Musculoskeletal Flashcards
Which autoimmune disease has IgG antibodies that destroy post-junctional, nicotinic, Ach receptors at the neuromuscular junction?
Myasthenia gravis
How does skeletal muscle weakness occur in myasthenia gravis?
There aren’t enough receptors to translate the extracellular signal into an intracellular response.
This manifests as skeletal muscle weakness.
Ach is present in sufficient quantity
What gland plays a key role in Myasthenia Gravis?
Thymus gland plays a key role.
A thymectomy brings symptom relief to many patients.
What is a key feature of myasthenia gravis in terms of the skeletal muscle function.
The skeletal muscle weakness becomes worse later in the day or develops with exercise.
Periods of rest allow for recovery of skeletal muscle function.
What are the symptoms of myasthenia gravis?
Diplopia, ptosis (earliest signs)
Bulbar muscle weakness (muscles of mouth and throat) which leads to dysphagia, dysarthria, and difficulty handling saliva
Dyspnea with exertion
Proximal muscle weakness
What are some situations that exacerbate symptoms of myasthenia gravis?
Pregnancy
Infection
Electrolyte abnormalities
Surgical and psychological stress
Aminoglycoside antibiotics
What do you have to worry about with pregnancy and the placenta with myasthenia gravis?
Pregnancy intensifies the symptoms of myasthenia gravis.
Anti-AchR IgG antibodies cross the placenta and cause weakness in 15-20 percent of neonates.
This can persist up to 2-4 weeks, which is consistent with the half-life of the Anti-AchR IgG antibodies in the neonate’s circulation.
These neonates may require airway management.
What are four ways to treat myasthenia gravis?
Anticholinesterases
Immunosuppression
Surgery
Plasmapheresis
What is the first line oral medical treatment for myasthenia gravis?
Oral Pyridostigmine is the first line medical treatment.
Overdoes in anticholinesterases causes cholinergic crisis and muscle weakness.
Cholinergic crises may be difficult to differentiate from myasthenic crisis.
What is the Tensilon Test?
It will determine if the patient is in cholinergic crisis or myasthenic crisis.
How do you administer the Tensilon Test?
Administering 1-2 mg IV edrophonium
Based on the Tensilon test, how can you tell if the patient is in cholinergic crisis or myasthenic crisis?
Administering 1-2 mg IV edrophonium.
If muscle weakness is made worse, then the patient has cholinergic crisis. An anticholinergic is the appropriate treatment for this patient.
If there is an improvement in muscle strength, then the patient had an exacerbation of myasthenic symptoms.
What four immunosppressions can you use for myasthenia gravis?
Corticosteroids
Cyclosporine
Azathioprine
Mycophenolate
What surgery can you perform for myasthenia gravis?
Thymectomy reduces circulating Anti-AchR IgG in most patients
Surgical approach may be via median sternotomy or by the transcervical approach.
What treatment for myasthenia gravis can provide a temporary relief during myasthenic crisis or prior to thymectomy?
Plasmapheresis
A patient with myasthenia gravis, they will have an increased sensitivity to which drugs as well as an increased resistance to which drug?
Because there is a reduction in the number of nicotinic receptors (type-M) at the neuromuscular junction, patients with myasthenia gravis have an increased sensitivity to NON-DEPLARIZING NMBs and a resistance to SUCCINYLCHOLINE.
How should you dose nondepolarizers in a patient with myasthenia gravis?
Patients will have an increased sensitivity with nondepolarizers.
This causes an increased potency.
Reduce dose by 1/2 to 2/3 and monitor the response with nerve stimulator.
Remember that volatile anesthetics cause skeletal muscle relaxation by acting in the ventral horn of the spinal cord. In many cases, this eliminates the need for neuromuscular blockers.
What would be the RSI dose for succinylcholine for a patient with myasthenia gravis?
1.5-2.0 mg/kg
Pyridostigmine is the mainstay of medical management.
It impairs the efficacy of pseudocholinesterase. This prolongs the duration of succinylcholine.
Remember that volatile anesthetics cause skeletal muscle relaxation by acting in the ventral horn of the spinal cord. In many cases, this eliminates the need for neuromuscular blockers.
What are some post operative concerns for a patient with myasthenia gravis?
Patient are very sensitive to the effects of residual neuromuscular blockade.
Bulbar muscle weakness (mouth and throat) manifests as difficulty oral secretions. This increases the risk of pulmonary aspiration.
Patients should be counseled on the need for post operative ventilation..
What would increase the risk for a patient for post operative ventilation, if they have myasthenia gravis?
