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Anaesthesia > Equine Anaesthesia > Flashcards

Equine Anaesthesia Flashcards

1
Q

What are the three types of anaesthesia in the horse?

A

Standing - sedative, plus local analgesia

Short term total IV anaesthesia (TIVA) - e.g castration. Should still have o2 nearby

Prolonged - Inhalation or TIVA need o2 and ability to ventilate

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2
Q

When should you be aware of when a horse is sedated?

A

They still have reactions - can kick etc

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3
Q

What drugs are contraindicated in standing adult horses?

A

Anything that causes muscle weakness e.g. benzodiazepines

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4
Q

How can ACP be administered in the horse?

A

IV
IM
Oral gel

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5
Q

What are the advantages of using ACP in the horse?

A

Mood changing - anxiolytic - good for shoeing and clipping

Limited apparent sedation, unless opioids are given

When used as premed halves anaesthesia risk

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6
Q

What are the contraindications of ACP in the horse?

A

Hypovolaemia
Stallions
Care re: abuse in competition

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7
Q

How can alpha 2 agonists be administered in the horse? What can they be given with?

A

Licensed for horses - can all be given IV.

Can be used for prolonged sedation

Can be given with opiods

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8
Q

What are the three alpha 2 agonists commonly used in the horse?

A

Xylazine
Detomidine
Romifidine

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9
Q

What are the side effects of alpha 2 agonists in the horse?

A 
Bradycardia - decreased CO
Initial hypertension then BP returns to normal
Increased urine output
Hyperglycaemia
Gut stasis 
Ecbolic (uterine contractions)
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10
Q

Why might an opioid be given with an alpha 2 agonist in the horse? Which one is commonly used?

A

Prevents response to touvh
Only small doses of opioid are given - no analgesia
Often butorphanol

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11
Q

What can be given as analgesia in the horse?

A

Local blocks

Epidural analgesia

NSAIDs (reducing swelling is good, especially in the limbs but care as overdose -> gut toxicity diarrhoea due to colonic ulceration)

Opioids

Alpha 2 agonsits

Lidocaine

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12
Q

How would you prepare for anaesthesia in the horse?

A
  1. Pre-anaesthetic exam
  2. Starvation for 12 hrs no water for 2
  3. Remove shoes
  4. Premedication - ACP unless specific reason not to e.g. hypovolaemia
  5. Catheterisation
  6. ABs/anti-ten
  7. Wash out mouth
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13
Q

What is included in the premedication of horses?

A

Almost always ACP
Sometimes give alpha 2 agonists - more commonly used as co-induction

Pre-emptive analgesia
NSAIDs
Opioids
Local

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14
Q

What are the problems associated with IV in the horse/

A
  1. Intracarotid injection
    Drugs have very rapid effect - often horse goes down on the end of the needle
  2. Air embolism
    Especially is catheters are going downwards
  3. Infection
  4. Jugular thrombosis
    Drug irritation
    Thrombin problems with endotoxaemia
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15
Q

Where should a catheter be place in a horse for surgery?

A

Jugular

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16
Q

What are the three ways of controlling a horse during induction?

A

Free fall
Gate
Tilting table

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17
Q

What are the two IV induction combinations in horses?

A
  1. Ketamine based
    Alpha 2/Ketamine +/- benzodiazepine
  2. Hyponotic based
    Alpha 2 and/or ACP plus thipental
    Propofol or alfaxalone have been used but currently too expensive to be practical
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18
Q

What should be given before ketamine in horse anaesthesia?

A

Alpha 2 agonist or other sedative

Horse must be well sedated before giving ketamine as it causes excitement

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19
Q

How is ET performed in the horse?

A

Blind
Very easy as little laryngeal reflex
Make sure that cuff is intact

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20
Q

How should anaesthesia of horses be maintained?

A

Inhalation (if >1hr)
TIVA
PIVA

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21
Q

Give examples of problems that horses can have during anaesthesia

A

Horses not designed for prolonged recumbency
Maintenance of anaesthesia and adequate provision of analgesia
Hypotension
Hypoxia
Hypercapnia
Cardiac arrest
Post-op complications - myopathy, neuropathy, spinal damage

22
Q

Which inhalation agents are used in horses?

A

Isoflurane - only one licensed in horses

Sevoflurane

Desflurane

23
Q

What breathing system is used in horses?

A

Circle - closed system or can’t give enough oxygen

IPPV very commonly needed so ventilator very helpful

24
Q

What should be monitored for a horse anaesthetised with a volatile agent?

A

Direct arterial BP - absolute
ECG
Capnography - ideal
Blood gas analysis
Pulse oximetry (although usually don’t work as horse too thick)
End tidal agent monitor (often included in capnography)

25
Q

What general nursing care should be performed to the anaesthetised horse?

A

Eye lubrication
Support limbs
Optimise ventilation
Catheterise bladder

26
Q

How should a horse be positioned in a later position in anaesthesia? Why?

A

Everything padded
Under front leg drawn forwards and under hind back
Upper limbs should be supported
Head should be slightly raised

Can get myopathy due to weight - must maintain venous return and blood to the muscles

27
Q

How should a horse be positioned in dorsal when anaesthetised?

