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POS 2 > Equine sedation and anaesthesia > Flashcards

Equine sedation and anaesthesia Flashcards

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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
What is the effect of benzodiazepines as a sedative in horses?
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
26
Why is the effect of benzodiazepines different in foals and adult horses?
blood brain barrier behavioural maturity
27
What are the differences between ACP and alpha 2 agonists as sedatives?
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
Why are opioids avoided in horses and what are the workarounds?
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
What are the main uses of opioids in horses?
excellent peri operative analgesic improve acp/alpha 2 based sedation localised prolonged pain relied
30
When are NSAIDs given in horses?
excellent for post op pain often given pre op in heathy horse should always be inclused unless contra-indicated
31
What are potential side effects of nsaids in horses?
all rarer GI toxicity (ulceration) renal toxicity
32
What are the different local anaesthetics in horses and their particularities?
mepivacaine: less swelling than lido, longer acting (2.5h) bupivacaine: longest duration (6-8h)
33
What is the typical protocol for standing sx in horses?
may give ACP in stables 1h prior alpha2agonist + opioid IV NSAID LA block of area maintain steady sedation alpha2 agonist
34
What is an essential thing to know post sedation?
no eating until well awake ~2hr oesophageal obstruction risk
35
What is a side effect of butorphanol and when should we avoid it?
muzzle twitches prefer mu agonist for head surgery or CT
36
What are the pre GA steps in horses?
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
What is the aim of induction in horses?
achieve unconsciousness and recumbency
38
What is used as drugs for induction in horses?
ketamine + muscle relaxant used universally usually midazolam or diazepam IV
39
Why is propofol impractical in horses?
poor quality induction not licensed imprcatical vs volume
40
What is the typical ASA1-2 pre med in horses?
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
What are the effects of ketamine as an induction agent in horses?
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
How do we control/restrain horses during induction?
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
What are the types of maintenance for GA?
total iV anaesthesia (TIVA) inhalation partial IV anaesthesia (PIVA)
44
When is it best to use IV anaesthesia?
GA under 1h or drugs can accumulate short procedures in healthy and not too heavy animals
45
What is a good example of protocol for a field castration?
alpha2 agonist +/- butorphanol ketmaine +/- benzodiazepine induction = 10-15min GA LA in testicle
46
What is a triple drip?
often combo of guaifenesin, alpha 2 agonist, ketamine or midazolam, alpha2 agonist and ketamine to maintain field anaesthesia
47
How do we position horse on the operating table?
everything padded limbs in neutral relaxed position no sharp edges raise head-end of table to reduce nasal oedema protect and lubricate eyes
48
What are the volatile anaesthetic agents used in equine anaesthesia?
isoflurane: licensed sevoflurane: 6mo
49
What are the side effects of the volatile anaesthetic agents on horses?
resp depression: reduced RR and tidal volume (may require IPPV to correct) hypotension: vasodilatation, myocardial depression (may require positive inotrope dobutamine to correct)
50
What are the common intra operative problems during inhalation anaesthesia?
hypotension hypercapnia hypoxaemia
51
What are the main causes of hypotension during anaesthesia?
vasodilation (drugs, endotoxin effects, shock) low CO: low HR, low contractility, low venous return (drugs, endotoxins, inhalants, position, hypovolaemia)
52
What can poor tissue blood flow during anaesthesia cause?
can lead to hypoxic damage which may only show during recovery
53
How can we prevent/treat hypotension during anaesthesia?
moditor direct BP treat hypovolaemia before GA avoid ACP
54
How can we treat hypotension if MAP is under 70mmHg in horse anaesthesia?
reduce inhalant agent % = less vasodilation improve CO give fluids + infuse beta 1 agonist dobutamine if no response: other sympathomimetics including vaspressors
55
What is hypercapnia?
elevated arterial CO2 due to reduced alvolar minute leading to CO2 retention, can develop resp acidosis
56
How do we treat hypercapnia under 60mmHg during equine anaesthesia?
ventilate IPPV
57
What is the main cause of hypoxaemia during equine anaesthesia?
compression atelectasis creating so called V/Q mismatch
58
How can we treat hypoxaemia in equine anaesthesia?
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
What is the main goal of anaesthesia recovery in horses?
slow but good quality!
60
What are problems seen during or after recovery?
trauma: fractures, lameness... Resp obstruction pulonary oedema neuropraxi and neuropathy myopathu myelopathy/myelomalacia
61
What is PA neuropathy?
nerve paralysis usually neuropraxia: transient deficit, not painful
62
What is PA myopathy?
ischaemia reperfusion injury inadequate oxygen delivery to muscles during GA very painful
63

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