E4 Flashcards
What is MAC?
Minimum alveolar concentration = measure of potency of anesthetics
Equilibrium concentration required to prevent the response to a painful stimulus in 50% of patients
What is MAC similar to?
EC50
What factors decrease MAC/increase potency?
Hypothermia Pregnancy Shock Increasing age Acute alcohol ingestion CNS-depressant drugs Decreased CNS NT release
How do opiates inhibit neurotransmission post-synaptically?
Signal via G-proteins –> K+ efflux or Cl- influx –> HYPERpolarizing
What is endogenous analgesia?
Endorphins release to cause absence of pain sensation. Stimulation of A-delta and C fibers stimulates release of endogenous opioids B-endorphin and dynorphin
Where are B-endorphin and dynorphin released?
B-endorphin: hypothalamus
dynorphin: PAG
How can dynorphins cause pain?
Bind to glycine site—which is involved in cross talk—can turn around and affect NMDA receptor and cause pain
How do opioid receptors work?
By decreasing synaptic transmission. Binding activates G proteins that, in turn, activate potassium channels or inhibit calcium channels, thereby inhibiting neurotransmitter release.
Naloxone blocks which receptors?
Mu receptors
Are opioid receptors presynaptic or postsynaptic?
Can be both
Endogenous opioids can be carried by ______, meaning they don’t have to be inside a _______.
Leukocytes / nerve
How do endogenous opioids work?
They are produced from pro-hormones, released from the synapse, and directly stimulate opioid receptors on the pre- and postysynaptic membranes.
B-endorphin and endomorphin receptor
Mu
Enkephalin receptor
Delta
Dynorphin receptor
Kappa
Which receptor does naloxone NOT act on?
ORL-1
Nociceptin receptor
ORL-1
Which receptor does morphine/codeine/heroin act on?
Mu
Which is more fat soluble: heroin or morphine?
Heroin
Opioid receptor location in pain fibers
Presynaptic terminal of afferent pain fibers : substantia gelatinosa, dorsal horn
Opioid receptor location in descending pathways
Limbic system / thalamus
PAG
How does nociceptin work?
Affects how we react to pain, not the pain itself
All opioid receptors are _____ and inhibit _____ _____.
GPCRs / adenylate cyclase
What is the net effect of opioid receptors?
Hyperpolarization / decreased release of neurotransmitter (e.g. substance P) / decreased pain fiber activity
Opioid receptors are inhibitory/excitatory.
Inhibitory. They inhibit the release of some NTs and enable the release of dopamine.
Where are opioid receptors located?
CNS, PNS, GI tract
How does heroin’s MOA increase abuse?
Rapidly enters the brain and breaks down to morphine
What are the cardiovascular effects of morphine?
Vasodilation –> decrease in blood pressure
How does morphine affect respiration?
There is a primary and continuous depression of respiration related to dose: decrease rate, volume, and tidal exchange
Which opioid receptor enhances mu agonists?
Delta
T/F: Morphine causes histamine release.
True
Which drug is similar to morphine, but 10x more potent (IV) and has less of a depressant effect on the respiratory center?
Oxymorphone
Fentanyl’s cardiovascular effects are less ____ than morphine, but respiratory effects are more _____.
Severe
What is fentanyl’s duration of action?
40-60 minutes
How are opiates converted to more polar metabolites?
Via hepatic conjugation to glucuronides or N-demethylated
Which opiate does Cytochrome P-450 metabolize?
Fentanyl
Where does opioid excretion occur?
Kidneys
What is the active metabolite of morphine and what is its potency?
Morphine-6-glucuronide –> 2x more potent
What is the triad of acute morphine poisoning?
Coma, miosis, cyanosis
What are two examples of synthetic mu-opioid agonists?
Fentanyl, meperidine
How long after morphine poisoning does respiratory failure occur?
2-4 hours
Oxycodone breaks down to ______.
Oxymorphone
Tramadol MOA
Blocks NE and 5HT reuptake
Pentazocine MOA
K agonist, and delta partial agonist
Which drug has a shorter duration and faster onset of action than morphine when taken orally?
Pentazocine
Buprenorphine MOA
Mu partial agonist, delta antagonist
Low doses of which drugs, in combination with opiates, have been found to enhance analgesic effect?
Opioid antagonists (e.g. naloxone)
Methadone MOA
Full opioid agonist on mu receptors
Inhibits serotonin reuptake
Non-competitive antagonist NMDA receptor
Which opiate is an absolute contraindication for taking MAO inhibitors?
Meperidine
Which opiate is more potent in women than in men?
Buprenorphine
Where does the spinal cord end?
L1
Clinical findings of UMN lesion
Spastic muscles Hyperactive reflexes Babinski Clonus (4 beats or more) Hoffmann's reflex No sensory changes
When a patient has a bowel/bladder dysfunction, where should you look for the lesion?
Conus medullaris
Clinical findings of LMN lesion
Flaccid muscles
Hypoactive reflexes
Numbness/tingling
What is the origin of a UMN lesion?
Brain or spinal cord
What is the origin of a LMN lesion?
Peripheral nerve or lumbar canal or limbs
What is myelopathy and how does it present?
