s2-L27-General anaesthetics

Question 1

What are the 4 stages of general anaesthesia ?

Answer 1

Stage I - ANALGESIA
-drowsiness; reflexes intact(still working); still conscious

Stage II - DELIRIUM (the INDUCTION phase)
-excitement, delirium(state of confusion), incoherent speech(communication that is difficult to understand due to lack of clarity and logical structure)
-loss of consciousness
-unresponsive to non-painful stimuli
-muscle rigidity, spasmodic movements(sudden, involuntary muscle contractions)
-cardiac arrhythmias(irregular heart beats)
-vomiting, choking
-DANGEROUS PHASE

Stage III - SURGICAL ANAESTHESIA
-unresponsive to painful stimuli
-breathing regular
-abolition of reflexes(complete loss of involuntary responses to stimuli)
-muscle relaxation
-synchronised ElectroEncephaloGraph

Stage IV - MEDULLARY PARALYSIS - OVERDOSE
-pupillary dilation
-respiration/circulation ceases;
-EEG wanes(gradual reduction of the brain wave activity)
→ death

Question 2

What makes a good anaesthetic? hint : induction and what does it mean ?

Answer 2

should be POTENT and FAST ACTING (ie:- speed of induction and recovery)

Induction - process of bringing a patient from a wakeful state to unconsciousness before surgery or a medical procedure. Done using intravenous or inhaled anaesthetic agents.

Question 3

How to measure anaesthetics potency in a person?

Answer 3

-MAC = Minimal Alveolar Concentration

• the concentration of anaesthetic in the alveoli
  required to produce immobility in 50% of patients when exposed to a noxious stimulus.

units - %v/v

Question 4

What is the relationship between MAC and lipid solubility?

Answer 4

MAC is inversely proportional to lipid solubility.

Question 5

What is the relationship between blood:gas partition coefficient and speed of induction?

Answer 5

blood:gas partition coefficient (lamba sign) is inversely proportional to speed of induction.

Question 6

Define balanced anaesthesia

Answer 6

using combinations of different drugs for
optimal clinical effect with lowest risk

Question 7

Name the 3 adjuncts to general anaesthetics

Answer 7

1. Premedication
   -Benzodiazepines (sedation, anxiolysis, amnesia) - e.g. lorazepam, midazolam
   -Opioids (pain relief) - e.g. morphine, fentanyl, pethidine.
   -Antimuscarinics (to facilitate intubation and ventilation) - e.g. atropine, hyoscine, glycopyronium.
2. Muscle relaxants
   * to relax deep abdominal, tracheal and diaphragm muscles without need for deeper anaesthesia.
   - Benzodiazepines
   - Neuromuscular blockers - e.g. tubocurarine, pancuronium, gallamine, suxamethonium
3. Anti-emetic
   * decrease peri-operative nausea - e.g. metoclopramide