:
1. extracellular Ca can enter and ^ rate of metabolism
- intracellular K can exit > hyperkalemia
- myoglobin is free to excit cell and can cause renal failure
what is the relationship between duschene muscular dystrophy and MH?
DMD is associated with MH like syndrome, but this is from rhabdomyolysis and not MH.
this has the same triggers as MH though including halogenated anesthetics and sux
what should you assume about any pt with DMD that codes on induction?
assumer this is hyperkalemic cardiac arrest and give calcium
what is the most sensitive indicator of MH?
increased EtCO2
has quickly does MH occur after exposure to triggering agent?
it can occur as late as 6 hours after exposure
how fast does core temp rise in MH?
can start rising as quickly as 15min after exposure, but profound hyperthermia is typically a late sign
what is trismus?
a tight jaw that can be opened. this is a normal response to sux, okay to proceed with surgery
what is massetter m. rigidity
tight jaw that can not be opened. you should assume MH
can NMBs treat masseter m. rigidity?
no, this is from increased Ca in myoplasm which is distal to NMJ so NMBs will have no effect
how do you offically diagnose MH
caffeine-halothane contracture test is the gold standard. it requires live muscle biopsy.
who should be refered for carreine-halothane contracture test?
anyone that experiences MH or masseter spasm.
what differential dx should you consider if concerned about MH?
thyroid storm
malignant neuroleptic syndrome
sepsis
pheochromocytoma
serotonergic syndrome
heat stroke
metastatic carcinoid
cocaine intoxication
should you give prophylactic dantrolene to pt at risk of MH?
no
how to prepare for patient who is at risk of MH?
fluhs machine with high flows for 20-100min
all external parts changed (bag circuit co2 absorber)
physically remove vaporizers
is it possible to develop MH after the first hour in a case?
yes, but very rare to develop after the first hour
how long should you monitor pt in PACU after case if they were at risk for MH but nothing happend? Is it okay to discharge them straight home?
for 1-4 hours. Okay to discharge home.
what can you use instead of flushing machine for 20-100min?
can use charcol filters
name one example of charcol filters
vapor clean filter
how do you appropriately use vapor-clean filters
place on inp and exp ports of machine
flush with high FGF for 90seconds
what is dantrolenes mech of action?
- decrease Ca++ release from RyR1 receptor in skeletal myocyte
- prevents Ca++ entry into the myocyte. This decreases stimulus for Ca++ induced Ca++ release
what is contained in one vial of dantrolene?
20mg dantrolene
3g mannitol
what do you reconstitute dantrolene with? What should you not use and why?
60ml sterile water
don’t use normal saline, it has more solute so will take longer to dissolve the dantrolene
what med class is dantrolene?
muscle relaxant
most common side effects of dantrolene?
muscle weakness, and muscle irritation
10 Steps for MH Treatment
- DC triggering agent
- Call for help
3a. hyperventilate with 100% FiO2 and min FGF of 10L/min
3b. apply charcol filter and change bag and circuit. - Admin ryanodex and dantrolene
- cool the patient
- correct lactic acidosis
- treat hyperkalemia
- protect against dysrhythmias
- maintain U.O > 2ml/kg/hr
- DIC is a late complication and signals impending demise.
what should you do after MH has been stabilized? why?
observe patient in ICU because MH can reoccur for up to 36 hours
what to do durign MH when you stop the triggering agent?
start TIVA
when should you tell surgeon to stop opperation during MH?
when you call for help
how does hyperventilation help in MH?
- facilitates CO2 elimination
- enhances O2 delivery
- drives K+ into cells
should you change CO2 absorber when dealing with MH?
no waste of time, just use high FGF
how often must you change vapor-clean filters?
change them every hour
what is the dantrolene / ryandoex dose?
2.5mg/kg
repeat every 5-10min as needed
when do you stop bolusing dantrolene / ryanodex?
after symptoms of hypermetabolism subside
how long to continue ryanodex / dantrolene gtt in the ICU?
for up to 48-72 hours
what is the max dose of dantrolene or ryanodex?
if given more than 20mg/kg and symptoms have not subsided reconsider diagnosis
how much ryanodex in one vial?
250mg
how do you reconstitute ryanodex?
5ml of sterile water
how do you correct lactic acidosis from MH?
titrate sodium bicarb to ABG and base deficit
which antiarrhythmics should you use in MH?
class 1
procanimide 15mg/kg
lidocaine mg/kg
what medications must you avoid with dantrolene? why?
