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Pharm Test 3 > Small Animal Anesthesia > Flashcards

Small Animal Anesthesia Flashcards

1
Q

4 phases of general anesthesia. what are they, and which are desired?

A
  1. induction
  2. excitement
  3. surgical plane/ maintenance
  4. overdose

> only 2 are desired!

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2
Q

what happens during the induction phase of general anesthesia?

A

¡ Administration of induction anesthetic agent and loss of consciousness

¡ Goes from sedation/analgesia with awareness from premedication agents to amnesia and unconsciousness
> Hearing remains initially
> Lose hearing and consciousness with some muscle relaxation

¡ Patient is endotracheally intubated in this stage
> Once appropriate signs achieved
> ET tube for airway protection, ventilation and maintenance delivery

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3
Q

what is the excitement phase of general anesthesia? what happens? what will we see?

A

a potential phase that we want to avoid

¡ Loss of consciousness but marked excitement occurs
> Rough induction, resistance, unable to intubate

¡ Will see vomiting, dilated pupil, tachycardia, irregular respiration, spastic movements, not deep enough

¡ Vomiting potential and with unprotected airway could result in
significant consequences

¡ Not as common with newer induction agents and previous sedation
> With proper dosing and sedation

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4
Q

what factors can contribute to creating a bad excitement phase?

A

¡ Inhalant induction (mask/tank)
¡ Barbiturates induction
¡ Inadequate dosing or poor sedation/excited animal
¡ Loud environment

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5
Q

what occurs during the maintenance or surgical anesthesia phase?

A
  • patient is unconscious
    -muscle relaxation present
    -periodic ocular rotation for the species
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6
Q

what are the 3 levels of depth of the maintenance phase of anesthesia?

A

light, medium, deep

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7
Q

what is the overdose phase of anesthesia? what occurs?

A

too deep

-significant hypoventilation to apnea
-significant reduction in CV function
>progress to arrest if not corrected
=> greater potential in critical ASA 4-5 patients

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8
Q

how can we avoid the overdose stage?

A

monitoring and patient stabilization

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9
Q

what will offset the decrease in resp and heart rate during the maintenance phase of anesthesia?

A

surgery

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10
Q

what is the response to surgery over the course of the 4 phases of anesthesia?

A

induction: +++

excitement : moving/rigid

maintenance:
>light +/-
>medium -
>deep -

overdose: N/A, ventilatory and cardiac arrest

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11
Q

what is the jaw tone over the course of the 4 phases of anesthesia?

A

induction: +

excitement : +++

maintenance:
>light +
>medium -
>deep -

overdose: N/A, ventilatory and cardiac arrest

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12
Q

what is the palpebral reflex over the course of the 4 phases of anesthesia?

A

induction: +

excitement : ++

maintenance:
>light +
>medium -
>deep -no eyelid tone; eye more central and dilated

overdose: N/A, ventilatory and cardiac arrest

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13
Q

???????what is the eye position over the course of the 4 phases of anesthesia????? not sure about this one

A

induction: central/up to ventromedial

excitement : nystagmus

maintenance:
>light: medial
>medium: lateral
>deep: central, big pupil

overdose: N/A, ventilatory and cardiac arrest

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14
Q

what is the RR and HR over the course of the 4 phases of anesthesia?

A

induction: depends on pre-med and induction agent

excitement : up

maintenance:
>light: -
>medium: - -
>deep: - - -; slow, shallow to apnea, decreased BP too

overdose: N/A, ventilatory and cardiac arrest

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15
Q

why should we fast small animals for anesthesia?

A

Most anesthetics reduce tone of Lower Esophageal Sphincter
>gastro-esoph-reflux (GER)

don’t want aspiration pneumonia, which has a high mortality rate

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16
Q

what factors impact gastro-esoph-reflux (GER)?

A

age - older increases GER
abdominal surgeries increase GER

> patient positioning in dorsal or lateral does not

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17
Q

fasting guidelines for small animal anesthesia

A

general guideline is 8 hours in dogs and cats

-food 6-12 hours
-water 0-2 hours (more important for big dogs who may try to gorge on water)

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18
Q

what happens if an animal is fasted for too long before anesthesia?

A

¡ Increase incidence of reflux and acidity has been shown in dogs

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19
Q

fasting guidelines for neonates/pediatric

A

<12 weeks old do not take away food > 1-2 hrs

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20
Q

fasting guidelines for toy breeds

A

< 2 kg do not take away food >3-4 hours
* Even if adult age

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21
Q

pre-anesthetic conditions requiring stabilization

A

-Significant dehydration (>5%)
-Blood loss
-Acidemia - pH < 7.2
-Hypokalemia (<2.5 mmol/L)
-Hyperkalemia (>6 mmol/L)
-Significant pleural disease
-Oliguria;anuria
-Congestive heart failure, Arrhythmias
-Seizures, High ICP
-Diabetes, Hyper/Hypothyroidism, Hypo/hyper Adrenocorticism

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22
Q

why should we stabilize a patient before anesthetic if they have certain conditions?

