Anaesthesia: Intro and Sedation and Premedication Flashcards
What is general anaesthesia?
The physiological state between being conscious and dead- the maintenance of ‘sleep’
What is the job of a vet for anaesthesia?
To anticipate, mitigate and minimise the risk of morbidity or mortality by:
Adequate preparation
Stabilisation
Protocol planning
Delivery
Monitoring
What are some general considerations of anaesthesia?
ASA status, aim of the anaesthesia, nature of the procedure, surrounding, equipment, knowledge, helpers
What skills are needed for anaesthesia?
(Day 1 Competencies)
- Ensure patient airway
- Giving O2
- Know how to apply IPPV- intermittent positive pressure ventilation
- IV catheter- give drugs IV
- Basic CPCR
Outline the general process of anaesthesia?
Premedication
Induction
Maintenance
Recovery
What is the ASA and what is the ASA status?
ASA is the american society of anesthesiologists
ASA status is the general health of the animal and the patient risk
What are the different ASA classifications?
ASA 1- Normal healthy animals
ASA 2- Mild systemic disease
ASA 3- Moderate systemic disease
ASA 4- Severe systemic disease, constant life threat
ASA 5- Moribund, not expected to survive following 24 hours
What ate the three aims of anaesthesia?
Unconsciousness
Analgesia
Muscle relaxation
What is balenced anaesthesia and what are the benefits of it?
Anaesthesia produced by safe doses of two or more agents or methods of anaesthesia, each of which contributes to the total desired effect
Benefits: reduction of dose of each component, reduction of the side effects, optimised post-operative analgesia
How does nature of the procedure influence general anaesthesia?
Duration of procedure
Pain level of procdure
Localisation- head/neck eg
Recovery time
How is analgesia managed in anaesthestic protocol?
Pre-emptive analgesia= treat pain before
Part of balanced anaesthesia/analgesia = reduction of requirment
Analgesia during recovery
What equimpent is needed for general anesthesia?
Depends but generally:
Oxygen source
Anaesthetic machine
Breathing system
IPPV/ventilator
Venous access/ infusion pumps
Monitoring
What is the risk of mortality of humans, cats, rabbits and horses?
1 in 2000 humans
0.11% of cats
just under 1 in 100 rabbits
1 in 100 horses will die
Most important factor is pre-exisitng disease
What is the difference between sedation and premedication?
Sedation:
may be used as an alternative to general anaesthesia
Non-invasive procedures
Non-painful procedures
Premedication- administered prior to anaesthesia
Terms often used interchangeably
Why sedate instead of premed?
To relieve patient anxiety
Facilitate handling
Analgesia
Muscle relaxation
To enable procedures
Why premedicate instead of sedate?
Smooth induction of anaesthesia
Smooth maintenance of GA
Smooth recovery of GA
Reduce required dose of induction/maintenance
What would the ideal premed or sedative do?
Relieve fear/anxiety
Be safe
Reliable and predictable effect
Quick onset, appropriate duration of action
Easy to administer (route, volume, non-irritating)
Minimal CV, Resp and other side effects
Provide analgesia
How can the cascade be used for sedatives and premeds?
Use the cascade to your advantage
Drugs for food producing animals must have an MRL
Use drugs to provide adequate analgesia
Use drugs to provide adequate sedation
What are considerations of sedation and premed?
- Reason for sedation/premed
- What drugs you can use- food producing/cascade
- Will there be pain
- Are your drugs safe to use in this case
- Will your drugs effectively sedate this patient
- What if it doesn’t work?
Why would you sedate/premed pre-appointment and what are your options?
For use of patients who are known to be anxious
Equine- acepromazine oral gel, detomodine oromucosal gel
Dogs and Cats- gabapentin 2 hours before appointment, Trazadone- caution if history of seizures
What opioids could be used for sedation/premed what are the advantages and problems?
Butorphanol
Buprenorphine
Methadone
Fentanyl
(morphine)
Advantages- may be adequate alone, often good sedation if the animal presents very painful
Disadvantages- Respiratory depression
What phenothiazines could be used for premed/sedation?
