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Anaesthesia > Clinical Equine Anaesthesia > Flashcards

Clinical Equine Anaesthesia Flashcards

1
Q

What are anatomical particularities of horses that must be considered during anaesthesia?

A
  • obligatory nasal breathers (long soft palate)
  • diaphragm inclined & arched so when animal is in dorsal, all weight including of the GIT is on the diaphragm, compressing lungs
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2
Q

Normal values of importance in horses

A
  • HR: 35-45 bpm
  • SAP 90-130
  • DAP 60-90
  • MAP 70-110
  • CRT 1-2 sec
  • RR 8-15
  • TV: 10-15 ml/kg
  • minute ventilation: 80-225 ml/kg/min
  • O2 consumption: 5 ml/kg/min
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3
Q

Pre-anaesthetic exam in horses

A
  • accurate p hx: prev/current dz, medications, exercise intolerance, lack of appetite, anaesthetic experiences
  • physical exam: BCS, temperament, TPR
  • CVS: Pulse rate/qlty/abnorm, mm colour, CRT, skin turgor, jugular vein hydration status (refill), heart murmurs
  • Resp system: RR, resp pattern, resp effort, lung sounds, temp
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4
Q

Pre-operative assessment

A
  • resp system: auscultate both sides, auscultate base of trachea, nasal integrity? nasal d/c?
  • COPD - check environment/mgmt
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5
Q

Lab tests pre-anaesthesia

A
  • haematology
  • total plasma protein
  • blood chemistry
  • blood gas
  • to correct blood chem/gas: check electrolyte disturbances, check pH, PaO2, abnormalities
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6
Q

Minimum blood tests in young adult, clinically healthy P

A

HCT, TP, fibrinogen

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7
Q

Minimum blood tests in clinically sick P

A
  • HCT, TP, fibrinogen
  • CBC
  • organ parameters according to suspicion
  • serum amyloid A
  • electrolytes
  • blood gas analysis
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8
Q

too long of starvation increases…

A

the incidence of post-op colic

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9
Q

Pre-op preparation

A
  • groom/clean
  • tie up/bandage tail
  • clean Sx site
  • pick out feet, remove shoes/clean
  • rinse mouth, esp for intubation
  • prophylactic txt for tetanus
  • AB txt if needed
  • place IVC
  • determine the weight of the horse
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10
Q

What are possible complications of IVC in horses

A
  • air embolism: anxiety, ataxia, cyanosis, collapse, loss of consciousness
  • infection or thrombophlebitis
  • carotid artery venipuncture
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11
Q

Procedures done with Sedation & standing

A

W/ or w/o local anaesthesia
* Diagnostic
* dental procedures
* orthopaedic procedures
* laparoscopy
* ophthalmologic procedures

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12
Q

sedation & standing procedure protocols depend on

A

procedure
temperament of horse

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13
Q

Sedation & standing procedures, the P should be…

A
  • immobile
  • unresponsive to manipulation (adeq analgesia, local anaesthesia technique)
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14
Q

Chemical restraint for sedation & standing procedures

A
  • phenothiazines
  • A-2 agonists
  • opioids
  • benzodiazepines
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15
Q

Standing sedation

Effect on P, requirements, other considerations

A
  • Less CV depression
  • Minimal resp impairment
  • No recovery phase
  • Cheaper?
  • Less staff req’d
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16
Q

GA

When is it used? Risks?

A
  • Allows longer & more complicated procedures
  • Uncooperative P’s
  • Procedures in dorsal recumbency
  • Less stressful for horse? Analgesia, Unconsciousness
  • Higher mortality &↑’d risk of post-op complications
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17
Q

Advantages of pre-medication

A
  • Reduces apprehension and fear
  • Helps in catheter placement
  • Sparing effect – less inhalant anaesthesia
  • Contributes to a calm induction
  • Contributes to a calm recovery
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18
Q

The sedated horse has what signs

A
  • dropped head
  • eyes partially closed
  • ears, lower eyelid & lower lip droop
  • ataxia possible
  • check rxns to noises
19
Q

Acepromazine in horses

Effect, Duration, Side Effects, Avoid in, Notes

A
  • Effect: calming effect for minor procedure, No analgesia
  • Duration: up to 6 hrs
  • Side Effects: Penile prolapse or priapism
  • Note: increasing dose only increases length of sedative effect or incidence of side effects, not the sedation
  • AVOID IN: anaemia, coagulation disorders, hypovolaemia, young foals, stallions?
20
Q

A-2 agonists in horses

Effect, Additive to, Procedure

A
  • sedation, analgesia, muscle relaxation
  • additive to Acepromazine
  • CV, resp, metabolic effects
  • standing procedures: more profound sedation than acepromazine
21
Q

Xylazine

Onset & Duration of Action

A

Sedation w/i 5-10 mins, lasts up to 30-45 mins

22
Q

Detomidine

Peak Sedation, Lasts?, AE

A

Peak sedation in 5 mins, lasts 1-1.5 hr
Higher ataxia, may avoid b/c of this

23
Q

Romifidine

onset, duration, Effects

A
  • Onset: 15 min following IV admin
  • Duration: up to 2 hr
  • Longer-acting
  • Effects: less severe ataxia, less lowering of head
24
Q

Ways of administration of alpha-2 agonists?

