Post-op Pain Management Flashcards

1
Q

What is the difference between primary and secondary hyperalgesia?

A

Primary - immediately surrounding a site of injury; secondary - occurs outside the immediate area of injury

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2
Q

Define allodynia

A

A painful response to a normally innocuous stimulus

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3
Q

What are the 5 steps of the pain pathway?

A

Transduction, transmission, modulation, projection, and perception

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4
Q

Define the step of pain transduction

A

Creation of the nociceptive signal

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5
Q

Define the step of pain transmission

A

The nociceptive signal (action potential) is transmitted to the spinal cord

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6
Q

What are the two types of nociceptive fibers and what types of signals do they transmit?

A

A delta - fast, sharp pain; C fibers - slow, dull pain

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7
Q

What are A beta fibers?

A

Normally transmit only low threshold, non-noxious stimuli (normal touch), but this response may be altered in chronic pain states

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8
Q

Where do nociceptive fibers synapse?

A

The dorsal horn of the spinal cord

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9
Q

Describe the step of pain modulation

A

Occurs in the spinal cord and is dependent upon many molecular mechanisms (neuron interactions, inter neurons, descending modulators pathways)

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10
Q

What does neuroplasticity mean?

A

The degree and duration of nociceptive stimulation alters the patient’s pain response

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11
Q

A long term noxious stimulus will cause activation of what type of receptors?

A

NMDA and AMPA; results in wind up/central sensitization and the development of chronic and neuropathic pain

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12
Q

Define the step of pain projection

A

Projection of the nociceptive signal to the brain via the spinal cord

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13
Q

Define the step of pain perception

A

The conscious perception of the noxious stimulus in the brain; without this step, pain has not truly occurred (ONLY nociception has), as pain is a CONSCIOUS process

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14
Q

Which nociceptive fibers are the smallest? Largest? Have the fastest conduction velocity?

A

C fibers; A beta; A beta

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15
Q

Describe visceral pain

A

mainly associated with smooth muscle/hollow organ nociceptors that respond to stretch, hypoxia and inflammation; characterized by poorly-localized and diffuse pain

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16
Q

Describe somatic pain

A

Associated with skeletal muscles, joints, and bones and it is usually well-localized and described as sharp and/or aching pain

17
Q

Describe acute pain

A

Usually associated with an injury, surgical procedure, or other short-term disease process (physiological pain)

18
Q

Describe chronic pain

A

Pain ongoing 3 months or longer; may be classified as pathologic as it infers changes in the CNS that alter the pain pathway; the constant nociceptive stimulus changes the body’s response to noxious stimuli via opening glutamate-coupled stimulatory receptors and activation of normally dormant/silent nociceptors, resulting in central sensitization, and A beta fibers may start to transmit nociceptive fibers causing allodynia

19
Q

What are the 3 most commonly used pain scales converted from human medicine?

A

SDS (descriptions), NRS (numbers to grade), and VAS (visual analog- line with no marks)

20
Q

Which pain scoring system is validated only in dogs?

A

The Short Form of the Glasgow Composite Pain Scoring System

21
Q

Which scale can be used to grade acute pain in cats?

A

Colorado State

22
Q

What are some chronic pain scales validated for dogs?

A

Liverpool Osteoarthritis in Dogs (LOAD), Helsinki Chronic Pain Index (HCPI), Canine Brief Pain Inventory (CBPI)

23
Q

Opioids typically work on which step of the pain pathway?

A

The modulation step, because opioid receptors are largely present in the dorsal horn of the spinal cord

24
Q

T or F: Full mu agonists can be administered into the joints of patients with inflammation/osteoarthritis

A

True; mu opioid receptor expression is unregulated in inflamed joints

25
Q

Describe tramadol’s efficacy as a postoperative analgesic

A

Provides some mu receptor agonist, however Tramadol itself has a very weak affinity for this receptor; the M1 metabolite has a much higher affinity (cat are better at producing this metabolite)

26
Q

How do NSAIDs work to block pain?

A

They block cyclooxygenase conversion of the arachidonic acid pathway and therefore the synthesis of inflammatory mediators like prostaglandins and thromboxane

27
Q

How does grapiprant work?

A

It’s is a direct EP4 prostaglandin receptor antagonist

28
Q

What step of the pain pathway do NSAIDs work on?

A

Transduction, because they have direct effects at the tissue level (though they do still have central effects as well)

29
Q

What step do local anesthetics work on in the pain pathway?

A

Transmission, because they block the sodium channels from propagating action potential up the nerve towards the spinal cord

30
Q

Which local anesthetic, if administered systemically, acts on the modulation step of the pain pathway?

A

Lidocaine

31
Q

NMDA receptor antagonists, such as ketamine, primarily work on what part of the pain pathway?

A

Modulation via antagonism of NMDA receptors in the spinal cord; however, also have effects in the periphery and CNS

32
Q

Ketamine has been demonstrated to have poor efficacy in treating what type of pain?

A

Visceral

33
Q

Which opioid (full mu agonist) also causes NMDA receptor antagonism?

A

Methadone

34
Q

NMDA receptor antagonists are best for treating what kinds of pain?

A

Chronic or neuropathic

35
Q

Alpha 2 agonists work on what step of the pain pathway?

A

Modulation via alpha 2 receptors in the spinal cord; also have some receptors in the brain and periphery and can have some local anesthetic activity

36
Q

What are some general considerations if using an alpha 2 for postoperative analgesia?

A

They should be used in conjunction with other drugs for adequate postoperative analgesia and they have profound cardiovascular effects in small animals

37
Q

Gabapentin and pregabalin are structurally similar to the inhibitory neurotransmitter, GABA, yet their effects are on what?

A

Calcium channels

38
Q

What is an example of neurokinin-1 receptor antagonist?

A

Maropitant (Cerenia)

39
Q

What does the concept of multimodal anesthesia mean?

A

Using multiple drugs with different MOAs to treat the various parts of the pain pathway; allows for synergistic effects between drugs and therefore decreased doses and side effects