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Anesthesia > Equine Anesthesia > Flashcards

Equine Anesthesia Flashcards

(53 cards)

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1
Q

general info

A

Most commonly anesthetized of all large animals
temperment and size pose a challenge
Stallions: penile prolapse/priapism from ace
Xylazine abortion in 3rd trimester

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2
Q

Common procedures

A

Colic
arthroscopy
castration
upper airway

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3
Q

Prep

A

Clinical exam

Lab tests

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4
Q

Clinical examination

A

hx
basics:
HR, RR, mm (color & CRT)
hydration status

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5
Q

Lab tests

A

Basic hematology and biochem:
PCV, TP, urine SG
compromised patients require more specific laboratory tests

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6
Q

Venous catheterization

A 
usually jugular vein 
Aseptic prepping of site
Local anesthetic infiltration
Catheter placement, 12 gauge (adult horse)
Suture catheter to skin with nylon
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7
Q

Preanesthetic preparation

A

Starve for 4-6 hours
Withhold water for at least 2 hours
Pull out all horse shoes
Rinse mouth with pressurized water to clear foreign matter that might attach to endotracheal tube and possibly contaminate/infect lungs

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8
Q

Premedication

A 
Analgesia
Butorphanol
Methadone/morphine
A2 adrenergic drug (xylazine, romifidine, detomidine)
Flunixine meglumine 1.1 mg/kg
Meloxicam
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9
Q

Considerations during premedication

A

preferably in an induction (-cum-recovery) box
Padded stall, swing door, tiltable table
Restrain horse properly during induction
quiet environment
effective communication within the team
be sure sedation (including muscle relaxation) has taken full effect before administering induction drug (ketamine)

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10
Q

Induction

A

Advisable to administer a muscle relaxant before the induction agent
-GGE
-Benzodiazepine: diazepam or midazolam
Ketamine 2.2 mg/kg

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11
Q

Intubation

A 
26mm diameter tube for average 500 kg horse
mouth gag to pull jaws apart
neck extended 
lubricate tube
intubate blindly- easy
inflate cuff
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12
Q

Positioning on theatre table

A

Depends on type of sx
cushion pressure points (head, shoulders, pelvis)
stretch and spread apart limbs- to encourage blood flow
Protect eyes from trauma, pressure
Turn while changing body positions slowly
Keep in only one lateral recumbency throughout

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13
Q

Maintenance

A

Isoflurane, sevoflurane
Large animal circle anesthetic circuit required
Oxygen flow rate: 20ml/kg/min soon after induction (30-60min) and towards recovery; 10ml/kg/min during maintenance
Mechanical ventilation (IPPV) recommended esp if anesthesia time longer than 45 min
IV drugs for partial or total anesthesia
Make use of local anesthetic drugs and techniques as much as possible

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14
Q

PIVA and TIVA

A

most IVA protocols in horses combine:
A2 adrenergic drugs (xylazine, detomidine, romifidine, medetomidine)
Muscle relaxant (GGE, midazolam)
Hypnotic agent (ketamine)

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15
Q

Maintenance PIVA

A 
combination of inhalational and IV drugs
attainment of balanced anesthesia
Goals: 
MAC (inhalation agent) reduction
Analgesia provision
Vital system adverse effects reduction
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16
Q

Maintenance: TIVA advantages

A

Less cardio system depression
Superior analgesia
less likelihood of movement in response to surgical stimulus
decreased surgical stress
lower morbidity and mortality
better quality of recovery from anesthesia

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17
Q

TIVA: field maintenance

A

TIVA protocols commonly known as
Triple drips
Double drips effective as well
Include any possible local anesthetic techniques for maintenance

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18
Q

TIVA

A

alternatively top up with intermittent boluses
Ketamine about 0.4 mg/kg
Diazepam or midazolam 0.1 mg/kg
a2 adrenergic agonist (xylazine, deromidine, romifidine)

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19
Q

Monitoring

A 
Anesthetic depth
Resp
Cardio
Regular arterial blood gas
Thermoregulatory
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20
Q

Anesthetic depth

A

CNS
Surgical: weak palpebral reflex/anal tone
too light: lacrimation, nystagmus, movement

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21
Q

Respiratory system

A

RR and depth (TV)

hypoventilation likely: IPPV mostly needed; asses ETCO2 (expired CO2)

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22
Q

Cardiovascular system

Study These Flashcards
A

Hypotension common: direct blood pressure

ECG lead I as for ruminants

23
Q

Regular arterial blood gas measurements

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A

Hypercapnea (high PaCO2)

hypoxemia (low PaO2)

