Introduction to Anaesthetics - Lecture

Question 1

What are the 3 types of anaesthesia and what do they do?

Answer 1

1. General anaesthesia = total loss of sensation.
2. Regional anaesthesia = loss of sensation to a region or part of body.
3. Local anaesthesia = topical.

Question 2

Define:

1. Amnesia
2. Analgesia
3. Akinesis

Answer 2

1. Lack of response and recall to noxious stimuli - unconsciousness.
2. Pain relief.
3. Immobilisation / paralysis.

Question 3

What do you need for general anaesthesia?

Answer 3

1. Monitoring
2. IV access
3. Start the process - induction of anaesthesia + start analgesia and muscle relaxation.
4. Maintain the process - maintenance agents + replace fluid loss blood loss.
5. Reverse muscle relaxation.

Question 4

What is the best induction agent for:

1. Burn dressing change?
2. Arm operation under GA with an LMA?
3. Hx of HF + requires GA?
4. Intestinal obstruction + requires emergency laparotomy?
5. Porphyria + needs inguinal hernia repair?

Answer 4

1. Ketamine - short procedure.
2. Propofol - commonly used.
3. Etomidate - haemodynamic stability (steady blood flow).
4. Thiopentone - RSI.
5. Porphyria - NOT thiopentone.

Question 5

1. What are the positives of using propofol.

2. What dose is used?

Answer 5

1. Excellent suppression of airway reflexes + decreases incidence of PONV.
2. Dose = 1.5 - 2.5 mg/kg

Question 6

What are the unwanted effects of propofol?

Answer 6

1. Marked drop in HR and BP.
2. Pain on injection.
3. Causes involuntary movements.

Question 7

1. What are positives of using thiopentone?

2. What dose is used?

Answer 7

1. Faster than propofol - used for rapid sequence induction.
2. Antiepileptic properties + protects brain.
3. Dose = 4 - 5 mg/kg

Question 8

What are the unwanted effects of thiopentone?

Answer 8

1. Drops BP but raises HR.
2. Rash
3. Bronchospasm
4. Intra-arterial injection = can cause thrombosis and gangrene.
5. Contraindicated in porphyria.

Question 9

1. When is ketamine used and what are the positives?
2. What is the dose?
3. How long does it take to act?

Answer 9

1. Sole anaesthetic for short procedures.
2. Raise HR/BP
3. Bronchodilation
4. Dose = 1 - 1.5 mg/kg
5. Slow = 90 seconds.

Question 10

What are the unwanted effects of ketamine?

Answer 10

1. N&V

2. Emergence phenomenon.

Question 11

What is emergence phenomenon?

Answer 11

Hallucinations, vivid dreams, illusions - basically, px trips out when coming around from anaesthesia.

Question 12

What are the positives of etomidate and what is the dose?

Answer 12

1. Rapid onset
2. Haemodynamic stability - good for HF px
3. Lowest incidence of hypersensitivity reaction.
4. Dose = 0.3 mg/kg

Question 13

What are the unwanted effects of etomidate?

Answer 13

1. Pain on injection.
2. Spontaneous movements.
3. Adreno-cortical suppression.
4. High incidence of PONV.

Question 14

How long do induction agents last for?

Answer 14

4 - 10 minutes

Question 15

What can be used to maintain amnesia?

Answer 15

1. Propofol infusion - total intravenous anaesthesia.

2. Inhalation agents = sevoflurane, desflurane, isoflurane, enflurane.

Question 16

What is MAC?

Answer 16

Minimum alveolar concentration - the concentration of vapour required, to prevent the reaction to a surgical stimulus, in 50% of px.

Question 17

What are the MAC values for:

1. Nitrous oxide
2. Sevoflurane
3. Desflurane
4. Isoflurane
5. Enflurane

Answer 17

1. 104%
2. 2%
3. 6%
4. 1.15%
5. 1.6%

Question 18

Best inhalation agent for:

1. Long, 8 hour, finger re-implantation.
2. Chubby child with no IV access.
3. Organ retrieval from a donor.

Answer 18

1. Desflurane - low lipid solubility + used for long operations.
2. Sevoflurane
3. Isoflurane - least effect on organ blood flow.

Question 19

What are analgesics required for?

Answer 19

Intubation, insertion of LMA, intra-operative pain relief and postoperative pain relief.

Question 20

1. What short-acting opioids are used?

2. What long-acting opioids are used?

Answer 20

1. Fentanyl, alfentanil, remifentanil.

2. Morphine, oxycodone

Question 21

What other analgesics are used?

Answer 21

• Paracetamol IV

- NSAIDS = Diclofenac, Parecoxib, Ketorolac

Question 22

Most commonly used analgesic?

Answer 22

Paracetamol

Question 23

Most commonly used oral opioid in adults?

Answer 23

Codeine

Question 24

IV NSAIDS?

Answer 24

Ketorlac, Parecoxib

Question 25

Name the only depolarising muscle relxant and what is its dose?

Answer 25

Suxamethonium - RSI | Dose = 1 -1.5 mg/kg

Question 26

What are the adverse effects of suxamethonium?

Answer 26

Muscle pains, fasciculations, hyperkalemia, malignant hyperthermia, rise in IOP/ICP

Question 27

How do non-depolarising muscle relaxants work?

Answer 27

Compete with acetylcholine for nicotinic receptors.

Question 28

What is the difference between suxamethonium and non-depolarising muscle relaxants?

Answer 28

Sux = rapid onset and rapid offset (RSI) + lots of side effects. Non = slow onset and variable duration + less side effects.

Question 29

What can be used to reverse the effects of atracurium?

Answer 29

Neostigmine or Glycopyrrolate.

Question 30

What drugs are commonly used to treat hypotension whilst px is undergoing surgery?

Answer 30

1. Ephedrine 2. Phenylephrine 3. Metaraminol (Vaso-active drugs)

Question 31

How does ephedrine work?

Answer 31

Acts directly and indirectly on alpha and beta receptors (adrenergic receptors) - causing vasoconstriction. Increasing HR and contractility = rise in BP.

Question 32

How does phenylephrine / meteraminol work?

Answer 32

Causes vasoconstriction - direct action on alpha receptors. Drops HR.

Question 33

Best vaso-active agent for: 1. Low BP, low HR 2. Low BP, high HR 3. ICU / severe sepsis

Answer 33

1. Ephedrine 2. Phenylephrine / Metaraminol 3. Noradrenaline / Adrenaline

Question 34

What % of px get PONV after GA?

Answer 34

20-30%

Question 35

Name the commonly used anti-emetic agents and what class of drug?

Answer 35

1. 5HT3 blocker = Ondansetron 2. Anti-histamine = Cyclizine 3. Steroid = Dexamethasone 5. Phenothiazine = Prochlorperazine (Stemetil) 6. Anti-dopaminergic = Metoclopramide

Question 36

What are the 4 steps to reversal of GA?

Answer 36

1. Stop anaesthetic vapours 2. Give o2 3. Perform throat suction 4. Give reversal muscle relaxant

Question 37

How does neostigmine work?

Answer 37

Anti-cholinesterase = prevents breakdown of acetylcholine