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Pharm Test 3 > Equine Anesthesia > Flashcards

Equine Anesthesia Flashcards

1
Q

how do risks of equine anesthesia compare with other species? how do inhalable and injectable compare?

A

-higher mortality rate compared to other species
-inhalational 3x greater risk of death than injectable

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2
Q

Challenges of Equine Anesthesia

A

¡ Horse size and personality
¡ Control for IV access
¡ People & Equipment needs
¡ Maintenance Duration
¡ Proper positioning for surgery
¡ Recovery can be problematic

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3
Q

what type of anesthesia gives us better recovieries?

A

Maintenance with injectable anesthetics promote better recoveries with less ataxia vs. maintenance with inhalational

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4
Q

Specific Risks with Equine Anesthesia

A

¡ Injury to handler and staff
¡ Injury to horse
¡ Hypoxemia with recumbency
¡ Cardiovascular complications
¡Nasal /ocularedema
¡ Corneal ulcers

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5
Q

when are there risks of hypoxemia for equine anesthesia?

A

¡ Can develop with inhalational or field injectable anesthesia
- Dorsal recumbency > lateral recumbency

¡ Significant if on room air without supplemental oxygen

¡ Significant in dorsal recumbency in colics due to gastrointestinal distension and reduced CO
>V/Q mismatch

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6
Q

what are the risks of hypotension for equine anesthesia?

A

¡MBP <60 - 70 mmHg
¡ Very common with inhalational anesthesia
> Even with healthy horses

¡ Prolonged hypotension increases morbidity and mortality
¡ Cardiovascular support necessary under inhalational
¡ Low BP NOT an issue with field injectable induction and maintenance techniques

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7
Q

considerations for injury prevention with proper positions for inhalant anesthetics

A

§ Surgical tables
§ Thick padding required
§ Upper limbs supported in lateral
§ Thorax/ hind end supports in dorsal recumbency

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8
Q

considerations for injury prevention with proper positions for injectable anesthetics

A

§ Lateral
* Relaxed head and neck position
* Lower fore-limb forward
* Hind limbs relaxed

§ Halter & Lead-rope on
* Towel protects eyes
* Towel or other padding for rings of halter

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9
Q

Specific Equine Considerations for fasting before anesthesia

A

Withhold Food but not WATER

¡ Remove Hay; Withhold grain
¡ 4-6 hours recommended
> to reduce abdominal fill and decrease compression of the diaphragm

not concerned about aspiration pneumonia as horses do not vomit

¡ <4 week old foals do not prevent nursing > 1-2 hrs

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10
Q

Pre-Anesthetic Conditions Requiring Stabilization

A

Significant dehydration (>5%)
Blood loss
Acidemia - pH < 7.2 / Electrolyte abnormalities
Any significant disease (cardiac/respiratory/other)
Support for a significant lameness

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11
Q

good seadation in equine will impact dose of injectable or inhalant anesthetic how?

A

reduce dose

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12
Q

do we titrate dose of induction agent to effect in LA? why?

A

no, administer as injectable full dose amount
* To attain recumbency safely
* We cannot titrate to effect due to level of ataxia without full unconsciousness
* Then we focus on ET intubation and positioning
* We can handle small foals the same as small animals

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13
Q

preanesthetic sedation main options, and some secondary options

A

Main:
Xylazine
Detomidine —
Romifidine

§Phenothiazines
* Acepromazine is key drug
* Given prior to sedation with alpha2-agonist

§Benzodiazepines
* Diazepam, Midazolam
* Not good sedation in standing adult horse
-in foals gives sedation

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14
Q

are benzodiazepines a food options for sedation in an adult horse

A

not, but can be used for foals

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15
Q

induction agents for equine anesthesia

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

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16
Q

how do we use ketamine as an induction agent

A

¡ Ketamine dose is mixed with Benzodiazepine dose
>not equal volume in equine

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17
Q

most common equine induction agent? does it have consistent results?

