Musculoskeletal Dz Flashcards
Myasthenia Gravis Patho
- autoimmune dz
- IgG antibodies destroy POST-junctional receptors (nicotinic Ach)
- thymus gland plays key role; thymectomy relieves s/s
- Ach quantity sufficient
- not enough Ach receptors
- manifests as skeletal muscle wknss
Myasthenia gravis s/s
- key features:
~ muscle wknss later in day or w/ exercise
~ improves w/ rest - diplopia, ptosis (early)
- bulbar wknss (dysphagia, dysarthria, drooling)
- dyspnea w/ exertion
- proximal muscle wknss
- may require postop ventilation
Myasthenia Gravis is exacerbated by:
Apple - aminoglycosides
P - pregnancy
I - infection
E - electrolyte abnormalities
S - stress
How does myasthenia gravis affect pregnant mother & fetus?
- Pregnancy intensifies s/s in 1/3 of pregnant women
- Anti-Ach IgG antibodies cross placenta in 15-20% of neonates & cause wknss (can last up to 2-4 weeks)
- neonates require airway mgmt
Myasthenia Gravis Tx
- 1st line = oral pyridostigmine
- corticosteroids, cyclosporine, azathioprine, mycophenolate (immunosuppression)
- thymectomy (reduces Anti-AchR IgG)
- plasmapheresis
How can you differentiate b/t cholinergic crisis & myasthenic crisis?
- pyridostigmine OD –> cholinergic crisis
- Tensilon test = 1-2 mg IV edrophonium
~ muscle wknss worse = cholinergic crisis –>
tx w/ anticholinergic
~ muscle wknss better = myasthenic crisis –>
tx w/ anticholinesterase,
immunosuppression, plasmapheresis
How do patients w/ myasthenia gravis respond to sux?
- Fewer nicotinic Ach (Nm) receptors
- Resistant
- Require increased dose (1.5- 2.0 mg/kg)
- pyridostigmine prolongs DOA of sux
How do patients w/ myasthenia gravis respond to ND-NMB?
- Fewer nicotinic Ach (Nm) receptors
- Sensitive (potency increased)
- Reduce dose by 1/2 to 2/3
5 perioperative risks that increase postop mechanical ventilation in pt w/ myasthenia gravis
- Dz > 6 years
- pyridostigmine > 750 mg/day
- VC < 2.9 L
- COPD
- Surgical approach: median sternotomy> transcervical thymectomy
Eaton-Lambert Syndrome (Myasthenic Syndrome) Patho
- IgG-mediated destruction of PRE-synaptic VG
Ca+ channels - Ca+ entry in presynaptic neuron decreased
- Decreased amount of Ach released into
synaptic cleft - 60% have small-cell lung CA (oat-cell)
ELS S/S
- Proximal muscles affected
- wknss worse in AM, gets better throughout
day - Respiratory muscles & diaphgram weak
- ANS dysfunction:
~ orthostatic hypotension
~ slowed gastric motility
~ urinary retention
ELS Tx
- 3, 4- diaminopyridine (DAP)
~ increases Ach release from presynaptic
nerve
AchE not helpful
Tensilon test does NOT aid diagnosis
How do pt w/ ELS respond to NMBs?
- Sensitive to sux & NDNMBs
- Reduce dose
ELS Mgmt
- Reversal may be inadequate
- High risk postop resp failure
ELS vs. Myasthenia Gravis
Guillain-Barre (acute idiopathic polyneuritis)
- Destruction of myelin prevents nerve conduction in peripheral nerves
- Precipitated by flu-like illness followed by paralysis
- Causes: epstein-barr, campylobacter, cytomegalovirus
Guillain-Barre S/S
- Flaccid paralysis begins in distal extremtities & ascends bilaterally
- Impaired ventilation (intercostal muscles)
- Difficulty swallowing (facial & pharyngeal muscles)
- Paresthesias, numbness, pain
- ANS dysfunction
~ tachycardia, bradycardia, hyper/hypotension, diaphoresis, anhidrosis
Guillain-Barre Tx
- plasmapheresis
- IV IgG
Guillain-Barre Mgmt
- avoid sux (hyperkalemia)
- sensitive to NDNMBs (decrease dose)
- increased aspiration risk
- may require postop ventilation
- autonomic dysfx = HD instability = a-line
- exaggerated response to indirect-acting sympathomimetics (avoid ephedrine)
Hypokalemic periodic paralysis
- Skeletal muscle wknss follows a glucose-insulin infusion
- pt becomes weak after K+ decreases
- Ca+ channelopathy
AVOID:
- glucose solutions
- K+ wasting diuretics
- B2 agonists
- Sux
- hypothermia
Safe:
- NDNMBs
- Acetazolamide
Tx: Acetazolamide (creates non-anion gap acidosis, protects against hypokalemia)
Hyperkalemic periodic paralysis
- skeletal muscle wknss follows oral K+ administration
- pt becomes weak after K+ increases
- Na+ channelopathy
AVOID:
- Sux
- LR (solutions w/ K+)
- hypothermia
Safe: everything listed in AVOID on hypokalemia card + acetazolamide
Tx: Acetazolamide (facilitates K+ excretion)
MH patho
- Inherited disease of skeletal muscle characterized by disordered Ca+ homeostasis
- Genetic mutation of ryanodine receptor (RYR1)
- Defective RYR1instructs SR to release too much Ca+ into cell
- Increase O2 consumption
- Increased CO2 production
Consequences of increased intracellular Ca+
- rigidity from sustained contraction
- accelerated metabolic rate
- depletion of ATP
- increased O2 consumption
- increased CO2 production
- increased heat production
- mixed resp & lactic acidosis
- sarcolemma breaks down
- K+ & myoglobin leak out into blood
Conditions NOT associated w/ MH
- Becker MD
- Neuroleptic malignant syndrome
- myotonia congenita
- myotonic dystrophy
- osteogenesis imperfecta
3 conditions associated w/ MH
- King-Denborough syndrome
- Central core dz
- Multiminicore dz
MH triggers
- VA
- sux
MOST sensitive indicator of MH
EtCO2
Early s/s MH
- tachycardia
- tachypnea
- masseter spasm
- warm soda lime
- irregular heart rhythm
Intermediate s/s MH
- cyanosis
- pt warm to touch
Late s/s MH
- muscle rigidity
- cola- colored urine
- coagulopathy
- overt hyperthermia
Trismus
- tight jaw that CAN still be opened
- normal occurrence w/ sux
Masseter spasm
- tight jaw that CANNOT be opened
- NMB will not relax jaw
What is the definitive test for MH?
Halothane Contracture Test
- requires live muscle biopsy
How do you prepare for a patient at risk for MH?
- flush anesthesia machine w/ high flow O2 (20-100 min depending on machine)
- replace all external parts (CO2 absorbent, circuit, breathing bag)
- remove vaporizers from machine
- monitor in PACU 1-4 hours
Alternative to flushing machine:
- charcoal filter (vapor-clean)
- place on inspiratory/expiratory limbs
- flush w/ 10 L O2 for 90 sec
Dantrolene MOA
muscle relaxant
- reduces Ca+ release from RyR1 in skeletal muscle
- prevents Ca+ entry into myocyte –> reduces stimulus for Ca+ induced Ca+ release
Dantrolene vial & reconsitution
each vial contains 20 mg dantrolene + 3 mg mannitol
reconstitute w/ 60 ml preservative free water
Dantrolene dose
- 2.5 mg/kg IV repeat q 5-10 min
- stop when s/s subside
- continue 1 mg/kg q 6 hr in ICU
- ## SE: venous irritation, muscle weakness
MH Treatment
- D/C triggering agent, convert to TIVA
- Call for help
3a. Hyperventilate w/ 100% O2 min FGF 10L/min (CO2 elim, O2 delivery, drives K+ into cell)
3b. Apply charcoal filter (change q 1 hr), change breathing circuit & bag - Administer Dantrolene or Ryanodex
- Cool until temp < 38 C
- Correct lactic acidosis
- NaHCO3 1-2 mEq/kg (titrate per ABG)
- Treat K+
- Cacl 5-10 mg/kg IV
- insulin 0.15 u/kg+D50 1ml/kg
- hyperventilate
- Protect against dysrhythmias
- Procainamide 15 mg/kg IV
- Lido 2 mg/kg IV
- Maintain UOP > 2 ml/kg/hr
- IVF, mannitol, furosemide
- DIC (late sign) –> check coags
Duchenne muscular dystrophy (DMD)
- dystrophin helps anchor actin & myosin to cell membrane
- absence destabilizes sarcolemma during muscle contraction & increases membrane permeability
- allows CK & myoglobin to enter blood
- Ca+ freely enters cell
- extrajunctional receptor populate (hyperkalemia)
DMD clinical presentation
- males
- atrophy, painless muscle degeneration
- kyphoscoliosis
- resp muscle wknss
- degeneration of cardiac muscle (reduced contractility, papillary muscle dysfx, mitral regurg, CHF, cardiomyopathy)
-EKG changes: ST, short PR interval, deep Q wave - impaired airway reflexes
Pt w/ DMD susceptible to what life-threatening condition?
