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ISVPS Ncert Anaesthesia & Analgesia > Analgesia and Pain Assessment > Flashcards

Analgesia and Pain Assessment Flashcards

(103 cards)

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1
Q

What happens when a tissue is damaged?

A

The tissue is damaged, inflammatory mediators release prostaglandins and leukotrienes. These lower the firing threshold of nociceptors so they respond to a lesser stimuli. This contributes to allodynnia and hyperalgesia

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2
Q

Define allodynia

A

pain that is created from a simulus that does not normally cause pain

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3
Q

Define hyperlagesia

A

A normally painful stimulus that causes more pain than usual

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4
Q

What is the difference between somatic and visceral pain?

A

Somatic pain arises from skin or msuscle whereas visceral pain arises from internal organs

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5
Q

What type of fibres are visveral nociceptors?

A

Polymodal C fibres. They are sparse in their distribution compared to skin.

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6
Q

What is transduction?

A

The first part of the pain pathway. The coversion of a noxious stimuli (pressure or temperature) into an electrical stimulus.

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7
Q

What is transmission?

A

2nd part of the pain pathway where electrical signals move up A and C nerve fibres to the dorsal horn of the spinal cord.

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8
Q

The transmission part of the pain pathway can be transmit the electrical signal via the A or C fibres. What is the difference between these?

A

A fibres are fast conducting, small fibres that are myelinated for shapr mechanical pain. C fibres are slow conducting, unmyelinated fibres for longer lasting, dull, burning pains.

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9
Q

What happens at the dorsal horn of the spinal cord once the electrical signal is received?

A

A reflex arc where if the animal is conscious, the motor nerves move the muscles to remove the area from the noxious stimuli.
Also, the decision is made whether to pass the information ot the brain (AKA MODULATION). Once it reaches the brain, the animla becomes aware of it (PERCEPTION)

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10
Q

List the 4 parts of the pain pathway

A

Tranduction
Transmission
Modulation
Perception

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11
Q

What is nociceptive pain?

A

From tissue injury

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12
Q

What is neuropathic pain

A

From nerve injury

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13
Q

What is nociplastic pain?

A

Pain from a sensitised nervous system

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14
Q

List the physiological consequences of pain

A

Increased sympathetic tone
Increased SVR and preload
Increased SV
Increased myocardial work
Increased metabolic rate
Altered clotting function
Decreased GI and urinary tone
Increased ACTH cortisol ADH renin and angiotensin
Hyperglycaemia
Increased protein muscle metabolism
Retention of sodium and water

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15
Q

Describe how you would carry out a pain score in a hospitalised animal

A
  • Observe the animal from outisde the kennel. Note any abnormal posture, restlessness, attention to any particular areas/wounds
  • Open door and attract animal, note willingness to interact and demeanor.
  • Allow animal out to move around and note any lameness/reluctance
  • Gently palapate animal’s painful focus, note response.
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16
Q

What are the 3 main types of pain score? What is the differences between them?

A

Visual analogue scales (VAS)
Numerical rating scales (NRS)
Simple descriptive scales (SDS)

All semi-objective scoring systems. VAS on a horizontal line scale, anchored either end with two phrases and mark where.
NRS uses pain score assigned to number usually 1-10. SDS categories and each assigned a number.

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17
Q

Where on the pain pathway do opiods work?

A

Modulation and perception

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18
Q

What type of agonists are Methadone, Buprenorphine and Butorphanol?

A

Methadone full mu agonist
Buprenorphine is partial mu agonist
Butorphanol is a kappa agonist and a mu antagonist

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19
Q

How do NSAIDs work?

A

By blocking cyclo-oxygenase enzymes (COX). COX enzymes convert arachidonic acid to prostagladins( which accumulate in areas of tissue injury). NSAIDs block these enzymes therefore blocking the transduction part of the pathway.

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20
Q

As well as analgesia, what else are NSAIDs used for?

A

Anti-inflammatory
Anti-pyretic
Anti-endotoxaemic

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21
Q

When are NSAIDs contraindicated? Why?

A
  • steroid use
  • renal failure
  • hypovoleamia
  • hypotension
  • any GI ulceration, v+ or d+
  • clotting dysfuncitons

Prostaglandins are also part of the kidney and gut’s homeostatic mechanisms and are needed to maintain function.

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22
Q

Why can paracetemol be used at the same type as other nsaids?

A

It does not work on the same part of the COX pathway

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23
Q

What part of the pain pathway do Alpha 2 adrenergic agonists work on?

A

Modulation and perception (can be given by epidural and affect the transmission stage)

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24
Q

Why is ketamine good for chronic pain?

