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VMS 4001 > Equine Anaesthesia & analgesia > Flashcards

Equine Anaesthesia & analgesia Flashcards

1
Q

What drugs used in staning sedation?

A
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2
Q

How do we ‘top up’ duration of sedation?

A
  1. ‘Top up IV
    Alpha 2 agonist infusion (detomidine, xylazine or romifidine)
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3
Q

AEs of Sedation? - Alpha 2 effects

A
  • Sweating
  • Ataxia
  • Sinus bradycardia, 1st & 2nd degree AVB, respiratory depression
  • Increased urination
  • Ileus, oesophageal choke (Starve for a couple of hours after sedation)
  • Gas distension, colic (repeated administration)
  • Tachypnoea in febrile horses.
  • Localised inflammatory response if drug accidently injected s/c or
    peri-vascular
  • Horses can appear profoundly sedated but still startle and react with
    well-directed kicks
  • Individual/breed differences in susceptibility – eg draft breeds very
    sensitive to sedation
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4
Q

AEs of sedation with opioids?

A
  • Ileus, Impaction colic
  • Horse can startle
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5
Q

Describe sedation of foals under 2 weeks old ?

A
  • Cardiac output directly related to heart rate: hypotension occurs quickly
  • Avoid alpha-2 agonists due to cardiovascular effects
  • Benzodiazepines and opioid combination readily causes recumbency
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6
Q

Multimodal analgesia - waht NSAIDS for equine?

A

Phenylbutazone, suxibutazone, fluxinin, melocixam, firocoxib, carprofen

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7
Q

What opioids in multimodal A?

A

Butorphanol, Morphine, Buprenorphine, Pethidine, Methadone

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8
Q

What locals can we. use?

A

Lidocaine, mepivicaine or bupivicaine

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9
Q

What adjunct analgesia ?

A

-> Infusions (of individual drugs or combinations)
-> Alpha 2
-> Paracetamol
-> Gabapentin

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10
Q

What does CEPEF stand for?

A

Confidential Inquiry into Perioperative Equine fatalities

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11
Q

What did SEPEF find was mortality within 7 d of procedure?

A
  • All Patients: 1% (Prev 1.9%)
  • ‘Noncolic’ patients: 0.6% (Prev 0.9%)
  • ‘Colic’ patients: 3.4% (Prev 7.8%)
  • Standing sedation 0.2%
  • Causes: Fracture in recovery, post-operative colic, others
  • Highest numbers of deaths during recovery
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12
Q

What factors increase the risk of Death ?

A

Total inhalant anaesthesia
Duration >2 hours
Increasing adult age
Out of hours anaesthesia
Midnight to 6am x 7.61
6pm to midnight x 2.15
Weekend x 1.52
Higher ASA physical status grade
Lack of premedication

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13
Q

What decreases risk of mortality?

A

Total intravenous anaesthesia (TIVA)
Duration <2 hours
Acepromazine premedication

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14
Q

What are some common Anaesthesia- associated complications?

A
  • Fractures, joint dislocation
  • Post-op colic, Post-anaesthetic ileus
  • Cardiac arrest, cardiac arrhythmia
  • Upper airway obstruction, Nasal Oedema, laryngeal paralysis
  • Endotracheal tube complications
  • Pulmonary oedema
  • Post anaesthetic myopathy
  • Neuropathy
  • Spinal cord myelopathy or cerebral necrosis
  • Hypoxaemia
  • Hypotension
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15
Q

What complication from arterial and venous cannulation?

A

Venous thrombophlebitis
Inadvertant placement of venous cannula into caroti Artery
Exsanguination and air embolism
Accidental breaking, cutting of canula or loss of guidewire

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16
Q

What contributing factors to anaesthetic -associated complications?

A
  • PAtient positioning
  • Anaesthetic drugs
  • Mechanical ventilation
  • Pre-existing dx
  • Human error
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17
Q

What common fractures during recovery?

A

Tibia, carpus, radius most common

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18
Q

Who gets more fractures?

A

Older TB mares over-represented - reduced bone density in PP mares?

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19
Q

What can they get as result of fractures during recovery?

A
  • Reduced limb strength after repair
  • Fatigue in severely ill horses
  • Fracture of contralateral limb after fracture repair
  • Also join luxations/ dislocations
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20
Q

What is the most common cause of peri-anaesthetic death?

A

Cardiac arrest

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21
Q

Risk factors to upper airwar obstruction?

A
  • PRe existing left laryngeal hemiplegia
  • Large body mass
  • Prolonged anaesthesia
  • Hypoxaemia
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22
Q

Signs of UAO?

A
  • resp distress
  • Blood stained foam pouring from nostrils and mouth
  • Deterioration with hypoxemia, collapse and cardiac arrest may be rapid
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23
Q

Tx for UAO?

A

Establish an airway (ET tube or tracheotomy followed by symptomati tx (oxygen, furosemide, bronchodilation)

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24
Q

What has bilat laryngeal paralysis been associated with?

A
  • Nerve damage due to neck extension
  • LAryngeal nerve ischaemia
  • Tissue oedema due to surgery
  • LAryngeal oedema and spasm
  • Functional airway collapse
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25
Q

Why can we get nasal oedema?

