(8.2) Anaesthesia

Question 1

What principal effects do anaesthetics have?

Answer 1

• Analgesia
• Hypnosis
• Depress spinal reflex
• Muscle relaxation

Question 2

What are the Geudel’s Sign?

Answer 2

• Stage 1: Analgesia + CONSIOUSNESS
• Stage 2: UNconsiousness + irregular breathing
• Stage 3: surgical anaesthesia: CNS depression (-cardiac & respiratory rates)
• Stage 4: respiratory & cardiac arrests -> death

Question 3

What are the mechanisms of action of anaesthetics?

Answer 3

• Positive allosteric modulation of Inhibitory receptors: GABA(A) & Glycine receptors -> hyperpolarisation -> -excitability
• Competitively antagonise excitatory receptors: Nicotinic Ach & NMDA receptors

Question 4

Name 4 anaesthetics that are administrated by inhalation

Answer 4

• Nitrous oxide
• Isofluranes
• Desfluranes
• Sevafluranes

Question 5

Name 2 anaesthetics that are administrated by IV

Answer 5

• Ketamine

- Propofol

Question 6

Why do you give Nitrous Oxide as adjuvant to Fluranes?

Answer 6

Reduce Fluranes’ Minimal Alveolar Concentration to initiate Analgesia

Question 7

What can you give as adjuvants to Fluranes to initiate sedation?

Answer 7

Propofol

Question 8

What effects does combining Bendrodiazepine and Fluranes have?

Answer 8

Increase on GABA(A) receptor effects -> anxiolysis (unconsiousness) & amnesia (memory loss)

Question 9

What can you give as adjuvants to Fluranes to increase analgesic effects?

Answer 9

Opipoids

Question 10

What measurements can be used to determine the absorption of inhalatory anaesthetics?

Answer 10

• Minimal Alveolar Concentration (MAC) = the minimum concentration of anaesthetics needed to cause 50% of patients losing reflex to surgical incision (e.g. the lower the MAC, the more potent the drug)
• Blood:Gas Coefficient = degree of absorption across alveoli

Question 11

Why do you get hangover symptoms after administrating inhalatory anaesthetics?

Answer 11

• Tissue:Blood Coefficient in the body = Adipose > Muscle > CNS
• Adipose & Muscles serve as reservoirs which prolong the recovery phase

Question 12

What majorly determines the distribution of IV anaesthetics?

Answer 12

Plasma protein binding

Question 13

Which of IV or inhalatory anaesthetics have shorter half life and why?

Answer 13

• IV shorter: hepatic & renal elimination

- Inhalation: needed to be breathed out slowly & reservoirs in adipose and muscle

Question 14

Suggest 6 ADRs of Fluranes.

Answer 14

• Respiratory & cardiac depression
• Hypotension
• Increased intracranial pressure
• Coughing & Laryngospasm
• Arrhythmia
• Malignant Hyperthermias

Question 15

Suggest 2 ADRs of Nitrous Oxide.

Answer 15

• Diffusion Hypoxia (elimination of N2O into alveoli displaces O2)
• Airway expansion (sinuses, middle ear, bowel obstructed areas)

Question 16

What receptors does Ketamine act on? How does it cause its effects?

Answer 16

Competitively antagonise NMDA receptor (glutaminergic) -> -Ca2+ -> -Neurotransmission

Question 17

Suggest 3 factors that affect the Minimum Alveolar Concentration.

Answer 17

• Pregnancy
• Age
• Body temperature

Question 18

Describe the distribution of Propofol after initial injection.

Answer 18

• Rapidly delivered to CNS, less the muscles and adipose (lower blood supple)
• Highly protein bond
• Little redistribution to fat and muscles