A

-required to reduce chance of arrest or significant morbidity
* Fluids, blood work, correction of electrolytes, medications

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23
Q

ways we can monitor a patient as they are stabilizing pre-anesthetic

A
  • CRT, HR, BP, bloodwork
  • correct deficits as much as possible
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24
Q

what can we do that will impact the initial dose of injectable anesthetic required?

A

Level of sedation achieved with pre-medication
>leads to injectable dose reduction

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25
Q

what drugs can reduce injectable anesthetic dose required and by how much?

A
  • Alpha2-agonists – 60-75%
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26
Q

what drugs can reduce inhalant anesthetic dose required and by how much?

A

(MAC reduction)

  • Alpha2-agonists – 50%
  • Acepromazine – 20-30%
  • Pure-MU opioid agonists – 50%
    > Butorphanol – 0-8% ; Buprenorphine – 9%
  • Ketamine (IM or CRI) – 25%
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27
Q

5 main induction agent categories for SA

A
  1. Propofol
  2. Alfaxalone
  3. Ketamine:Benzodiazepine
    ¡ Midazolam or diazepam
  4. Mask/Tank Inhalant
  5. Opioid and Benzodiazepine
    ¡ In very critical cases
    > ASA 4-5
    ¡ Will not work in healthy patient

¡ Barbiturates - not as common now
¡ Etomidate; Telazol - not available in Canada

28
Q

propofol advantages as induction agent

A

¡Sedation achieved at low doses

¡Titration to effect possible**
> Excitement phase not as common due to this advantage

¡Rapid onset /short duration

¡ decreased CMRO2 (cerebral metabolic oxygen consumption)
>can be used to treat seizures

¡Can be given as constant rate infusion (CRI) – TIVA
>to maintain general anesthesia

¡Non-irritant if injected perivascular

¡Cardio-respiratory effects minimized with clinical doses in stabilized patients

¡Can be used in liver disease patients
¡Can be used in neonates
>Propofol clearance exceeds hepatic blood flow

¡Can be used in renal disease patients

¡Can be used in C-section cases

29
Q

propofol disadvantages as induction agent

A

¡ Potential negative CV effects of lowered BP, HR and cardiac output in unstabilized or very critical patients

¡ Apnea, reduced minute ventilation and PaO2
>with high doses and rapid admin
>when oxygen not available

¡ Paddling and rigidity can be seen with induction
>cholinergic effect

¡ Heinz body formation with repeated daily use in cats

¡ Pain, irritating with injection

¡ Large volumes required in larger animals

¡ Have to discard/waste unused volumes after 6 hours

30
Q

Ketamine & Diazepam or Midazolam Advantages as induction agent

A

¡Titration to effect is possible
>not as fast acting as propofol or alfaxalone

¡Lowered doses can be used for sedative effect

¡Sympathomimetic effects of ketamine (in some cases)
> Which maintains or increases HR, BP and CO

31
Q

Ketamine & Diazepam or Midazolam Disadvantages as an induction agent

A

¡ Sympathomimetic effects of ketamine
>Possible increase in HR may not be ideal in cases already tachycardic or with certain cardiac diseases

¡ Salivation potential

¡ Increases CMRO2 (cerebral metabolic oxygen consumption)

¡ A sick patient without remaining sympathetic stores will have
myocardial depression and reduced CO from the ketamine
>Noted in sick compromised animals – not healthy

¡ Both Ketamine and Benzodiazepines are scheduled drugs

32
Q

Alfaxalone Advantages as an induction agent

A

¡Titration to effect is possible IV
>Similar to propofol – large advantage

¡Rapid onset /Short duration

¡Cardio-respiratory effects minimized with clinical doses in stabilized patients

¡Non-irritant if injected perivascular

¡Can be administered IM

¡No significant effects on hepatic or renal function
>Used in patients with disease – less information

¡Can be used in C-section cases

¡(Minimal information on CMRO2)

¡Can be given as constant rate infusion (CRI) – TIVA
>To maintain general anesthesia
>Still optimal recovery times

33
Q

Alfaxalone Disadvantages as an induction agent

A

¡Excitement in recovery without premedication

¡Potential negative CV effects of lowered BP, HR and cardiac output
>Unstabilized or very critical patients

¡Apnea, reduced minute ventilation and PaO2
> With high doses and rapid administration
> When oxygen not available

34
Q

what are do-induction agents and what are the most common ones?? what are they used with? what do they do?