A
  • single bolus for short procedures
  • intermittent dosing
  • as CRI
  • level of sedation
  • alone or in combo w/ opioid
25
Q

Analgesics

NSAIDs, Alpha-2s

A
  • NSAID: flunixin meglumine, phenylbutazone
  • Alpha-2 agonists: Detomidine, Romifidine, Xylazine
26
Q

Opioids (Morphine, buprenorphine, butorphanol)

Response is…, Mix w/, Morphine note, Effects if unsedated/pain-free

A
  • Response is: dose-dependent & opioid-dependent
  • Mixed w/: alpha2, acepromazine
  • Note on Morphine: give A-2 first, then morphine
  • commonly observed effects if unsedated/pain-free: muzzle twitching, muscular spasms, shifting of limbs, vocalizing, ataxia, head pressing, reduced gut motility, dose-dependent resp depression
27
Q

Benzodiazepines (Midazolam, Diazepam)

Receptor binding, effects, stage of life to use, AEs

A
  • Receptor Binding: inhibitory GABA receptors
  • Effects: anxiolytic, muscle relaxant, anticonvulsive
  • combined w/ ketamine: dose-dependent resp depression
  • enhance sedative effect of other anaesthetic drugs
  • Stage of Life: FOALS ONLY
  • AE: pronounced ataxia, esp adults; muscle relaxation up to recumbency
28
Q

Aims of Induction

A
  • Perform in quiet environment
  • Controlled, slow, gentle induction & intubation
29
Q

Induction options for the horse

Positioning/stabilisation of the horse

A

free fall, against a wall, swing gate, tilt table, sling

30
Q

Ketamine Induction

A
  • Main drug used for induction of GA
  • Lateral recumbency in 1-3 min
  • Effects: poor muscle relaxation,
  • Combined w/: (muscle relaxants), benzodiazepines, guaifenesin
31
Q

Guaifenesin induction

A
  • req’s large vol
  • give when ataxic, give induction, then keep giving until full dose given
  • no analgesia, no reversal
32
Q

Thiopental induction

A
  • careful w/ perivascular injection
  • rough induction/recovery
  • need good premed
  • quick-acting
33
Q

Tracheal intubation

A
  • usually performed blind
  • oral or nasally
  • gag helpful
34
Q

Nasotracheal intubation

A
  • Procedures in mouth: dental, mandibular fractures
  • ETT not > 20 mm ID
  • ETT should be directed over the ventral meatus into the trachea
35
Q

Field anaesthesia:

A
  • monitor: HR, RR, breathing pattern, eye reflexes/nystagmus
  • Time limited: 60 min
  • combo of ketamine & A-2 agonist induction
  • Bolus: Butorphanol or guaifenesin to enhance analgesia &/or muscle relaxation or benzodiazepines
  • CRI: triple drip or benzodrip
36
Q

inhalation anaesthesia

A

Isoflurane, sevoflurane

37
Q

Anaesthetic-related complications

A
  • disturbances of cardiopulmonary fxns
  • muscle or nerve damage
  • complications during recovery phase
38
Q

Disturbances of cardiopulmonary fxns

A
  • inhalants cause: vasodilation, myocardial depression & decrease HR & CO
  • hypotension causes: BP/perfusion problems in periphery
  • Myopathy
39
Q

Disturbances of the resp fxns

A
  • Hypoxaemia
  • hypoventilation
  • atelectasis in lungs
  • alveolar dead space
  • V/Q mismatch
40
Q

V/Q mismatch in dependent and non-dependent areas

A
  • dependent areas: poor ventilation, good perfusion, low V/Q ratio, hypoxaemia
  • non-dependent: proper ventilation, poor perfusion, high V/Q ratio, hypercapnoea, alveolar dead space
41
Q

Muscle & nerve damage

A
  • pay attention to positioning of the animal
  • myopathy: hypoperfusion, risk factors incl duration of anaesthesia, intraop hypotension
42
Q

Ideal recovery situation

A
  • quiet
  • keep airways patent
  • non-slippery floor, padding
  • sufficient analgesia
  • assisted or not (ropes, sling, swimming pool)
43
Q

Grading Recovery Quality

A

1 → Standing on first attempt, minimal ataxia
2 → one or two attempts to stand, horse calm, slight ataxia
3 → more than three attempts to rise, horse calm but moderate ataxia
4 → multiple attempts to stand, stumbling, ataxic, mild excitation
5 → as for 4, but extreme excitement, horse injures itself, possibly fatally

44
Q

Problems in recovery

A
  • apnoea
  • hypoventilation
  • respiratory obstruction
  • excitement/dysphoria
  • nerve injury
  • fractures/dislocations/abrasions
  • corneal ulcers
  • poor qlty recoveries
  • death

Anaesthesia (23 decks)

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