Anaesthesia Flashcards
why should a cuffed endotracheal tube be used to intubate dogs, cats, ruminants?
at risk of regurgitation
what does IPPV stand for?
intermitent positive pressure ventilation
what does ASA stand for?
American society of anaesthesiologists
what is the ASA status of the patient for?
attempt to classify the risk of anaesthesia according to an animals physiological status (not surgical risk)
what are the aims of anaesthesia?
unconsciousness
analgesia
muscle relaxation
(autonomic stability)
why is balanced anaesthesia needed?
no agents provide analgesia, unconsciousness and muscle relaxation
what is balanced anaesthesia?
anaesthesia from two or more agents/methods of anaesthesia
what are the benefits of balance anaesthesia?
reduction of dose/side effects
post-operative analgesia
what type of procedures is sedation used for?
non-invasive
non-painful
what is sedation used for?
relieve patient anxiety facilitate handling provide analgesia provide muscle relaxation enable procedures
what is premedication used for?
smooth induction, maintenance, recovery of GA
reduce dose of induction/maintenance agent
what must drugs used via the cascade for food producing animals have?
maximum residue limit (withdrawal period)
what can be given to an anxious horse pre-appointment?
acepromazine or detomidine oral gel
what can be given to an anxious dog/cat pre-appointment?
gabapentin or trazadone
what are examples of opioids?
butorphanol buprenorphine methadone fentanyl (morphone)
what is an example of a phenothiazine?
acepromazine
what are examples of alpha 2 receptor agonists?
xylazine detomidine romifidine medetomidine dexmedetomidine
what are examples of benzodiazepines?
diazepam
midazolam
what are some adjuncts for sedation?
ketamine
alfaxalone
propofol
physical restraint
what patients are opioids good at sedating?
very painful/sick animals
what is the main side effect of opioids?
respiratory depression
what cases can acepromazine be used for?
mitral valve disease
BOAS patients
laryngeal paralysis
what are the main side effects of acepromazine?
vasodilation
unreliable
what is acepromazine often used in combination with?
alpha 2 agonists (acepromazine for calming effect)
what situations is acepromazine not suitable for?
very young animals hepatic impairment haemorrhage hypotension sepsis
what are the disadvantages of acepromazine?
no analgesia
not reversible
long duration
moderate MAC sparing
what are the side effects of alpha 2 agonists?
peripheral vasoconstriction (reflex bradycardia)
reduce cardiac contractility
increase urine production
how reliable is alpha 2 agonist sedation?
very
what are the advantages of alpha 2 agonists?
analgesia
reversible (atipamezole)
duration depends on drug/dose
large MAC sparing
what are alpha 2 agonists not suitable for?
mitral valve disease
very young animals
if bradycardia would be a problem
urinary obstruction
what animals are benzodiazepines useful for?
very young, old and sick
how reliable is benzodiazepine sedation?
poor
what animals are benzodiazepines not suitable for?
farm animals
portosystemic shunts
what are the advantages of benzodiazepines?
reversible (flumazenil)
duration depends on dose
what are the disadvantages of benzodiazepines?
no analgesia
moderate MAC sparing
what can be used to sedate food producing animals?
butorphanol
xyalzine
detomidine
what drug are ruminants very sensitive to?
xylazine
when giving a horse opioids and alpha 2 agonists, what should be given first?
alpha 2 agonist (stops pacing)
what equine cases should acepromazine not be used in?
colic (vasodilation)
what small animal cases is acepromazine useful for?
long duration that require calming
what are possible agents used for induction?
propofol alfaxalone ketamine tiletamine pentobarbital thiopental etomidate
what are possible co-induction agents?
ketamine
benzodiazepines
guaifenesin
opioids
what species considerations need to be considered when inducing cats?
mask subclinical disease well
don’t tolerate restraint
variable temperament
what species considerations need to be considered when inducing horses?
don’t like being recumbent
flight animals
what are the possible inhalation maintenance agents?
isoflurane
sevoflurane
what are possible injectable maintenance agents?
propofol
alfaxalone
ketamine
what is TIVA?
total intravenous anaesthesia
what is MAC?
minimal alveolar concentration
how can the plane of anaesthesia be assessed using the eye?
pupil size
eye position
palpebral reflex
what are adjuncts for maintain of anaesthesia?
multimodal analgesia
locoregional technique
PIVA
monitoring
what is PIVA?
partial intravenous anaesthesia
what are the ways the airway can be managed?
face mask
endotracheal tubes
supraglottic airway devices (LMA, V-gel)
what are two types of supraglottic airway devices?
