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Supporting life block > Anaesthetic agents (sedatives and opioids) > Flashcards

Anaesthetic agents (sedatives and opioids) Flashcards

1
Q

Name some induction agents

A 
Propofol
Benzodiazepines 
Barbiturates
Etomidate
Ketamine
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2
Q

Name some opiods

A 
Morphine
Fentanyl
Codeine
Tramadol
Remifentanil
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3
Q

What are some of the characteristics of propofol?

A

-Quick onset for sleep
-Rapid onset/offset with distribution
-Gives a Euphoric feeling
-Use; Anaesthetic induction, maintenance
of anaesthesia, sedation, anti-emesis
-Decreases serotonin in area postrema (antiemetic)
-Enhances GABA-induced chloride currents +
inhibits NMDA glutamate receptors
-Increases dopamine in nucleus accumbens
(sense of well-being)

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4
Q

What is propofol used for?

A
  • Anaesthetic induction
  • maintenance of anaesthesia
  • sedation
  • anti-emesis
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5
Q

Outline the pharmacokinetics of Propofol

A

-Oxidized and conjugated in liver
-Excreted by kidneys
-Competitive inhibitor of CYP3A4, increases duration
of action of midazolam

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6
Q

What is one of the pros of propofol for someone with MH(malignant hyperthermia)

A

-Doesn’t cause a fast rise in body temp and severe muscle contractions when someone with MH gets general anesthesia

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7
Q

What are some of the characteristics of barbiturates?

A

-Bind to GABA-A receptor and enhance
GABA effects (low doses)
-Directly stimulates GABA receptors (high
doses) causing increased chloride current
and hyperpolarization.

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8
Q

What are barbiturates used for ?

A
  • Thiopental: Induction, cerebral protection (e.g. status epilepticus)
  • Methohexital: Induction, especially for ECT
  • Phenobarbital: Seizure suppression
  • Anxiolysis
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9
Q

Outline the pharmacokinetics of barbiturates

A

-All hepatically metabolized then excreted in
urine except phenobarbital (60-90% renal
unchanged)
-Rapid redistribution terminates action of
single dose
-Much longer context sensitive half-time
than propofol

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10
Q

What are some of the characteristics of benzodiazepines?

A

-Bind to GABA-A receptor, enhance response
to GABA
-Leading to hypnotic, sedative, anxiolytic,
amnestic, anticonvulsant, muscle-relaxation
properties
-Increases seizure threshold
-Midazolam (short acting)
-Lorazepam and Temazepam (intermediate)
-Diazepam (long acting)

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11
Q

Outline the pharmacokinetics of benzoazepines

A

 Midazolam
- Rapid onset <1min, peak 2-3 min
-Distribution half life 6-15 min
-Hepatically metabolized by CYP system including active metabolite 1-hydroxymidazolam
 Lorazepam
- Conjugated in liver (not by CYP) to inactive compounds. Liver failure
can prolong effect.
-Infusion can cause propylene glycol toxicity
 Remimazolam
-New, cleared by non-specific tissue esterases

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12
Q

What are some of the characteristics of ketamine?

A

-Phencyclidine-binds to NMDA Receptor
(antagonist)
-Racemic mixture of S and R ketamine. (S
isomer is more potent)
-Produces “dissociative anesthesia” because
patients may not appear asleep (eyes open,
reflexes intact)

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13
Q

What are the uses of ketamine?

A
  • Dissociative anaesthesia / Anaesthetic induction
    -Sedation (maintains RR, common in paeds)
    -Analgesia (opioid sparing / acute procedures)
    -Bronchodilatation
    (Particularly in haemodynamically unstable patients)
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14
Q

Outline the pharmacokinetics of ketamine.

A
  • Metabolized in liver to norketamine and hydroxynorketamine
  • Norketamine has some activity but less than ketamine
  • Metabolites excreted in urine
  • Bioavailability orally is 20-30%, intranasally is 40-50%
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15
Q

What are some of the characteristics of flumazenil?

A

-Competitive antagonist
-Short half-life, may get rebound effect of agonist, can use infusion (30-
60mcg/min)
-Rapid onset, 1-3 min, lasts 3-30 min
-Can cause seizures in patients on chronic benzos

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16
Q

What are some of the characteristics of Etomidate?

