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pos 2 > Equine sedation and anaesthesia > Flashcards

Equine sedation and anaesthesia Flashcards

1
Q

What is the main thing about equine anaesthesia?

A

+++ about risk management
team effort
risk procedure for ptx and staff

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2
Q

What are the legal aspects regarding different drugs in equine passports?

A

licensed agents: on a special essentials list or active substance on GB list of known MRLs, use needs to be recorded
Others: NOT to be used unless passpoty is signed as not for slaughter, permanent

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3
Q

Why is the risk of anaesthesia much higher in horses?

A

temperament/character: panic/flee causing trauma/fracture
size/strength: hard to restrain/help
weight and build

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4
Q

What potential problems do the weight of horses cause during anaesthesia?

A

large body weight squashing tissues = ischaemia
large displaceanle GI tract = colic
horizontal coursing diaphragm = ventilation and circulation compromise
obligate nasal breathers = airway obstruction
delicate limbs = trauma/fracture

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5
Q

What are the potential risks during each phase of anaesthesia in horses?

A

induction: excitement, IV mishap, trampling
maintenance: adverse effects from anaesthetic drugs and recumbency
recovery: trauma/fracture or complications induced during maintenance

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6
Q

How can we limit the anaesthetic risk in horses?

A

avoid GA, consider standing sx under sedation
keep deviations from normal small/transient
always minimise duration of anaesthesia
case selection: setting/support suitable for ptx and procedure

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7
Q

What are good agreed core protocols for equine sedation/premed?

A

alpha 2 adrenoceptor agonist +/- opioids

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8
Q

What are good agreed core protocols for equine induction?

A

ketamine + benzodiazepine

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9
Q

What protocols for equine anaesthesia/sedation are to never be used?

A

benzodiazepines for standing sedation: muscle weakness = panic
azaperone (pig sedative) causes violent excitement in horses

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10
Q

What are the surgical requirements for standing sedation?

A

cooperative stress free ptx
stand still
stock, collar, rope, head support
adequate analgesia: systemic analgesics+local on area operated

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11
Q

What are the drug options for sedation and analgesia during standing sedation?

A

acepromazine
alpha2 agonists (xylazine, detomidine, romifidine, dexmedetomidine)
opioids (butorphanol, morphine, methadone, buprenorphine)
nsaids

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12
Q

Which sedation and analgesia drugs are licensed for horses during standing sedation?

A

alpha2: xylazine, detomidine, romifidine
opioid: butorphanol

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13
Q

Which sedation and analgesia drugs need a not for slaughter signature during standing sedation?

A

methadone and buprenorphine

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14
Q

Which local anaesthetic block drugs are used during standing sedation?

A

mepivacaine, lidocaine
bupivacaine

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15
Q

What are the general points and limitations of equine sedation?

A

not an anaesthetic = can still react
all sedatives work best if animal is calm to start with
surprise arousal can occur
ensure quiet environment
give time to take effect

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16
Q

How responsive are horses when sedated?

A

can be VERY
do not pat on backside
can startle and kick

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17
Q

What drugs can help with touvh responsiveness in horses during sedation?

A

opioids
butorphanol (licensed)
morphine (6mo)/methadone

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18
Q

What is acepromazine?

A

a phenothiazine
dopamine antagonist but also alpha 1 adrenoreceptor block
limited sedative potential
slow onset long duration

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19
Q

What are the side effects of acepromazine?

A

main: vasodilation which causes hypotension, hypothermia

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20
Q

What are contraindications for acepromazine?

A

hypovolaemia, dehydration!
extreme stress/shock
+/- in foals
+/- in stallions

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21
Q

What is the side effect of acepromazine that is specific to male horses?

A

penile dysfunction/protrusion
can cause physical damage if longstanding
priapism and penile apralysis may occur
not a major problem if treated immediately

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22
Q

What are the alpha 2 agonists used for sedation in horses?

A

xylazine
detomidine (very concentrated)
romifidine (longes acting, less ataxia, less deep sedation)

dose dependent effect, reliable and profound sedation/analgesia

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23
Q

What are the most reliable equine sedatives?

A

alpha 2 agonists

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24
Q

What are the side effects of alpha2 agonists in horses?

A

ataxia, swaing (try limit dose)
CVS: periph. vasoconstriction, bradycardia
reduced GI motility: colic risk when prolonged/high doses
increased uterine tone (avoid in preg)
reduced ADH and insulin release: increased urine output and blood glucose

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25
Q

What is the effect of benzodiazepines as a sedative in horses?

A

NO appreciable sedative effect in adult horses
gives effective muscle relaxation can cause awake horses to panic
NEVER USE TO SEDATE AWAKE ADULT
useful sedative up to 2-3 week old foals

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26
Q

Why is the effect of benzodiazepines different in foals and adult horses?

A

blood brain barrier
behavioural maturity

27
Q

What are the differences between ACP and alpha 2 agonists as sedatives?

A

ACP: not licensed for food producing
ALPA: licensed IV

ACP: long duration of action, 20-30 min onset
ALPHA: shorter depending on drug, 2 min onset

ACP: limited sedative depth
ALPHA: dose dependent reliable deep sedation

ACP: limited ataxia
ALPHA: ataxia, dose dependent

ACP: not analgesic
ALPHA: analgesic

28
Q

Why are opioids avoided in horses and what are the workarounds?

A

risk of reduced GI motility, colic
risk of central excitation, box walking/locomotor stimulation

prudent peri-operative use at common dosages avoids these risks
laxative diet/mineral oil prophylaxis if prolonged systemic use

29
Q

What are the main uses of opioids in horses?

