LS Anaesthesia Flashcards
What is the definition of pain?
An unpleasant sensory and emotional experience associated with (actual or potential) tissue damage
What is the definition of nociception?
The neural process of encoding noxious stimuli
What is the difference between nociception and pain?
Nociception is the wiring part
Pain is how the patient interprets nociception
What is nociceptive pain?
Pain that arises from damage to non-neural tissue that activates nociceptors
What is neuropathic pain?
Pain caused by a lesion or disease of the somatosensory nervous system
What is hyperalgesia?
Increased pain from a stimulus that normally provokes pain
What is allodynia?
Pain due to a stimulus that does not normally provoke pain
What are the physiological signs associated with pain?
Increased HR, BP, temp, resp, stress hormones
What are behavioural signs of pain in cats and dogs?
Hunched
Pain face
Lack of grooming
Inappetence
What are different behavioural signs of pain in dogs?
Cats hide, dogs seek attention
Cats have fear aggression, dogs are submissive
What are behavioural signs of pain in rabbits?
Immobile, hunched
Depression and isolation
Eyes shut
What are behavioural signs of pain in horses?
Low head Vocalisation Tail swishing and restless Lame/limb lifting Hunched Sweating
What are methods of scoring pain?
Composite pain scales
Numerical rating scale
Visual analogue scale
Simple descriptive scale
What is a method of monitoring chronic pain?
Client specific outcome measures - client chooses activities animal usually does
What is preventative analgesia?
Analgesia given before, during and after the surgery/procedure
Why do you give preventative analgesia?
To prevent upregulation of the nervous system from noxious stimuli
What is multimodal analgesia?
Using different classes of analgesic agents to block pain pathways
Why do you give multimodal analgesia?
More effective analgesia
Lower doses needed
What are the main analgesic agents?
Opioids
NSAIDS
a2 agonists - analgesic sedatives
What category of controlled drugs are opioids?
Full opioid agonists - schedule 2
Partial - schedule 3
What receptor do opioids target for analgesia?
Mu (backwards u) opioid receptor in the brain and spinal cord
What type of pain are opioids best for treating?
More for acute
What does potency mean?
The amount of drug needed to have an effect
What does efficacy mean?
The magnitude of the effect of a drug
What opioid has the highest potency and efficacy?
Fentanyl
What opioids are full mu agonists?
Fentanyl
Methadone
What opioids are partial agonists?
Buprenorphine
Butorphanol
What opioid is the longest acting?
Buprenorphine
What opioid is the shortest acting?
Fentanyl
What are side effects of opioids?
Resp depression
Sedation/excitation
Nausea and vomiting
What do NSAIDs inhibit?
Cyclooxygenase which inhibits prostaglandin production (inflammatory mediators)
Where are NSAIDs metabolised?
In the liver
What is the most common NSAID?
Meloxicam
What are side effects of NSAID use?
GI ulceration
Renal ischaemia
Vomiting and diarrhoea
What is always the ending of local anaesthetics?
-caine
How do local anaesthetics work?
Block voltage gated Na+ channels in nerves
What are the two types of linkages in local anaesthetics?
Ester
Amide
How can you tell if the local anaesthetic is an ester or an amide?
Esters have no i in the name before the caine whereas amides do
Which type of local anaesthetic is more stable?
Amide
Which type of local anaesthetic has a short plasma half life?
Ester
What are some side effects of local anaesthetics?
CNS toxicity
CV toxicity
Due to high doses
What local anaesthetics are used in small animals?
Lidocaine and bupivicaine
What local anaesthetic is used in large animals?
Procaine
What kind of drug is tramadol?
Centrally acting analgesic with multimodal action
How should tramadol be used?
In dogs
Only injected
Co-analgesic - not alone
What is amantadine sued for?
Antihyperalgesic
What is epidural anaesthesia?
Anaesthetic injected into the epidural space
What is spinal anaesthesia?
Anaesthetic injected directly into cerebrospinal fluid
How are ester local anaesthetics metabolised?
Hydrolysis of ester link by plasma esterases
How are amide local anaesthetics metabolised?
Broken down by cytochrome P450 enzymes
What are the different formulations of local anaesthetics?
Solutions
Aerosol sprays
Topical patches
What is baricity?
Weight of one substance compared to the same volume of another
When is baricity an issue?
Need local anaesthetic to be heavier than cerebrospinal fluid so it doesnt spread up the epidural space too far so add glucose
What is used to prolong the duration of action, reduce systemic absorption and reduce toxicity of local anaesthetics?