A

ketamine
¡Predictable induction and recovery for field
¡Predictable induction inhalational

Benzodiazepines are mixed with ketamine in the same syringe

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18
Q

effects of ketamine & diazepam or midazolam and advantages

A

¡Sympathomimetic effects of ketamine
>Which maintains HR, BP and CO
> This benefit can last for up to 10 minutes, while ketamine concentrations in the blood are higher

¡Smooth consistent induction
> Approximately 30 seconds for recumbency

-can use appropriate volume

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19
Q

disadvantages of ketamine & diazepam or midazolam

A

-both are scheduled drugs

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20
Q

what is Guaifenesin? what are its uses and effects? pros and cons?

A

-central acting muscle relaxant

-minimal anesthetic properties
-no resp muscle paralysis

-may cause cardiovascular depression
-no analgesia

-precipitation at room temp
-irritating; need an IV catheter

¡ Part of induction protocol when support
¡OR
¡ Maintenance with “triple drip” GKX

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21
Q

what is Guaifenesin? what are its uses and effects? pros and cons?

A

-central acting muscle relaxant

-minimal anesthetic properties
-no resp muscle paralysis

-may cause cardiovascular depression
-no analgesia

-precipitation at room temp
-irritating; need an IV catheter

¡ Part of induction protocol when support
¡OR
¡ Maintenance with “triple drip” GKX

22
Q

typical options of equine induction? what are considerations? when would we not want to use one of these options?

A

-ketamine
-ketamine and diazepam
> 9-12 min sx time

ketamine and guaifenesin (gg)
÷GG only when can support ataxia
÷Swing gate
>GG NOT for open free Induction

23
Q

what type of drug is theopental and what are its advantages as an induction agent?

A

Barbiturate
Advantages; cheap, short onset

24
Q

disadvantages of thiopental as an induction agent

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
¡Less optimal phase to recumbency
¡Poor recovery with greater ataxia

25
Q

disadvantages of thiopental as an induction agent

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

¡Less optimal phase to recumbency

¡Poor recovery with greater ataxia

26
Q

foal <1wk anesthesia induction agent and protocol

A

÷Consider the age and disease
÷Sick = referral

<1 week old:
¡ Propofol, ketamine, Alfaxalone ¡ low dose, IV
Less Ideal:
¡ Mask induction
¡ Nasotracheal intubation and inhalant

— Pre-anesthetic Sedation Ideal

27
Q

foal 1-2wks sedation and induction

A

§ Diazepam or midazolam, butorphanol sedation
§ Low dose alpha2-agonist
§ Ketamine, propofol, or alfaxalone induction

28
Q

foal >2wks and healthy sedation and induction protocol

A

§ Alpha2-agonist sedation as necessary
§ Benzodiazepine and ketamine induction
§ Propofol or alfaxalone possible too
§ Watch Temperature and resp rate

29
Q

what should we be mindful of/ look out for with propofol induction of a foal?

A

—Careful as may see:
-greater respiratory depression —
-decreased PaO2
-Lower blood pressures!
>Vs. adult horse —
>Vs. SA

30
Q

what should we be mindful of/ look out for with propofol induction of a foal?

A

—Careful as may see:
-greater respiratory depression —
-decreased PaO2
-Lower blood pressures!
>Vs. adult horse —
>Vs. SA

31
Q

induction process, general

A
  1. Assess Sedation level; Attain IV access; Equipment prepared
  2. Assess cardiorespiratory status
    *HR, RR, MM colour, CRT
    *Monitors and pre-oxygenation possible in foals
  3. Give FULL induction dose all at once
    *Support case to positioning in lateral recumbency
    *For field injectable anesthesia – once positioned, start surgery – no ET tube
  4. Perform ET intubation and cuff inflation, transfer to inhalant/maintenance anesthesia and permit further positioning and padding for the procedure
32
Q

free induction safety measures and positioning

A

¡ Person on the head > Supporting

¡ Person on the tail (optional)
>Wait 30 sec before grab tail
=> ↓CO from sedation
=> Note this time
> Pull straight back

¡ Pull to preferred lateral

33
Q

techniqe for ET intubation in euquine? when do we use/ not use?