Disease duration > 6 years
Daily pyridostigmine > 750mg/day
Vital capacity < 2.9L
COPD
Surgical approach: Median sternotomy > transcervical thymectomy
What are other names for Myasthenic Syndrome?
Eaton-Lambert Syndrome
Lambert-Eaton Myasthenic syndrome (LEMS)
What is Eaton-Lambert Syndrome?
A disorder of the neuromuscular junction that results in skeletal muscle weakness.
AKA Lambert-Eaton Myasthenic syndrome (LEMS) or Myasthenic Syndrome
NOT the same as myasthenia gravis.
What is the pathophysiology of Eaton-Lambert syndrome?
IgG mediated destruction of the PRESYNAPTIC voltage-gated calcium channel at the presynaptic nerve terminal.
When the action potential depolarizes the nerve terminal, Ca+2 entry into the presynaptic neuron is limited, thereby reducing the amount of Ach that is released into the synaptic cleft.
The postsynaptic nicotinic receptor is present in normal quantity and functions normally.
What are the clinical presentation of Eaton-Lambert syndrome?
The proximal muscles are most affected, and weakness is generally worse in the morning and gets better throughout the day.
The respiratory musculature and diaphragm become weak.
Autonomic nervous system dysfunction causes orthostatic hypotension, slowed gastric motility, and urinary retention.
What is the treatment of Eaton-Lambert syndrome?
3,4-diaminopyridine (DAP) increase Ach release from the presynaptic nerve terminal and improves the strength of contraction.
Anticholinesterases are not helpful and the Tensilon test does not aid in diagnosis.
Which disease will cause a patient to be sensitive to succinylcholine AND nondepolarizers?
Eaton-Lambert syndrome
doses should be reduced.
Volatile anesthetics provide enough muscle relaxation for most surgical procedures.
What is a common co-morbidity with patients with Eaton-Lambert syndrome?
Upwards of 60 percent of patients have small-cell carcinoma of the lung (oat-cell carcinoma).
Consider the possibility of this disorder in all patients with suspected lung CA undergoing mediastinoscopy, bronchoscopy, or thoracoscopy.
Will anticholinesterasese be effective for a patient with Eaton-Lambert syndrome?
Reversal with anticholinesterases may be inadequate despite proper dosing.
Patients are at high risk for post-operative ventilatory failure.
What is the pathophysiology of Guillain-Barre?
AKA acute idiopathic polyneuritis
Is an immunologic assault on the myelin in the peripheral nerves.
Action potential can’t be conducted, so the motor endplate never receives the incoming signal.
How long does Guillain-Barre last?
Usually persists for ~ 2 weeks and ends with full recovery in ~ 4 weeks
About two percent of those affected with GBS will develop chronic inflammatory demyelinating polyneuropathy.
What is the clinical presentation of Guillain-Barre?
A flu-like illness usually precedes paralysis by 1-3 weeks.
The most common culprits are Campylobacter jejuni bacteria, Epstein-Barr virus, and cytomegalovris. Other causes include vaccinations, surgery, and lymphomatous disease.
What are some signs and symptoms of Guillain-Barre?
Flaccid paralysis begins in the distal extremities and ascends bilaterally towards the proximal extremities, trunk, and face.
Intercostal muscle weakness impairs ventilation.
Facial and pharyngeal weakness causes difficulty swallowing
Sensory deficits include: paresthesias, numbness, and/or pain.
Autonomic dysfunction is common: tachycardia or bradycardia, hypertension or hypotension, diaphoresis or anhidrosis, and orthostatic hypotension
What is the treatment for Gullain-Barre?
Medical treatment includes plasmapheresis and/or IV IgG
In contrast to multiple sclerosis, steroids and interferon do not improve this condition.
What are the major anesthetic concerns with a patient with Gullain-Barre?
Skeletal muscle denervation
Impaired ventilation
Autonomic dysfunction
How does Succinylcholine and nondepolarizers affect a patient with gullain-barre?
Avoid succinylcholine. There is a risk of hyperkalemia from proliferation of extrajunctional Ach receptors.
There is an increased sensitivity of nondepolarizers
What is the response to indirect acting sympathomimetics and a patient with gullain-barre?
There is an exaggerated response to indirect acting sympathomimetics due to up-regulation of postjunctional adrenergic receptors.
Patients with autonomic dysfunction and gullain-barre are at risk for?
Hemodynamic instability from anesthesia, position changes, positive pressure ventilation, and blood loss.
They require intra-arterial pressure monitoring
What drugs are not useful in a patient with gullain-barre?
Steroids
What type of anesthesia is controvesial with a patient that has gullain-barre?
Regional anesthesia
There is inconclusive data for this.
