Principles and Pharmacology of Anaesthesia

Question 1

What is general anaesthesia

Answer 1

Produces insensibility in the whole body, usually causing unconsciousness

Question 2

What is regional anaethesia

Answer 2

Producing insensibility in an area or region of the body. Applied to nerves supplying relevant areas.

Question 3

What is local anaesthesia

Answer 3

Producing in sensibility in only the relevant part of the body. Local anaesthetics applied directly to the tissue

Question 4

List the drugs used in anaesthetics

Answer 4

Inhalational anaesthetics
Intravenous anaesthetics
Muscle relaxants
Local anaesthetics
Analgesics

Question 5

List the techniques of administrating anaesthetic drugs

Answer 5

Tracheal intubation
Ventilation
Fluid therapy
Regional anaesthesia
Monitoring

Question 6

Describe the current use of anaesthesia

Answer 6

Triad of anaesthesia, analgesia, hypnosis and relaxation

Question 7

State the purpose of relaxation

Answer 7

refers to muscle relaxation necessary to provide immobility for certain procedures, allow access to body cavities and to permit artificial ventilation amongst other things.

Question 8

State the advantages of balanced anaesthesia

Answer 8

Titrate doses seperately and therefore more accurately to requirements.

Avoid overdosage.

Enormous flexibility.

Question 9

State the disadvantages to balanced anaesthesia

Answer 9

Polypharmacy results in an increased risk of drug reactions and allergies

Muscle relaxation makes way for the requirement of artificial ventilation.

Seperation of relaxation and hypnosis - awareness

Question 10

State the function of general anaesthetic agents

Answer 10

Provide unconcsciousness and small degree of muscle relaxation, they may also provide a small degree of analgesia

Question 11

How do general anaesthetic agents work

Answer 11

They interfere with neuronal ion channels causing them to hyperpolarise (thus making them less likely to fire).

Inhaled agents dissolve in the membranes

IV agents - allosteric binding on GABA receptors thus open chloride channels

Question 12

State the current IV anaesthetic agents

Answer 12

Thiopentone or propofol

Question 13

Describe the bodies reaction to IV anaesthetics

Answer 13

Rapid onset of unconciousness and rapid recovery due to the disappearance of drug from circulation

Question 14

What type of chemical are inhaled anaesthetics

Answer 14

Halogenated hydrocarbons

Question 15

MAC

Answer 15

Minimum alveolar concentration, a measure of potency

Question 16

Describe the induction period in inhaled anaesthesia

Answer 16

Slow

Question 17

How is a patient awakened when on inhalation anaesthetics

Answer 17

Stop the inhalation admin and washout by breathing a gas mixture containing no anaesthesia

Question 18

State the most common sequence of general anaesthesia

Answer 18

IV induction followed by inhalation maintenance

Question 19

How does general anaesthetic act on CVS centrally

Answer 19

It depresses cardiovascular centre reducing the sympathetic outflow, creating a negative inotropic/chronotropic effect on the heart. Also results in reduced vasoconstrictor tone - vasodilation

Question 20

How does general anaesthesia act on the CVS directly

Answer 20

Negative inotropic effect resulting in vasodilation and venodilation (decreased venous return and decreased cardiac output)

Question 21

How does general anaesthetic act on the respiratory system

Answer 21

Depressants. Reduce hypoxic and hypercarbic drive and decreased tidal volume and increased respiratory rate.

Paralyses cilia

Decreased FRC

Question 22

State the indications for muscle relaxants

Answer 22

Ventilation and intubation, when immobility is essential and body cavity surgery

Question 23

How do Non-depolarising NMBs work in muscle relaxation

Answer 23

They competetively block nicotinic acetylecholine receptors at the neuromuscular junction (preventing opening of sodium ion channels)

Question 24

How can the effects of

non-depolarising NMBs be reversed

Answer 24

Anticholinesterases stop the removal of Ach from the synapse

Question 25

How do Depolarising NMBs work

Answer 25

Depolarise motor end plate and render the post-junctional membrane refractory to further stimulus

Question 26

State the most commonly used Depolarising NMB

Answer 26

Suxamethonium which has very rapid onset and a short duration of action

Question 27

Why are intraoperative analgesia used

Answer 27

Prevention of arousal and opiates contribute to hypnotic effect of general anaesthesia and suppression of reflex responses to painful stimuli

Question 28

State the main local anesthetic drugs

Answer 28

Lignocaine, bupivacaine and prilocaine

Question 29

How do local anaesthetic drugs work

Answer 29

Sodium channel blockers which prevent propagation of action potential

Question 30

LA’s must be… to cross membranes

Answer 30

Un-ionised

Question 31

Define LA toxicity

Answer 31

High plasma levels of IV injection LA. Results in reduced blood flow and reduced absorptin - they are vasoconstrictors

Question 32

State the most toxic LA

Answer 32

Bupivacaine

Question 33

State the signs and symptoms of local anaesthetic toxicity

Answer 33

Circumoral and lingual numbness and tingling
Light-headedness
Tinnitus,  visual disturbances
Muscular twitching
Drowsiness
Cardiovascular depression
Convulsions
Coma
Cardiorespiratory arrest

Question 34

Describe what is meant by differential blockade of LA

Answer 34

Some nerves are easier to block than others - motor fibres harder than pain fibres. Means analgesia without paralysis.