Anaesthetics

Question 1

What are the two types of anaesthetic that can be given?

Answer 1

General and local

Question 2

What is meant by the term MAC

Answer 2

Minimum alveolar concentration - the concentration at which 50% patients fail to move to surgical stimulus.
At equilibrium alveolar concentration is equal to spinal cord.

It is a measure of potency for volatile anaesthetics.

Question 3

Typically, what medication is given at the pre-op stage

Answer 3

Benzodiazepines- hypnotic

Question 4

Most anaesthetics have which element group attached to their structures?

Answer 4

Fluorine or chlorine

Question 5

Which chemically inert element is commonly used in children as an anaesthetic?

Answer 5

Xenon

Question 6

What three things do anaesthetics affect?

Answer 6

Muscle tone
Eye movement
Breathing

Question 7

What is the first thing to be affected by anaesthetic?

Answer 7

Memory closely followed by consciousness

Question 8

Why is volatile anaesthetic often given as a mixture with NO?

Answer 8

Reduces the MAC, therefore less dose is required for therapeutic effect

Question 9

Why is analgesia also given to patients?

Answer 9

To aid recovery

Question 10

Why are muscle relaxants given before intubation?

Answer 10

Anaesthetic whilst causing relaxation, doesn’t allow complete access to the airways and therefore relaxants aid intubation.

Question 11

Why is intubation essential in the anaesthetised patient?

Answer 11

Because the muscles of inspiration become paralysed due to the systemic effect of muscle relaxation; without intubation, the patient will die.

Question 12

In which ways can general anaesthesia be administered?

Answer 12

Inhaled or IV

Question 13

What is meant by the term conscious sedation?

Answer 13

Small amount of anaesthetic or benzodiazepine to induce a ‘sleep-like state’ where maintain verbal contact but feel comfortable.

Question 14

Which drug is given to patients before they are in recovery?

Answer 14

An anti-vomiting and nausea agent.

Question 15

What is unusual about Guedel’s signs in stage 2?

Answer 15

Unconscious, erratic breathing and delirium can occur, leading to an excitement phase.

Question 16

Anaesthesia is a combination of what 4 things?

Answer 16

Analgesic
Hypnotic
Depression of spinal reflexes
Muscle relaxant

Question 17

What factors impact on MAC?

Answer 17

Age 
Hyperthermia/hypothermia
Pregnancy
Alcoholism 
Central stimulants 
Other anaesthetics 
Opioids

Question 18

What partition coefficients affect induction and recovery of anaesthesia?

Answer 18

Blood:gas partition
Oil:gas partition

Question 19

What are the main receptors which are targeted by anaesthetics?

Answer 19

GABAa receptors - with the exception of Xe,N2O and ketamine.
NMDA is the other potential target

Question 20

What specific brain systems are targeted by anaesthetics?

Answer 20

Reticular formation
Hippocampus
Brainstem
Spinal cord dorsal horn and motor neurones

Question 21

Name the main intravenous anaesthetics

Answer 21

Propofol- rapid
Barbiturates -rapid
Ketamine - slower

Target sites are GABAa except ketamine which is NMDA.

Question 22

Potency in IV anaesthetics

Answer 22

Plasma concentration to achieve specific end point:
Induction in mixed anaesthesia - bolus to end point and then switch to volatile

TIVA (TOTAL IV ANAESTHESIA) use a defined PK based algorithm to infuse at a rate to maintain set point. Proceeded by a bolus.

Question 23

Give examples when a local or regional anaesthetic may be used?

Answer 23

Dentist 
Obstetrics 
Regional/minor surgery 
Post op 
Chronic pain management

Question 24

Name local anaesthetics

Answer 24

Lidocaine
Bupivacaine
Ropivacaine
Procaine

Question 25

What are the main anaesthetic side effects?

Answer 25

Post operative nausea and vomiting
Hypotension
Post operative cognitive dysfunction
Chest infection

Question 26

What are the important characteristics of local anaesthetic?

Answer 26

Lipid solubility- potency
Dissociation constant (pKa)- time of onset
Chemical link- metabolism (amide or ester)
Protein binding - duration

Question 27

What is a regional anaesthesia and where is it administered?

Answer 27

Local anaesthetic +/- opioid
Upper extremity - interscalene, supraclavicular, infraclavicular, axillary

Lower extremity- femoral, sciatic, popliteal, saphenous

Extra dural, intrathecal or combined (labour)

Question 28

How does bupivacaine act as an anaesthetic?

Answer 28

It blocks small myelinated afferent nerves in preference. It needs to diffuse across the membrane and then be positively charged. Once charged it can sit within the voltage gated sodium channel and prevent depolarisation.