A

Antagonises NMDA receptors which are involved in the development of central sensitisation

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25
What are the only analgesics that can provide total absence of pain ? How?
Local anaesthetics work on the transmission part of the pathway. They block the pain by stopping the nerves conducting the pain signals by blocking sodium channels in the nerve fibres. Affects sensory and motor nerves.
26
What are the 2 groups of local anaesthetics?
Amide linked - undergo hepatic metabolism (e.g. lidocaine, bupivicaine) Ester linked e.g. procaine - broken down in the blood by enzymes.
27
How does maropitant cause analgesia?
Provides some visceral analgesia by antagonising the NK1 receptors
28
What are the treatment on the pain ladder for mild, mild to mo, and mod to seveere pain?
Mild: Non-opiod (NSAID) +/- adjuvant Mild-Mod: weak opiod +/- non-opiod +/- adjuvant Mod-Severe: strong opiod +/- non-opiod +/- adjuvant
29
Decribe the action/use of gapiprant?
Used for OA pain in dogs Works as an antagonist at EP4 receptor for PGE2 - providing analgesia for OA wihtout affecting 'housekeeping'enzymes.
30
How does librela (Bedvetinmab) work? And frunevetmab in cats (solensia)
contains canine monoclonal antibody (mAb) which targets nerve growth factor (NGF).
31
Where does paracetemol act on?
Spinal cord level on COX enzymes, opioid, serotonninergic and cannabinoid systems
32
How does codeine work?
Acts as an opioid by binding to opioid receptors. Converted to morphine in the liver. Also used as an anti-tussive and anti-diarrhoea.
33
How do pregabalin and gabapentin work?
Bind to calcium channels in the CNS, reducing the production of pro-nociceptive inputs and facilitating descending inhibitory pathways. Good for chronic and neuropathic pain.
34
What receptors does tramadol act on? Why is it sometimes ineffective?
mu opioid receptors 5HT receptors Noradrenaline receptors Needs to be converted to the active metabolite to have an anlgesic effect.
35
What is meant by adjunctive therapies?
Acupuncture, physio etc.
36
How does acupuncture work?
suppresses transmission of signals along the c fibres
37
What is meant by a dissociative anaesthetic?
Provides: - profound analgesia - light sleep - amnesia - catatonia (state of immobility and rigidity)
38
What drugs used in practice would fall under schedule 2?
Morphine Methadone Pthidine Ketamine Fentanyl
39
Who is involved in the re-classification of ketamine?
Commission of Narcotic Drugs (CND) World Health Organisation (WHO)
40
Why is ketamine under review for international scheduling? Why is this not right?
China called for the international scheduling because they have abuse problem with it. Ketamine is unlikely to be fatal if abused and the problem is local as its produced in china so international scheduling wont affect it. Ketamine would no longer be available in poor countries for anaesthesia - it is often the only available drug. Its cheap and has a high safety profile so is ideal for these situations of war and poverty. Will also probably become unavailable for veterinary use.
41
What is the onset of action and duration of action of lidocaine?
Onset 10 minutes Duration 1-2 hours
42
What is the onset of action and duration of action of bupivicaine?
Onset 20-30 minutes Duration 2-6 hours
43
What is the dose onset of action and duration of action of ropivacaine?
0.1-2mg/kg Onset 2-20 mins Duration 2-6 hours
44
Where is an infraorbital dental block inserted?
To the infraorbital foramen - between rostrodorsal border of zygomatic arch and canine root tip.
45
Where is a maxillary nerve block inserted?
Injected into the pterygopalatine fossa - between the rostral alar foramen and teh maxillary foramen.
46
Where is the mental nerve block inserted?
Where the middle nerve exits from the middle mental foramen.
47
Where is the mandibular nerve block inserted?
Mandibular foramen. Guided by feel from inside.
48
What block can be used for ocular surgery? What nerves does it block?
Retrobulbar nerve block. Cranial nerves 2,3,4,& 5 (opthalamic and maxillary branches) and 6 (densensitising globes, lids, conjunctiva and upper face and ocular muscles producing a central eye. Palpebral reflex (7) may remain
49
What block is good for ear surgeries including TECA
Auriculo-temporal and greater auricular nerve blocks. Desensitises the inner surface of the auricular cartilage and the external ear canal
50
Where would you disperse your block when performing a auriculotemporal block?
Needle inserted down the vertical ear canal towards the base of the V (formed by the caudal aspect of the zygomatic arch and the vertical canal)
51
Where would you disperse your block when performing a greater auricular nerve block?