What is Familial periodic paralysis?
It is characterized by acute episodes of skeletal muscle weakness accompanied by changes in the serum potassium concentration.
What are the two variants of familial periodic paralysis?
Hypokalemic
Hyperkalemic
Even though the cause of familial periodic paralysis is unknown, what are a few things that are understood about it?
It is disorder of the skeletal muscle membrane (reduced excitatbility)
It is not a disease of the neruomuscular junction
Hypokalemic periodic paralysis is associated with calcium channelopathy.
Hyperkalemic periodic paralysis is associated with sodium channelopathy.
Which type of Familial periodic paralysis is associated with sodium channelopathy?
Hyperkalemic periodic paralysis
Which type of Familial periodic paralysis is associated with calcium channelopathy?
Hypokalemic periodic paralysis
What is the diagnosis for hypokalemic periodic paralysis ?
It is present if skeletal muscle weakness follows a glucose-insulin infusion.
The patient became weak after the serum K+ was reduced.
What is the diagnosis for hyperkalemic periodic paralysis ?
It is present if skeletal muscle weakness follows oral potassium administration.
The patient became weak after the serum K+ was increased.
What is the treatment for Familial periodic paralysis?
Acetazolamide is the treatment for both forms of this disease.
It creates a non-anion gap acidosis, which protects against hypokalemia, and it also facilitates renal potassium excretion, which guards against hyperkalemia.
How does acetazolamide treat hypokalemic periodic paralysis?
It creates a non-anion gap acidosis
This protects against hypokalemia
How does acetazolemide treat hyperkalemic periodic paralysis?
It facilitates renal potassium excretion
This guards against hyperkalemia
What are some anesthetic considerations for a patient familial periodic paralysis?
Hypothermia must be avoided at all costs. It is recommended that these patients remain normothermic even when they are placed on cardiopulmonary bypass!
Serial serum potassium monitoring is indicated.
What should you not administer with a patient that has hypokalemic periodic paralysis?
Glucose containing solutions
Potassium wasting diuretics
Beta-2 agonists
What should you not administer with a patient that has hyperkalemic periodic paralysis?
Succinylcholine
Potassium containing solutions (LR)
What is safe to administer with a patient that has hypokalemic periodic paralysis?
Succinylcholine
Nondeoplarizers
Acetazolamide
What is safe to administer with a patient that has hyperkalemic periodic paralysis?
Glucose containing solutions
Potassium wasting diuretics
Beta-2 agonists
Nondepolarizers
Acetazolamide
What is Malignant Hyperthermia?
It is an inherited disease of skeletal muscle that is characterized by disordered calcium homeostasis.
What are the two classes of drugs that is know to trigger malignant hyperthermia?
Halogenated agents
succinylcholine
What is the pathophysiology of malignant hyperthermia?
When the T-tubule is depolarized, extracellular Ca+2 enters the myocyte via the dihydropyridine receptor.
This activates the defective ryandoine receptor (RyR1), which instructs the sarcoplasmic reticulum to release way too much calcium into the cell.
(RyR1 is like a Ca+2 faucet that can not be turned off)
Not only is there more Ca+2 to engage with the contractile elements, but the cell attempts to return the excess Ca+2 to the SR via the SERCA2 pump.
Both processes consume a substantial amount of ATP, increase O2 consumption, and increase CO2 production.
What are the consequences of Increased intracellular calcium in the myocyte?
sustained muscle contraction
accelerated metabolic rate and rapid depletion of ATP
increased O2 consumption
Increased CO2 and heat production
Mixed respiratory and lactic acidosis
Sarcolemma breaks down
Potassium and myoglobin leak into the systemic circulation
Rigidity from sustained contraction
What are the three co-existing diseases that MH is linked to?
King-Denborough syndrome
Central core disease
Multiminicore disease
What is Duchenne Muscular Dystrophy?
The patient does not code for dystrophin.
The absence of dystrophin destabilizes the sarcolemma during muscle contraction and increases membrane permeability.
What happens to extracellular Ca+ in Duchenne Muscular Dystrophy?
Extracellular Ca+2 is free to enter the cell, which can increase the rate of metabolism
What happens to intracellular potassium in Duchenne Muscular Dystrophy?
Intracellular potassium is free to exit the cell, which can result in hyperkalemic cardiac arrest.
What happens to myoglobin in Duchenne Muscular Dystrophy?
Myoglobin is free to exit the cell, which can cause renal failure.
An MH-like syndrome is associated with Duchenne muscular dystrophy, this is due to what?
It is due to rhabdomyolysis.
It is not true MH.
Dantrolene will not treat this.