A
  • with dorsal recumbency
  • can lead to upper airway obstruction
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26
Q

Prevention of nasal oedema?

A
  • Use lateral recumbency
  • Orotracheal tube in situ or naso-pharyngeal tube placed for recovery to bride gap until nasal passages return to normal function
  • Intra-nasal phenylephrine into ventral meatus at end of anaesthesia to reduce congestion and obstruction
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27
Q

What ET intubation complications can they get?

A
  • Mild-moderate mucosal damage is common
  • Haemhorrhage with potential for airway obstruction by
    blood clots, aspiration
  • Laryngeal oedema, ecchymosis and haematomas, paresis
  • Bilateral larnygneal paralysis (rare)
  • Pharnygeal trauma
  • Tracheal damage from cuff
  • Secondary bacterial infection, pleuropneumonia
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28
Q

What can cause pulmonary oedema?

A
  • UAO
  • Micro-embolism
  • Drug-associated capillary leakage
  • Venous air embolism
  • Mechanical causes (hydrostaticeffects)
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29
Q

what does PAM stand for?

A

Post Anaesthetic Myopathy and Neuropathy

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30
Q

What is PAM associated with?

A
  • Dec muscle perfusion related to hypotension (MAP < 65mmHg)
  • Prolonged duration of GA
  • LAteral recumbency
  • Larger body mass
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31
Q

Neuropathy?

A

slightly less common than myopathy but contributing factors similar to PAM

32
Q

How do we PREVENT PAM ?

A
  • Reduced pressure on all points
  • Ensure major veins unobstructed
  • Avoid tension (no overextended limbs)
  • Facilitate muscle perfusion (positioning)
  • Prevent hypotension (appropriate drug & dosage, close monitoring)
33
Q

Who and how do horses get Spinal Cord Myelopathy

A
  • Rare
  • Young male and heavier breeds over represented
  • Dorsal recumbency mostly
34
Q

Aetiologies suggested for spinal myelopathy?

A
  • Reduced perfusion and ischemia of the spinal cord in dorsal recumbency
  • Reduced venous return due to compression of the vena cava by abdominal
    contents
  • Vitamin E deficiency destabilizing spinal cord membranes
  • Stretch ischaemia of the spinal cord
  • Verminous arteritis
  • Embolism
35
Q

Hypoxiaemia is when PaO2 <?

A

PaO2 < 60mmHg

36
Q

What causes of hypoxaemia?

A
  • Low Fi02 (inspired oxygen fract)
  • Hypoventilation
  • Diffusion impairment
  • Ventilation/perfusion (V/Q) mismatch
  • CV shunting
37
Q

Hypotension value?

A

MAP < 60 mmHg

38
Q

When is hypotension more problematic?

A

with inhalational anaesthesia compared to TIVA (total IV a)

39
Q

What physiology of hypotension?

A

Peripheral vasodilation -> dec peripheral resistance -> dec MAP -> dec tissue perf

40
Q

T/F Hypotension is a contribution factor for myopathy/neuropathy

A

True

41
Q

How would u treat hypotension?

A
  • Dobutamine
  • IVFT
42
Q

What is the most commonly described per-anaesthetic complication in horses?

A

Post-operative colic (POC)

43
Q

Incidence of POC?

A

1/3 - 1/10 cases

44
Q

Describe POC

A
  • Multifactorial
  • Often no diagnosis - impaction implication tho
  • Ortho seems to inc risk
  • Morphine inc risk?
  • sodium benylpenicillin or ceftiofur ?
45
Q

What is a specific cause of POC?

A

Post-op ileus (POI)

46
Q

What risk factors to POI?

A
  • Duration of anaesthesia and surgery
  • Type of surgery
  • PCV at induction
  • Inc TP
  • Arabians
  • Inc age
47
Q

What considerations for field anaesthesia?

A
  • Location (clean field)
  • Tetanus prophylaxis
  • Contigenecy planning (emergency drugs, ET tube? )
48
Q

What is step 1a?

A

History, signalment, clinical exam -> consider anaesthetic risk

49
Q

step 1b?

A

equipment checks & prep ->

  • Check all anaesthetic and monitoring equipment is ready and working if
    working in a hospital
  • Check for leaks
  • Draw up medications (including emergency top-ups etc).
  • Label syringes
50
Q

What is step 2?

A

G I V E A C E P R O M A Z I N E ( A N D N S A I D )

* (Technically part of pre-med but done earlier than the rest)

51
Q

What dose of ACP?

A

0.04-0.05mg/kg IM
i.e. 20mg for standard horse and 10mg for standard pony

52
Q

What desirable effects of ACP?

A
  • Mild sedation
  • Improves recovery quality
  • Anti-arrythmic
  • Vasocilation

caution with entire males?

53
Q

Describe step 3?

A
  • IV Catheter
  • Rinse mouth
  • If hospital anaesthesia: remove or cover shoes
54
Q

Step 4?

