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Surgery & Anaesthesia - NSULA Vet Tech Program Spring 2016 > General Anesthesia I > Flashcards

General Anesthesia I Flashcards

1
Q

Define general anesthesia.

A

controlled and reversible lack of consciousness, lack of pain sensation, lack of memory, depressed reflexes

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2
Q

What are the four anesthetic procedure phases?

A

pre-anesthesia, induction, maintenance, recovery

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3
Q

Define induction.

A

animal leaves normal state of consciousness and enters the anesthetized state

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4
Q

What are two routes of anesthetic induction?

A

injectable - often followed by gas for maintenance

inhalation - face mask, induction chambers, intubation

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5
Q

Define maintenance.

A

stable level of anesthetic depth, stage during which the surgical procedure is performed

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6
Q

Define recovery.

A

when concentration of anesthetic in the brain begins to decrease

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7
Q

How are injectable anesthetics excreted by the body?

A

most metabolized by the liver and excreted by the kidneys, but there are exceptions

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8
Q

How are inhalent anesthetics excreted by the body?

A

most commonly used agents are eliminated by the respiratory tract, some older agents have variable amounts of liver metabolism

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9
Q

What is the most important factor in anesthetic safety?

A

monitor

there is no substitute for using your senses

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10
Q

What are the classic stages and planes of anesthesia?

A 
Stage I - beginning of induction
Stage II - excitement phase
Stage III - 
Plane 1 - can intubate at this point
Plane 2 - heart rate, breathing rate steady
Plane 3 - 8 breaths per minute or less, 
Plane 4 - dying
Stage IV
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11
Q

Define endotracheal intubation.

A

placement of breathing tube in airway, which minimizes dead space, decreases risk of aspiration, allows direct delivery of oxygen o assist respiration, more efficient delivery with less waste gas

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12
Q

What patients are most at risk for aspiration?

A

oral surgery/dentistry, unfasted patients

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13
Q

What are the risks of endotracheal intubation?

A
  • stimulates parasympathetic nervous system
  • brachycephalic breeds
  • laryngospasm, especially cats
  • species problems -> blind intubation
  • tube too far in, past tracheal bifurcation
  • increased dead space - trim length of tube
  • cuff inflation - too much -> pressure necrosis/occlusion of tube lumen
  • tube obstruction
  • loss of tube into airway during recovery
  • infection transfer -> disinfect between patients
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14
Q

What brachycephalic traits cause anesthetic risks?

A

stenotic nares
elongated soft palate
everted pharyngeal ventricles

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15
Q

Which dog breed has the highest anesthetic risk?

A

English bulldog

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16
Q

What is the inhalation anesthesia mechanism of action?

A

gas anesthesia within the brain is poorly understood

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17
Q

What is the distribution/elimination route of inhalation anesthesia?

A

liquid anesthesia -> vaporized into oxygen -> air passages -> alveoli -> bloodstream -> brain

18
Q

What is the distribution/elimination of inhalation anesthesia control mechanism?

A

concentration gradient from alveoli -> bloodstream

lipid solubility -> agents leave bloodstream -> brain

19
Q

What does inhalation anesthetic maintainance require?

A

requires that enough gas be delivered to alveoli to maintain concentrations in blood and brain

20
Q

inhalation anesthetic recovery

A

reduce flow to alveoli -> concentration gradient now favors flow to alveoli from bloodstream and then from brain to bloodstream

running 100% oxygen during recovery will speed process

21
Q

inhalation anesthetic agent vapor pressure

A

measure of the amount of liquid that will evaporate at 20 C

22
Q

high vapor pressure

A

volatile - vaporizes easily
need precision vaporizers wth a maximum delivery of 5-8% depending on the agent used

examples - sevoflurane, isoflurane, halothane > 30%

23
Q

blood to gas solubility coefficient

A

also known as partition coefficient - measure of distribution of age between blood and gas phases of the body