A

— Blind technique
— Placed for inhalational
— Not used with injectable and short procedures

—ET tubes expensive >Mouth gag

34
Q

inhalant anesthesia maintenance drugs and safety considerations? Risks?

A

¡Isoflurane, Sevoflurane
¡↑ morbidity and mortality with sx time ≥ 4 hrs
>And in sick animals

Risks:
¡ localized / generalized myopathy
¡ neuropathy
¡ hypotension
¡ hypoxemia
¡ recovery excitement +/- injury

¡ Partial IV anesthesia (PIVA)

35
Q

maintenance phase consideration for field anesthesia? how do we do it? risks?

A

To prolong surgery time up to 30 min:
> Additional xylazine /ketamine mixed together given IV
>30-50% of each initial dose
>give every 5 min of surgery time based on monitoring signs

Injectable anesthesia > 45min to 1 hour:
¡ increased­ risks
¡ Worsens recovery from > ataxia
¡ Watch your time
¡ Hypoxemia develops and more significant with prolonged times

36
Q

what is the use of a triple drip mixture? what is in it? considerations?

A

For Maintenance of GA

-GG bag
>add xylazine or romifidine or detomidine
and
>ketamine

-administer IV
-careful monitoring of depth

-poor recoveries if >60min

37
Q

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

A

HR: +/- down
CO: down
contractility: down
SVR: very down
BP: very down
arrhythmia potenital: +

38
Q

cardiovascular effects of GG (HR, CO, contractility, SVR, BP, arrrythmia potential)

A

HR: -
CO: down?
contractility: down?
SVR: down?
BP: very down?
arrhythmia potenital: -

39
Q

cardiovascular effects of ketamine & diazepam or medazolam (HR, CO, contractility, SVR, BP, arrrythmia potential)

A

HR: NC or up
CO: up, NC, or down (related to symp tone)
contractility: up, NC, or down (related to symp tone and stores, sickness of petient)
SVR: NC
BP: NC or up, maybe down in sick
arrhythmia potenital: ++ mostly if high rate produced

40
Q

cardiovascular effects of inhalant anesthetics (HR, CO, contractility, SVR, BP, arrrythmia potential)

A

HR: NC +/- down
CO: super down
contractility: super down
SVR: very down
BP: super down
arrhythmia potenital: less with iso and sevo than older older agents

41
Q

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

A

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

42
Q

resp effects of GG (RR, TV, incidence of apnea, ventilatory pattern)

A

RR: down
TV: down
incidence of apnea: possible from depth. Does not paralyze diaphragm
ventilatory pattern: -

43
Q

resp 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

44
Q

resp effects of inhalants (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 increased depth

45
Q

what should we monitor while horse in under anesthetic?

A

Eyes
* Position
* Reflexes
* Tearing
* Nystagmus

§ Muscle tone, movement
* Ears, tongue, eyelids
* Tail, neck, legs

§ Cardio-respiratory parameters

46
Q

how much time should we give for equine recovery phase?

A

¡Do not rush it
¡Ideal 20 min field
¡Ideal 1 hr inhalational
¡Sedation in recovery for inhalational

47
Q

what should we give for recovery from inhalational anesthetic?

A

sedation

48
Q

positioning for equine recovery

A

want a sternal phase

49
Q

methods of equine recovery dependant on:

A

¡Type of anesthesia
¡Time down
¡Surgery (fracture/colic)
¡Personality of horse
¡Facility you have

50
Q

what should be allowed to move in sternal phase of recovery after injectable anesthetic? what will the process look like?

A

head
-should be free recovery, can have a person on halter rope if wanted but dont try to restrict movement
>be patient and encourage only when appropriate

51
Q

what should the recovery after inhlalational anesthetic look like? what safety precatiouns should we make?

A

¡Free – alone in stall
¡ Padded room/floor
¡ Post-Inhalant
> Horse sedated > Xylazine and acepromazine

52
Q

when should we extubate a horse?

A

When swallowing
* If you can safely remain in
recovery stall with horse while lateral
OR
§ When standing

Pharm Test 3 (16 decks)

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