Inhalant Anesthetics Flashcards
What is a good rule of thumb when it comes to inhalant anesthetics?
The lower the anesthetic vaporizer percent the fewer adverse effects
What factors affect the uptake of inhalant anesthetics into the bloodstream?
- Concentration of inhaled gas
- Degree of alveolar ventilation
- Cardiac Output
- Abnormal Alveoli
- Solubility in the blood
What factors are in your control that affect the uptake of inhalant anesthetics in the system?
- Concentration of inhaled gas -by controlling the vaporizer settings
- Degree of alveolar ventilation - by giving breaths using the rebreathing bag
Explain how the degree of alveolar ventilation affects anesthesia?
Shallow breathing reduces the amount of fresh gas mixture the patient is receiving therefore making them in a lighter plane of anesthesia
Explain how cardiac output affects anesthesia
The faster the cardiac ouput causes a decrease in anesthetic absorption in the bloodstream. This is why when an animal is super worked up and is being masked down it take them longer to go down because there blood is pumping so fast it doesn’t absorb the gas anesthetic molecules as quickly.
Explain why you should never anesthetize an animal with abnormal lungs?
Abnormal Alveoli - Fluid &/or inflammation can negatively affect the anesthetic absorption rate which is why you should never anesthetize an animal with abnormal lungs
Explain solubility in the blood
The gas anesthesia molecules must be absorbed into the bloodstream & then the bloodstream is what takes the gas anesthesia molecules to the brain. Anesthetic mixes with the blood at different degrees called solubility: High solubility & Low solubility
Explain High Solubility
This means that the gas anesthetic molecules have a high absorbable rate therefore more gas anesthesia molecules are needed to get the animal to a moderate plane of anesthesia. This can so affect how quickly you can change there plane of anesthesia.
Explain low solubility in the blood
Limited to no absorption within the blood therefore the blood is releasing it right away & taking it directly to the central nervous system.
This also effects how quickly you can change there plane of anesthesia - example if a patient is getting to deep under anesthesia it will take much less time to see the effects of them going into a lighter plane of anesthesia when you adjust the vaporizer. This is because the molecules are not being absorbed by the blood stream.
Gas partition coefficient refers to?
Refers to how the anesthetic mixes with the blood and how quickly it goes to the central nervous system
What are the common gas anesthetics used in vet med?
- Methoxyflurane
- Halothane
- Isoflurane
- Sevoflurane
- Nitrous Oxide
Which gas anesthetics has the highest solubility?
Methoxyflurane
What is the 2nd most soluble gas anesthestic?
Halothane
What is the least soluble gas anesthetic?
Nitrous Oxide - Not widely used in Vet Med. Next would be Sevoflurane than Isoflurane.
List the gas anesthetics from least soluble to most soluble
- Nitrous Oxide
- Sevoflurane
- Isoflurane
- Halothane
- Methoxyflurane
Minimum Alveolar Concentration (MAC)
Defined as the lowest concentration of an anesthetic agent that produces no painful response to painful stimuli in 50% of anesthetized patients.
This indicates the potency of the anesthetic gas.
Halothane Effects.
2nd most soluble.
Provides:
Moderate Analgesia
Moderate Muscle Relaxation
Possible cardiovascular & respiratory depression
Halothane liver metabolism percentage
20%
Is Halothane rubber soluble?
Yes
Halothane induction percentage
2-3%
Halothane maintenance percentage
1.25-2%
Methoxyflurane effects
Good Analgesia
Good Muscle Relaxation
Possible Cardiovascular & Respiratory depression
Methoxyflurane liver metabolism percentage
50%
Methoxyflurane induction percentage
2-3%
Methoxyflurane maintenance percentage
0.2 - 1%
Isoflurane effects
Moderate Analgesia
Moderate Muscle Relaxation
Possible Cardiovascular & Respiratory Depression
Which gas anesthetic is the most popular?
Isoflurane
Isoflurane induction percentage
3 - 4%
Isoflurane maintenance percentage
1.5 - 2%
Sevoflurane effects
Moderate Analgesia
Moderate Muscle Relaxation
Possible cardiovascular & Respiratory Depression
Isoflurane metabolism percentage
1% in the body
Sevoflurane metabolism percentage
3% in the body
Sevoflurane induction percentage
4 - 5%
Sevoflurane is?
The newest inhalant & is less pungent
Sevoflurane maintenance percentage
2.5 - 3.5%
Nitrous Oxide Effects
Mild Anaglesia
No Muscle Relaxation
No Cardiovascular Depression
No Respiratory Depression
No metabolization
Nitrous Oxide administration rate
2x calculated oxygen flow rate
What must you do after nitrous oxide is administered?
Administered oxygen after administration
Minimum Alveolar Concentration (MAC): Nitrous Oxide
188%
Minimum Alveolar Concentration (MAC): Sevoflurane
2.36%
Minimum Alveolar Concentration (MAC): Isoflurane
1.2%
Minimum Alveolar Concentration (MAC): Halothane
0.87%
Minimum Alveolar Concentration (MAC): Methoxyflurane
0.23%
Halothane can be toxic to?
The liver which is why it is not widely used in vet med anymore
Methoxyflurane has excessive metabolization in the?
Liver
Methoxyflurane can be toxic to the?
Kidney which is why it is not widely used in vet med anymore
What are some health hazards of waste anesthetics gases?
- Headache
- Nausea
- Fatigue
- Irritability
- Pruritus
- Abortion
How do you reduce waste anesthetic gas exposure in a veterinary practice?
- Use a scavenging system
- Use tight fitting masks
- Contain fresh gas in induction chamber until it is evacuated
- Perform endotracheal intubation when possible
- Keep the vaporizer turned off until the animal is connected
- Empty the rebreathing bag before disconnecting the animal
- Leave the animal connected after the vaporizer is turned off
- Keep the recovery area well ventilated
- Refill the vaporizers at the end of the day
What are scavenging systems?
- Activated charcoal canister
- Passive Evacuation Scavenging System
- Active Evacuation Scavenging System
Which is the preferred scavenging system?
Passive Evacuation Scavenging System
What is a passive evacuation system
Uses positive pressure in the gas line to drive the gases out of the machine. Must be located adjacent to the outside of the building to have a vent hose connected to the anesthesia machine that goes to ouside of the building
What is an active evacuation?
Has no pressure rather it uses the suction from a vacuum power unit to draw gases from the breathing system. The scavenging system goes through pipes into the ceiling to the vacuum unit which then expels it outside.
This is the type of system Pierce College uses
