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202T1 > Anaesthetic drugs > Flashcards

Anaesthetic drugs Flashcards

1
Q

Define anaesthetia?

What is an anaesthetic?

A

A reversible drug-induced absence of sensation and awareness

Any lipid-soluble agent that causes depression of the brain in a predictable order: cortex, midbrain, spinal cord, medulla

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2
Q

Outline the stages of effects of Ethanol

A 
Tranquillization
Excitation
Dysarthria - slurred speech
Ataxia- lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes and abnormalities in eye movements
Sedation/hypnosis
Anaesthesia
Coma
Medullary depression
DEATH
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3
Q

How do anaesthetics work?

A

Lipid-soluble
Stereo-selective
Modulation of ligand gated channels

Act on cell membrane:

  • interaction with membrane proteins
  • stimulation of inhibitory receptors, GABA/glycine
  • inhibition of excitatory receptors

CAUSE GLOBAL DEPRESSION IN NEURONAL ACTIVITY

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4
Q

How are GABAa receptors involved in anaesthetic drug action?

A

The GABAa receptor is a pentomer and is the most abundant fast inhibitory neurotransmitter receptor in the CNS

-ligand gated ion channel selective for single amino acids causing influx of Cl- which leads to hyperpolarisation

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5
Q

Oxygen is used in anaesthesia.

At what temperature is it a gas?
Where is it derived from?
How is it stored?
Method of administration?
Side effects?
A

Gas >-119 degrees c

Derived from distilled air

Supports combustion, not flammable in itself. Stored in black cylinder with white shoulders

Inhaled

SIDE EFFECTS:

  • Oxygen free radicals
  • CNS convulsions
  • Pulmonary oxygen toxicity
  • Retrolental fibroplasia
  • CO2 narcosis

GENERALLY GOOD FOR YOU

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6
Q

Nitrogen oxide is used in anaesthesia.

What does it look like?
When is it a vapour?
Method of administration?
Analgesic or anaesthetic?
Side effects?
A 
Odourless, gas stored in blue cylinder
Vapour at 44bar
Inhaled agent
Poor anaesthetic (MAC 105%), Good analgesic 
Quick onset and offset
CARDIO RESPIRATORY DEPRESSANT
Side effects: neuropathy/bm depression
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7
Q

State the physical properties to be considered for inhalation agents

A 
Cost
Chemical stability
Non-flammable/explosive
Vapourizable
Environmentally stable
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8
Q

State the chemical properties to be considered for inhalation agents

A 
Non-toxic
Non-irritant
Low blood: gas solubility
High potency (MAC)
Minimal side effects (pharmacodynamics)
Biotransformation (pharmacokinetics)
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9
Q

Consider the older anaesthetic agents. What was wrong with them?

  • Ether
  • Chloroform
  • Cyclopropane
  • Methoxyflurane
  • Halothane
  • Enflurane
A

Ether- emetic

Chloroform- dysrhythmia

Cyclopropane- VERY explosive

Methoxyflurane- F- (bad for kidneys)

Halothane- Liver failure/hepatitis

Enflurane- prone to fitting

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10
Q

Describe Isoflurane

What is it?
Physical and chemical properties?
Side effects?

A 
GENERAL ANAESTHETIC-inhaled
Halogenated ether
Relatively cheap
Stable and non-flammable
Vapourizable at 49degrees c
Relatively potent (MAC 1.1%)
0.2% metabolised

Side effects: irritable to airway

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11
Q

Describe Sevoflurane

What is it?
Physical and chemical properties?
Side effects?

A 
GENERAL ANAESTHETIC-inhaled
Halogenated ether
Non-irritable
Quick onset/offset
MAC 2%
5% metabolised (few bad breakdown products)
CVS stability
Expensive \$\$

Side effects: emergence phenomena

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12
Q

Describe Desflurane

What is it?
Physical and chemical properties?
Side effects?

A 
GENERAL ANAESTHETIC- inhaled
Halogenated ether
Very quick onset/offset
0.02% metabolised 
Moderately expensive
Needs a specialised vapouriser due to boiling point
MAC 6.35%

Side effect: irritant

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13
Q

Describe Thiopentone

What is it?
Physical and chemical properties?
Side effects?

