Inhalation anaesthetics and intravenous anaesthetics

Question 1

How do volatile anaesthetics work?

Answer 1

Likely through the promotion of GABA in the CNS and glycine modulation in the spinal cord. Likely stimulation of GABA receptors = more chloride goes into cell causing it to hyperpolarise making it less likely to fire.

Question 2

What do inhalation anaesthetics do? Pros and cons.

Answer 2

Cause hypnosis, amnesia, and some muscle relaxation.
It decreases the cerebral metabolic rate of oxygen.
Bronchiodilator

Negative:
Does increase cerebral blood flow and intracranial pressure.
Decreases peripheral blood pressure through peripheral vasodilation
Respiratory depressants

Question 3

What are the features of nitrous oxide?

Answer 3

Low potency (MAC 101%), rapid onset, analgesic, 
Causes nausea and vomiting.

Question 4

What are the features of sevoflurane?

Answer 4

Not pungent, means that it can be given to concious people. God for use with child because it avoids the use of a needle.
It dos react with CO2 absorber creating nephrotoxic bypoducts

Question 5

What are the features of isoflurane?

Answer 5

Relatively cardiovascular stable

Question 6

What are the features of desflurane?

Answer 6

Rapid onset and ofsett, good for long cases.

Question 7

What are the types and an example of an intravenous agent?

Answer 7

Barbiturates - thiopentone
Phenols - propofol
imadizoles - etomidate
Phenycyclidine derrivatives - ketamine
Benzodiazopine - midazolam

Question 8

How do intravenous anaesthetics work?

Answer 8

To all but ketamine: they inhance GABA = hyperpolarisation of neuron an difficult to depolarize.
For ketamine: antagonizes NMDA receptor by binding the PCP section of the receptor and blocks the channel.. NMDA receptors are also found in pain pathways and so ketamine is also an analgesic agent.

Question 9

What are the features of thiopentone?

Answer 9

Is a barbutate
Rapid onset (10s) (good for rapid onset need for surgery like c-section)

Rapid offset because of redistribution
Slow clearance - won’t wake up properaly immediately (hangover)
Metabolized in the liver.
Decreases PVR and BP (careful in shocked patients)
Resp depression and loss of airway reflexes

Question 10

What are the features of propofol?

Answer 10

Is a phenol. Has replaced thiopentone.

Moderately rapid onset (30s)
Rapid offset by redistribution.
Fast clearance (10x thiopentone) - thus can be used for as continous infusion and have less hangover

Decreases intracranial pressure and cerebral blood flow

Metabolized in liver
Significant decrease in PVR and BP (carful with shocked patients)
Resp depression and loss of airway reflexes

Question 11

What why would you use etoidate over propofol and what are the features of etomidate?

Answer 11

Etomidate would be used if you were concerned about cardiac stability in the patient.

Is a imadazole.
Remarkable CV stability.
Less respiratoy depression
Rapid clearance and good recovery.
But it has adrenocortical inhibition - problem for recovery

Question 12

What are the features o ketamine and when is it good for?

Answer 12

It is a cardiovascular stimulant (increase HR, vasoconstriction and pressure) - good for shocked patient.
Preserves airway reflexes and respiratory drive
It is an analgesic
Increases cerebral metabolic rate of O2, intracranial pressure, and cerebral blood flow - not good for head trauma.
Causes a dissociate state - slower complicated recovery.

Question 13

What are the pros and cons of total intravenous anaesthesia?

Answer 13

Avoids inhalation route, avoids the complications of noxious agents, such as malignant hyperthermia, nausea and vomiting.

Cons: expensive, cannot measure conc in patient like you can with using noxious agents with expiration conc.