CNS and Anesthesia Flashcards
(80 cards)
Triptans
5HT agonists Prevent release of 'inflammatory soup' of prostaglandins, substance P and histamine Drugs: Sumatripan - most common Zolmitriptan Rizatriptan - no nasal spray Naratriptan - longer acting, for recurrence Use: - stop migraines
Dihydroergotamine
Rescue medication and for refractory migraines (with metoclopromide)
Barbiturates
IV anesthetics
Mechanism:
- binds to specific sites on GABA A receptors, enhances affinity of GABA, increases Cl influx
Drugs:
- thiopental
- methohexital
Uses:
- induction of anesthesia
- neuroprotection - treat raised ICP and focal cerebral ischemia
Effects:
CNS
- sedation, anesthesia, not analgesic (anti-analgesic), cerebral vasoconstriction, decrease CMRO2 (EEG can flatline)
- methohexital activates epileptic foci
CV
- peripheral vasodilation, decrease in BP
Respiratory
- respiratory depressant
- decrease ventilatory response to hypercapnea and hypoxia
- inadequate suppression of airway and laryngeal reflexes
Other
- precipitation when mixed with acidic drugs
- pain and tissue injury in paravenous tissue
- pain, vasoconstriction, gangrene if arterial injection cuz alkaline pH
- exacerbation of acute intermittent porphyria - stimulates D-ALA synthetase
Desflurane
Inhaled anesthetic
- immobility
- amnesia
- CNS depression - enhance GABA, block NMDA
- not analgesic
Needs highest concentration to achieve MAC
Least soluble - fast onset/offset
Use:
- gastric bypass, obese pts
- peds tonsillectomy
Pros:
- rapid onset/offset
Cons:
- pungent, expensive, tachycardia
Effects:
- decrease MAP due to decreased TPR - vasodilators
- increased HR
- increase RR, decrease tidal volume (maintain minute ventilation)
- decrease FRC, increase dead space
- increase PaCO2, less responsive to it, lead to apnea
- bronchodilation - good for asthma
- depression of pharyngeal and laryngeal reflexes - can intubate
- cerebral vasodilation - increased CBF and ICP
- decrease CMRO2
- dose dependent EEG depression
- dose related skeletal muscle relaxation
- decreased renal blood flow
- decreased hepatic blood flow
Side effects:
- airway irritant - don’t use for mask induction
- expensive
- may prolong QT
Sevoflurane
Inhaled anesthetic - immobility - amnesia - CNS depression - enhance GABA, block NMDA - not analgesic Most commonly used in OR Medium solublity, medium potency Not expensive Use: - inhaled induction in peds - least noxious and least irritating to airways - quicker adult cases - induction agent Pros: - rapid, pleasant Cons: - emergence delirium Effects: - decrease MAP due to decreased TPR - vasodilators - increased HR after 1 MAC - increase RR, decrease tidal volume (maintain minute ventilation) - decrease FRC, increase dead space - increase PaCO2, less responsive to it, lead to apnea - bronchodilation - good for asthma - depression of pharyngeal and laryngeal reflexes - can intubate - cerebral vasodilation - increased CBF and ICP - decrease CMRO2 - dose dependent EEG depression - dose related skeletal muscle relaxation - decreased renal blood flow - decreased hepatic blood flow Side effects: - nephrotoxic effects - keep flow higher - may prolong QT
Isoflurane
Inhaled anesthetic
- immobility
- amnesia
- CNS depression - enhance GABA, block NMDA
- not analgesic
Needs lowest concentration to achieve MAC - most potent
Most soluble - longer emergence
Most economical
Pros:
- inexpensive, hemodynamic stability
Cons:
- long acting
Use:
- longer cases, especially if pt doesn’t get extubated
Effects:
- decrease MAP due to decreased TPR - vasodilators
- increased HR
- increase RR, decrease tidal volume (maintain minute ventilation)
- decrease FRC, increase dead space
- increase PaCO2, less responsive to it, lead to apnea
- bronchodilation - good for asthma
- depression of pharyngeal and laryngeal reflexes - can intubate
- cerebral vasodilation - increased CBF and ICP
- decrease CMRO2
- dose dependent EEG depression
- dose related skeletal muscle relaxation
- decreased renal blood flow
- decreased hepatic blood flow
Side effects:
- may prolong QT
Nitrous Oxide N2O
Inhaled anesthetic
- immobility
- amnesia
- CNS depression - enhance GABA, block NMDA
- mild analgesic
Cannot achieve 1 MAC
Not expensive
Use:
- in combination with volatile anesthetics
- induction agent
- only use alone to calm kids down before inserting IV
- don’t use in surgeries with air cuz diffuses fast into air filled spaces
- labor analgesia
Pros:
- inexpensive, combined with VA, rapid
Cons:
- not used alone, caution with air spaces
Effects:
- little change in MAP or TPR
- bronchodilation - good for asthma
- depression of pharyngeal and laryngeal reflexes - can intubate
- cerebral vasodilation - increased CBF and ICP
- decrease CMRO2
- dose dependent EEG depression
- dose related skeletal muscle relaxation
- decreased renal blood flow
- decreased hepatic blood flow
Side effects:
- increases nausea/vomit
Benzodiazepines
Sedatives/anxiolytics Highly lipid soluble and protein bound, fast BBB penetration Mechanism: - enhance affinity of GABA receptor for GABA, increase Cl flux; BDZ site on GABA receptor Metabolism - midazolam inactive metabolites; diazepam active metabolites so longer duration and hangover effect Drugs: - Midazolam, Diazepam Uses: - pre-medication - sedate pt, anti-anxiety, amnesia - sedation for short procedures (midazolam) - suppression of seizure activity in status epilepticus Effects: CNS - sedation, hypnosis - anterograde amnesia - anticonvulsant - decrease CMRO2 and CBF - not neuroprotective Respiratory - minimal respiratory depression CV - decrease in TPR and BP - CO not affected, so CV stable Other - pain on injection with diazepam
Propofol
Isopropylphenol IV anesthetic - lecithin and soybean oil - need sterile technique Mechanism: - inhibition of neurotransmission via GABA potentiation - increase Cl current Not analgesic Wake up 8-10 mins after induction bolus due to redistribution Uses: - induction agent - maintenance of anesthesia - sedation - flexible use - neuro rooms, seizure, brain tumor, trauma Pros: - rapid onset, short acting - anti-emetic - bronchodilaion - use for asthmatics, smokers - amnesia - neuroprotective Cons: - pain on injection - hypotension - CV and resp depression - allergy to soy, eggs - propofol infusion syndrome - lactic acidosis - not analgesic Effects: CNS - hypnotic, anesthetic, amnesic - decreased CBF, decreased CMRO2, decreased ICP - anticonvulsant - neuroprotective during focal brain ischemia CV - vasodilation, decreased BP, inhibits baroreceptor reflex Respiratory - respiratory depressant - apnea after induction bolus - upper airway reflex suppressed - use for airway instrumentation like bronchoscopy Other - anti-emetic - reduces post op N/V
Etomidate
Imidazole, acidic IV anesthetic Mechanism: - binds GABA A receptor, enhances affinity of GABA for receptor, increases Cl influx Ionized, penetrates brain rapidly Uses: - induction agent for CV unstable Pros: - less respiratory depression/apnea - CV stability - cardiac dysfnx, shock, hypovolemia are good uses Cons: - adrenal suppression - pain on injection - myoclonus Effects: CV - cardiovascular stability after IV bolus - minimal change in BP, HR, TPR, myocardial contractility Respiratory - minimal depressant of ventilation - apnea after IV bolus CNS - cerebral vasoconstrictor, decreased CBF and CMRO2 - myoclonic activity so don't use in seizure disorders Endocrine - adrenocortical suppression - inhibits 11 beta hydroxylase so no cortisol so don't use in critically ill
Ketamine
Phencyclidine
IV anesthetic
Mechanism:
- NMDA receptor antagonist
- binds opioid receptors also
Stimulant and sedative
Highly lipid soluble - rapid onset and short duration of action
Uses:
- induction of anesthesia
- maintenance of anesthesia
- sedation - dressing changes or suturing
- dissociative amnesia
- analgesic affect, post-op pain
- cardiac tamponade
- kids
Pros:
- less respiratory depression
- bronchodilator
- analgesic
- vasoconstrictor
- dissociative state
Cons:
- increase HR and BP
- psychotropic side effects - emergence delirium
- direct cardiac depression in pts with high symp tone - hemorrhage
- increased ICP
- salivation/increased secretions
Effects:
CNS
- dissociative anesthesia
- analgesic
- cerebral vasodilation and increased CBF - increase ICP and CMRO2
- myoclonic and seizure activity so don’t use for neurosurg, brain tumors, seizures, trauma
CV
- symp stimulation centrally - increase HR, BP, CO, myocardial O2 consumption so don’t use in ischemic heart disease
- myocardial depression in pts who can’t raise symp nerve activity - don’t use in shock
Respiratory
- no significant resp depression; apnea if IV bolus
- bronchodilation - use in asthma
- increases salivary and tracheobronchial secretions so treat with glycopyrrolate
Other
- emergence reaction - nightmares, hallucinations, etc. so pretreat with midazolam
Opioids
