Anesthetic drugs 2

Question 1

What is the use of anesthetic drugs?

Answer 1

to induce &/or maintain general anesthesia (state of complete unconsciousness)

Question 2

Can general anesthesia be interrupted?

Answer 2

cannot be interrupted by stimulation

Question 3

Injectable anesthetics

Answer 3

Used for short procedures, but not as a single agents
• Rapid induction
• Not easy to control depth
• Slow recovery
- Lipid soluble
- Redistribution –> Action terminated –> metabolism

Question 4

Barbiturates
• MOA
• admin
• Precautions

Answer 4

MOA 
- Facilitate GABA-binding to receptors 
--> Cl- influx --> hyperpolarization
• controlled substances
• Anesthetic / poor analgesia

• IV Only!
     - necrosis if extravascular
• Small safety margin 
• Profound resp. depression
• Cardiac arrhythmia 
• Don't us alone in Sighthounds
• Stormy recovery?

Question 5

Clinical use of Barbiturates in Small animal vs Large animal

Answer 5

Small

• induce general anesthesia
• Titration effect

Large
- Used in combo w/ guaiacolate

Question 6

Ultrashort acting Barbiturates

Answer 6

Thiopental

 - Induce anesthesia * * redistributes away from brain quickly! But not quickly metabolized 

• • lasts 2-3 minutes in brain
• -> redistributed to muscles & fats

Question 7

Propofol

Answer 7

non-barbiturate
• Enhances GABA effects
• Only IV (emulsion)
• induce & maintain general anesthesia

• Titrated to effect
• Preferred to barbiturates bc rapid metabolism
• Used when endotracheal intubation not suitable

Question 8

Precaution of Propofol

Answer 8

Hypotension & Respiratory depression

• Apnea (especially horse)
• NO analgesia
• Lipid metabolism disorders can be aggravated

Question 9

Etomidate

Answer 9

non-barbituate
• Induce & maintain anesthesia 
• Bradycardia
• Hypotension
• PVCs
• Bradypnea to apnea
• IV hemolysis 
    (propylene glycol = high osmolarity)

Question 10

Non-barbiturate drugs

Answer 10

1. Propofol
2. Etomidate
3. Chloral hydrate

Question 11

Dissociative drugs

Answer 11

Controlled substances

1. Ketamine (Cats/primates)
2. Tiletamine

• P seems to be dissociated from environment
• Analgesia & light unconsciousness, but reflexes maintained

MOA
- NMDA receptor antagonist

Question 12

Precautions of dissociative drugs

Answer 12

• ↑ muscle tone & secretions
• spontaneous muscle movement
• tachycardia
• Slow / stormy recovery in dog
      - slow metabolism 
      - faster & smoother than in cat
          (no metabolism)
• Ketamine = use w/ pre-anesthetic drugs in dogs & horse 
--> prevents cataleptoid anesthesia

• Ketamine
- induces amnesia & nightmares (in humans)

Question 13

Inhalation anesthesia

Answer 13

Major elimination route = Respiratory tract

-All depress cardiopulmonary function in a Dose-dependent manner

1. Methoxyflurane
2. Halothane
3. Isoflurane
4. Sevoflurane
5. Nitrous oxide

Question 14

What is MAC

Answer 14

Minimal alveolar conc of anesthesia @ which 50% of P population will not respond to painful stimuli

Question 15

What is Second gas effect?

Answer 15

Nitrous oxide (low solubility) is used to facilitate rate of induction & change of anesthetic doth in combo with 1° anesthetic (halothane / servoflurane)

Question 16

What is a rxn to inhalation anesthetics in swine?

Answer 16

Malignant hyperthermia

- life threatening myopathy due to hyper metabolic rxn in skeletal muscles

Question 17

What affects the potency of an inhalant anesthetic?

Answer 17

• lower MAC = more potent
• Sx - requires 1.2 -1.35 MAC
• Weakest = Nitrous oxide
• ↑ solubility, slower rates, & ↑ Amt of inhalant is needed to ↑ partial pressure in blood & longer it takes to reach equilibrium & anesthetic depths in the brain

Question 18

Methoxyflurane

Answer 18

• High blood/gas solubility

Question 19

Halothane

Answer 19

• Rapid induction & recovery
- low enough blood/gas solubility
• highly volatile
- requires precision vaporizer

Question 20

Isoflurane

Answer 20

• Low blood/gas solubility
- rapid induction & recovery
• gold standard in inhalant anesthesia

Question 21

Sevoflurane

Answer 21

• Smaller safety margin than isoflurane
• Cannot be used for extended periods
- dose & time dependent nephrotox

Question 22

Nitrous Oxide

Answer 22

Used for 2nd gas effect

Question 23

Clinical use of Inhalants

Answer 23

Used for induction & maintenance of general anesthesia
• Reversible by ventilation
- 1° route for inhalant elimination
• Depth of anesthesia = easily controlled
• Rapid recovery compared to injectable anesthesia

Question 24

What risks are assoc’d with inhalant anesthetic in the air?

Answer 24

• Headache to personnel

* Risk of fetal anomaly

Question 25

Maintenance of general anesthesia w/ inhalant drugs

Answer 25

Conc reduced by pre-meds w/ tranquilizer or opioid & concurrent use of NO

Question 26

Anesthesia of Lagomorphs

Answer 26

• watch for stress, compression of thoracic cavity, upper respiratory, & renal infection
• Do NOT use Telozol
- Risk of renal failure

Question 27

Anesthesia of Guinea pigs

Answer 27

• Watch for
  * stress,
  * obstruction of glottis by food / chewed paper,
  * regurgitation,
  * bronchial secretion during anesthesia

Question 28

Anesthesia of Small rodents

Answer 28

• Irritating agents
–> self mutilation
• Watch for hypothermia

Question 29

Anesthesia of Ferrets

Answer 29

Watch for 
• hypoglycemia 
    - monitor BG
• hypothermia
• hypotension