Neurology, Monitoring, & Associated Pharmacology Flashcards
This device records electrical activity in the brain?
Electroencephalogram (EEG)
Irregular patterns on an EEG can help dx these neurological dysfunctions
- Seizure disorders
- Head injury
- Encephalitis(inflammation of the brain)
- Brain tumor
- Encephalopathy
- Sleep disorders
- Stroke
- Dementia
Name some Clinical Scenarios where an EEG may be appropriate
- Carotid endarterectomy
- Aneurysm clipping
- CV surgery
- Seizure observation
- DBS surgery
- Observation of physiologic derangement
- Determination of brain death
What kind of waves are indicative of seizures on an EEG?
Sharp, spiking waves
What are slow EEG waves (delta waves) indicative of?
- Tumor
- Stroke
- Deep Sleep
- Anesthesia
Amplitude and frequency of delta waves.
- High amplitude
- Low frequency (1-4 Hz)
What may cause interference on an EEG?
- Hypoglycemia
- Body or eye movement during the test
- Lights, especially bright or flashing ones
- Benzo’s, sedatives
- Caffeine
What is burst suppression?
When EEG shows quiet brain activity and decreased CMRO2
When will burst suppression be used?
- May be used during aneurysm clipping
- This will significantly reduce the brain’s metabolic rate, allow for safer manipulation of blood vessels, and minimize the risk of ischemic damage caused by clips
How will you induce burst suppression?
Bolus + Maintenance gtt Propofol
How will you know you are in burst suppression?
- Communication with evoke techs
- Flat tracings interspersed w/ “burst” of activity
What will the EEG tracing look like if you are too deep?
Isoelectric, zero amplitude
What is a Bispectral Index?
Data derived from EEG compressed into single measurement
How does a BIS monitor work?
- Proprietary Algorithm
- Use of 4 fronto-temporal EEG monitors
- Signal over 5-10 seconds analyzed (this is called an epoch)
- Histogram of each frequency is plotted [proprietary algorithm!]
- Deeper anesthesia = lower frequencies dominate
What BIS score will indicate cortical electrical silence?
0
What BIS score will indicate normal awake cortical activity?
85-100
What BIS score will be consistent with general anesthesia?
40-60
What causes seizures?
Sudden uncontrolled discharge of groups of neurons
What transient abnormalities may single seizures result from?
- Hypoglycemia
- Hyponatremia
- Hyperthermia
- Brain injury
- Drug toxicity
Characteristics of a Focal Seizure
- Also called a “Partial” seizure
- Start in a particular part of brain
- Feel/see/hear things that aren’t there
- Can be mistaken for mental illness
Characteristics of a Generalized Seizure
- Occurs in BOTH sides of brain
- Muscle spasms
- LOC possible
- Several types of Generalized Seizures
Characteristics of an Unknown-onset Seizure
May start as one kind, become another kind
Tonic-Clonic seizure
- Grand-mal seizure
- Full body shaking
Clonic seizure
- Rhythmic jerking
- Last 1-3 minutes
Tonic seizure
Sudden increase in muscle tone that causes the body, arms, or legs to become stiff or tense.
Atonic seizure
- Part or all of the body may become limp.
- Risk of falling, may wear a helmet
Myoclonic seizure
These seizures are characterized by short, sudden, lightning-quick jerking or twitching movements of the body.
Absence Seizure
- Type of seizure that can cause brief lapses in awareness due to abnormal brain activity
- Eyes roll back/staring
- Common in kids
How are seizures diagnosed?
- MRI
- EEG
- Electrocorticography
Treatment progression for seizures.
- Single antiepileptic drug
- Followed by drug combinations
- Final option, surgical resection/ablation
MOA of Antiseizure Drugs
- Reduce the inward VG positive currents, Na+ and Ca+ (Lamictal, Carbamazepine)
- Increase GABA (Valproate)
- Decrease Glutamate, Aspartate (Keppra)
Describe the MOA of Keppra
- Keppra binds to SV2 (synaptic vesicle protein 2A to inhibit the release of NT)
- Commonly given to neurosurgical patients for the prevention of seizures
What concerns would the anesthesia providers have with older-generation anti-seizure drugs?
