MSK diseases Flashcards
pathophysiology of MG
IgG antibodies destroy post junctional nicotinic Ach receptors at NMJ
-aka theres enough Ach just not enough functional receptors which is why it presents as skeletal muscle weakness
key feature of MG
gets worse throughout day or after exercise. rest allows for recovery
surgical option for MG
thymus gland plays a role and a thymectomy brings relief to patients
sx of MG
(earliest: 2)
earliest signs: diplopia, ptosis
bulbar muscle weakness (muscles of mouth and throat). dysphagia, dysarthria, difficulty handling saliva. dyspnea with exertion, proximal muscle weakness.
situations that exacerbate sx of MG (5)
pregnancy
infection
electrolyte abnormalities**
surgical and psychological stress
aminoglycoside abx**
MG antibodies and neonates
(including how long it lasts)
anti AchR IgG antibodies cross placenta and cause weakness in 15-20% of neonates.
-can persist for up to 2-4 weeks, consistent with half life of these antibodies
-neonates may need aw management
tx for MG (4)
-anticholinesterases: PO pyridostigmine is first line
-immunosuppression: corticosteroids, cyclosporine, azathioprine, mycophenolate
-surgery: thymectomy (reduces anti AchR IgG- median sternotomy OR trans cervical approach)
-plasmapharesis: temporary relief for MG crisis before thymectomy
MG and pyridostigmine OD (cholinergic crisis) sx, dx, tx
-pt with MG on pyridostigmine becomes acutely weak
-dx via tensilon test (edrophonium 1-2mg IV). if sx get worse, patient is in cholinergic crisis–> tx with anticholinergics
if sx improve, patient had MG crisis
MG and ND NMB’s
increased sensitivity
-potency is increased so reduce dose by 1/2-2/3
MG and depolarizing NMB’s
decreased sensitivity
-if RSI required, dose should be 1.5-2mg
-since pyridostigmine is mainstay of medical management, it descreases pseudocholinesterase and increases DOA of succ
postop concerns for a patient with MG
- residual NMB/muscle weakness
- bulbar dysfunction- difficulty handling PO secretions
- educate on plausible need for postop MV and what increases their risk (disease duration >6y, daily pyridostigmine >750mg/day, VC <2.9L, COPD, if the surgical approach was the median sternotomy> trans cervical thymectomy
lambert eaton syndrome or LEMS pathophysiology
-IgG mediated destruction of presynaptic Vg Ca channels at the pre synaptic nerve terminal
-for this reason, Ca entry via depol is limited and so is Ach released into synaptic cleft
-post synaptic nicotinic receptor is present in normal quantity and functions normally
clinical presentation of LEMS
-proximal muscles are most affected and weakness is worst in the AM but gets better throughout the day (probs because more Ach can say hello)
-resp musculature and diaphragm become weak
-ANS dysfunction causes orthostatic HoTN, slowed gastric mobility, urinary retention
LEMS tx
3,4 diaminpyridine (DAP) increases Ach release from presynaptic nerve terminal and improves strength of contraction.
-acetylcholinesterase are not helpful and tensilon test does not aid in dx
anesthetic considerations for LEMS patient
-reversal with acetylcholinesterase may be inadequate despite proper dosing
-at high risk for postop vent failure
-~60% of LEMS patients have small cell (oat cell) carcinoma of lung.