A

-GABA-A facilitation (lower dose of GABA
required to activate receptor)
-At higher doses can activate receptor
independently

17
Q

Outline the pharmacokinetics of Etomidate

A

-Rapid onset 15-45 seconds
-Initial offset due to redistribution
-Cleared by Liver by ester hydrolysis then
excreted by kidneys and in bile, metabolites
not active

18
Q

What are the endocrine effects of etomidate?

A

-Dose dependent inhibition of 11B-hydroxylase.
-Occurs at lower doses than hypnosis by more than 20x so suppression lasts much
longer, up to 72h
-Can be used to treat hypercortisolaemia

19
Q

What are some of the characteristics of Dexmedetomidine?

A

-Alpha-2 receptor agonist (brain /spine)
-Used for sedation, anxiolysis, withdrawal,
delirium, opioid sparing analgesia.
-Useful for awake craniectomy / fibreoptic
intubation (sedation without respiratory
depression)

20
Q

Outline the pharmacokinetics of dexmedetomidine.

A

-Almost complete biotransformation in liver
with P450 system involvement
-Clearance is impaired in liver failure but not
renal impairment due to inactive
metabolites

21
Q

What is the ascending pain pathway used for?

A

Transmitting stimulus.

-Made up of fast& slow afferents

22
Q

What is the descending pain pathway used for?

A

Inhibiting transmission

-Made up of Substantia Gelatinosa.

23
Q

List the 4 opiod receptors?

A
  • MOP (mu)
  • KOP (kappa)
  • DOP (delta)
  • NOP (nociceptin)
24
Q

List the different opiods.

A
  • Morphine
  • Codeine
  • Fentanyl
  • Tramadol
  • Remifentanyl
25
Q

What are the benefits of TIVA?

A
  • Avoids conventional anaesthetic gases
  • Improved cardiovascular profile
  • Less nausea and vomiting
  • Improved tube tolerance
26
Q

What are the cons of TIVA?

A
  • Need dedicated IV line
  • Based on algorithms ( Compartment model assumptions)
  • Risk of awareness
27
Q

What are some of the characteristics of morphine?

A

Highly potent opioid ( MOP>DOP/KOP)

  • Used for - analgesia
  • palliation
  • peri-operative
  • Oral (poor bioavailability; 40-60%)
  • Subcutaneous/IV/intrathecal/transdermal
  • Metabolised in liver (glucorinated)
  • Active metabolite (morphine 6 – glucoronide)
  • potent + longer lived
  • Excreted via urine
  • Low lipid solubility - slow BBB penetration
  • slow onset
28
Q

What is the vomiting center of the brain?

A

-The fourth ventricle of the brain hosts the vomiting centre.
The floor of the fourth ventricle contains an area called the chemoreceptor trigger zone (CTZ).aka area postrema. When the CTZ is stimulated, vomiting may occur.

29
Q

What are some of the characteristics of fentanyl ?

A

Synthetic opioid

  • 80-100 times more potent than morphine
  • Few cardiovascular effects
  • Less histamine release.
  • Targets mu + delta receptors
30
Q

What are some of the characteristics of codeine?

A
  • 50% analgesic potency compared to morphine
  • Given orally
  • PRO-DRUG > Active metabolites (codeine – 6 glucuronidate morphine;
    10%)
  • Metabolized by CYP2D6
  • Caution in ultra-rapid metabolizers
  • Lack of efficacy in poor metabolizers
  • Susceptible to drug-drug interactions.
  • Risk to neonate ( breast feeding if mothers rapid
    metabolizers)
  • Half life – 3 hrs
    -Weakly targets mu + kappa receptors
31
Q

What are some of the characteristics of Tramadol?

A 
Atypical opioid ( analogue of codeine)
- Administered oral / iv
- 1/10 potency of oral morphine
- Dual action – mu agonist (weak)
- serotinergic/noradrenergic reuptake inhbition (
enhances descending inhibition)
- Safer cardio - respiratory profile
- Risk of serotonin syndrome ( caution with other drugs)
-targets mu receptors 
-NA /5HT reuptake
32
Q

What are some of the characteristics of Remifentanil?

A

-Potent mu receptor agonist
-Ultra-short acting drug
-Unique pharmacokinetics
- Rapid onset (1.3 mins)
- Rapid offset (context sensitive ½ time = 3.7 min) (metabolized by non specific
blood/tissue esterases

33
Q

What are some of the uses of Remifentanil?

A
  • Sedation in ICU
  • PCA in obstetrics
  • Pain relief during surgery
  • Total IntraVenous Anaesthesia ( TIVA)

Supporting life block (28 decks)

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