Anesthetic drugs 2 Flashcards
(29 cards)
What is the use of anesthetic drugs?
to induce &/or maintain general anesthesia (state of complete unconsciousness)
Can general anesthesia be interrupted?
cannot be interrupted by stimulation
Injectable anesthetics
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
Barbiturates
• MOA
• admin
• Precautions
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?
Clinical use of Barbiturates in Small animal vs Large animal
Small
- induce general anesthesia
- Titration effect
Large
- Used in combo w/ guaiacolate
Ultrashort acting Barbiturates
Thiopental
- Induce anesthesia * * redistributes away from brain quickly! But not quickly metabolized
- lasts 2-3 minutes in brain
- -> redistributed to muscles & fats
Propofol
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
Precaution of Propofol
Hypotension & Respiratory depression
- Apnea (especially horse)
- NO analgesia
- Lipid metabolism disorders can be aggravated
Etomidate
non-barbituate
• Induce & maintain anesthesia
• Bradycardia
• Hypotension
• PVCs
• Bradypnea to apnea
• IV hemolysis
(propylene glycol = high osmolarity)Non-barbiturate drugs
- Propofol
- Etomidate
- Chloral hydrate
Dissociative drugs
Controlled substances
- Ketamine (Cats/primates)
- Tiletamine
- P seems to be dissociated from environment
- Analgesia & light unconsciousness, but reflexes maintained
MOA
- NMDA receptor antagonist
Precautions of dissociative drugs
• ↑ 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)
Inhalation anesthesia
Major elimination route = Respiratory tract
-All depress cardiopulmonary function in a Dose-dependent manner
- Methoxyflurane
- Halothane
- Isoflurane
- Sevoflurane
- Nitrous oxide
What is MAC
Minimal alveolar conc of anesthesia @ which 50% of P population will not respond to painful stimuli
What is Second gas effect?
Nitrous oxide (low solubility) is used to facilitate rate of induction & change of anesthetic doth in combo with 1° anesthetic (halothane / servoflurane)
What is a rxn to inhalation anesthetics in swine?
Malignant hyperthermia
- life threatening myopathy due to hyper metabolic rxn in skeletal muscles
What affects the potency of an inhalant anesthetic?
- 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
Methoxyflurane
• High blood/gas solubility
Halothane
• Rapid induction & recovery
- low enough blood/gas solubility
• highly volatile
- requires precision vaporizer
Isoflurane
• Low blood/gas solubility
- rapid induction & recovery
• gold standard in inhalant anesthesia
Sevoflurane
• Smaller safety margin than isoflurane
• Cannot be used for extended periods
- dose & time dependent nephrotox
Nitrous Oxide
Used for 2nd gas effect
Clinical use of Inhalants
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
What risks are assoc’d with inhalant anesthetic in the air?
- Headache to personnel
* Risk of fetal anomaly