A

-Used with propofol, or alfaxalone
>Benzodiazepines most common (Midazolam or Diazepam)
>lidocaine or ketamine can also be used

¡ Goal is to reduce dose and volume of and potentially the negative cardiorespiratory effects of propofol and or alfaxalone
¡ Co-induction does smooth the induction process allowing ET intubation
> Minimize cough
¡ Promotes smooth transition from stage 1-3 GA

35
Q

when do we administer a co-induction agent?

A

Given right before or after initial IV bolus of primary induction agent (propofol, alfaxalone)

36
Q

why is pre-medication recommended even if face mask is used for unduction

A

smoothes process of induction
reduces stress
Reduce duration of phase 2 excitement

37
Q

Isoflurane and Sevoflurane for Induction - advantages

A

÷Administered with oxygen through mask or in tank
÷Pre-oxygenation…..
÷IV access not required (??)

§ Minimal metabolism by liver or kidneys

38
Q

Isoflurane and Sevoflurane for Induction - disadvantages

A

§ Dose rises quickly
§ Titration to effect NOT possible
§ Stressful and with Excitement phase
§ No IV access
§ No airway support or protection as go through excitement phase
§ Require the use of costly anesthetic machine, vaporizer, breathing system
§ Must have equipment knowledge to be able to use safely
* Health and Safety of Staff
* Scavenging required to prevent pollution

§ Dose dependent cardiovascular and respiratory depression
÷ Significant
÷Requires careful monitoring during induction***

39
Q

Induction Agents for the Very Sick Patient? why?

A

Opioid /Benzodiazepine Combinations

  • On their own to enable ET intubation
  • Most Cardiovascular Sparing in Compromised Dog

÷Will not work in healthy dog or cat
÷Does not allow for ET intubation even in critical CATS

40
Q

Opioid /Benzodiazepine Combinations as induction agent drawback for critical cats

A

÷Does not allow for ET intubation even in critical CATS

41
Q

eye position, jaw tone, resp signs after using Opioid /Benzodiazepine Combinations for induction

A

÷Eye does not rotate ventrally; more jaw tone; animal panting

42
Q

Thiopental - what kind of drug is this

A

barbiturate

43
Q

thiopental advantages for induction

A

cheap, short onset

44
Q

thiopental disadvantages for induction

A

¡–ve CV effects-reduced BP, CO, arrhythmias likely
> Bigeminal rhythm – normal complex, then PVC
¡Respiratory effects-apnea, hypoventilation
¡Excitement on induction possible
¡ Irritating if given perivascular = tissue slough
¡Scheduled - records required
¡Currently low availability
¡Prolonged recovery if repeated doses
¡Prolonged recovery in sight hounds

45
Q

cardiovascular effects of propofol (HR, CO, contractility, SVR, BP, arythmia potential)

A

HR: +/-down
CO: down
contractility: down
SVR: very down
BP: very down
Arythmia potential: +

46
Q

cardiovascular effects of barbiturate (HR, CO, contractility, SVR, BP, arythmia potential)

A

HR: +/- up
CO: down
contractility: very down
SVR: NC +/- down
BP: down
Arythmia potential: ++++

watch those arythmias!!!

47
Q

cardiovascular effects of alfaxalone (HR, CO, contractility, SVR, BP, arythmia potential)

A

HR: NC or up
CO: down
contractility: down
SVR: down
BP: down
Arythmia potential: +

48
Q

cardiovascular effects of ketamine and diazepam or midazolam (HR, CO, contractility, SVR, BP, arythmia potential)

A

HR: very up
CO: up, NC, or down (related to symp. tone)
contractility: up, NC, or down (related to symp. tone)
SVR: NC
BP: NC or up, can go down in sick
Arythmia potential: ++ mostly if high rate produced

49
Q

cardiovascular effects of inhalant inductors (HR, CO, contractility, SVR, BP, arythmia potential)

A

HR: NC +/- down
CO: super down
contractility: super down
SVR: very down
BP: super down
Arythmia potential: less with iso or sevo, compared to older drugs

50
Q

respiratory effects of propofol (RR, TV, incidence of apnea, ventilatory pattern)

A

RR: down
TV: down
incidence of apnea: ++
ventilatory pattern: apnea with fast injection

51
Q

respiratory effects of barbiturates (RR, TV, incidence of apnea, ventilatory pattern)

A

RR: super down
TV: down
incidence of apnea: ++
ventilatory pattern: apnea with fast injection

52
Q

respiratory effects of alfaxalon (RR, TV, incidence of apnea, ventilatory pattern)

A

RR: down
TV: down
incidence of apnea: ++
ventilatory pattern: apnea with fast injection

53
Q

respiratory effects of ketamine/BZD (RR, TV, incidence of apnea, ventilatory pattern)

A

RR: NC or down
TV: NC
incidence of apnea: +
ventilatory pattern: apneustic, irregular

