CNS - anesthetics

Question 1

What are the four stages of anesthesia

Answer 1

1. Analgesia
2. Disinhibition
3. Surgical anesthesia
4. Medullary Depression

Question 2

Name five factors that increase the speed of anesthesia induction.

Answer 2

1. Solubility (low blood:gas partition coefficient)
2. High partial pressure of inspired gas
3. High ventilation rate
4. High pulmonary blood flow
5. Arteriovenus concentration gradient

Question 3

How is the potency of anesthetics measured?

Answer 3

• minimum alveolar anesthetic concentration (MAC)

alveolar concentration required to eliminate painful stimulus in 50% of patients

Question 4

What is the CNS effects of inhaled anesthetics?(2)

Answer 4

• Decrease brain metabolic rate

- increase cerebral blood flow (OBS high ICP)

Question 5

What is the cardiovascular effects of inhaled anesthetics? (2)

Answer 5

• Decrease BP moderately

- Decrease liver and kidney blood flow

Question 6

What is the respiratory effects of inhaled anesthetics? (2)

Answer 6

• Decrease in tidal volume and minute ventilation
  (OBS CO2 retention!)
• Bronchodilation ( Desflurane may give spasm)

Question 7

Desflurane
Enflurane
Halothane
Isoflurane
Sevoflurane
Nitrous Oxide

1. Mehcanism?
2. Effects (4)?
3. Adverse effects?

Answer 7

1. GABA mediated inhibition
   block brain NMDA and Ach-N receptors
2. Less CO (Halothane/Enflurane)
   Lung irritant (Desflurane)
   vasodilation
   Decrease resp. function

Question 8

Thiopental
Thioamylal
Methohexital

1. Mehcanism?
2. Effects?(2)
3. Adverse effects?

Answer 8

1. Barbituates - GABA mediated inhibition
2. Circulatory and respiratory depression
   decrease ICP

High lipid solubility

Question 9

Midazolam

1. Mehcanism?
2. Effects?
3. Adverse effects?

Answer 9

1. Benzodiazepine
2. less cardio/resp depressant than barbituates

Slower onset, longer duration than Barbituates

Question 10

Ketamine

1. Mehcanism?
2. Effects? (2)
3. Adverse effects?

Answer 10

1. Blocks NMDA receptors for Glutamate
2. Analgesia, amnesia, catatonia
   with retained consciousness
   Cardiovascular stimulation

Increase ICP

Question 11

Etomidate (imidazole)

1. Mehcanism?
2. Effects? (2)

Answer 11

1. ?
2. Minimal CV/resp effect
   No analgesia

short duration

Question 12

Fentanyl
Alfentanil
Remifentanil
Morphine

1. Mehcanism?
2. Effects? (2)

Answer 12

1. binds kappa, my, and delta receptors

2. analgesia, resp depression

Question 13

Propofol
Fosfpropofol

1. Mehcanism?
2. Effects? (2)

Answer 13

1. Uncertain
2. Vasodilation and hypotension
   Negative inotropy

Fast onset and recovery (inactivation)

Fospropofol is water soluble

Question 14

What is the mechanism of local anesthetics?

Answer 14

• Binding of Na+ channels from inside the cell.
  (Fat soluble acts faster, but have shorter duration)
• Rapidly firing channels are prefered.
  (Pain sensation is selected)

Question 15

What are the adverse effects of local anesthetics? (5)

Answer 15

• CNS effects (i.e convulsions)
• vasodiltaion (not cocaine)
• (heart block if preexisting CV disease)
• Methhemoglobeinemia (Prilocaine)
• antibody formation (ester types)

Question 16

Articaine
Bupivacaine
Levobupivacaine
Lidocaine
Mepivacaine
Prilocaine
Ropivacaine

What kind of drugs?
How are they metabolised?

Answer 16

Local anesthetics - amides

P450 metabolism

Question 17

Benzocaine
Cocaine
Procaine
Teracaine

What kind of drugs?
How are they metabolised?

Answer 17

• Local anesthetics - esters
• Rapid metabolism via plasma esterases
  short half lives

Question 18

Which amide local anesthetisc have the shortest half-lives? (2)

Which one has the fastest action?

Answer 18

• Lidocaine, Prilocaine

- fastest: Articaine