Module 5: Anaesthetics

Question 1

Ester-type Local Anaesthetics

Answer 1

• short DOA
• addictive
• systemic side affections (convulsions)
• vasoconstricting (keep anaesthetic localized to region of injection)
• used for bronchoscopy (topical to nasal fosse)
• ex. Cocaine

Question 2

Amide-type Local Anaesthetics

Answer 2

• prototypes of local anaesthetics, most widely used
• admin parenteraly (IV or topically
• more intense local anaesthetic effect than ester-type
• fastest onset of action
• often combined with epinephrine to prolong its effect
• ex. Xylocaine (Lidocaine)

Question 3

examples of Esters

Answer 3

cocaine
procaine
benzocaine
tetracaine

Question 4

examples of Amides

Answer 4

lidocaine
bupivacaine
mepivacaine
prilocaine
(remember, always have 2 "i"'s)

Question 5

2 types of General Anaesthetics

Answer 5

• inhalation

- intravenous

Question 6

Stages of Anaesthesia

Answer 6

I-analgesia and conscious sedation occur
II-CNS excitation
III-surgical anaesthesia stage (when surgery can be safely performed without pain to pt.)
IV- to be avoided, can lead to CV collapse

Question 7

Factors that achieving surgical anaesthesia depends on

Answer 7

1-solubility of gas
2-alveolar anaesthetic partial pressure or concentration
3-pulmonary ventilation
4-pulmonary blood flow

Question 8

Solubility of Gas

Answer 8

• determines rate at which anaesthetic molecules dissolve into blood
• measurement= blood:gas partition coefficient
• the lower the b:gpc, the lower the solubility of gas in blood, the faster its partial pressure in blood will increase=the faster its rate of induction

Question 9

Alveolar Anaesthetic Partial Pressure or Concentration

Answer 9

-increased concentration of gas inspired = increased alveolar partial pressure = promotes transfer of gas into blood = increasing partial pressure of gas = increasing rate of induction

Question 10

Pulmonary Ventilation

Answer 10

increased ventilation = increase in alveolar pp = increased arterial pp

*this effect is more important in anaesthetics with high blood solubility vs those with lower blood solubility

Question 11

Pulmonary Blood Flow

Answer 11

• increased pulmonary blood flow results in exposure of more blood to anaesthetic = arterial pp rises more slowly
• decreased flow increases extraction of anaesthetic into blood from lungs

Question 12

Elimination of Anaesthetics

Answer 12

• recovery is dependant on rate of elimination from brain
• anaesthetics that are relatively insoluble in blood and brain are eliminated more rapidly than are more soluble anaesthetics
• clearance occurs primarily via the lungs