24
Q

low solubility coefficent

A

tends to remain in gas phase in lungs rather then dissolving into tissues and blood, steep concentration gradient, rapid induction/recovery

ex. isoflurane, sevoflurane

25
Q

high solubility coefficient

A

“sponge effect” - slow induction and recovery

26
Q

endotracheal intubation materials

A

3 tubes in size range with cuffs checked for leaks

  • stylet for small tubes
  • lubricant (water soluable)
  • lidocane/cotton tipped applicators
  • oral speculum
  • laryngoscope
  • 2-3 gauze sponges
  • roll gauze cut to length appropriate to tie in place
  • syringe to inflate cuff
  • eye ointment
  • gas machine checked and ready to attach to trach tube
27
Q

Minimum Alveolar Concentration (MAC)

A

Lowest concentration that produces no response in 50% of patients exposed to a painful stimulus.
A measure of strength or potency of an agent
Low MAC value = more potent than a high MAC value

28
Q

Factors Influencing Absorption & Elimination

A

concentration, ventilation, diffusion, pulmonary blood flow, tissue absorption, lipid content of tissues

29
Q

concentration

A

Greater the concentration, the greater the pressure gradient -> more rapidly anesthetic will diffuse across alveoli

30
Q

ventilation

A

Increased rate/depth will aid in moving more anesthetic vapor across the alveoli

31
Q

diffusion

A

Is a physical process determined by:
The agent’s solubility coefficient
The molecular weight of the gas
The pressure gradient from the alveoli and plasma

32
Q

pulmonary blood flow

A

The more blood exposed to the anesthetic gas, the more molecules will move into the blood

33
Q

tissue absorption

A

Highly perfused tissues receive and absorb most of the gas taken up by the alveoli (brain, heart, lungs, liver, kidneys, intestine, endocrine glands)

34
Q

lipid content of tissues

A

Lipid-rich cells take up more of an anesthetic than lipid-poor cells
Brain highly lipid-rich

35
Q

halogenated organic compounds

A 
Modern common inhalation agents
Isoflurane – most common
Sevoflurane - common
Halothane – not used today
Methoxyflurane – not used today
Enflurane – little use vet med
Desflurane – little use vet med
36
Q

Isoflurane

A 
Good margin of safety
High vapor pressure
Low solubility coefficient
Rapid induction/recovery
High MAC value (low potency)
Stable at room temp with no preservative
Fewest adverse effects on heart, lungs, etc.
Eliminated by lungs
No post-operative analgesia provided
37
Q

sevoflurane

A

Rapid induction/recovery (faster than isoflurane)
Best agent for mask/chamber inductions (use 6-8%)
Also good agent for C-sections
Rapid/quiet recovery in horses
Some myocardial depression and vasodilation
Sensitizes myocardium to catecholemine-induced arrhythmias
Causes some respiratory depression
Depresses temperature regulation
Avoid in patients susceptible to malignant hyperthermia
No analgesic effect in recovery period

38
Q

halothane

A 
Introduced in 1956, use dwindling today
Up to 20% eliminated by liver metabolism
Mixed with preservative thymol
Sensitizes heart to catecholemines (i.e. epinephrine)
Some myocardial depression/vasodilation
Increases intracranial pressure 
Avoid in head trauma patients
Associated with malignant hyperthermia
Increased temp, muscle rigidity, cardiac arrhythmias, may die
39
Q

Methoxyflurane

A

Introduced in 1959, not available today
Low vapor pressure (use in non-precision vaporizer)
Slow induction/recovery
Low MAC (most potent of class)
Considerable solubility in rubber/plastics

40
Q

enflurane

A

Used in human medicine
Rapid induction/recovery
Profound respiratory depression, with mechanical ventilation generally required
In dog, may produce seizure-like muscle spasms

41
Q

Desflurane

A 
Little use in veterinary medicine
Lowest solubility coefficient
Therefore, most rapid induction/recovery
Extremely volatile (high vapor pressure)
Requires special high-cost vaporizer
42
Q

Nitrous Oxide

A

Little used in vet med today
Stored in blue cylinders as compressed gas
Administered via flowmeter, like oxygen
Mixed with oxygen at concentrations of 33-67%
Was used to speed induction and recovery, and provide additional analgesia
Because newer agents have rapid induction/recovery, not used much today except in human dentistry

Surgery & Anaesthesia - NSULA Vet Tech Program Spring 2016 (27 decks)

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