Insert needle ventral to ring of atlas and caudal to the vertical ear canal and directing it parallel to vertical ear canal.
52
Describe a scenario when and how IV regional anaesthesia would be appropriate?
Distal limb block. Lidocaine given IV on a tourniquet'd limb at top. Drain blood by wrapping tow up then tourniquet and undo bandage. Inject lidocaine in down-facing catheter. Tourniquet for max 60-90mins.
53
What is the maximum injectable volume per site for inter-digital blocks?
0.5mls
54
Where is a saphenous nerve block placed?
Cranial to the femoral artery on the medial thigh
55
Where is the peroneal block placed?
Inject distally into the fibular head
56
Where is the tibial nerve blocked?
Needle inserted deep into the medial and lateral heads of the gastrocnemius
57
Where does saphenous, common peroneal and tibial nerve blocks work on?
Anything distal to the stifle
58
What area do radial, ulnar and median blocks work on in a cat?
The fore paw
59
Where would a radial block be inserted in a cat?
SC dorsomedial to carpus and proximal to the joint
60
How are the medial and ulnar nerves blocked in a cat?
inject medial and laterally to the accessory carpal pad on the palmar surface of the paw.
61
What area do radial, ulnar and median blocks work on in a dog?
Forelimb distal to the elbow
62
Where would a radial block be inserted in a dog?
Inject proximal to the lateraly epicondyle of the humerus and direct between brachialis and lateral head of the triceps
63
How are the medial and ulnar nerves blocked in a dog?
Inject proximal to the medial epicondyle of the humerus and direct between biceps brachii and medial head of triceps
64
Where is a brachial plexus block inserted and where does it numb?
Inject 10-15ml into the axillary space at the level of the point of the shoulder. THis blocks the lower forelimb but not eh shoulder or the proxmal humerus.
65
Why shoudl we exercise caution on bilateral brachial plexus blocks?
Could block the phrenic nerve which is required for movement of diaphragm and breathing
66
Describe how to perform an intercostal nerve block
Block at least 2 ribs cranial and caudal to desired zone. Inssert needle perpendicuar to body wall on caudal edge of rib and proximal to the wound. Inject as close to the intervertebral foramen as possible. Use 0.25-1ml per site
67
How would an interpleural block be administered? Where does it block?
Via a catheter or chest drain. Cranial organs, cranial mammary glands and pleural cavity
68
What strength is electric muscle stimulation performed at? Why?
initally 1mA and then once in place with most twitching, turn down gradually to 0.4mA. This is to ensure tip of needle is not inside nerve bundle inteslf before injecting.
69
Where is an epidural usually inserted?
At the lumbo-sacral (L7-S1) site into the epidural space. The bevel faces the direction of where you want the action .e.g abdomen, point crainially.
70
What surgeries/conditions can an epidural provide pain relief for?
Surgery/pain of hindlimbs, tail, perineal region, pelvis, abdomen and thorax, acute pancreatitis. Also cats with aorto-iliac thrombosis - as local anaesthetics have an effect on the sympathetic outflow tract, they cause vasodilation and this may help move the thrombus.
71
Describe the anatomy of the dog and cat lumbo-scaral spine
Dogs spinal cord terminates at l6-l7 so no CSF should be aspirated when persorming an epidural. The needle should be inserted halfway across the dip between l7 and s1. Cat spinal cord terminates at s1-s3 so theere is a cance CSF will be aspirated. The slope of the L7 spinous process is less steep than in dogs. The needle should be inserted in the distal third of the dip between l7 ands1
72
What ligament are we aiming to penetrate with an epidural?
Ligamentum flavum
73
Describe how to perform an epidural
Patient under GA, sternal and straight. Clip and prep area. Find line connecting the iliac spines of the pelvis. These should meet at the spinous process of L7. There will be a 'dip' caudal to this between L7-S1. Nick the skin with a scalpel, insert spinal needle at 90o to the skin, advance to hear popping sensation. Withdraw the stylet, using other hand to steady needle. Aspirate to check for blood/CSF, slowly inject drug over 30-40 secs.
74
When would an epidural not be approprite?
When the anatomy has been distorted e.g. trauma to pelvis. Patients with coagulopathies, possible bleeding round spinal cord as floor of epidural space contains lots of blood vessels. If there is evidence of skin infections.
75
What are the complications of epidurals?
- LA toxicity (max 1ml/5kg roughly) - Introduction of infection - Spinal cord/nerve damage - Urine/faecal retention - pruritus - Poor hair regrowth - Poor results - Hypoventilation (from cranial spread) - Sympathetic block and vasodilation