A

Premed -> neuroleptanalgesia

  • ALpha 2 agonist + Opioid
    give alpha 2 first THEN once effect seen give opioid
55
Q

PREMED doses or duration of aciton

A
56
Q

Step 5 ?

A

Induction -> (ensure well sedated)

Ketamine (2.2mg/kg IV) and a central muscle relaxant (benzo) i.e. Diazepam or Midazolam (0.5mg.kg)

KEtamine and midazolam licensed in UK

57
Q

What alternatives for induction?

A
  • Combinations of ket plus another drug e.g.g propofol or thiopental or GGE
  • GGE IV to effect
58
Q

What happens after induction?

A
  • Et tube
  • inital checks and prep
  • Urinary cath
59
Q

What point of putting urinary cath?

A
  • Urinary catheters placed during most equine anaesthetics in the theatre setting
  • Enables monitoring of urine production
  • Avoid excessive urination in the recovery box resulting in a wet, slippery floor
  • (Alpha-2 agonists result in increased urine production)
60
Q

describe Step 6

A

Maintenane with TIVA:
- Field environment or short surgery
- KEt induction gives 10 mins of surgical anesthesia

61
Q

What to do if need more than 10 mins?

A
  • Short procedures: maintain with intermittent bolus doses
  • Longer: infusion rate
62
Q

How do we do top up bolus of KET?

A
  • Ket every 8 mins (2 min onset time)
  • 1/3 induction dose

alternative: thiopental (when patient moves)

63
Q

In addition to KET bolus we can also give …?

A
  • If used xylazine for premed give 1/2 premed dose with every ketamine top up
  • If used detomidine for premed: give 1/2 premed dose with every other ketamine top up
64
Q

How would u formulate a variable rate infusion (“triple dip)

A

ADVANTAGESmore stable plane of A
DISAD: relative cost ; 90 mins max

65
Q

How do we get maintenance with inhalants?

A

Iso or Sevo in longer surgeries

Trend now towards PIVA (Partial IV anaesthesia) instead of Inhalant ALONE

66
Q

What can PIVA involve?

A

Can involve CRIs of ALpha2 , lidocaine, ket, opioids

67
Q

Is spontaneous ventilation used much?

A
  • Spontaneous ventilation possible but in theatre environments, controlled
    ventilation is commonly used for adult horses
68
Q

Why do we use controlled ventilation more?

A
  • Recumbency and most aneasthetic drugs induce hypoventilation
    • Hypoventilation is when ventilation unable to match the metabolic
      rate of the body and is characterized by a rising partial pressure of
      arterial CO2
      (PaCO2
      ).
  • Values of PaCO2 of > 4.7-6KPa (35-45mmHG) = hypercapnia
69
Q

What monitoring in field?

A

PHYISOLOGYICAL Parameters:
- Pulse (facial artery ; rate 30-45 in adult anaesthetised)
- MM
- RR
- Shivering & inc muscle tension= inadequate plne of anaesthesia (movement)

Eye position & reflexes (unreliabel with ket
Anal reflex

70
Q

Monitoring in theatre?

A
  • Physiological parameters & reflexes including temp
  • Eye position
  • Pulse oximeter
  • BP (invasive via arterial cath of facial artery or non invasive)
  • ECG
  • Capnography
71
Q

Detail eye position for theatre monitoring ?

A
  • Surgical anaesthesia: central with sluggish palpebral
    Too light: eye rotates, palpebral brisk
  • Too deep: eye central, no palpebral reflex
72
Q

Detail ECG?

A
  • Min 3 points of contact
  • Base-apex orientation
73
Q

DETAIL Capnography

A
  • Monitoring for hypercapnia
  • Evidence that circulatory system is capable of CO2
    transport (a
    fall in cardiac output results in a reduced EtCO2 when
    ventilation is constant).
  • Also useful for confirming ET intubation, identifies gas
    leakages and reveals abnormal ventilation patterns
74
Q

Detail Arterial Blood gas analysis

A
  • Rapid, direct, intermittent measurements of PaCO2
    and PaO2
    ,
    calculated values for SaO2
    , acid-base balance, electrolytes,
    lactate, urea and creatinine
  • Evaluating ABG and pH recommended in cases where
    hypoxaemia and/or hypercapnia is suspected or likely to occur
  • Not usually necessary in healthy, routine cases.
75
Q

Describe Theatre environemnt Recovery?

A
  • Additional sedation if pre-med worn off
  • (alpha 2 + opioid)
  • Oxygen supplementation in recovery box
  • Observe from a distance (peep holes, CCTV)
  • If entering the box, ensure clear escape route
    Safety
  • ET tube often removed once light/swallowing, and
    nasopharyngeal tube placed
  • Unassisted or assisted rope recovery both common
76
Q

Detail Field Environment Recovery?

A
  • Anaesthetist usually stays with horse until ready
    to stand
  • Headcollar and lead rope
  • Kneeling on neck
  • Keep in lateral as long as possible
  • Additional sedation if pre-med worn off
  • Less likely to be needed in field
77
Q

FOr ANY recovery what to remember?

A

Minimise noise/ light stimulation (towel over upper eye, pack ears?

VMS 4001 (17 decks)

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