Pain Assessment

General behavioral indications of pain

- abnormal posture

- abnormal gait

- change in vocalization

- restlessness

- grooming changes/self mutilation

- aggression

- attention to area

- anorexia

- abnormal elimination

- changes in interaction

- bruxism (teeth grinding in ruminants)

What are the 3 common unidimensional pain scales?

- simple descriptive scale

- numerical rating scale

- visual analog scale

Simple descriptive scale of pain

- simple verbal descriptors to choose

- discrete

- non continuous

Numerical rating scale of pain

- numerical pain score assigned

- non continuous

Visual analog scale for pain

- a 10 cm continuous line where an evaluator marks pain intensity and measures distance

- continuous

Advantages to unidimensional pain scales

- simple

- easy and fast to use

Disadvantages to unidimensional pain scales

- highly subjective

- prone to bias

- variability among scorers

- only assessing intensity

5 facial features scored in the feline grimace scale

- ear position

- orbital tightening

- muzzle tension

- whisker change

- head position

Analgesic intervention cut-off score for the feline grimace scale

4 out of 10 or more

Advantages of the feline grimace scale

- assesses pain intensity and affective impact

- validated

- less subjective than unidimensional scales

- good agreement among observers

- similar among mammals

- easy to use

Disadvantages of the feline grimace scale

- altered by factors such as sedation, temperament, anatomical variation

- species limitations

Cut-off score requiring analgesia on the glasgow composite pain scale for dogs

Score of 6/24 (or 5/24 if section B cannot be performed)

Glasgow composite pain scale cut-off for cats

Score of 6/20 or higher

Advantages of composite multidimensional pain scales

- guided questions give structure

- validated

- less variability between scorers

- established cut off scores for analgesia

- gold standard

Disadvantages of composite multidimensional pain scales

- some subjective assessments

- need instructional material

Goals of pain management

- reduce pain as much as possible

- increase comfort

- return animal to normal behavior/function as quickly as possible

How to we approved treating pain in general?

Treat the nociceptive pathway - often need to treat more than 1 phase

Why do we still need to treat pain when an animal is under anesthesia?

Only perception is affected by general anesthetics - inflammation, nociception, and sensitization still occurs

Failure to treat nociception results in worse post op pain

Multimodal analgesia and the benefits

Combining analgesics targeting different phases of the nociceptive pathway to maximize efficacy and minimize side effects

What drugs work at the perception stage of the nociception pathway?

- general anesthetics

- opioids

- alpha 2 agonists

- benzos

- phenothiazines (ace)

What drugs work at the modulation stage of the nociception pathway?

- local anesthetics

- opioids

- alpha 2 agonists

- tricyclic antidepressants

- NMDA antagonists

- NSAIDs

- anticonvulsants

What drugs work at the transmission stage of the nociception pathway?

- local anesthetics

- alpha 2 agonists

What drugs work at the transduction stage of the nociception pathway?

- local anesthetics

- opioids

- NSAIDs

- corticosteroids

Pre-emptive analgesia

Administering analgesic treatment before the noxious stimulus occurs to prevent sensitization

Ways to provide preemptive analgesia

- perform locoregional anesthetic techniques before surgery

- administer systemic analgesics before surgery

- maintain analgesic therapy to avoid analgesic gaps

Key drug targets for managing chronic pain

Medications acting on the transduction and modulation phases of nociception

Sensitization is a key component

Examples of drugs/drug classes used for chronic pain

- NSAIDs

- gabapentin

- amantadine (oral ketamine)

- methocarbamol

- cannabinoids

Examples of non-pharmaceutical pain management modalities

- splints/bandaging

- acupuncture

- rehabilitation

- exercise modification

- massage

- nutraceuticals

- environmental adaptations (stairs, bedding)