- CYP 450 upregulation
- Fast metabolizers
Anesthetic Management to Prevent Seizures in the Neurosurgical Patient
- Be aware of retraction, incision = cortical irritation. Can induce seizure activity.
- Be aware of tumors, bleeds, fever, encephalitis, hypoxia, stroke…Can all cause seizures
- Keppra 500-1000 mg IV
- Hypoglycemia can cause seizures.
Good Anesthetic Agents with Seizure Patients?
- Barbiturates & Propofol
- BZD (↑ GABA)
- Magnesium (Inhibits glutamate)
- Nitrous oxide
- Ketamine – can increased CMRO2 but it may be safer used with prop or a benzo
What induction drug can lower the seizure threshold?
Etomidate
What drug has an active metabolite that can induce seizures?
Meperidine (Demerol)
What is Status epilepticus?
- Life-threatening medical emergency
- Two or more seizures without return of consciousness or a continuous seizure
Treatment for Status epilepticus?
What should be done first?
- Airway and Ventilation (Priority)
- Treatment of hypoglycemia
- Antiepileptic anesthetics– i.e. benzos, barbs, prop
- Arterial Blood gases
- Muscle relaxants
What is Multiple Sclerosis?
- Autoimmune disease affecting the central nervous system
- Damages myelin (demyelinating)
- Interferes with nerve conduction
Hallmark Sign of MS
- Symptoms develop over a few days, remain stable a few weeks, then improve
- Remission-Exacerbation cycle
What age does the onset of MS usually occur?
After 35 (usually a slow progression)
Symptoms that reflect site of demyelination. What is usually the first sign of MS?
- Optic nerve: visual disturbance (1st sign)
- Cerebellum: gait disturbance
- Spinal Cord: paresthesia , weakness, incontinence
- May see autonomic dysfunction
Pharmacological treatment of MS
- Corticosteroids: anti-inflammatory effects, help restore blood/brain barrier
- Interferon: limited to patients with rapidly progressing symptoms. Cardiac toxicity.
- Azathioprine: purine analogue
Immunosuppressant - Methotrexate: Immunosuppressant/anti-inflammatory. Slows progression.
Anesthetic Management: MS
- Pre-operative assessment of symptoms/recent exacerbations
- Consider stress dose, steroid coverage
- Continue MS medications on the day of surgery
- Note that some medication regimens for MS (immunosuppressants) can have negative effects on CV system & Liver
Anesthesia considerations for individuals on Baclofen Pump
- Increases sensitivity to NDMR
- Use the lowest possible dose of ROC recommended
- Avoid succinylcholine (Ach receptors may be upregulated, increase K+)
Avoid these risk factors for MS relapse
- Fever
- Hyperthermia (Even temp increase of 1 degree can exacerbate sx)
- Infection
- Emotional stress – Versed pre-op!
What is Guillain-Barré Syndrome (GBS)
- Rare neurological disorder that occurs when the body’s immune system attacks the peripheral nervous system
- Acute inflammatory demyelinating polyradiculoneuropathy
Hallmark Signs of GBS.
What is usually the first sign?
- Sudden onset of skeletal muscle weakness or paralysis
- First sign is usually “Pins and needles”/numbness
- Weakness begins in legs and spreads to upper body
- Muscle denervation = upregulation of Ach receptors
- Autonomic nervous system dysfunction
Most serious signs of GBS
- Difficulty swallowing
- Impaired ventilation
Symptoms of Autonomic Dysfunction
- BP fluctuations
- HTN with laryngoscopy
- HOTN with position/positive airway pressure
- Resting tachycardia
- Profuse diaphoresis
- Orthostatic hypotension
- Sudden death
Anesthetic Management: GBS
- GETA (MAC likely not appropriate)
- Could have airway reflex dysfunction
- Respiratory compromise
- Consider arterial line
- Avoid succinylcholine, use NMDR judiciously
- Prepare for postop ventilation.
What are Neurodegenerative Diseases?
Progressive loss of structure or function of neurons
Parkinson’s Disease
- Neurodegenerative disorder of unknown cause
- Characterized by loss of dopaminergic fibers from the basal ganglia (affecting movement)
- Results in decreased norepinephrine production (ANS function)
- Can cause clumps of protein: alpha-synuclein (Lewy bodies)
What is the single most important risk factor of Parkinson’s?
