WSAVA Nov 2021 Proceedings - Flipbook - Page 38
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THE ANAESTHESIA PLAN
- Acepromazine is often removed from the protocol
• Age
T. Farry
- Very young and older animals can have an altered ability to metabolise
drug and may have decreased organ function
Brisbane/Australia
• Cats and small dogs are susceptible to hypothermia
Qualifications:
• Cats are prone to laryngospasm
Trish Farry
RVN AVN VTS (ECC) (Anaes & Analgesia) GCHEd
t.farry@uq.edu.au
“By failing to prepare, you are preparing to fail” Benjamin Franklin
The process of developing a patient specific anaesthetic plan should
always be a priority in managing any patient undergoing anaesthesia. An
individualised plan that follows a step-by-step procedure will ensure that
we can identify and assess common risk factors and safety concerns
associated with anaesthesia and plan how to manage and mitigate identified concerns. The anaesthesia plan should include the pre-anaesthetic
patient exam and assessment, anticipated anaesthesia and procedural
considerations, drug and support therapy and monitoring along with post
anaesthesia and recovery plans. This may sound like a great deal of work
for each case, but by systematically following a plan we will achieve better
outcomes for our patients and allow us to be better prepared to respond
to complications that may occur during the anaesthesia period.
How To Devise an Anaesthetic Plan
Using the acronym SHEAP (Signalment, History, Examination, Assessment, Plan) will aid in the preparation of a comprehensive anaesthetic
plan.
Signalment
This will include species, breed, and age factors. Some examples of breed
and species specific considerations for anaesthesia are:
• Greyhounds
- Have the potential for prolonged recovery following anaesthesia with
thiopentone
- More rapid clearance of methadone so may require more frequent doses
of methadone
- Susceptible to fibrinolysis and may require pre-treatment with either
tranexamic acid or aminocaproic acid
• Cats have altered ability to metabolise some drugs as they have:
- Reduced UDP-Glucuronosyltransferase (UGT) which is involved in the
conjugation of many substances
- Reduced phase I metabolism (oxidation, reduction, hydrolysis) compared
to other species
- Propofol is metabolised via glucuronidation and hydrolysis
As the return to consciousness is a result of redistribution cats can be
induced successfully with propofol
Constant rate infusions may result in prolonged recovery as metabolism
is required
History
A thorough history is vital. Attention should be paid to:
• Current medications
- eg. NSAIDs or glucocorticoids, cardiac medications
• Evidence of wellness
- Is the patient eating, drinking, urinating, and defecating normally?
- Abnormalities in these normal bodily functions may indicate ill health
and co-morbidities that can have a significant effect on anaesthesia
• Has the patient presented for ill health such as vomiting which may
suggest dehydration and electrolyte abnormalities?
• Presence of previous co-morbidities and ill health
- eg. diabetes, hyperadrenocorticism, hyperthyroidism, seizures, heart
disease
• Fasting status
- Anaesthesia of an animal that has eaten may predispose it to vomiting,
regurgitation and aspiration
• Any previous anaesthesia history
• Boxers
Examination
- May exhibit a vasovagal response following premedication with acepromazine
This is the cornerstone of planning for any anaesthetic event. Every patient must be examined prior to anaesthesia and evaluated focussing on
factors that may affect the animal’s physiological homeostasis. Particular
attention should be placed on the respiratory and cardiovascular systems.
Examination of the cardiovascular system should include as a minimum,
auscultation of both sides of the heart including all heart valves and palpation of the pulse while auscultating the heart to identify pulse deficits.
Any patient with pulse deficits or an arrhythmia should have an ECG if
one is available. The heart rate should be recorded along with rhythm and
assessment of pulse quality, capillary refill time and mucous membrane
colour.
- May develop arrhythmogenic right ventricular cardiomyopathy
• Brachycephalic breeds are prone to obstruction and increased vagal tone
• Presence of a genetic mutation in the adenosine triphosphate driven
pump (ABCB1) which was formerly known as multi resistant drug 1
(MDR1) gene. This gene encodes a p-glycoprotein pump, present in the
blood brain barrier. Provides protection from the accumulation of toxic
levels of drugs in the CSF
- Breeds affected include collies, border collies (usually only a problem in
imported show dogs), Australian Shepherd and Shetland sheepdogs
- Acepromazine and opioids (especially butorphanol) can accumulate in
the CSF and their dosages should be reduced by at least 25%
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WSAVA GLOBAL COMMUNITY CONGRESS
The respiratory system examination should include as a minimum, observation of the respiratory rate and pattern prior to physical examination,
noting any evidence of airway obstruction or increased respiratory effort.
The nares should be examined for presence of exudate and airflow and
the oral tract examined (if possible) for presence of masses or ulcers.