IV anesthetics

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ghrelin23187
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226336
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IV anesthetics
Updated:
2013-07-11 16:45:10
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IV anestretics
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  1. General anesthesia (components)
    Hypnosis, amnesia, analgesia, ms relaxation
  2. Sedation
    • Moderate sedation (still conscious) --> used for not painful procedure
    •            -amnesia and analgesia
    • Deep sedation (unconscious) --> used for painful procedure
    •            -hybrid state (pt placed in moderate sed. (1 min unconscious))
  3. Uses for IV anesthetic agent
    • --Induction agents for inhalational general anesthesia in the OR
    • --Adjuncts to inhalational anesthesia
    • --Total IV anesthesia (completely unconscious and asleep)
    • --IV sedation (breathing on your own, unconscious but arousable)
  4. Pharmacokinetics of IV anesthetics
    •Rapid onset (highly lipophillic)

    •Rapid redistribution (termination of effects)

    • •Often short elimination half-lives -->
    • gone quickly
  5. Peaked plasma [] for IV vs oral drug. Which is give you certain info?
    IV: know when the plasma [] peaked. No first pass metabolism
  6. true or false:
    For IV sedation, termination of drug is not how fast they eliminated but how fast they are redistributed
    True
  7. True or False:
    For oral drug, termination of drug is not how fast they eliminated but how fast they are redistributed
    false
  8. Order of drug distribution in the body
    VRG (kidney, heart, brain and liver) --> Muscle --> Fat
  9. Clinical characteristic of IV anesthetics
    •Single administration - short cases

    •Repeated administration or continuous infusion - long cases
  10. General anesthesia
    • State in which patients are completely
    • unconscious and do not respond to surgical stimulus; no sympathetic response to painful stimuli
  11. True or False
    There is IV general anesthesia that has all of the following chracteristic: amnesia, analgesia and ms relaxation
    False
  12. Moderate sedation
    • Conscious
    • Maintain their own airway
    • could induce amnesia (good)
    • not used for painful procedure
  13. Deep sedation
    a brief period during moderate sedation where pt become unconscious, used for painful procedure.
  14. continuous infusion of Propofol and fentenyl for 3 hours, know that Propofol half-time during this period is 20 min and Fentenyl is 110 min. Which drug is better for patient?  why?
    Propofol because it's easier for patient to wake up from Propofol than Fentenyl during continuous infusion.
  15. Disadvantages of IV anesthesia
    •Patient cooperation for venipuncture

    • •Rapid onset can magnify overdosage or
    • side effects

    •Pharmacologic antagonists are available for only some agents (benzodiazepines, opioids)
  16. Which receptor is the main target for most anesthetic agent?
    GABA receptor
  17. Ultrashort acting barbiturates (what are those?)
    Thiopental, MEthohexital and propofol
  18. Thiopental
    • cause histamine release
    • slow onset
  19. Methohexital
    • more potent than thiopental
    • short distribution half-life
    • short elimination half-life
    • may reduce seizure threshold and cause hiccup
  20. Propofol (pharmacokinetics)
    • Rapid onset
    • Rapid, clear recovery
    •            quick initial distribution
    •            huge volume of distribution (drop plasma [] quickly --> quick to deliver and eliminate)
  21. Propofol - repiratory and CV effect
    • •Respiratory depression (in small dose)
    •            apnea

    • •Mild direct myocardial depression ( dec
    • cardiac contractility)

    • •Profound peripheral vasodilation ( given in bolus fashion)
    •             Decreased blood pressure ( could invoke reflex tachycardia) but… Propofol also depressed baroreflex response --> Little increase in heart rate
    •              (young ppl fine, old people not fine)
  22. Propofyl - other effects
    • anti-emetic
    • painful on injection
  23. Propofol - formation
    • •Formulated in an oil-in-water emulsion containing:
    • soybean oil --> cause the burning sensation
    • glycerol
    • egg lecithin

    •Potential allergic reactions

    •Potential bacterial growth (soybean oil and egg lecithin) --> need aseptic technique and can’t reuse

    •Contributes dietary lipid

    •Fatalities in children given prolonged infusions
  24. Ketamine (mechanism and usage)
    Antagonist to NMDA receptors (class of glutamate receptor) --> block excitation

    • Dissociative anesthetics (body can't communicate with cortex)
    •       Analgesia, amnesia, staring into space, horizontal nystagmus
    •  
    • Used for incorporated pt (induce ms relaxation)
  25. Ketamine - pharmacokinetic
    •Lipophillic

    • •Rapid onset (30-60 sec after IV injection and 4 min after IM injection)

    • •Rapid recovery (distribution half-life 11-16 min & duration of action 10-15 min after IV bolus)
  26. Ketamine - CV effects
    • ---CC stimulation
    • THE ONLY DRUG increase heart rate, blood pressure, cardiac output --> inc NE release and block reuptake --> symp surge, but mild direct myocardial depression (masked by NE) --> not given for old pt)

    • ---Respiratory maintained
    • ---Bronchodilation
    • ---no histamine release (good for asthmatic pt)
  27. Ketamine -- systemic effects
    •Increased secretions