Adrenaline - vasoconstrictor
What reduces plasma protein binding?
Lower pH
How is toxicity linked to plasma protein binding?
Better binding to plasma proteins means longer duration of action and lower risk of toxicity
What are used to help with seizures due to CNS toxicity?
Benzodiazepines
Why are premeds used?
Balanced anaesthesia
Reduce stress and injury
Which premed drugs have an analgesic action?
A2 agonists
Opioids
What premed drugs work as a dopamine receptor antagonist?
Phenothiazines - ACP
What premed drugs act on the GABA receptor?
Benzodiazepines
What is ACP usually given with? Why?
Opioid
Provides analgesia as ACP doesnt
How is ACP administered?
Subcut injection
What effect does ACP have?
Sedation
Anxiolysis
What is a potential side effect of ACP?
Fall in body temp as peripheral vasodilation
Decrease in blood pressure
What is the duration of action of ACP?
4-6 hours - long
How long does ACP take to have a clinical effect?
30-40 mins
What is the antagonist of a2 agonists?
Atipamezole
What effect do a2 agonists have on CV function?
Bradycardia
Reduced CO
What effect do a2 agonists have on GI function?
Depress GI activity
Emetic - vomit
What effect do a2 agonists have on pregnant animals?
Increase uterine contractility - abortion
Avoid in near term animals
How long do a2 agonists take to have an effect?
5 mins - rapid
What are the clinical effects of benzodiazepines?
Muscle relaxation
Anticonvulsant
Minor tranquilliser
When should you give benzodiazepines as sedation?
Good in sick or young animals
Unreliable in healthy animals - excitement
How are benzodiazepines administered?
Slow IV
What is the reversal agent of benzodiazepines?
Flumazenil
How does flumazenil work as a reversal agent?
Competitively antagonises benzodiazepines binding site
What is an example of a butyrophenone?
Fluanisone
How must fluanisone be administered?
In combination with opioid fentanyl
What is the combination fluanisone and fentanyl licenced in?
Rabbits and small furries
When is fluanisone and fentanyl used?
Minor surgery and diagnostic techniques - poor muscle relaxation
What premeds are given to ASA grade 1 and 2?
ACP + opioid
a2 agonist + opioid
What premeds are given to ASA grade 4 and 5?
Benzodiazepines + opioid
BDZ + ket
Opioid alone
What are some safety issues with sedation?
NO control over airway
No option to deepen sedation without going to full GA
What are two examples of a2 agonists?
(Dex)medetomidine
What kind of sedation is the most likely to be reversed?
a2 agonists
What should you do if there is a low SpO2 from pulse oximeter?
Check pulse ox
Check correctly intubated, no leak from cuff
Check breathing pattern - may need ventilation
Check for obstruction
Check machine works
What are some causes of tachycardia in anaesthesia?
Inadequate depth of anaesthesia
Hypercapnia (increased CO2)
Hypovolaemia - need fluids
Drugs - directly
What are some causes of bradycardia during anaesthesia?
Deep anaesthesia
Opioids and a2 agonists
Hypothermia
What counts as hypotension?
Mean arterial pressure below 60mmHg
What can cause hypotension during anaesthesia?
Drugs
Blood loss
Pre-existing condition
What local anaesthetic is used for eye examination?
Proparacaine
What local anaesthetic is used for an intratesticular block for castration?
Lidocaine
What is used for topical anaesthetic on the larynx?
Lidocaine
How is procaine licenced for administered in large animals?
Subcut injection
What is the withdrawal period for procaine?
Zero
What can be an issue with cornual nerve block in goats?
Have two branches of nerves - cornual nerve and cornual branch of intratrochlear nerve
Toxicity levels in kids
What are the 3 different techniques of abdominal flank surgery local anaesthesia?
Paravertebral
Inverted L block
Local infiltration along incision site
What nerves are desensitised in paravertebral block?
T13, L1 and L2
What is found between the dorsal and ventral branches of the spinal nerves in a paravertebral block?
Intertransverse ligament
How do you identify the first transverse process?
Count back from L5 transverse process
Which way do you walk the needle off the transverse processes?
Forward off L1
Back off L1
Back off L2
What are the disadvantages of an inverted L block?
Large amount of LA
Not as effective analgesia
Where do you inject for a sacrococcygeal epidural?
Most movable space if pump tail up and down - sa5-co1