Increased age
Triad Symptoms of Parkinson’s
- Skeletal muscle tremor
- Rigidity
- Akinesia
Complications associated with Parkinson’s
- Autonomic dysfunction
- Respiratory obstruction
- Aspiration pneumonia
Where does muscle rigidity first appear in Parkinson’s?
Proximal muscles of the neck
Movement abnormalities associated w/ Parkinson’s
- Reduced arm swinging
- Pill rolling
- Tremors at rest
Pharmacological treatment of Parkinson’s
- Increase dopamine in basal ganglia
- Levodopa - Crosses BBB, ↑ dopamine
- Carbidopa - prevents Levodopa breakdown prior to reaching BBB
Side effects of Levodopa
- Dyskinesias
- Altered myocardial contractility
- Orthostatic hypotension
- N/V
Surgical Treatment of Parkinson’s Disease.
Who is it reserved for?
- Deep Brain Stimulator (~70% success rate)
- Reserved for patients with disabling and medically refractory symptoms
Anesthetic Consideration for Alzheimer’s
Consider TIVA (quicker recovery)
What is Huntington’s disease?
- Rare, genetic neurodegenerative disease causing enlargement of lateral ventricles
- Movement disorder
- Can cause outburst and depression
What is Amyotrophic Lateral Sclerosis (Lou Gehrig Disease)
- Progressive degeneration of motor neurons
- Will cause paralysis, respiratory failure, fatal
- No cure, treat symptoms
Myasthenia Gravis (MG) is an autoimmune disorder that destroys what receptor?
Post-synaptic nicotinic ACh receptor (as much as 80% may be loss)
Factors that can trigger MG
- Stress
- Surgery
- Pregnancy
Hallmark symptoms of MG
- Weakness
- Rapid exhaustion of voluntary muscles (skeletal) followed by partial recovery with rest
How is MG diagnosed?
- Blood test
- EMG (Electromyography)
- Nerve Stimulation test
- Tensilon Test (Edrophonium)
- Check for a tumor on the thymus gland
Pharmacological Treatment of MG
- Anticholinesterase drugs: inhibit enzyme responsible for breakdown of acetylcholine = more Ach
- Pyridostigmine
- Neostigmine
What are the causes of Cholinergic Crisis
- TOO MUCH Ach or substances that mimic Ach
- Dose of anticholinesterase medication is too high
- Also caused by pesticides, nerve gas
- Profound weakness d/t continuous depolarization of the postsynatpic membrane
Edrophonium Effect on Myasthenic Crisis vs Cholinergic Crisis
- Myasthenic Crisis improves with edrophonium
- Cholinergic Crisis worsens with edrophonium
Why do you want to avoid Calcium Channel Blockers with MG?
CCB inhibit ca2+ from entering cell; blocking nerve impulse at NMJ
Why do you want to avoid magnesium with MG?
Mag causes muscle weakness
What is indicated when skeletal weakness is not adequately treated with anticholinesterase drugs?
- Immunosuppression Drugs
- Steroids
- Azathioprine
- Cyclophosphamide
- Cyclosporin
What are the effects of short-term immunotherapy in treating MG?
- Removes antibodies from circulation by plasmapheresis
- Temporary effect but useful in preparation for thymectomy
What is the surgical treatment for MG if there is a tumor on the thymus gland?
- Thymectomy
- Post-op 75% show improvement or remission
Anesthetic Management: Myasthenia Gravis
- High risk for aspiration
- Pharyngeal/laryngeal muscles VERY commonly affected
- PPI, H2 blocker, prokinetic (Reglan)
- Extubate AWAKE
- Continue MG medications
- Sensitive to opioid & benzo effects… use with caution!
- Volatile anesthetics may be sufficient for relaxation
- Resistant to depolarizers (SUX)
- Very sensitive to non-depolarizers (Roc)
- Use Sugammadex
Where do the antibodies attack in Lambert-Eaton syndrome?
Antibodies directed against presynaptic calcium channels at the NMJ
What happens to muscle strength with repeated use in Lambert-Eaton syndrome?
Improve muscle strength
__________ muscles are affected more in LE syndrome than in MG
Proximal
Lambert-Eaton Syndrome is associated with this cancer
Small-cell lung cancer
LES vs. MG Chart