Mechanism: - bind opioid receptors, decrease Ca influx presynaptically and increase K efflux postsynaptically Drugs: - fentanyl - CV stability, fast acting - alfentanyl - sufentanil - remifentanil - fastest onset, shortest duration - hydromorphone - morphine - methadone - meperidine Pros: - analgesia - minimal cardiac depression - reduces inhalational agents - versatile Cons: - respiratory depression - decrease RR - increase apneic threshold - blunts ventilatory response to hypoxia - bradycardia - skeletal muscle rigidity - nausea, vomit - constipation/ileus - pruritis Effects: - CNS - analagesia, sedation - respiratory system - depression via decreased brainstem ventilation, loss of CO2 responsiveness - antitussive - methorphan, codeine - muscle rigidity - miosis - excitation at E-W nucleus - CV - hypotension due to bradycardia from decreased central symp tone and incrased vagal activity, depressant on SA node, histamine release leads to decreased TPR - GI - decreased peristalsis and increased sphincter tone, constipation, increased biliary pressure from sphincter of Oddi narrowing; nausea and emesis are most common via chemoreceptor trigger zone - GU - urinary retnetion - skin - histamine release, urticaria, cutaneous vasodilation - placenta - neonatal respiratory depression and dependence
Neuromuscular blockade agents
Depolarizing - succinylcholine - rapid onset/short duration, rapid sequence induction Non-depolarizing - rocuronium - fastest onset - cisatracurium - Hoffman elimination - vecuronium - pancuronium - tachycardia - reverse via neostigmine and glycopyrrolate
Dexmedetomidine
Imidazole
IV anesthetic
Mechanism:
- stimulation of alpha 2 receptors in locus coeruleus, inhibits NE release
Uses:
- sedation short term, radiologic procedurs
- general anesthesia, needs loading dose
Pros:
- sedation and analgesia without respiratory depression
Cons:
- hypotension and bradycardia, with bolus
- longer onset and offset
Effects:
CNS
- sedation
- analgesia
- not much on CRMO2 or ICP so good for brain stuff, getting an MRI
CV
- cardiovascular depression - bradycardia, hypotension due to NE decrease
Respiratory
- minimal depressant effects on respiration, no effect on respiratory rate
- response to CO2 unchanged
- so use if no airway experts around
NSAIDs
Mechanism: - block COX - reduce PGE2 and other prostaglandin production Actions: - analgesia - antiinflammatory - anti-pyretic via inhibition of IL1 and IL6 production of prostaglandins in hypothalamus - synergistic with opioids Adverse events: - inhibit platelet aggregation - gastric ulceration - renal dysfnx - hepatocellular injury - allergic rxn - asthma - tinnitus - myocardial infarction
Salicylates
Irreversibly acetylates COX Actions: - analgesic - low intensity pain - anti-pyretic - anti-inflammatory - rapidly absorbed from small intestine - liver metabolism Side effects: - GI upset - dyspesia - bleeding - tinnitus - allergic rxn
Ibuprofen, naproxen
Propionic acid derivatives Actions: - analgesic - anti-pyretic - anti-inflammatory - less GI irritation, dyspepsia compared to aspirin Side effects: - renal toxicity in renal pts Naproxen - longer half-life
Acetaminophen
Actions: - analgesic - anti-pyretic - no interaction with platelets - no GI irritation Side effects: - NAPQI - hepatotoxic - treat with N-acetylcysteine
Ketorolac
Actions: - potent analgesic - moderate anti-inflammatory - potentiates opioid action - absence of ventilatory and cardiac depression Side effects: - inhibits platelet aggregation - bronchospasm in ASA sensitive pts - GI irritation - renal toxicity in renal pts - hepatic toxicity
Celecoxib
COX 2 selective inhibitor Actions: - analgesic - anti-inflammatory - crosses BBB - well absorbed from GI - lacks platelet aggregatoin - decreased GI side effects Uses: - arthritis and post-op pain
Morphine
Delayed onset and peak effect due to poor CNS penetration
- poor lipid solubility and mostly ionized and protein bound
Metabolism:
- most to M3G
- some to M6G - active, analagesia and respiratory depression
- removed in urine, worry about renal pts
Effects:
- analgesia, euphoria, sedation
- histamine release
Worry about renal pts and build up
Meperidine
Less potent than morphine Metabolism: - to normeperidine which can cause seizures and myoclonus - worry about renal pts cuz build up Uses: - post-op shivering Side effects: - decreased cardiac contractility - mydriasis, tachy - like atropine - seziures - histamine release
Fentanyl
Much more potent than morphine
More rapid and shorter duration than morphine - lipophilic
No myocardial depression or histamine release, no active metabolites
Sufentanil
More potent than fentanyl
Rapid onset/offset - lipophilic
Uses:
- big incision with lots of pain