What agents can initiate a MH-like syndrome in the patient with Duchenne Muscular Dystrophy?
Halogenated agents
Succinylcholine
avoid these agents
ANY pt with Duchenne muscular dystrophy or other muscular dystrophy who sustains a cardiac arrest on induction should be assumed to have what electrolyte abnormalitiy?
Hyperkalemia
Should be immediately treated with calcium chloride
The risk of MH is NOT increased in which disorders?
Becker muscular dystrophy
Neuroleptic malignant syndrome
Myotonia congentia
Myotonic dystrophy
What factors will increase the risk of MH?
Male sex
Youth
Geography - families from Wisconsin, Nebraska, West Virginia, and Michigan
What is the most sensitive indicator for malignant hyperthermia?
EtCO2 that rises out of proportion to minute ventilation
MH can occur how much later after exposure to a triggering agent?
Can occur as late as six hours after exposure to a triggering agent.
What are the early symptoms of MH?
Tachycardia
Tachypnea
Masseter spasm
Warm soda lime
Irregular heart rhythm
What are the intermediate symptoms of MH?
Cyanosis
Patient warm to touch
Irregular heart rhythm
What are the late symptoms of MH?
Muscle rigidity
Cola-colored urine
Coagulopathy
Irregular heart rhythm
What is trismus?
It is a tight jaw that can still me opened
What is Masseter Muscle rigidity?
It is a jaw that cannot be opened
If a patient has this, assume MH until proven otherwise.
What medications causes trismus?
Succinylcholine
This is a normal response, it’s okay to proceed with surgery if trismus occurs in isolation.
It’s probably wise to convert to a non-triggering agent for MH.
What are some conditions that should be considered in the differential diagnosis of MH?
Thyroid storm
Malignant neuroleptic syndrome
Sepsis
Pheochromocytoma
Serotonergic syndrome
Heat stroke
Metastatic carcinoid
Cocaine intoxication
Who should have a halothane contracture test?
Anyone who has experienced MH or masseter spasm should have the halothane contracture test for diagnosis.
Although this is the definitive test for diagnosis, it only has an 80 percent specificity, so there is a risk of a false-negative result
What are the two mechanisms of action for Dantrolene?
- It halts Ca+2 release from the RyR1 receptor
2. It prevents Ca+2 entry into the myocyte, which reduced the stimulus for calcium-induced calcium release
What is the most common side effect of Dantrolene?
Dantrolene is classified as a muscle relaxant.
Most common side effects are muscle weakness and venous irritation
Dantrolene comes in what amount per each vial?
Each vial contains 20mg of dantrolene + 3g of mannitol
How do you reconstitute dantrolene?
Each vial must be reconstituted with 60 mL of preservative free water.
NaCl introduces additional solute, which prolongs the time required for dantrolene to dissolve into the diluent.
What is the treatment for MH after stabilization?
After the patient is stabilized, he should be observed in the ICU. MH may reoccur up to 36 hours.
How do you prepare for a patient at risk for MH?
Prophylaxis dantrolene is unwarranted.
Flush anesthesia machine with high flow O2. About 20 to over 100 minutes depending on the model.
All external parks should be removed and replaced (Co2 absorbent, circuit, breathing bag)
Vaporizers must be physically removed from the machine.
If patient doesn’t present with s/sx of MH within the first hour of the procedure, it us unlikely that it will occur later.
Patients should be monitored for 1-4 hours in the PACU. Discharge home is ok.
What are the first two steps of treating MH according to Nagelhout?
- Discontinue the triggering agent (volatile agent and/or succinylcholine)
- Call for help, and inform the surgeon to end the procedure.
What is the third step in treating MH according to Nagelhout?
Hyperventilate with 100 percent O2 at a minimum FGF of 10L/min
What is the fourth step in treating MH according to Nagelhout?
Administer dantrolene
What will hyperventilating with 100 percent of O2 at a minimum FGF of 10L/min do when treating a patient with MH?
This facilitates CO2 elimination
It enhances O2 delivery
It drives K+ into cells
When should you stop dantrolene?
Stop dantrolene with symptoms of hypermetabolism subsides
What is the dose for dantrolene?
2.5 mg/kg IV and repeat q 5-10 min
How much does each vial of Ryanodex contain?
Each vial contains dantrolene 250mg and only requires 5mL of sterile water diluent
What is the fifth step in treating MH according to Nagelhout?
Cool the patient until temp drops below 38 degrees C
How can you cool the patient that is experiencing MH?
Cold IVF
Cold fluid lavage of stomach and bladder
Ice Packs
What is the sixth step for treating MH according to Nagelhout?
Correct Lactic acidosis