LMA (laryngeal mask airway)
V-gel
where do supraglottic devices sit?
don’t go into trachea (sit over larynx)
what can be used in cases when emergency airway access is needed?
urinary catheter
stomach tube (guide ETT)
tracheostomy
what is pain?
unpleasant sensory/emotional experience associated with actual/potential tissue damage
what is nociception?
relay of noxious stimuli from the periphery to the CNS
what is the difference between pain and nociception?
pain is when the nociceptive input is processed and perceived
what are the types of acute pain?
somatic
visceral
neuropathic
what causes visceral pain?
chemical, thermal, mechanical stimuli to bone, skin, muscle… (localised)
what causes visceral pain?
inflammation, ischaemia or distention of viscera (diffuse)
what is neuropathic pain?
lesions within the nervous system (localised/diffuse)
what is hyperalgesia?
exaggerated pain sensation in response to noxious stimuli
what is allodynia?
perception of pain to a normally non-noxious stimuli
what is peripheral sensitisation?
increased responsiveness of nociceptors (reduced activation threshold)
what causes peripheral sensitisation?
tissue damage and inflammation
what does peripheral sensitisation cause at the site of injury?
hyperalgesia and allodynia
what is central sensitisation?
increased efficiency of nociceptive signal transmission that can persist after cessation of nociceptive input
what is central sensitisation due to?
prolonged/repeated nociceptive input
why is acute pain associated with behavioural changes?
minimise damage
optimise tissue healing
what are the 4 stages of the nociceptive pathway?
transduction
transmission
modulation
perception
what drug types are available for acute pain?
NSAIDs Opioids Paracetamol Local anaesthetics Alpha 2 agonists NMDA antagonists
what do NSAIDs inhibit?
COX enzyme
what stages of the nociceptive pathway do NSAIDs effect?
transduction, modulation, perception
what stages of the nociceptive pathway do opioids effect?
modulation, perception, transduction
what receptors do opioids effect?
mu
what opioids are full mu agonists?
pethidine
morphine
methadone
fentanyl
what opioid is a partial mu agonist?
buprenorphine
what opioid is a mu antagonist and kappa agonist?
butorphanol
what is generally the first choice opioid in small animals?
methadone
what opioid should not be administered IV?
pethidine
what are the mechanisms of action of tramadol?
weak mu receptor agonist
inhibit serotonin and noradrenaline reuptake
alpha 2 agonist
what are the side effects of tramadol?
salivation, vomiting, seizures
what stage of the nociceptive pathway does paracetamol effect?
modulation
what is the mode of action of local anaesthetics?
sodium channel blockers
what stage of the nociceptive pathway do local anaesthetics effect?
transmission (true analgesics)
what stages of the nociceptive pathway do NMDA antagonists effect?
modulation, perception
what is the mode of action of gabapentinoids?
calcium channel blockers
what stages of the nociceptive pathway do gabapentinoids effect?
modulation, perception
what is an example of a NK-1 antagonist?
maropitant
what is a multidimensional composite pain scale used for dogs?
Glasgow composite measure canine pain scale
what is a multidimensional composite pain scale used for cats?
Glasgow feline composite measure pain scale
chronic pain can cause changes to central pain processing, what are these?
hyperalgesia
allodynia
what are the types of chronic pain?
nociceptive/inflammatory neuropathic neoplastic mixed referred myofascial
what is referred chronic pain?
pain that is projected from the source to a distant site (makes identification difficult)
what causes myofascial trigger points?
general wear/tear of muscles (damage to motor end plates)
what muscles are commonly effected by myofascial pain?
postural (neck, shoulders, lumbar spine)
what implications are associated with chronic pain?
sensory emotional cognitive (conditioned responses) motor welfare
what can be used to assess lameness associated with chronic pain?
force plate analysis
how is the majority of chronic pain assessed?
owner questionnaires
what are the steps in a chronic pain consult?
identify owners concerns identify problem assess degree of pain classify pain components identify source of pain identify aims of management devise treatment implement plan
what does PLATTER stand for?
plan anticipate treat evaluate return (management of chronic pain)
what does ABCDE stand for in regards to treating chronic pain?
analgesia bodyweight control of complications and comfort disease modification exercise
what are some possible analgesic interventions for chronic pain?
acupuncture physiotherapy hydrotherapy laser therapy transcutaneous electrical nerve stimulation
what drugs are commonly used for nociceptive/inflammatory pain?
NSAIDs
what should be monitored in animals on long term NSAIDs?
serum biochemistry and urinalysis (check for side effects)
what is the mode of action of grapiprant?
prostaglandin receptor antagonist
what drugs can be used to treat chronic pain?
NSAIDs grapiprant paracetamol tramadol NMDA antagonist gabapentin tricyclic antidepressants
what are the side effects of longterm NMDA antagonist use?
GI signs
agitation
restlessness
how does acupuncture work?
needles cause local vasodilation and nerve growth factors stimulate wound healing
what is physiotherapy used for?
muscle strengthening
myofascial pain
how does laser therapy for chronic pain work?
reduces pro-inflammatory mediator and cytokines
what can exacerbate pain/inflammation in obese animals?
adipokines
what can be used to treat chronic pain in food producing animals?
