Clinical Lecture: General Anaesthesia

Question 1

What 3 states are achieved by general anaesthesia?

Answer 1

Amnesia, Akinisis and Analgesia.

Question 2

What is the arm-brain time?

Answer 2

This is the time it takes for the blood to travel from the site of induction to the vein. This is about 10-20 seconds. Within 1-2 brain-circulation times, the patient becomes unconsciousness.

Question 3

What is Cp50?

Answer 3

Cp50 : the concentration of the agent in the blood that could prevent movement after a skin incision in 50% patients

Question 4

Which GA has excellent suppression of airway reflexes?

Answer 4

Propofol

Question 5

What are the unwanted effects of Ketamine as an indication agent?

Answer 5

• Unwanted effects: Nausea and vomiting and emergence phenomenon (patient describes to have depression, excitation, different feelings)
• It is only used in a small number of patients

Question 6

Which GA has good haemodynamic stability and so mainly used in patients with CVS compromise, heart failure etc.?

Answer 6

Etomidate

- Lowest incidence of hypersensitivity reaction as it is steroid based
- Unwanted effects: Pain on injection, spontaneous movements, adrenocortical suppression and high incidence PONV 
- Not used more widely due to the adrenocortical suppression - can be for up to 72 hours. Support is needed postoperatively to maintain haemodynamic stability.

Question 7

What is MAC?

Answer 7

MAC - Minimum alveolar concentration - is defined as the end-expiratory concentration of an inhalational anaesthetic that is required to suppress gross purposeful movement to a painful stimulus in 50% of subjects.

Question 8

Give prosperities of Sevoflurane.

Answer 8

• Sweet smelling

- Inhalation induction e.g. children or where IV access cannot be established

Question 9

Which induction agent has the least effect on organ blood flow and so is used on organ transplants or revival?

Answer 9

Isoflurane

Question 10

Give properties of Desflurane.

Answer 10

• Low lipid solubility
• Rapid onset and offset
• Used in long operations

Question 11

What are the adverse effects of general anaesthesia?

Answer 11

• Vasodilation
• Increases cardiac contractibility - fall in BP and HR
• Can potentially affect organ perfusion

It can also lead to malignant hypothermia in volatile magnets and some agents such as halothane can cause hepatotoxicity.

Question 12

What is the most common non-opioid post-operative analgesic?

Answer 12

Paracetamol

Question 13

Give a depolarising muscle relaxant.

Answer 13

Suxamethonium

Question 14

How do we reverse depolarising skeptic agents?

Answer 14

Neostigmine and Glycopyrrolate