Anaesthesia Flashcards
What are the types of anaesthetic medication?
- sedatives/tranquilisers
- analgesics
- anticholinergics
What animals do sedatives/tranquilisers commonly apply for?
Rodents but commonly used in larger speceis
What is the effect of sedatives?
Drowsiness with sluggish arousal response
What is the effect of tranquilisers?
Some relaxation and drowsiness but with rapid arousal response
Give some examples of sedative/tranquilisers.
phenothiazines
alpha-2 agonists
benzodiazepines
butyrophenones
What are the properties of phenothiazine and what are some examples of phenothiazine?
- Light sedation only
- Can be used in many species, but not in rodents
- Best not used in very old/young
- No analgesic properties - no pain release effect
- acepromazine -‘ACP’
wha are the properties of ACP?
-effective, inexpensive drug, capable of reducing induction and maintenance needs significantly.
-In fit and healthy animals of all species, ACP is a very useful and safe drug, producing light sedation.
-it should be avoided in very young animals (<12 weeks in cats/dogs) and used with care in geriatric animals.
-it has no analgesic properties of its own
-Potential adverse effects of ACP include hypotension and peripheral vasodilation
What are the properties of Alpha2 adrenoreceptor agonists and what are some examples of Alpha2 adrenoreceptor agonists?
- xylazine and medetomidine
- Commonly used in many species
- Very powerful sedatives
- Also some analgesic properties
What are the properties of Medetomidine?
-it produces stress reduction, dose related analgesia, muscle relaxation, good maintenance of core body temperature, stable anaesthesia, freedom from respiratory depression and is anti-arrhythmic.
-High doses of medetomidine can produce pronounced peripheral vasoconstriction (animal extremities become very pale), marked hypertension (blood pressure rises) and bradycardia (slow heart rate).
-When used in combination with an opioid, such as butorphanol or buprenorphine, the potential for unwanted side effects is quite low
What are the properties of Xylazine?
-It is the sedative of choice for cattle, and also works well in horses, but in most other species does not have any significant advantages over medetomidine.
-it is frequently used in combination with ketamine in the rodent species to
provide light surgical anaesthesia.
What are the properties of Benzodiazepines and what are some examples of Benzodiazepines?
- midazolam* – ‘Hypnovel’
diazepam** – ‘Valium’
[Controlled drugs * Schedule 3, **Schedule 4] - Typical tranquilisers
- Provide good “sedation” in rodents, rabbits, pigs and sheep
- Very good for old and young animals
- Less anaesthetic sparing effect compared with true sedatives - need to give higher concentration than normal sedatives
- usually in combination with an opioid, as this combination has minimal effects on the cardiovascular and respiratory systems.
What are the properties of Butyrophenones and what are some examples of Butyrophenones?
Examples: azaperone – ‘Stresnil’
* fluanisone – component of ‘Hypnorm’
* Limited use in veterinary practice
* Produces mild sedation with some anaesthetic sparing effect
* Used as a sedative in pigs
* Combined with fentanyl in ‘Hypnorm’ (widely used neuroleptanaesthetic mixture)
What is analgesics?
- Analgesia is the temporary abolition or diminution of pain perception.
- Analgesics are more effective when given pre- operatively (i.e. BEFORE experiencing painful stimuli)
- Some analgesics may cause mild sedation
- Analgesics can also reduce the total amount of anaesthetic required.
The types of analgesia?
a) Opioids
a) Non Steroidal Anti-Inflammatory Drugs (NSAIDs)
a) Local anaesthetics
What are the properties of opioids?
-Nearly all opioids are controlled drugs (strict recording & storage rules)
-Classically used to control SEVERE pain.
-Different drugs have different effects at different receptors.
-Many side effects – especially respiratory depression. Most opioids are short acting.
-Antagonists are often available.
What are the examples of opioids?
1) μ agonists
2) Buprenorphine
3) Butorphanol
What are the examples and properties of μ agonists?
Examples: morphine, pethidine, oxymorphone, fentanyl.
* Very potent analgesic action.
* Generally have short duration of action, which
makes their practical use difficult.
* Fentanyl is a component of the neuroleptanaesthetic ‘HYPNORM’.
* Schedule 2 controlled drugs.
What are the examples and properties of Butorphanol？
- Useful for controlling mild pain.
- Has moderate sedative action.
- Rapid onset, but short duration.
- Can be combined with other drugs * in“anaestheticcocktails”.
*Butorphanol can also be combined with either ACP or medetomidine in healthy animals or with either midazolam or diazepam in aged and/or less healthy animals for premedication. It is not effective orally.
What are the examples of NSAIDS?
meloxicam -‘Metacam’
carprofen– ‘Rimadyl’
flunixin - ‘Finadyne’
ketoprofen-‘Ketofen’
What are the properties of NSAIDS?
- Aspirin or paracetamol-like like drugs.
- Suitable for controlling mild or chronic pain.
- Often given post-operatively or as a part of a multi-modal analgesic protocol.
What are the properties of Buprenorphine?(布洛芬？？？？）
- Controls moderate to severe pain.
- Duration of action 6-8 hours or longer.
- Slow onset of action (30-60 minutes).
- Widely used in rodents, rabbits and other lab animals.
- Schedule 3 controlled drug.
What are the disadvantages of NSAIDS?
- Long-term use can induce gastric ulceration
- Can interfere with some studies
What are the advantages of NSAIDS?
- Can be given by injection (typically s/c) * Can be given orally
- As drops into the mouth * In drinking water
- In palatable gel
What are the properties of Local anaesthetics?
- Local anaesthetics are very potent analgesics.
- They block sensory nerve endings in tissues, and the
effects may persist for several hours. - Available as topical or injectable preparations.
Local and Regional Anaesthesia
- Commonly used in (sedated, conscious) large animals for surgery.
- Can also be used to block nerves before surgery under general anaesthesia.
- Can infiltrate into surgical wounds at closure.
What is multi-modal analgesia?
Principles:
* Pain control is best achieved by giving analgesics BEFORE the onset or experience of pain.
* There are multiple pain pathways, each blocked by different analgesic agents.
* “Multi-modal analgesia” uses a combination of analgesics which together provide optimal pain control.
What is anticholinergics?
- Block acetylcholine in the central and peripheral nervous systems.
- Reduce bronchial and salivary secretions.
- Protect the heart from vagal inhibition due to some
surgery. - Contra-indicated in ruminants.
- Not often used in rodents.
What are the examples of anticholinergics?
atropine, glycopyrrolate
What are the properties of fentanyl?
-has a short duration of activity, which makes it unattractive as a pre-anaesthetic medication.