LEMS response to succ
sensitive
LEMS response to ND NMB’s
sensitive
Guillian Barre syndrome
aka acute idiopathic polyneuritis
-immunologic assault on myelin in peripheral nerves
-AP cant be conducted to motor end plate never receives the signal
clinical presentation of Guillian barre (acute idiopathic polyneuritis)
-flu like illness usually precedes paralysis by 1-3w
-GBS usually persists for 2 weeks with full recovery in ~4w
-about 2% affected with GBS will develop chronic inflammatory demyelinating polyneuropathy
common etiologies of Guillian barre
campylobacter jejuni bacteria, epstein barr, and cytomegalovirus. other causes include vaccines, surgery, and lymphomatous disease
s/sx of GBS
-flaccid paralysis begins in distal extremities and ascends bilaterally towards proximal extremities, trunk, and face
-intercostal muscle weakness impairs ventilation
-facial and pharyngeal weakness causes difficulty swallowing
-sensory deficits include parasthesias, numbness, and pain
-autonomic dysfx is common- tachycardia or bradycardia, HTN or HoTN, diaphoresis or anhidrosis, orthostatic HoTN
tx of GBS
plasmapheresis and IV IgG
(-in contrast to MS, steroids and interferon do not improve this condition)
anesthetic considerations for GBS
(resp, steroids?, adrenergic drugs, type of anesthesia)
-facial and pharyngeal weakness causes difficulty swallowing and increases risk of aspiration
-may require postop MV
-with autonomic dysfunction youre at risk for hemodynamic variability and should do aline
- exaggerated response to indirect sympathomimetics due to up regulation of post junctional adrenergic receptors
-regional anesthesia is controversial
-steroids are not useful
-immobility increases risk of DVT
succ and GBS
sensitive, avoid. up regulation of post junctional receptors
ND NMB’s and GBS
increased sensitivity
is familial periodic paralysis a disease of the NMJ
no its a DO of the skeletal muscle membrane (reduced excitability)
hypokalemic periodic paralysis is associated with which type of channelopathy
calcium
dx of hypokalemic periodic paralysis
present if skeletal muscle weakness follows a glucose insulin infusion. patient becomes weak as serum k decreases
dx of hyperkalemic periodic paralysis
if skeletal muscle weakness follows PO potassium administration.
tx for either hyper or hypokalemic periodic paralysis
acetazolamide. creates non anion gap acidosis (HCO3- fall is matched by Cl- rise) which protects against hypokalemia while facilitating renal K excretion which guards against hyperkalemia
anesthetics considerations for familial periodic paralysis: temperature
hypothermia avoided at all costs. normothermia even on CPB bro
with hypokalemic periodic paralysis, what drugs are safe to administer
non depolarizers, acetazolamide
with hypokalemic periodic paralysis, what drugs are NOT safe to administer (4)
glucose containing solutions
K wasting diuretics
B2 agonists
succ
with hyperkalemic periodic paralysis, what drugs are safe to administer (5)
glucose containing solutions
K wasting diuretics
B2 agonists
non depolarizers
acetazolamide
with hyperkalemic periodic paralysis, what drugs are NOT safe to administer (2)
succ
K containing solutions
hypokalemic periodic paralysis and succ
association between this and MH, dont admin
hyperkalemic periodic paralysis and succ
no association with MH BUT at much higher risk for hyperkalemic issues r/t succ
ND NMB’s and familial periodic paralysis
slight increased sensitivity but safe to use. use shorter acting if possible
2 classes of drugs known to trigger MH
halogenated agents and depolarizing NMB’s
MH pathophys
- when T tubule is depolarized, Ca enters myocyte via dihydropyridine receptor
- activates defective receptor RYRY1, which instructs SR to release way too much Ca into cell.
- not only is there more Ca for contraction, SERCA2 pump is trying to pump Ca back in
- both increase O2 consumption, take a lot of ATP
- breakdown of sarcolemma allows K and myoglobin (toxic to the kidneys) to enter the system circulation
consequences of increased intra cellular calcium in myocyte
-rigidity from sustained contraction
-accelerated metabolic rate and rapid depletion of ATP
-increased O2 consumption
-increased CO2 and heat production
-mixed resp and lactic acidosis
-sarcolemma breaks down
-K and myoglobin leak into systemic circulation
3 diseases definitively associated with MH
- king den borough syndrome
- central core disease
- multi mini core disease
DMD in comparison to MH
absence of dystrophin destabilizes sarcolemma during muscle contraction and increases membrane permeability. This allows myoglobin to exit cell. Creates MH like syndrome but it is due to rhabdo not true MH
halogenated agents/depolarizing NMB’s and DMD
creates MH like syndrome (and really rhabdo) so still avoid
any DMD or muscular dystrophy who has cardiac arrest on induction should be treated as if
if its hyperkalemic and should receive CaCl immediately
conditions NOT associated with MH include (5)
Becker muscular dystrophy
neuroleptic malignant syndrome
myotonia congenita
myotonic dystrophy
osteogenesis imperfecta
factors that increase risk of MH include
- geography (families in wisconsin, nebraska, WV, michigan)
- male sex
- youth
earliest signs of MH include
tachycardia
masseter spasm
increased EtCO2
warm soda lime
irregular heart rhythm
intermediate signs of MH include
cyanosis
irregular heart rhythm
patient warm to touch
late signs of MH include (5)
muscle rigidity
cola colored urine
coagulopathy
irregular heart rhythm
overt hyperthermia
most sensitive indicator of MH
EtCO2 that rises out of proportion to MV
MH can occur as late as how many hours after exposure to triggering agent?
