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Pharm Test 3 > Small Animal Anesthesia > Flashcards

Small Animal Anesthesia Flashcards

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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
what drugs can reduce injectable anesthetic dose required and by how much?
* Alpha2-agonists – 60-75%
26
what drugs can reduce inhalant anesthetic dose required and by how much?
(MAC reduction) * Alpha2-agonists – 50% * Acepromazine – 20-30% * Pure-MU opioid agonists – 50% > Butorphanol – 0-8% ; Buprenorphine – 9% * Ketamine (IM or CRI) – 25%
27
5 main induction agent categories for SA
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
propofol advantages as induction agent
¡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
propofol disadvantages as induction agent
¡ 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
Ketamine & Diazepam or Midazolam Advantages as induction agent
¡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
Ketamine & Diazepam or Midazolam Disadvantages as an induction agent
¡ 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
Alfaxalone Advantages as an induction agent
¡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
Alfaxalone Disadvantages as an induction agent
¡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
what are do-induction agents and what are the most common ones?? what are they used with? what do they do?
-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
when do we administer a co-induction agent?
Given right before or after initial IV bolus of primary induction agent (propofol, alfaxalone)
36
why is pre-medication recommended even if face mask is used for unduction
smoothes process of induction reduces stress Reduce duration of phase 2 excitement
37
Isoflurane and Sevoflurane for Induction - advantages
÷Administered with oxygen through mask or in tank ÷Pre-oxygenation..... ÷IV access not required (??) § Minimal metabolism by liver or kidneys
38
Isoflurane and Sevoflurane for Induction - disadvantages
§ 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
Induction Agents for the Very Sick Patient? why?
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
Opioid /Benzodiazepine Combinations as induction agent drawback for critical cats
÷Does not allow for ET intubation even in critical CATS
41
eye position, jaw tone, resp signs after using Opioid /Benzodiazepine Combinations for induction
÷Eye does not rotate ventrally; more jaw tone; animal panting
42
Thiopental - what kind of drug is this
barbiturate
43
thiopental advantages for induction
cheap, short onset
44
thiopental disadvantages for induction
¡--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
cardiovascular effects of propofol (HR, CO, contractility, SVR, BP, arythmia potential)
HR: +/-down CO: down contractility: down SVR: very down BP: very down Arythmia potential: +
46
cardiovascular effects of barbiturate (HR, CO, contractility, SVR, BP, arythmia potential)
HR: +/- up CO: down contractility: very down SVR: NC +/- down BP: down Arythmia potential: ++++ watch those arythmias!!!
47
cardiovascular effects of alfaxalone (HR, CO, contractility, SVR, BP, arythmia potential)
HR: NC or up CO: down contractility: down SVR: down BP: down Arythmia potential: +
48
cardiovascular effects of ketamine and diazepam or midazolam (HR, CO, contractility, SVR, BP, arythmia potential)
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
cardiovascular effects of inhalant inductors (HR, CO, contractility, SVR, BP, arythmia potential)
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
respiratory effects of propofol (RR, TV, incidence of apnea, ventilatory pattern)
RR: down TV: down incidence of apnea: ++ ventilatory pattern: apnea with fast injection
51
respiratory effects of barbiturates (RR, TV, incidence of apnea, ventilatory pattern)
RR: super down TV: down incidence of apnea: ++ ventilatory pattern: apnea with fast injection
52
respiratory effects of alfaxalon (RR, TV, incidence of apnea, ventilatory pattern)
RR: down TV: down incidence of apnea: ++ ventilatory pattern: apnea with fast injection
53
respiratory effects of ketamine/BZD (RR, TV, incidence of apnea, ventilatory pattern)
RR: NC or down TV: NC incidence of apnea: + ventilatory pattern: apneustic, irregular
54
respiratory effects of inhalant induction (RR, TV, incidence of apnea, ventilatory pattern)
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
steps of induction process
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
sign required for endotrancheal intubatoin
¡ 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
Assessing Proper Placement of Endotracheal Tube
-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
considerations for tubing felines
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
advantages to isofluoranve and sevofluorane for maintenance phase
* 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
disadvantages to isofluoranve and sevofluorane for maintenance phase
¡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
Factors Affecting MAC
¡ 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
Factors Affecting MAC
¡ 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
how do we prepare for the recovery phase?
¡ 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
indications for extubation in the dog
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
indications for feline extubation
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

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