Spinal cord compression:
Painless
Non-dermatomal
Clumsiness
What is radiculopathy and how does it present?
Nerve root compression:
Painful
Dermatomal muscle weakness
Muscle atrophy and bone loss
What is the calling card of ALS?
Tongue fasciculations
How is ALS diagnosed?
EMG –> confirms in upper and lower limbs
How is ALS treated?
Riluzole
IV Ig therapy
Where is the most common location of syringomyelia?
Lower cervical
Life expectancy after ALS diagnosis
4-5 years
Cervical syringomyelia symptoms
Loss of sensation in UEs --> shawl distribution UE weakness UE reflexes absent LE spasticity Hyperhidrosis
Lumbar syringomyelia symptoms
LE muscle atrophy
Sensory loss: lumbar and sacral dermatomes
DTRs absent in LEs
Impairment of sphinchter function
Calling card of tabes dorsalis
Loss of DTRs at knees and ankles
Argyll Robertson pupils
What aspect of the spinal cord is affected by B12 deficiency?
White matter more than grey matter
Exam finding in B12 deficiency
Romberg sign
What is the most common inherited neurological disease?
Charcot-Marie-Tooth
Lab finding in myasthenia gravis
Acetylcholine receptor antibody –> positive in 90% of cases
Myasthenia gravis treatment
Pyridostigmine bromide
What is the deficiency in PKU?
Phenylalanine hydroxylase –> results in buildup of phenylalanine, which is then converted to phenylpyruvic acid, which is then excreted in the urine
What would be present/elevated in the urine of a PKU patient?
Phenylpyruvic acid
Phenylketones
What is the role of tyrosine in PKU?
Tyrosine deficiency –> dopamine decrease –> melanin decrease (PKU patients tend to have blonde hair and blue eyes)
What are the three types of neurological alterations in PKU?
***question
Interference with normal brain growth
Defective myelination
Diminished pigmentation of substantia nigra and locus ceruleus
What causes Lesch Nyhan?
***question
Deficiency in HGPRT (involved in salvage pathway of purine synthesis) –> INCREASED purines (de novo synthesis)
Gaucher cells accumulate ______ in lysosomes.
Glucosylceramides
What is the deficit in MLD?
Sulfatase A
What is the accumulation in Hurlers?
Sulfated polysaccharides in ECM
How do the basal ganglia appear in Wilson disease?
Brick red, spongy, small cavities
What is the deficit in Wilson disease?
Deficit in Cu transport –> copper accumulates in pericapillary area of astrocytes –> protoplasmic astrocytes
What are the clinical findings of Wilson disease?
Tremor Dysarthria Unsteady gait Speech loss Drooling Rigid arms/legs
What is dementia?
Disorder characterized by problems with cognition and functional impairment (must have both)
What is the prevalence of Lewy Body dementia?
15%
When do cognitive impairment and hallucinations appear in someone with LBD?
Before or at the same time as Parkinson-like symptoms
What does a mini mental status exam measure?
Global cognitive function by examining memory, language, orientation, and executive function.
What is the MMSE score for normal or mild impairment?
25-30
What is the MMSE score for severe dementia?
< 10
What are the steps of MMSE?
- Ask patient to repeat three words
- Ask patient to draw face of a clock, then draw hands to read “ten past eleven”
- Ask patient to recall three words
What is the most important predisposing factor for delirium?
Baseline cognitive impairment
What is the main difference between depression and dementia?
Depression: loss of pleasure
Dementia: loss of interest
How is delirium treated?
Treat underlying cause:
R/o infection
Check medications
R/o constipation, dehydration, UTI
First line of treatment for partial and tonic-clonic seizures
Phenytoin
Valproate
Carbamazepine
Phenytoin MOA
Alters Na, Ca, and K conductances
What are the broad spectrum anticonvulsants?
Valproic acid
Benzos
How does phenytoin act on Na channels?
Increases Na+ channel inactivation / keeps the channel in refractory state
Carbamazepine MOA
Increases Na+ channel inactivation (similar to phenytoin)
Potentiates postsynaptic effects of GABA
What is Lamotrigine used for?
Add-on therapy with valproic acid
What is a critical side effect of Lamotrigine?
Stevens-Johnson syndrome
Which anticonvulsant increases GABA-A action and prolongs opening of Cl- channels and what is it used for?
Phenobarbital / partial seizures
Why is valproate contraindicated in pregnancy?
Can cause spina bifida
Which anticonvulsant causes a decrease in neuronal calcium currents by binding of alpha-2-delta subunit of the calcium channel?
Gabapentin (designed as GABA analog)
Ethosuximide MOA
Blocks thalamic T-type Ca2+ channels
Tiagabine MOA
Increases GABA by inhibiting reuptake
Increases neuronal GABA
Increases glutamic acid decarboxylase
Binds alpha-2-subunit of VGCC –> decreases calcium
Used for partial seizures, shingles, diabetic neuropathy, fibromyalgia
Pregabalin
Major side effect of valproate
Hepatotoxicity
What are the safest of all antiepileptic drugs and most free from severe side effects?
Benzos