A

excellent peri operative analgesic
improve acp/alpha 2 based sedation
localised prolonged pain relied

30
Q

When are NSAIDs given in horses?

A

excellent for post op pain
often given pre op in heathy horse
should always be inclused unless contra-indicated

31
Q

What are potential side effects of nsaids in horses?

A

all rarer
GI toxicity (ulceration)
renal toxicity

32
Q

What are the different local anaesthetics in horses and their particularities?

A

mepivacaine: less swelling than lido, longer acting (2.5h)
bupivacaine: longest duration (6-8h)

33
Q

What is the typical protocol for standing sx in horses?

A

may give ACP in stables 1h prior
alpha2agonist + opioid IV
NSAID
LA block of area
maintain steady sedation alpha2 agonist

34
Q

What is an essential thing to know post sedation?

A

no eating until well awake
~2hr oesophageal obstruction risk

35
Q

What is a side effect of butorphanol and when should we avoid it?

A

muzzle twitches
prefer mu agonist for head surgery or CT

36
Q

What are the pre GA steps in horses?

A

risk assessment owner consult
exam: temperament, behviour, GE, auscultation, lameness, jug veins
fasting/starrving? short (under 4h) if at all
remove shoes: avoid damage to rubber floors and avoid soft tissue trauma

37
Q

What is the aim of induction in horses?

A

achieve unconsciousness and recumbency

38
Q

What is used as drugs for induction in horses?

A

ketamine + muscle relaxant used universally
usually midazolam or diazepam IV

39
Q

Why is propofol impractical in horses?

A

poor quality induction
not licensed
imprcatical vs volume

40
Q

What is the typical ASA1-2 pre med in horses?

A

In stable:
ACP IV/IM 30min-1h before
low dose of alpha 2 IV just before

in theatre:
sedate with alpha 2 agonist
opioid, nsaids if not already

41
Q

What are the effects of ketamine as an induction agent in horses?

A

dissociative anaesthetic: eyes open, can still blink and swallow
CVS: sympathomimetic, vasoconstriction and HR increase
Resp: irreg pattern but maintain minute volume
motor: no muscle relaxation
sensory: good somatic analgesia

42
Q

How do we control/restrain horses during induction?

A

people or swing gate
horse squeezed to go down along passes wall
head restrained to go down with hind end first

OR free fall in field/padded box

43
Q

What are the types of maintenance for GA?

A

total iV anaesthesia (TIVA)
inhalation
partial IV anaesthesia (PIVA)

44
Q

When is it best to use IV anaesthesia?

A

GA under 1h or drugs can accumulate
short procedures in healthy and not too heavy animals

45
Q

What is a good example of protocol for a field castration?

A

alpha2 agonist +/- butorphanol
ketmaine +/- benzodiazepine induction = 10-15min GA
LA in testicle

46
Q

What is a triple drip?

A

often combo of guaifenesin, alpha 2 agonist, ketamine
or midazolam, alpha2 agonist and ketamine
to maintain field anaesthesia

47
Q

How do we position horse on the operating table?

A

everything padded
limbs in neutral relaxed position
no sharp edges
raise head-end of table to reduce nasal oedema
protect and lubricate eyes

48
Q

What are the volatile anaesthetic agents used in equine anaesthesia?

A

isoflurane: licensed
sevoflurane: 6mo

49
Q

What are the side effects of the volatile anaesthetic agents on horses?

A

resp depression: reduced RR and tidal volume (may require IPPV to correct)
hypotension: vasodilatation, myocardial depression (may require positive inotrope dobutamine to correct)

50
Q

What are the common intra operative problems during inhalation anaesthesia?

A

hypotension
hypercapnia
hypoxaemia

51
Q

What are the main causes of hypotension during anaesthesia?

A

vasodilation (drugs, endotoxin effects, shock)
low CO: low HR, low contractility, low venous return (drugs, endotoxins, inhalants, position, hypovolaemia)

52
Q

What can poor tissue blood flow during anaesthesia cause?

A

can lead to hypoxic damage which may only show during recovery

53
Q

How can we prevent/treat hypotension during anaesthesia?

A

moditor direct BP
treat hypovolaemia before GA
avoid ACP

54
Q

How can we treat hypotension if MAP is under 70mmHg in horse anaesthesia?

A

reduce inhalant agent % = less vasodilation
improve CO
give fluids + infuse beta 1 agonist dobutamine

if no response: other sympathomimetics including vaspressors

55
Q

What is hypercapnia?

A

elevated arterial CO2 due to reduced alvolar minute leading to CO2 retention, can develop resp acidosis

56
Q

How do we treat hypercapnia under 60mmHg during equine anaesthesia?

A

ventilate IPPV

57
Q

What is the main cause of hypoxaemia during equine anaesthesia?

A

compression atelectasis creating so called V/Q mismatch

58
Q

How can we treat hypoxaemia in equine anaesthesia?

A

tell surgeon to speed up

give FiO2 (100% O2)
recruitment manoevre and applying positive end expiratory pressure
tilt table 7 degrees head up
bronchodilator (salbutamol) via ETT

59
Q

What is the main goal of anaesthesia recovery in horses?

A

slow but good quality!

60
Q

What are problems seen during or after recovery?

A

trauma: fractures, lameness…
Resp obstruction
pulonary oedema
neuropraxi and neuropathy
myopathu
myelopathy/myelomalacia

61
Q

What is PA neuropathy?

A

nerve paralysis
usually neuropraxia: transient deficit, not painful

62
Q

What is PA myopathy?

A

ischaemia reperfusion injury
inadequate oxygen delivery to muscles during GA
very painful

63
Q
A

pos 2 (10 decks)

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