NSAIDs
paracetamol
ketamine
why is anaesthesia monitored?
maintain physiology maintain anaesthetic depth prevent pain safety legal implication
how is the CNS monitored during anaesthesia?
reflexes (palpebral, corneal) anal tone eye position/movement lacrimation autonomic tone (sweating...) muscle tone (jaw...) movement response to surgery
where do small animals eyes rotate in an adequate plane of anaesthesia?
ventromedially
what is the HR of a horse?
20-40bpm
what is the HR of a dog?
50-100bpm
what is the HR of a cat?
80-160bpm
what is the respiratory rate of a horse?
4-10bpm
what is the respiratory rate of a dog?
10-20bpm
what is the respiratory rate of a cat?
15-30bpm
what is an oesophageal stethoscope used for?
auscultating heart/lungs even if animal is covered by drapes
what does an ECG monitor?
electrical activity of the heart
what is arterial blood pressure used to monitor?
indication of cardiac output and perfusion
what are the three values given for arterial blood pressure?
systolic pressure
diastolic pressure
mean pressure
what is normal systolic arterial blood pressure?
80-140mmHg
what is normal diastolic arterial blood pressure?
50-90mmHg
what is normal mean arterial blood pressure?
60-90mmHg
what are the two ways of monitoring arterial blood pressure?
invasive (gold standard)
non-invasive
what does pulse oximetry measure?
% saturation of haemoglobin with oxygen
what is normal haemoglobin oxygen saturation?
> 95%
what are the limitations of pulse oximetry?
hypoperfusion bright lights movement anaemia probe can blanch capillary bed
what does capnography measure?
end tidal CO2
what is normal end tidal CO2?
35-45mmHg
what can capnography tell you? (other than CO2)
correct ETT placement
confirms cardiac output indicates problem with breathing system
what are the three common complications of anaesthesia? (Hs)
hypotension
hypothermia
hypoventilation
what figure should mean arterial blood pressure stay above during surgery?
> 60mmHg
what can cause hypotension during surgery?
reduced cardiac output (reduced stroke volume and HR)
reduced systemic vascular resistance
what are the steps for treating hypotension under anaesthesia?
check cuff (repeat reading) check plane of anaesthesia check HR give fluid drugs change position
what drugs can be given to treat hypotension during anaesthesia?
vasoconstrictors
positive inotropes
what are the main organs/tissues are we concerned about being damaged during hypotension from anaesthesia?
acute kidney injury
myopathy
why does hypothermia occur under anaesthesia?
increase heat loss
reduced heat production
no behaviour responses (shivering)
alterations to hypothalamic function
what are the consequences of hypothermia?
arrhythmias
coagulopathies
reduced immune function and drug metabolism
what can hypoventilation cause?
hypercapnia
hypoxaemia
when should hypercapnia be treated?
end tidal CO2 >60mmHg
how is hypercapnia treated?
increase minute ventilation - lighten plane and mechanical ventilation
when should hypoxaemia be treated?
saturation O2 <90%
how can hypoxaemia be treated?
increase oxygen delivery mechanical ventilation increase gas exchange (bronchodilators) check ETT blockage fluids
what can cause bradycardia under anaesthesia?
increased parasympathetic system activation (drugs)
hypothermia
disease (hyperkalaemia)
what can cause tachycardia during anaesthesia?
increased sympathetic tone
hypovolaemia
hyperthermia
hypercapnia
why is recovery phase of anaesthesia so dangerous?
physiological support reduced
monitoring is reduced
some problems manifest after a delay
what are the most common recovery problems?
hypotension
hypothermia
emergence delirium
hypoxaemia
what are the consequences of hypothermia in recovery?
reduced MAC requirement
shivering
delayed recovery
wound healing problems
what is emergence delirium?
state of dissociated consciousness where the patient is incoherent, irritable and uncooperative
what can be done to treat/prevent emergence delirium?
sedate/restrain
reduce stimulation, noise and light
analgesia
what are the clinical signs of hypoxaemia?
cyanotic MM
tachypnoea
stertor/stridor
reduced consciousness
when do you extubate an animal?
once they can protect their own airway (once swallowing)
what issues are seen in dogs/cats during recovery?
gastric reflex/aspiration
tracheal tear (cats)
blindness (cats)
what issues are seen in horses during recovery?
colic
myopathy/neuropathy
fracture
what issues are seen in ruminants during recovery?
regurgitation/aspiration
bloat
what issues are seen in pigs during recovery?
respiratory obstruction
hyperthermia
what needs to be assessed in an emergency patient?
ABC
mentation
problems (prioritise)
what basic diagnostic tests can be done on emergency cases?
PCV/TP, electrolytes, glucose
T-FAST, A-FAST
thoracic/abdominal radiographs
how is fluid therapy given in emergency cases?
(bolus) - 10-20ml/kg of crystalloid over 10 minutes
what are potential problems when anaesthetising emergency cases?
CV
respiratory
pain
temperature
what drugs can be used to sedate emergency cases?
alpha 2 agonists acepromazine benzodiazepines ketamine opioids
what alpha 2 agents would be most suitable for IM administration to a horse?
detomidine
which opioid is good for very painful 3-4 hour procedures in a cat?
methadone