CCBs because if given with dantrolene can precipitate life-threatening hyperkalemia
the most common muscular dystrophy is?
duchenne muscular dystrophy
duchenne muscular dystrophy is passed on genetically in what way?
x-linked recessive
explain pathophys of duchenne muscular dystrophy
dystrophin is a critical structural component of cytoskeleton of skeletal and cardiac muscle cells. It helps anchor actin and myosin to the cell membrane.
without dystrophin, sarcolema becomes de-stabilized > creatine kinase and myoglobin can center systemic circulation
Ca also freely enters cell > activates proteins that destroy contractile elements and cause inflammation, fibrosis, and cell death
absence of dystrophin also allows for extrajunctional receptors to populate sarcolemma.
duchenne muscular dystrophy is more common in males or females?
males
how does duchenne muscular dystrophy present?
with atrophy and painless muscle degeneration
how does duchenne muscular dystrophy progress during the first decade of life?
progressive deterioration of skeletal muscle strength culminating in profound weakness
patients with duchenne muscular dystrophy rarely live past?
30 years old
patients with duchenne muscular dystrophy often need surgical correction of what?
scoliosis and contractures
key respiratory considerations for patients with Duchenne muscular dystrophy
kyphoscoliosis > restrict lung dz
resp. muscle weakness
key cardiac considerations for patients with duchenne muscualr dystrophy
cardiac m. degeneration >
decreased contractility
papillary m. dysfunction
mitral regurg
cardiomyopathy
CHF
pt should get full cardiac workup before surgery
GI considerations for pt with duchenne muscular dystrophy
impaired airway reflexes and gastric hypomotility > ^ risk of pulm aspiration
what is kyphoscoliosis
post. curvature of the spinal column
what is the cause of 80% of kyphoscoliosis cases?
idopathic
describe the Cobb angles and associated considerations
40-50 indication for surgery
60: decreased pulm reserve
70: pump symptoms present
100: gas exchange is significantly impaired > higher risk for post-op pulm complications
are are lung volumes affected by scoliosis?
decreased VC TLC FRC and RV
what to know about scoliosis and PVR?
scolisosis can increase PVR > RHF > mitral valve prolaps, mitral regurg, and coarctation of the aorta
which nerve can be damaged in prone position for scoliosis surgery?
lat fem cutaneous nerve from pressure on the iliac crest
hip flexion from positioning in scoliosis surgery places the patient at risk for what?
femoral vein occlusion > DVT
which type of OR table is best for scoliosis surgery?
jackson frame is better than wilson frame
VC < x% of predicted correlates with requirement of post op ventilation in scoliosis surgery?
VC < 40% of predictied
other anesthetic considerations for scolisosis surgery
risk of major blood loss
risk of VAE
what is the wake up test?
super old school, not used now because of neuromonitoring. if pt can move hands but not feed surgeon needs to reduce distraction on spinal rods
what are the main 3 impacts of RA?
TMJ:
cricoarytenoid joints
c-spine:
main RA impact on TMJ?
limited mouth oppening
main RA impact on cricoarytenoid joints?
decreased diameter of glottic oppening
main RA impact on c-spine
atlanto-occipital subluxation with flexion and limted extension
what are presenting s/s of cricoarytenoid effects of RA?
presents with hoarsness, stridor, dyspnea, and an result in airway obstruction
edema or erythemia of vocal cords in pt with RA suggests what?
cricoarytenoid arthritis
risk of post exubation airway obsturction comes from what part of RA?
RA effects on cricoarytenoid joint
what is the most common airway complication in RA?
atlanto-axial subluxation
what is the risk of atlanto-axial subluxation
risk of quadriparesis or paralysis
is flexion or extension worse with atlano-axial subluxation?
flexion is worse than extension
how is AO subluxation diagnosed?
> 3mm between ant arch of atlas and dens
how is AO subluxation best assessed?
lateral x-ray of cervical spine
can subluxation occur at other places in spine besides atlano-axial?
yes, C5-C6 is most common
how is throacolumbar spine affected by RA?
it is usually not affected by RA
what is the pathophysiology of RA?
autoimmune dz of synovial joints with widesepread systemic involvement.
immune complexes get into small and medium arteries > vasculitis
hallmark sign of RA?
morning stiffness that improves with acitivity
RA is more common in men or women?
2-3x more common in women
what lab results are affected by RA?
rheumatic factor ^ in 90% of cases
c-reactive protein ^
erythrocyte sedimentation rate is ^
what are the two options for medical mgmt of RA?
- decrease inflammation
- disease modifying antirheumatic drugs
what antiinflammatories are used for RA?
anti-rheumatics
glucocorticoids
NSAIDS
how do disease modifying anti-rheumatics work?
inhibit: TNF, IL-1, IL-6, T cells, B cells
disease modifying anti-rheumatics increase the risk of what?
cancer and infection
list some disease modifying anti-rheumatics
methotrexate
cyclosporine
etanercept
side effects of methotrexate
liver dysfunction
supress bone marrow
side effects of etanercept
prolonged DOA of Sux
