General Anaesthetics

Question 1

What are the aims of General Anaesthetics?

Answer 1

Analgesia (Pain relief), relaxation of skeletal muscles, amnesia (loss of memory)

Question 2

The higher the solubility of inhalent GA in blood, the _____ (faster/slower) the onset

Answer 2

slower

Question 3

What are the different type of inhalant GA?

Answer 3

• Halothane
• Enflurane
• Desflurane
• Isoflurane
• Sevoflurane
• Nitrous Oxide

Question 4

What are the stages of anaesthesia?

Answer 4

1) analgesia
2) excitement
3) Surgical Anesthesia (loss of eye movement, eye reflexes, as dept of anesthesia increases)
4) Medullary depression

Question 5

What is the significances of Minimum Alveolar Concentration (MAC)

Answer 5

low MAC = High potency
MAC is the minimum concentration of drug in the alveolar air that will produce immobility in 50% of patients exposed to a painful stimulus.

Question 6

What must be noted when giving sevoflurane?

Answer 6

Unstable when exposed to cardon dioxide absorbents in anaesthetics machines, degrading to a compound that is potentially nephrotoxic.

Question 7

What is a major and unique concern of Nitrous oxide?

Answer 7

Postoperative nausea and vomiting
rapid onset and recovery but MAC is very high, least potent –> need other anesthetic agents

Question 8

What are the different types of intravenous GA?

Answer 8

Thiopentone
Etomidate
Propofol
Ketamine
Midazolam

Question 9

What is unique about thiopentone? What is its Mechanism of Action?

Answer 9

-Barbiturate with extremely high lipid solubility ( can enter BBB easily)
- rapid onset of action

MOA: Cause CNS depression by potentiating the action of neurotransmitters GABA on the GABAa receptor gated chloride ion channels

Question 10

Characteristic of Propofol (5)

Answer 10

• Rapid onset
• short duration of action as rapid redistribution from brain to other tissues
• recovery is faster than thiopentone
• reduced postoperative vomiting
• significant cardiovascular effect during induction –> hypo tension (used with caution with pts w compromised cardiac function, hypovolemic patients)

Question 11

Characteristic of ketamine (5)

Answer 11

• Produces a state known as dissociative anaesthesia
• rapid induction
• metabolized in liver, excreted in urine
• Large Vd, rapid clearance, suitable for continuous infusion without lengthening in duration of action
• only IV anesthetic that possess analgesic property

Question 12

What are some anesthetic adjuncts and what do they do?

Answer 12

Benzodiazepines (midazolam), alpha2 adrenergic agonists, analgesics (NSAIDs), neuromuscular blocking agent (succinylcholine)
They augment GA –> reduce doses of GA needed –> reduce GA side effects