Sux can cause hyperkalemia & cardiac arrest leading to sudden death
Also avoid VA
Scoliosis
lateral & rotational curvature of spine & ribcage
Cobb angle
Describes magnitude of spinal curvature
- 2 most displaced vertebrae identified
- line is drawn parallel to each
- perpendicular line drawn from each of these lines
- angle where they intersect = cobb angle
Cobb angle 40-50
indication for surgery
Cobb angle 60
decreased pulmonary reserve
Cobb angle 70
pulmonary symptoms
Cobb angle 100
- impaired gas exchange
- increased risk postop pulmonary complications
Scoliosis pulmonary changes
Scoliosis cardiac changes
- RV hypertophy
- EKG: RV strain RA enlargement
- MV prolapse
- mitral regurg
- coarctation of aorta
Scoliosis Mgmt
- cervical scoliosis - difficult intubation
- N2O increases PVR
- correction higher than T8 may require one-lung ventilation
- significant blood loss
- at risk VAE
Somatosensory Evoked Potentials (SSEP_
- monitors posterior spinal cord (dorsal column), which is perfused by posterior spinal arteries
- monitors sensory fx
- NMBs do not interfere w/ monitoring
Motor Evoked Potentials (MEPs)
- monitors anterior spinal cord, which is perfused by anterior spinal artery
- monitor motor fx
- do NOT use NMBs
6 potential risk of wake-up test
- IV removal
- extubation
- awareness
- pain
- air embolism
- damage to spinal instrumentation
Rheumatoid arthritis: airway
- TMJ- limited mouth opening
- Cricoarytenoid joints
- decreased diameter of glottic opening
- hoarseness, stridor, dyspnea, airway
obstruction - use smaller ETT
- c-spine
- atlanto-occipital subluxation w/ flexion
- limited extension
- at risk for quariparesis or paralysis
RA patho
- autoimmune dz targeting synovial joints
- systemic involvement
- cytokines play central role
- Hallmark: AM stiffness that improves w/ activity
- painful, swollen, warm joints
-more common in women - affects proximal interphalangeal & metacarpophalangeal joints in hands & feet
Complications of RA
What labs are increased w/ RA?
- C-reactive protein
- Erythrocyte sedimentation rate
RA Tx
- antirheumatics (methotrexate, cyclosporine, entanercept)
- NSAIDs
- glucocorticoids
Systemic Lupus Erythematosus (SLE) patho & S/S
- autoimmune dz characterized by proliferation of antinuclear antibodies
What can exacerbate SLE?
SLE Tx
- corticosteroids
- NSAIDs
- immunosuppressants
- antimalarials
SLE Mgmt
- cricoarytenoid arthritis = airway obstruction, swelling; smaller ETT
What immunosuppressant drugs increased DOA sux?
cyclophosphamide
Marfan Syndrome
Connective tissue d/o w/ autosomal dominant inheritance
- associated w/: aortic insufficiency, AAA, aortic dissection, mitral prolapse, spontaneous pneumo (high)
- tall w/ pectus excavatum (sunken chest), kyphoscoliosis, hyperflexible joints
- pregnancy increases risk of CV complications
Ehlers-Danlos Syndrome
Inherited d/o of procollagen & collagen
- associated w/ aneurysms, increased bleeding tendency, AAA
-* bleeding into joints
- avoid regional
- risk of pneumo
Osteogenesis imperfecta
Connective tissue d/o w/ autosomal dominant inheritance
- * brittle bones
~ careful w/ positioning, BP cuff
- careful airway mgmt (risk cspine fracture)
- kyphoscolisos
- pectus excavatum
- increased serum thyroxine ( increased BMR & VO2 –> hyperthermia)
- *Blue sclera
Multiple Sclerosis
Demyelinating dz of CNS
- sensory, motor, ANS dysfunction
- bulbar muscle dysfx
- AVOID sux (hyperkalemia)
- S/S exacerbated by stress and increased temp
- Tx w/ corticosteroids, interferon, azathioprine
Myotonic Dystrophy
Prolonged contracture after a voluntary contraction
- dysfx Ca+ sequestration by SR
- can interfere w/ ventilation & intubation
- at risk for:
~ aspiration
~ resp muscle wknss
~ cardiomyopathy, dysrhythmias
~ sensitive to anesthetic agents
3 things that increase risk of contractures in pt w/ myotonic dystrophy
- Sux
- NMB reversal w/ AchE
- Hypopthermia
Scleroderma
Excessive fibrosis in skin & organs, particularly microvasculature
CREST syndrome
CREST syndrome
Calcinosis
Raynaud’s
Esophageal hypomotility
Sclerodactyly
Telangiectasia (spider veins- increase risk mucosal bleeding; problematic during airway manipulation-esp nasal intubation)
Paget’s Dz
Excessive osteoblastic & osteoclastic activity causes thick, weak bone deposits
- excessive PTH or Ca+ deficiency
- pain & fractures most common