6 hours
core temperature usually (but not always) rises how many minutes after exposure to triggering agent?
15 minutes
trismus versus masseter spasm
trismus describes a tight jaw that can be opened
masseter spasm describes a tight jaw that cannot be opened
when will you see trismus
succ admin
why will a NMB not relieve a spasm
muscle rigidity is due to increased calcium in the myoplasm which is distal to NMJ
if a patient experienced masseter muscle rigidity, what should you do
assume MH until proven otherwise
describe halothane contracture test
requires a liver muscle biopsy
gold standard for dx of MH
anyone who has experienced MH or masseter spasm should be referred to for this test
this test has a high sensitivity and a low specificity
differential dx to consider with MH
thyroid storm
malignant neuroleptic syndrome
sepsis
pheo
serotinergic syndrome
heat stroke
metastatic carcinoid
coke intoxication
what class of drugs are contraindicated with MH tx
CCB, co administration with dantrolene can cause life threatening hyperkalemia
how long to flush anesthesia machine with MH and what else to do
20-200 minutes depending on machine
-all external parts should be removed and replaced
-includes CO2, absorbent, circuit, breathing bag
-physically remove vaporizers
monitoring for MH intra op and PACU when suspected/known
if they dont develop MH within 1 hour of procedure starting, then they probably won’t
monitor for 1-4h in PACU
charcoal filters and MH
will keep halogenated anesthetic concentration below 5ppm for up to 12h with a minimum FGF of 3L/min
-flush anesthesia machine with high FGF (10L/min) for 90 seconds with filters on prior to using machine on patient.
2 MOA’s of dantrolene
- reduces Ca release from RYRY1 receptor in skeletal myocyte
- prevents calcium entry into myocyte which reduces stimulus for calcium induced calcium release
each vial of dantrolene contains
20mg of dantrolene and 3mg of mannitol
how to reconstitute a vial of dantrolene
60mL of preservative free water
MH tx acute phase
- d/c triggering agent and continue anesthesia with IV technique
- call for help
- hyperventilate with 100% FiO2 and FGF > or = 10L/min
- if you have charcoal filters, apply them and new circuit/reservoir bag
- administer dantrolene/ryanadex
- cool patient until under 38 (cool IVF, cold lavage of stomach and bladder, ice packs)
- correct acidosis (NaHCO3 1-2mEq/kg IV titrated too ABG and base deficit)
- tx hyperkalemia (CaCl 5-10mg/kg IV, until .15 units/kg +D50 1mL/kg)
- protect against dysrhythmias with class 1 antiarrhythmics (procainamide 15mg/kg IV, lidocaine 2mg/kg IV. NO CCB’s)
- maintain UOP >2mL/kg/h (mannitol .25g/kg IV, furosemide 1mg/kg IV, fluids)
- check coag panels. DIC is indicative of impending demise
benefits of hyperventilation during acute phase of MH tx
CO2 elimination
O2 delivery
drives K into cells
how often to change vapor clean charcoal filters intra op
every hour
review administration of dantrolene/ryanadex in acute phase of MH and tx continuation to ICU
2.5mg/kg IV and repeat q5-10m
-stop dantrolene when sx of hyper metabolism subside
-continue in ICU at 1mg/kg q6h or 0.1-0.3mg/kg/h for 48-72h
-venous irritation is common, use largest vein possible
-if patient requires more than 20mg/kg, reconsider MH dx
ryanodex contains
250mg dantrolene and requires 5mL of sterile water dilutent
after stabilization they should be monitored for reoccurrence of MH in the ICU for up to
36h
for DMD, the breakdown of sarcolemma allows what into the blood stream
creatinine kinase and myoglobin enters circulation. calcium also freely enters the cell which activates proteases that destroy contractile elements and cause inflammation, fibrosis, and cell death
clinical presentation of DMD
more common in males, presents with atrophy and painless muscle degeneration. profound weakness in 1st decade of life.
