- 50:50 nitrous oxide : oxygen - French blue with quartered shoulders - Analgesic - Labour - Trauma

General Anaesthesia Flashcards by Joe Bloggs

What are the 3 commonly used IV induction agents?

Propofol (most common)
Thiopentone
Etomidate

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Name 4 inhalational agents

Nitrous oxide
Isoflurane
Sevoflurane
Desflurane

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What is general anaesthesia?

Reversible, drug induced loss of consciousness, usually to allow a surgical procedure to be performed

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What are other reasons other than surgery to give general anaesthetics?

ECT (severe depression)
Impaired understanding (e.g infants, dementia, learning difficulties) need general anaesthesia for more simple procedures like imaging, dental fillings

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What is the most common general anaesthetic?

Propofol

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When are general anaesthetics given via inhalation?

Induce anaesthesia in children

- More commonly to maintain anaesthesia

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What is entonox?

50:50 nitrous oxide : oxygen
French blue with quartered shoulders
Analgesic
Labour
Trauma

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What are the different molecular structures of anaesthetic drugs?

Propofol - phenol derivative
Sevoflurane, isoflurane - Haloginated hydrocarbons
Thiopentone - Barbiturate
Etomodate - immidasol ring

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A greater lipid solubility leads to what?

A greater potency of drug and lower MAC

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A higher MAC (atomsopheres) leads to what?

The lower the potency

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A more blood soluble inhalational agent leads to what?

A slower onset of drug

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Isoflurane is a structural isomer of what drug?

Enflurane (same solubility, different potencies)

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Etomidate exists as what?

2 stereoisomers (only R isomer is active)

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Ketamine exists as what?

2 different isomers (both have activity but different potnecy)

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Inhibition of luciferase enzyme leads to what?

Anesthetic potency

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How are general anaesthetics though to affect ion channels?

Potnetiate inhibitory neurotransmitters (GABA primarily, change configuration of GABA receptor) and inhibit excitatory neurotransmitters (glutamate)

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What is the structure of a GABA(A) receptor?

Pentameric arrangement (2x alpha 2x Beta 1xGamma)
Central ion channel pore
18 possible sub units
Approx 30 forms of receptor
Some subunits location specific
Anaesthetics allosterically activate the receptor

What part of the GABA(A) receptor are the IV anaesthetics thought to bind to?

Beta sub unit

What part of the GABA(A) receptor are the inhalational anaesthetics thought to bind to?

Somewhere between alpha and Beta sub unit

What drugs act on GABA(A) receptors?

Propofol
Etomidate
Barbiturates
Block neuronal excitibility

What does Ketamine inhibit?

Excitatory NMDA receptors where glutamate act

What are the advantages of ketamine?

Maintain own airway
CV stable not so much of a BP drop
Used in field surgery

What class of drug is ketamine?

Class C

What organ can Ketamine affect?

The bladder “stone bladder” - cannot expand or contract

What part(s) of the brain do general anaesthetics act on?

- Thalamus - Cerebral cortex - Brain stem - Reticular formation - Spinal cord

How do general anaesthetics generally affect the heart?

- Negative ionotropic effect - Reduce systemic vascualr resistance - Therefore decrease BP

What anaesthetic does not cause a negative ionotrpic affect on heart and does not reduce vascular resistance?

Ketamine (may cause tachycardia)

What did Michael Jackson die of?

Propofol

What kind of anaesthetic affects the tidal volume more; inhalatory or IV anaesthetic?

Inhalatory (IV more a drop in respiratory rate)

What are the properties of an ideal anaesthetic agent?

- Act rapidly - Pleasant - Cheap - Stable - Analgesic effect - Amnesic effort - Minimal 'hangover' - Does not irritate veins or airways - Not an emetic - Minimal effects on respiratory and cardiovascualr systems - Does not produce toxic metabolites - Does not cause histamine release / anaphylaxis

Why is soda lime a component of some anaesthetics?

Absorbs Co2 making it stable

What is desflurane?

Inhalational agent which is growing in popularity as it has a very rapid onset and offset - very irritable, so no t used initially, causes coughing, works well to wake up

Why is Nitrous oxide not used as much as it used to be?

Effects on bone marrow

What anaesthetic agent is best to use on someone with low BP e.g septic shock?

Etomidate - cardiovascularly stable, decreases respiratory rate

What general anaesthetics are painful on injection?

- Propofol | - Etomidate

What are some advantages of thiopentone?

- Marginally quicker than propofol - Rapid sequence induction patient may have full stomach and at risk of aspiration - Not painful on injection

What is the most effective inhalatory anaesthetic?

Sevoflurane (less irritable than desflurane and isoflurane)

What inhaled anaesthetic do patients wake up quickly from?

Desflurane - useful maintenance agent, also preferred in some obese patients

What is balanced anaesthesia?

- Selection of different drugs and anaesthetic agents - Used to minimise patient risk and maximise patient safety and comfort Bearing in mind: - Health and requests of the patient - Properties of the drugs - Requirements of surgery

When a surgeon needs access to the abdomen what drug is useful to add in balanced anaesthesia?

A muscle relaxant