A

Intravenous general anaesthetic

  • Thiobarbituate
  • Antiepileptic
  • Powder
  • Smells like garlic
  • Causes CVS and RS depression
  • Anaphylaxis/arterial
  • Half life 10 hours
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14
Q

What can be said intravenous general anaesthetics?

A 
NEWER
Uses induction agent/ IV opiate
Rapid and unpleasant
Lipid soluble
Wear off by redistribution -this is when you wake up(moves from brain to fat and muscle)
Metabolised
Cause CVS and RS depression
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15
Q

Describe Propofol

What is it?
Redistribution and elimination half lives?
Side effects?

A 
Solvent
-General anaesthetic
-Anti emetic
-Anti epileptic
Redistribution half life: 4 minutes
Elimination half life: 4 hours

Minimal accumulation

SIDE EFFECTS:
Painful to inject (use carrying agent and local anaesthetic), abnormal movemenets, SEVERE CVS depression

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16
Q

What other anaesthetic agents exist?

A

Ketamine- anaesthetic and analgesic

Etomidate

Mildazolam- any administrayion,sedation in ICU, induction agent

17
Q

Muscle relaxants are used only be anaesthetics. Why is that?

Indication?

A

VERY DANGEROUS

Muscle paralysis

Facilitates intubation (endotracheal tube entry)

Maintains paralysis for surgery/ventilation

2 Types depolarising and non-depolarising

18
Q

Give an example of a depolarising muscle relaxant

Where does it act?
Physical and chemical properties?
Side effects?

A

e.g. Suxemethonium

Act on post-synaptic membrane, plasma cholinesterase. Mimics ACh

Rapid onset and offset

Short half life = 2 mins

MULTIPLE SIDE EFFECTS such as anaphylaxis

19
Q

Consider non-depolarising muscle relaxants

Where do they act?
Physical and chemical properties?
Side effects?

A

Compete with ACh
ACh moiety blocks Na channels with size

Duration is variable

Slower onset/offset

Steroid group

Benzylisoquinoliniums

20
Q

What is pain

A

An unpleasant sensory and emotional experience associated with actual or potential tissue damage

21
Q

Briefly outline the gate theory

A

C fibres transmit pait information

Ab fibres stimulate inhibitory neurons

Descending pathways prevent central passage

22
Q

How can we score pain?

A

Linear?

Smiley/sad faces?

Mild/moderate/severe/excrutiating

23
Q

Consider the pain ladder. What types of drugs are used at each stage?

A

NSAIDs/paracetamol

Weak opiates (e.g. codeine) / local anaesthetics

Strong opiates

24
Q

Give an example of an opioid

Where do they act/where are its receptors?

Side effects?

A

Morphine

Receptors in pons/midbrain
Peripheral tissue
Spinal cord posterior horn 1 and 2
GIT
PAQ Grey matter

Respiratory depression/airway loss
Nausea and vomiting
Constipation and pruritis
Miosis (excessive contriction of pupil)

25
Q

Where does ketamine act?

What is it?

Side effects?

A

NMDA receptors
Kappa and delta receptors (not GABA)

Local and general analgesic
Anaesthetic

Side effects: emergence phenomena

26
Q

What are NSAIDs?

Where do they act?
Use?

Side effects?

A

Non-steroidal anti-inflammatory drugs

Act by inhibiting COX1 and 2

Analgesic, antipyretic, anti-inflammatory

Side effects: bronchospasms, renal impairment, platelet dysfunction (ASPIRIN)

27
Q

Aspirin is an example of a….

Mechanism of action?
Side effects?

A

NSAIDS

Oxidative phosphorylation

Air hunger, reyes syndrome, platelet dysfunction

28
Q

What is the Ramsay sedation scale?

A

A sedation scoring system used in ICU

29
Q

Describe the mechanismof action of benzodiazepines and barbituates in sedation

What other sedatives are there?

A

Benzodiazepines (Midazolam, Diazepam, Lorazepam), Baribituates

Bind to GABAa receptor at different allosteric sites

Facilitates GABA action

Barbituates increase duration and Benzos increase frequency of Cl- channel opening

Membrane hyperpolarisation

CNS depression

Low dose vapours (Isoflurane/Sevoflurane/Desflurane),Ketamine, Hyoscine, Propofol low dose, major tranquillisers, alpha-2 agonists

30
Q

What are the side effects of benzodiazepines

A
  • Over sedation
  • Loss of airway
  • Respiratory depression

202T1 (19 decks)

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