    •Airway reflexes intact

    •Skeletal muscle hypertonus (not associate with EEG changes)

    • •Emergence delirium
    • floating feeling, vivid dreams, hallucinations, delirium
    • more common in adults than children
    • related to dose and rate of administration
    • decreased by concomitant benzodiazepines
  28. what is the drug interaction of ketamine with benzodiazepines?
    Ketamine's effect decrease with benzodiazepines
  29. Etomidate - CV effect
    •Minimal cardiovascular change

    •Minimal respiratory depression
  30. Etomidate - pharmacokinetics
    • rapid onset
    • rapid recovery
  31. Etomidate - Side effect
    Wiggle juice --> involuntary myoclonic movement and painful on injection

    inhibition of adrenocorticosteroid synthesis --> block stress hormone production

    increase nausea and vomiting
  32. Benzodiazepines
    • Dose-dependent and cause amnesia
    • Small bolus induce minimal risk of respiratory depression
    • Big bolus induce unconsciousness and stable CV
  33. Benzodiazepine - medazolam
    Major metabolism by CYP3A4 in liver

    Interaction with CYP3A4 inhibitor (erythromycin, cimetidine, grape fruit juice)

    • Rapid onset
    • Duration of action: 45 min
  34. Benzodiazepines - Diazepam
    rapid onset and 45 min duration of action, metabolised by CYP3A4

    cause venous irritation and slow metabolism
  35. Dexmedetomidine (mechanism and usage)
    Selective a2-adrenergic receptor agonist

    Use for ADH pt with insomnia --> mainly work in CNS for suppression of sympathetic tone
  36. Dexmedetomidine - unique characteristic in pt's sedative state
    •Patients are easily arousable despite apparent deep sedative state
  37. Dexmedetomidine - CV issue
    hypotension and bradycardia
  38. Dexmedetomidine - true anesthetic
    False
  39. Dexmedetomidine's recovery period
    long
  40. how does opioid aid propofol in achieving general anesthesia
    Analgesics effect which propofol doesn't have
  41. opioid -general characteristic
    •Analgesia

    •Sedation, euphoria

    •Respiratory depression

    • Tolerance (involve down-regulation – need 2 weeks of continuous infusion), physical
    • dependence (end up with withdrawal effect – even with beta blocker --> cause rapid HR inc), addiction (psychological state)

    •Nausea, vomiting

    •Cough suppression

    •Chest wall rigidity --> unable to breath
  42. Opioid - cause of death for overdose
    respiratory suppression --> body can't inc ventilation in the presence of inc CO2
  43. Morphine
    •Slow Onset (Peak Effect 15-30 Min. IV)

    • •Long Duration (1.5 – 2 hrs)
    • Active Metabolite = Morphine-6-Glucuronide
    • May Be Useful for Dental Sedation In Long Case

    •Mild Histamine Release

    •Bradycardia (Vagal Stimulation)

    •Inexpensive

    •Not very popular
  44. Opioid - Meperidine
    •Synthetic, Resembles Atropine  (anticholinergic )

    •HR neutral

    • •Pharmacology
    • Onset 2 - 4 Minutes IV
    • Duration 1 – 2 Hours
    • Active Metabolite: Normeperidine

    • •Issues:
    • Histamine Release (>< asthmatic pt)
    • Interaction With MAO Inhibitors
    • Inexpensive
  45. Fentanyl
    •Synthetic - derivative of Meperidine

    • •Pharmacology
    • Onset ~ 1 Minute
    • Highly metabolized by CYP3A4
    •     Elimination half-life of 3 to 7 hours
    • Duration 20 - 30 Minutes

    • •Issues:
    • No Histamine Release
    • Chest-wall Rigidity
    • Inexpensive
  46. opioid - syfentanil
    more potent than fentanyl

    Duration of action 45-60 minutes after single dose

    • Used in hospital-setting general anesthesia
    • e.g., cardiac anesthesia
  47. Alfentanil
    1/5 to 1/10th as potent as fentanyl

    Shorter duration of action than fentanyl (15-20 minutes)
  48. Remifentanil
    •2 times as potent as fentanyl

    •Shortest duration of action (10 minutes)

    •Rapid ester hydrolysis by nonspecific  esterases to inactive metabolites

    •Used in TIVA, duration of action similar to propofol
  49. Potency of Remifentanil, Alfentanil, sulfentanil and fentanyl
    Sulfentanil > Remifentanil > Fentanyl > Alfentanil
  50. Duration of action: Remifentanil, Alfentanil, sulfentanil and fentanyl
    Sulfentanyl > Fentanyl > Alfentanyl > Remifentanyl
  51. Therapeutic Uses of IV Anesthetic
    Agents: Propofol
    used 90% of the time
  52. Therapeutic Uses of IV Anesthetic Agents: Etomidate and midazolam
    for CV compromised pt (etomidate >midazolam)
  53. Therapeutic Uses of IV Anesthetic Agents:
    Propofol + opioid
    TIVA

    •Usually Remifentanil or Alfentanil
  54. Therapeutic Uses of IV Anesthetic Agents:
    Midazolam + Fentanyl
    • Moderate sedation
    •         Midazolam = amnesia
    •         Fentanyl = analgesia

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