A

Soft padding

Do not extend hind legs - if stifle locks for a long time results in muscle and nerve damage

Head up but not stretch out - can get laryngeal paralysis

28
Q

How can you stabilise volatile anaesthetic in the horse?

A

Can be difficult - can wake up without much warning

IV agent should be kept to hand preferable thiopental - ketamine takes too long

29
Q

What can be used for intraop analgesia in the horse?

A

Difficult to assess need as often no CV changes

Local blocks
More inhalation
Top up - small doses of ketamine or thipental

PIVA

  • Ketamine infusions
  • More alpha 2 agonists
  • Bolus doses or infusions
  • Lidocaine infusions
  • Opioids eith alpha 2
30
Q

Why can hypotension occur in the anaesthetised horse?

A

Myocardial depression and low heart rate (=> low CO)

Vasodilation (isoflurane worse) - however when vasoconstrict, high TPR means greater cardiac work, so further fall in CO and poor peripheral perfusion

31
Q

What is the result of hypotension in the anaesthetised horse?

A

Cardiac arrest if severe

Myopathy is moderate and prolonged

32
Q

How can hypotension be treated in the anaesthetised horse?

A

Improve CO

  • Positive inotropes (e.g. dobutamine, ephidrine)
  • Reduce volatile agent
  • Give fluids

Do not give drugs to vasoconstrict unless hypotension is v v severe (increases blood pressure but not flow)

33
Q

Why are horses prone to hypoxaemia during anaesthesia?

A

Recumbency
Hypoventilation
Leads to atelectasis and V/Q mismatch

34
Q

How can hypoxaemia be treated during inhalational anaesthesia in the horse?

A

IPPV using 100% oxygen - doesn’t always work

Bronchodilator (salbutamol)

Improve CO - improves o2 delivery

35
Q

What causes hypercapnia in the anaesthetised horse? How should it be treated?

A

Possible response to hypoxia
- Hypoxic horses usually breathe well and are not hypercapnic

IPPV gets rid of excess CO2 but removed the advantangeous effects of moderate hypercapnia on circulation (high CO2 best CV stimulant)

36
Q

What is the problem with detection of cardiac arrest caused by anaesthesia in the horse?

A

Can be detected with electronic monitoring
Goes on breathing for a long time after heart stops
Cerebral hypoxia = looks like waking up but actually dying

37
Q

What are the possible reasons for a cardiac arrest caused by anaesthesia in the horse?

A

High vagal tone

Severe hypotension means heart is underperfused

38
Q

How can you treat intra-anaesthesia cardiac arrest in the horse?

A

Switch off volatile agent
IPPV with 100% O2
External cardiac massage
When have obtained a circulation, continue massage and give adrenaline/atropine IV

39
Q

What is PIVA?

Which drugs can be used in the horse?

A

Partial IV anaesthesia
Infusions of analgesic drugs to reduce inhalation agent
Lidocaine, alpha 2, midazolam and ketamine are used
All reduce amount of iso needed so better BP
Only ketamine gives better CO than higher doses of iso alone

40
Q

What can be used for induction of field anaesthesia in horses? What are the pros of this?

A

Alpha 2, ketamine (+/- diazepam)

Good induction
Minimal CV depression
High safety margin
Add local analgesia to prolong effect
Excellent recovery (esp if no benzo)
41
Q

How can field anaesthesia be maintained in the horse? Pros?

A

Triple drip TIVA
Guiaphenesin, alpha 2 agonist and ketamine
- Gives stable anaesthesia for short procedures (ideally <1hr)
- Best used after no guaiphensin at induction

42
Q

What can be used to prolong anaesthesia beyond a trip drip in horses?

A
  1. Reversible anaesthesia
    - Benzo bases
    - Opioid base
  2. Propofol based
    - Pro and ket
    - Pro and alpha 2
    - Pro/alpha/ket
  3. Alfaxalone
43
Q

What is immobilon?

A

Etorphine plus ACP
Very potent
Licensed for horses IV

44
Q

Give examples of potential problems in horse anaesthesia recovery…

A

Airway obstruction
Hypoxia
Physical damage

45
Q

What should be done during equine anaesthesia recovery?

A
  1. Maintain airway
    - Nasal swelling - reduced by phenylephrine nasal drops
  2. Give oxygen
  3. Sedate
  4. Assist recovery
  5. Analgesia and empty bladder
46
Q

What are the three main methods of recovery in horses?

A
  1. Free recovery
  2. Rope assisted
  3. Pool
47
Q

Give examples of problems showing during or after equine anaesthesia recovery…

A
  1. Injury (corneal abrasion, fractures)
  2. Nasal oedema and resp obstruction
  3. Myopathy
  4. Neurapraxia and neuropathy
  5. Pulmonary oedema
  6. Myelomalacia
48
Q

What is myopathy in horse anaesthesia?

A

Re-perfusion injury due to lack of perfusion of muscle during surgery - very painful

49
Q

How can myopathy be avoided in equine anaesthesia?

A

Short surgery
Careful positioning and padding
Adequate blood pressure
Good cardiac output

50
Q

Which animals can spinal cord malacia be seen in?

A

Young cobs - happens when on back for a long time

Anaesthesia (9 decks)

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