often require surgical tx of scoliosis and contractures and rarely live past 30y
respiratory considerations for DMD
-kyphoscoliosis (posterior curvature of spine) and therefore restrictive lung disease–>decreased p.reserve–> increased secretions and risk of PNA
-respiratory muscle weakness
cardiac considerations for DMD
degeneration of cardiac muscle–> reduced contractility–>papillary muscle dysfunction, mitral regurg, cardiomyopathy, congestive heart failure
-signs of cardiomyopathy include resting tachycardia, JVD, S3/S4 gallop, displacement of PMI (point of maximal impulse)
-patients should receive cardiac work up before surgery (EKG, echo, cardiac MRI)
EKG changes and DMD
impaired cardiac conduction- ST and short PR interval
scarring of posterobasal aspect (back/bottom) of LV manifests as increased R wave amplitude in lead I, and deep Q waves in the limb leads
GI considerations and DMD
impaired aw reflexes and GI hypo motility = increased risk of aspiration
etiology of scoliosis (lateral and rotational curvature of spine) (5)
-idiopathic (incidence 80%)
-congenital
-myopathic (MD and amyotonia congenita)
-neuropathic (CP, syringomyelia, Friedrichs ataxia)
-traumatic
how to measure cobb angle
two most displaced vertebrae are ID’d
line is drawn parallel to each
perpendicular line is drawn from each these lines
angle where they intersect is the cobb angle
degree of cobb angle and significance:
40-50
60
70
100
early respiratory complications of scoliosis
-restrictive ventilatory defect (FEV1 and FRC are decreased but FEV1/FVC is normal
-decreased VC, TLC, FRC, RV
-decreased chest wall compliance
late respiratory complications of scopliosis
VQ mismatching
hypoxemia
hypercarbia (sign of impending resp failure)
p.HTN
reduced response to hypercapnea
cor pulmonale
cardiorespiratory failure
CV changes with scioliosis
EKG may show RV strain and right atrial enlargement r/t increased PVR
complications of the prone position:
airway
neck
eyes
UE’s
LE’s
abdomen
thoracic correction of scoliosis higher than _____ may require one lung ventilation with DLT or bronchial blocker
T8
anesthetic considerations for scoliosis patient
-assess resp reserve with exercise tolerance, ABG, VC. <40% predicted VC correlates with postop ventilation
-cervical scoliosis may cause difficult intubation
-N2O increases PVR
-prep for significant blood loss
-deliberate HoTN to MAP 60mmHg carries risk of hype-perfusion and ION
-monitor end organ perfusion with ABG and UOP
-use active warming such as forced air, fluids, etc
-VAE risk
-wake up test v monitoring SSEP/MEP’s
if, during wake up test, patient can move hands and not feet, what is the next step
reduce distraction on spinal rods
2 names for the structure in this image
odontoid process (dens)
3 ways RA impacts aw
- limited mouth opening (TMJ r/t synovitis)
- decreased diameter of glottic opening- use smaller tube (cricoaretynoid joints)
- cervical spine (Atlanta occipital subluxation with flexion and limited extension)
s/sx cricoaretynoid arthritis
hoarseness, stridor, dyspnea, may result in aw obstruction
edema or erythema of vocal cords suggests it
also at risk for post extubation aw obstruction
how to dx AO subluxation for RA
lateral x ray to assess if distance between anterior arch of atlas and odontoid process is >3mm
surgical correction of AO subluxation r/t RA entails
odontoid decompression and posterior cervical fusion
pathophysiology of RA
autoimmune disease that targets synovial joints
-cytokines (TNF and interleukin 1) play a large role in this
-infiltration of immune complexes into small and medium arteries resulting in vasculitis
-RA affects proximal interphalangeal and metacarpophalangeal joints (whereas osteoarthritis typically affects weight bearing)
complications of RA
eyes
aw
nervous system
endocrine
renal
pulmonary
cardiac
GI
heme
lab testing of RA
rheumatoid factor is an anti immunoglobulin antibody that is increased in 90% of RA patients
-c reactive protein and erythrocyte sedimentation is also increased
medical management of RA
-reducing inflammation, anti rheumatics, glucocorticoids, NSAIDS
RA and DMARDS
(3 drug examples)
-disease modifying anti rheumatic drugs
-inhibit TNF and IL-1 and IL-6 and T cells and B lymphocytes
-suppress immune system and increase risk of infx and CA
-examples: methotrexate, cyclosporine, etanercept
SE of methotrexate
causes liver dysfunction and suppresses bone marrow
cyclosporine and succ