76
When should epidural doses be reduced?
Geriatric animals (less spreads sideways due to fibrous tissue blocking it so more drug travels forwards) Pregnant animals (reduced space in spinal cord due to engorged blood vessels and IAP thereofre more cranial spread) Obese (same as pregnant - less space)
77
What are the recommended doses of drugs for epidurals?
Lidocaine 4mg/kg Bupivicaine 1mg/kg Morphine 0.1mg/kg Buprenorphine 0.005-0.015mg/kg Medetomidine 0.01mg/kg Morphine and Bupivicaine: 0.05-0.1mg/kg+0.5-1mg/kg Morphine and Medetomidine: 0.1mg/kg + 0.001-0.005mg/kg
78
What is the onset of action and duration for lidocaine, bupivicaine, morphine, buprenorpine, medetomidine and combinations of morphine/bupivicaine and morphine/medetomidine?
Lidocaine: 5-10m, 1-2 hours Bupivicaine: 15-20m, 4-6+hours Morphine: 20-60m, 16-24 hours Buprenorphine: 60m, 16-24hours Medetomidine: 5-10m, 1-8hours M/Bup: 15m, 16-24hrs M/Med: 10m, 16-24hours
79
Why does pre-emptive analgesia have an effect?
Because it blocks afferent input to the nervous system to prevent central and periphheral sensitisation
80
What is peripheral sensitisation?
increased responsiveness and reduced threshold of nociceptive neurones in the periphery to the stimulation of their receptive field.
81
What does central sensitisation cause?
Hypersensitivity to stimuli, responsiveness to non-noxious stimuli and increased pain resposnse by stimuli outside the area of injury
82
What is the difference between primary adn secondary phase of injury
Primary phase = noxious stimulation of the incision and secondary phase = release of chemicals and enzymes from damaged tissues. Secondary phase lasts well into post-operative period
83
What part of the pain pathway does local anaesthetics work on ?
Transduction and Transmission
84
What part of the pain pathway does NSAIDs work on?
Transduction (reduces the formation of prostaglandins that form the inflammatory soup that sensitises the nociceptors lowering their firing threshold)
85
List some side efffects of opioids
Nausea Vomitting Constipation Pruritis Sedation Decreased central respiratory drive Decreased respiratory rate Decreased tidal volume Repiratory depression Bradycardia
86
What are the sider effects of alpha 2 adrenergic agonists
Vomitting Polyuria Hypersalivation Hypothermia Diarrhoea Bradydysrhytmias Respiratory depression Hypertension
87
What are the side effects of local anaesthetics?
sedation nausea cardiotoxicity
88
What are the side effects of Ketamine?
High BP Tachycardia Respiratory depression Muscle tremors Spastic body movements Vocalisation Very rare - seizures
89
What are the side effects of NSAIDS
Nephrotoxicity GI distrurbance Hepatotoxicity Effects on platelet aggregation Chondrodestructive
90
Define pharmacokinetics
The process which describes the way in which the body handles drugs after we have administered them e.g. how it absorbs, distrubutes and eliminates them
91
Why is a loading dose given before a CRI?
Want to get the plasma level of the drug to a therapeutic level - otherwise we'd have to wait 5 half lives of the drug.
92
Define half life
Time taken for the plasma concentration to fall to 50% of its initial value
93
How can we calculate the loading dose of a drug?
Loading dose = volume of distribution x required plasma concentration. The volume of distribution is the apparent volume into which a drug disperses
94
What is a steady state (in terms of a CRI)?
Where the rate of drug administration is equal to the rate of drug elimination. So we need to work out how fast the body is eliminating the drug so we can match it.
95
How do we calculate how quick the body is eliminating a drug?
Rate of elimination = clearance x plasma concentration Clearance = the volume of plasma from which a drug is completely removed per unit time.
96
What is the loading dose and infusion rate of ketamine?
0.5mg/kg and 10-20ug/kg/min
97
What is the loading dose and infusion rate of Morphine?
0.3mg/kg and 100-200mg/kg/hr
98
What is the loading dose and infusion rate of Lidocaine
2mg/kg and 50-100ug/kg/min
99
What is the loading dose and infusion rate of fentanyl?
1-5ug/kg and 2-5ug/kg/hr
100
What is the loading dose and infusion rate of Alfentanil?
0.5-1 ug/kg and 0.5-1ug/kg/min
101
What is the loading dose and infusion rate of Remifentanil?
1ug/kg and 0.1-0.2 ug/kg/min
102
What is the loading dose and infusion rate of Medetomidine?
5ug/kg and 1-2ug/kg/hr
103
What is the loading dose and infusion rate of dexmedetomidine?
2-3ug/kg and 1ug/kg/hr

ISVPS Ncert Anaesthesia & Analgesia (8 decks)

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