24
Q

Ideal anesthetic depth

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A 
weak palpebral reflex
no nystagmus
weak anal tone
Stable autonomic reflexes
non-responsive to noxious stimulus
25
Too light
``` Blinkng lacrimating nystagmus corneal reflex present tachypnea, tachycardia movement of limbs/neck in response to surgical stimulus ```
26
Too deep
Absent palpebral reflex absent corneal reflex dry cornea bradypnea, apnea, bradycardia, hypotension
27
Recovery from anesthesia
Highest risk period of equine anx- characteristically excitable 'flight' animals and myopathy risk soft-padded, non-slip recovery boxes dim light and quietness in recovery boxes sedate with a2 adrenergic agonist (romifidine) to delay standing attempts nasotracheal intubation supplement o2 keep same lateral recumbency from in sx- sacrifice only one lung side to inevitable atelectasis may be supported with robes or left alone in recovery box Analgesia temperature control
28
Techniques used in assisted recovery
``` manual assistance within recovery box head and tail rope recovery -deflating air pillow -sling recovery -pool recovery ```
29
Complications
``` sudden heart failure hypotension hypoventilation hypoxemia myopathies: postanesthetic rhabdomyolysis Myelopathies: esp radial n, obturator n, facial n excitement and ataxia nasal obstruction jugular vein thrombosis ```
30
Hypotension: treatment options
MAP < 70 mmHg; SAP <90 mmHg treat specific underlying cause reduce administration rate of anesthetic drugs, if indicated volume resuscitation (crystalloids 10 mL/kh; colloids 5mL/kg; blood- if hemorrhagic) cardio-active drugs: dobutamine, ephedrine etc
31
Hypoventilation management
mechanical ventilation set RR and volume (pressure) target 35-45 mmHg expired CO2
32
Myopathy in horse
``` Most common cause of morbidity/mortality during horse anesthesia various types of myopathies arising from different causes Anesthesia associated myopathies with rhabdomyolysis -compartmental myopathy -malignant hyperthermia Without rhabdomyolysis -hyperkalemic periodic paresis ```
33
Myopathy-- clinico-pathological changes
``` myoglobinuria & hyperglobinemia muscle enzymes (CK, AST, LDH elevated) electrolytes (P & K elevated, Na, Cl, Ca decreased BUN and creatinine elevated CBC: inflammatory leukogram ```
34
compartmental myopathy- predisposing factors
muscle and nerve tissue ischemia associated with poor perfusion - heavily muscles horse: >600kg - fit or nervous horse - persistently low MAP: <70 mmHg - improper positioning: perioperatively - prolonged anesthesia (recumbency) time: > 2hours - halothan maintenance
35
compartmental myopathy- signs and symptoms
6 ps (pain, paresis, paralysis, palloe, pulselessness, poikilothermia) failure to stand on specific muscle group: forelimb, hindlimb muscle feels hard (tense and firm) and is severely painful Myoglobinuria and subsequent renal failure
36
compartmental myopathy- treatment
symptomatic: -fluids -analgesics, muscle relaxants &/or sedatives -o2 radical scavengers:DMSO -PT -tender love and care Fasciotomy-decompression
37
Malignant hyperthermia: predisposing factors
life-threatening skeletal muscle pharmaco-genetic disease humans, pigs, horses susceptible- rare mutations in ryanodine gene causes dysfunctional release of excessive calcium into sarcoplasm -halothane -stress -depolarizing muscle relaxants (succinyl choline) -improper positioning: laying on hard surface, legs compressive each other for too long, etc
38
Malignant hyperthermia: signs and symptoms
hyper-metabolic state: hyperthermia, hypercapnea, lactic acidosis - profuse sweating - tachypnea - tachycardia and arrythmias - hypertension - prolapse of third eyelid - flared nostrils - contracted masseters - muscle rigidity and twitching - myoglobinuria - death and per acute rigor mortis
39
Malignant hyperthermia: prevention
correct positioning and padding pre-anesthetic dantrolene in susceptible maintain normal blood pressure
40
Malignant hyperthermia: treatment
``` dantrolene water/alcohol baths ACP for vasodilation Na+ bicarb for acidosis TLC ```
41
Hyperkalemic period paralysis (HYPP)
Rare genetic trait that affects quarter horses (most commonly), less commonly in Appalosas and their crosses Mutation results in failure of Na+ channels to deactivate- excessive Na+ influx and K+ outward flux in mm cells Episodes can be triggered by: -transportation -stress -sedation -anesthesia
42
Hyperkalemic period paralysis (HYPP)- signs and symptoms
``` can be a challenge to intubate might develop myopathy at recovery -respiratory distress, laryngeal paralysis -swaying -staggering -dog-sitting -recumbency -prolapse of eyelid ```
43
Hyperkalemic period paralysis (HYPP)- treatment
increase K+ excretion by: - ace - dex - Ca gluconate - TLC
44
Neuropathy- general info
commonly concurrent with myopathy Ischemia, pressure and stretching possible causes nerves on dependent weight bearing parts -facial, radial, spinal malacia (draught horses- always fatal)
45
Neuropathy- prevention and tx
``` correct positioning and padding Remove head halter during anesthesia Maintain normal blood pressure not painful nerves may revitalize once swelling subsides symptomatic treatment TLC ```
46
Nasal edema
due to gravitational (hypostatic) fluid extravasation which then restricts diameter of nostrils place nasal tube until horse stands- otherwise risk horse will panic at threat of asphyxiation and try to jump up prematurely oxygen supplementation
47
Excitement during recovery
Minimize stimulation during recovery sedate with romifidine/detomaidine/xylazine to delay attempts at standing. romifidine causes least ataxia excited horses may suffer bone fractures re-anesthetize to repair fracture or euth
48
Foal
Presents a different challenge from adult be aware of physiological differences Premed in presence of mother Benzos are v effective sedative in foals may combine with butorphanol for analgesia
49
Foal induction and maintenance
inhalation induction: through nasotracheal tube or face mask inductionL propofol, ketamine isoflurane, sevoflurane, for maintenance
50
Foal-recovery
usually requires some human physical support during recovery - delay attempts at getting up by keeping down manually - support head and pull on tail base once up
51
Donkey
Stoic animal fight rather than fright and flight thick skin over jugular furrow cut down for venous catheterization
52
donkey- drugs
less prone to excitement during induction or recovery periods more resistant to sedatives, anesthetics and analgestics- inc dose by 30% ketamine half life also shorter anticipate more frequent top ups more sensitive to GGE
53
donkey-recovery
smoother than the horses rarely noticeable emergency delirium/excitement nasal tube may be used to counter adverse effects of nasal edema human physically assisted recovery: watch out for kicks

Anesthesia (12 decks)

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