prolongs DOA of succ
pathophysiology of SLE
autoimmune disease characterized by proliferation of anti nuclear antibodies
-most consequences are r/t antibody induced vasculitis and tissue destruction
systemic manifestations of SLE
aw
nervous system
renal
pulmonary
cardiac
hematologic
exacerbation of SLE: PISSED CHIMP
medical tx for SLE (4)
aimed at suppressing immune system
-corticosteroids
-nsaids
-immunosuppression (cyclophosphamide, azathioprine, methotrexate, mycophenylate)
-antimalarials (hydroxychloroquine and quinacrine)
anesthetic considerations for SLE
-cricoaretynoid arthritis may present as hoarseness, stridor, aw obstruction. risk of post extubation laryngeal swelling and aw obstruction, necessitating steroids, consider smaller ETT for cricoaretynoiditis
-antiphospholipid antibodies may develop. although aPTT is prolonged, theyre at risk for hyper coagulability and thrombosis. at risk for stroke, DVT, PE
what exacerbates sx of SLE
pregnancy, stress, infection, surgery
cyclophosphamide and succ
inhibits plasma cholinesterase and increases DOA of succ
marfan syndrome pathophysiology
connective tissue DO with autosomal dominance and inheritance (think AAA and aortic insufficiency)
marfan syndrome sx/risk
-dilated aortic root that sets the stage for aortic insufficiency and dissection (minimize wall stress with BB)
-AAA, cardiac tamponade (if aortic dissection), mitral prolapse, spontaneous PTX (careful with PIP)
-pregnancy increases risk of CV complications
marfan syndrome and patient stature/appearance
tall with pectus excavatum (sunken chest), kyphoscoliosis, and hyperreflexive joints (careful with positioning)
Ehlers danlos syndrome
inherited DO of pro collagen and collagen (think spontaneous bleeding into joints and AAA)
-common problems include arterial aneurysms, increased bleeding tendency (due to poor vessel integrity not coagulopathy)
-due to bleeding risk, avoid regional anesthesia and IM injections. excessive bleeding can also occur during invasive line placement and trauma during aw management
osteogenesis imperfecta
connective tissue DO with autosomal dominant inheritance (think weak bones)
-brittle bones (careful during positioning). even BP cuff can fx bones.
-careful with aw management (cspine fx risk increased, cervical ROM decreased)
-kyphoscoliosis and pectus excavatum reduce chest wall compliance and VC which creates VQ mismatch and hypoxemia
-serum thyroxine is increase in 50% of patients (increased BMR and VO2–> hyperthermia)
-risk of MH not increased *
-blue sclera….which are susceptible to fx
MS
-demyelinating disease of CNS
-CN involvement causes bulbar muscle dysfx (increases aspiration risk)
-patients are tx with corticosteroids, interferon, azathioprine
-s/sx can be exacerbated by stress and increased body temp
-literature (is weak but suggests) epidural is safe but spinal is not ?
-NO SUCC!!!!! hyperkalemia city
myotonic dystrophy
(and can they get halogenated anesthetics)
-prolonged contracture after voluntary contraction
-result of dysfunctional calcium sequestration by SR
-succ, NMB reversal with anticholinesterases, hypothermia r/t shivering and sustained contractions increased risk of contractions
-also at risk for: aspiration, resp muscle weakness, cardiomyopathy and dysrhythmias, sensitivity to anesthetic agents
-can get halogenated anesthetics, not at risk for MH
scleroderma
excessive fibrosis in skin and organs, particularly in microvasculature
-aw: skin fibrosis limits mouth opening and mandibular mobility (FOI)
-lungs: p.fibrosis and p.HTN
-heart: dysrhythmias and CHF
-BV: decreased compliance, HTN
-kidneys: renal failure and renal artery stenosis- HTN
-peripheral cranial nerves: nerve entrapment by tight connective tissue- neuropathy
-eyes: dryness predisposes to corneal abrasion
-telangiectasiasis: spider veins that bleed easily and can become an aw issue- consider FOI
CREST and scleroderma
calcinosrs, raynauds, esophageal hypo motility, sclerodactyly, telangiectasia
Pagets disease
excess osteoblastic and osteoclastic activity that causes abnormally thick but weak bone deposits
-excessive PTH or calcitonin deficiency
-pain and fx are most common problems
-peripheral nerve entrapment can occur
-no vascular involvement (yay one win!)
common drugs that cause drug induced SLE (CHIMP)
hydralazine and isoniazid
which immunosuppressant increases DOA of succ
cyclophosphamide (plasma cholinesterase inhibitor)