Acepromazine
What alpha 2 receptor agonists could be used for sedation/premed?
Xylazine, Detomidine, Romifidine, Medetomidine, Dexmedetomidine
Sympathomimetics
What benzodiazepines can be used for sedation/premed?
Diazepam, midazolam
affect GABA receptors
GABA is exitatory
What adjuncts can be used for sedation/premed? PAK
Propfol
Alfaxalone
Ketamine
What is acepromazine sedation/premed useful for?
What are its side effects?
How long is the onset?
What are the problems?
Useful for:
Mitral valve disease cases
Patients with BOAS
Laryngeal paralysis/URT disease
In combination with alpha-2 agonist for background calming effect
Side effects- vasodilation
Onset 20-40 minutes
Problems- unreliable sedation, no analgesia, not reversible, long duration of action
Has moderate MAC sparing effect
What is acepromazine not suitable for?
Very young patients <3 months
Hepatic impairment
Haemorrhage (actual or anticipates)
Anticipated hypotension during general anaesthesia
Sepsis
What are alpha 2 agonists useful for?
What are its side effects?
How long is it’s onset?
Useful for:
All adult horses, Farm animals, Most dogs/cats
Side effects:
peripheral vasoconstriction/reflex bradycardia, reduced cardiac contractility, increased urine production
Onset- depends on route: IV almost immediate, very reliable sedation
- What is the sedation of alpha 2 agonists like?
- Does it give analagesia?
- Is it reversible?
- How long does it last?
- Small or large MAC sparing effect?
- Very reliable sedation
- Does give analgesia
- Is reversible- atipamezole
- Duration depends on drug and dose
- Large MAC sparing effect
When are alpha 2 agonists not suitable?
Mitral valve disease
Very yound <3 months
Resulting bradycardia may be a problem
Urinary obstruction
- What are bezodiazepines useful for?
- How long is onset?
- What are their side effects?
- What is the sedation like?
- Does it give analgesia?
- Is it reversible
- What is the MAC sparing effect like?
- Useful for very young, very old, very sick
- Depends on ROA- IV 5 mins
- Minimal side effects
- Sedation unreliable
- No analgesia
- Is reversible- flumazenil
- Moderate MAC sparing effect
When are benzodiazepines not suitable?
Farm Animals
Potrosytemic Shunt cases
What are the options for adjuncts and wht are they used?
Adjuncts ‘help things along’
Propofol
Alfaxalone
Ketamine- more analgesia, increased sedation reliability
Physical restaints- not suitable for analgesia
How do you decide on route of administration?
Safety
Minimal stress
Will the drug work through said route?
How could you administer opioids?
IV- rapid onset
IM
SC- less reliable
TM- fentanyl
How can you administer acepromazine and what varies with ROA?
IV- lower doses
IM
SC
Oral- gel in horses, tablets in dogs/cats- less reliable
Sedation onset similar
How can Alpha 2 agonists be administered how do ROA vary?
IV- rapid onset, lower doses
IM
SC- less reliable
TM
How can you administer benzodiazepines what varys with ROA?
IV- more rapid onset, lower doses- could have paradoxical effect
IM- midazolam- less reliable
Oral- diazepam, not cats
Rectal
What can be given to food producing animals for sedation/premed?
Butorphanol
Xylazine- very sensitive
Detomidine
Azaperone- for pigs
Recumbancy following alpha 2 agonists administration
What adjuncts can be used for food producing animals?
Physical retraint
Ketamine
Ear twitch
Nose pliers
Crush
What drugs can be administered for Equidae?
Alpha 2 agonists give reliable sedation of adult horses
Choose drug to provide appropriate duration of sedation
Alpha 2 agonists first, opioid 5 mins later
Acepromazine to smooth recovery- not colic
What adjuncts can be usefd for horses?
Neck twitch
Ear twitch
Twitch
What is usually used for dogs and cats sedation/premed?
Alpha 2 receptor agonists very reliable
Acepromazine useful for calming for long duration
Benzodiazepines if very old, sick, young