54
Q

respiratory effects of inhalant induction (RR, TV, incidence of apnea, ventilatory pattern)

A

RR: super down with high depth apnea
TV: very down
incidence of apnea: ++ increased depth causes apnea which is protective
ventilatory pattern: shallow and poor with increasing depth

55
Q

steps of induction process

A
  1. Assess Sedation level; Attain IV access; Equipment prepared
  2. Assess cardiorespiratory status
    *HR, RR, MM colour
    *Critical cases- additional monitors also attached (ECG, BP)
    *Decide if pre-oxygenation indicated
  3. Give appropriate initial first “bolus” volume (mls) of injectable anesthetic agent
    *Each drug has a dose range with general guidelines
    *Assess depth level to proceed to ET intubation
  4. Give appropriate additional incremental IV boluses to intubate, perform ET cuff inflation, transfer to inhalant/maintenance anesthesia and permit positioning
56
Q

sign required for endotrancheal intubatoin

A

¡ Relaxation & lowering of head
¡ Eye rotation
¡ Loss of lateral palpebral
¡ Relaxed jaw tone
¡ No tongue movement
¡ No response to handler
¡ No response to laryngoscope placement

57
Q

Assessing Proper Placement of Endotracheal Tube

A

-Direct Visualization as you intubate
-See condensation, or feel breath at end of ET tube
-See anesthetic bag movement
>Once attached to circuit
-When you ‘bag’ or breathe for animal
>Chest moves
-Can perform ET cuff inflation
>If you cannot get a seal and still hear air leakage – you are in the esophagus not trachea

58
Q

considerations for tubing felines

A

Oral cavity -Overall Small Size
¡ Less ability to open mouth
¡ Tongue and tissue very Friable – be gentle

Larynx is Sensitive – prone to Laryngospasm
¡ Use laryngoscope - DO NOT touch epiglottis
¡ Lidocaine spray used before attempt

59
Q

advantages to isofluoranve and sevofluorane for maintenance phase

A
  • Added patient safety
    > Administered with oxygen through endotracheal tube (ET)
    > May be delivered with mask (but less safe)
  • Act rapidly
    > Quick changes of anesthetic depth and recovery
  • Minimal metabolism by liver or kidneys
  • Produce less cardiac arrhythmias compared to older inhalants
60
Q

disadvantages to isofluoranve and sevofluorane for maintenance phase

A

¡Require the use of costly anesthetic machine, vaporizer, breathing system and ET tubes
÷Must have equipment knowledge to be able to use safely

¡Health and Safety of Staff
÷Scavenging required to prevent pollution

¡Dose dependent cardiovascular and respiratory depression
÷Significant
÷Requires careful monitoring ***

61
Q

Factors Affecting MAC

A

¡ MAC determined in healthy with controlled conditions but…. This is NOT the clinical situation

Isoflurane and Sevoflurane decrease MAC Level with:
¡ Pre-medication, intravenous agents, analgesics
¡ High PaCO2 ( if poor ventilation and >90mmHg under GA)

¡ Increasing age – geriatric
¡ Hypothermia
¡ Pregnancy
¡ Concurrent illness

61
Q

Factors Affecting MAC

A

¡ MAC determined in healthy with controlled conditions but…. This is NOT the clinical situation

Isoflurane and Sevoflurane decrease MAC Level with:
¡ Pre-medication, intravenous agents, analgesics
¡ High PaCO2 ( if poor ventilation and >90mmHg under GA)

¡ Increasing age – geriatric
¡ Hypothermia
¡ Pregnancy
¡ Concurrent illness

62
Q

how do we prepare for the recovery phase?

A

¡ Want quiet, smooth and slow recovery

¡ Prepare for it:
>Do not necessarily turn the animal off anesthetic or wean them down when closing skin
>Keep them at an appropriate depth even with closing

¡ Assess last analgesia given
> Top up dose of opioid; NSAID potential

¡ Decide based on personality of patient if sedatives required
¡ Check airway
¡ Prepare anesthetic machine

63
Q

indications for extubation in the dog

A

STRONG medial palpebral & swallow reflex indicate patient ready to extubate

¡ May also see dogs stretch move legs or head

¡ Return of swallow important if you have seen gastro-esophageal reflux
> Or have not seen!

¡ Blowing/yelling in ear; flipping the dog not necessary

Brachycephalic dogs have different criteria for extubation:
¡ Need to be more awake and holding head up especially in cases with extreme upper airway noise

64
Q

indications for feline extubation

A

Extubate when a medial palpebral reflex present
§ Look also for ear flick, whisker reflex, tongue curl
§ Extubate earlier than return of swallow reflex, or movement to prevent laryngospasm at recovery
§ Look also for ear flick, whisker reflex

Pharm Test 3 (16 decks)

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