PEER REVIEWED Feline Acute Pain Series ASSESSMENT OF …€¦ · Pain scoring scales2-4 and pain management guidelines for cats1 have been developed for use in veterinary medi-cine.

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Pain is a multifactorial experience, with sensory (“ouch”) and affective (emotional) components.1 Untreated pain can delay recovery, decrease quality

of life, and disturb the human–animal bond.1 Pain also increases the body’s stress response to traumatic injury and causes alterations in metabolic and endocrine function.

It is now well established that animals and humans have similar neuro-anatomical pathways for the transduction, transmission, and modulation of pain.1 A fundamental part of quality, compassionate veterinary care is prevention and management of pain and, therefore, it must be quickly rec-ognized, assessed, and treated by the veterinary team.

IDENTIFICATION OF PAIN IN CATS Unfortunately, cats cannot verbally communicate to us that pain exists or where it is located—the veterinary team must determine these answers. In this species, pain assess-ment relies on owners’ communication with clinic staff, clinical judgement, and measurement of various parame-ters that have been shown to correlate with pain.

Pain scoring scales2-4 and pain management guidelines for cats1 have been developed for use in veterinary medi-cine. Standardized pain scoring scales and pain manage-ment guidelines promote a standard of care for hospital-ized patients and facilitate optimal pain management, even though different personnel care for a patient during its stay. However, pain assessment is subjective, and changes in pain may be subtle and difficult to evaluate without an experienced eye.

Signs of pain and response to drugs vary greatly between patients based on genetics, breed, and age.3,5,6 For this rea-son, pain should be assessed visually and physically, pro-viding the animal cooperates during handling.

Objective Measures of PainPhysiological changes, such as changes in heart rate, blood pressure, and plasma cortisol, occur in response to sympa-thetic stimulation caused in part by pain.7 However, clini-cal experience should be used when assessing these objec-tive measures of pain because fear, stress, anesthesia, and pharmacologic interventions also cause these parameters to change.7

Pain Assessment Scales for CatsCurrently there is no gold standard for assessing acute pain in cats. Several research groups, including Brondani and colleagues, are in the process of developing and vali-

Feline Acute Pain Series

ASSESSMENTOF ACUTEPAIN IN CATSSheilah Robertson, BVMS (Hons), PhD, MRCVS, Diplomate ECVAA, ACVAA, ACAW, & ECAWBM (Welfare Science, Ethics and Law)Michigan State University

it’s not just how it feels but how it makes you feel.—Professor Jackie Reid, University of Glasgow

PEER REVIEWED

Figure 1. Gentle palpation of a surgical wound in a cat; note the lack of response from the cat, which indicates appropriate analgesic use.

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dating pain scales for clinical use.8 A survey of veterinary nurses reported that only 8.1% of veterinary practices used a pain scoring system, yet 80.3% agreed it was a useful clinical tool.9

Some scales that have been used to assess pain in cats include:•Visual Analog Scale (VAS): Consists of a line 100 mm

long that has 0 (no pain) on one end and 100 (extreme pain) on the other.10 Based on visual observation, the user marks the point on the line that best correlates with the patient’s pain intensity. The VAS is scored by measuring the distance between “0” and the user’s mark.

•Numerical Rating Scale: Pain is scored on a numerical scale; for example, 0 to 5 or 0 to 10 based on different observational and physical characteristics.3,4

•Descriptive Scale: Allows user to describe cat as having no, mild, moderate, or severe pain.11

These scales are unidimensional and, although easy to use and interpret, they are not very useful in distinguishing subtle changes in pain, which prevents observers from “see-ing the whole picture” or, in other words, noting the nuanc-es that would provide a better assessment of the animal’s wellbeing. When using these scales, the variability in pain scoring among veterinary staff looking at the same patient can be as high as 35%,12 which highlights the difficulties encountered when different personnel care for a patient.

Dynamic Interactive Visual Analog Scales (DIVAS) have been used in cats in an attempt to improve on the above scales.13 These scales use a 100-mm line, but the final assessment is based on observation and interaction with the cat, including palpation of wounds or other known painful areas.

Importance of PalpationWound palpation is a frequently overlooked component of assessing comfort levels in animals following surgery. If analgesics have been used appropriately, the cat should not flinch or bite when gentle pressure is applied on and around a surgical wound (Figure 1). During palpation, gently restrain the cat’s head for protection in case the cat responds, and assess the response—from no response to the cat flinching, hissing/growling, turning toward han-dler, or turning and attempting to bite.

PAIN SCORING SYSTEM COMPONENTS The characteristics of an optimal pain scoring system for cats are listed in Table 1. It is now accepted that, in non-verbal patients, pain scoring systems must be heavily based on behavior observation. These scales are multidimension-al and often referred to as composite pain scales.8

SELECTING & USING SCORING SYSTEMSWhen considering a scoring system, it is important to select a system that will suit the needs of the clinic. The system should be:1. User friendly—consider those who will be scoring pain,

such as veterinary technicians and owners; the system should be suitable for their needs.

2. When possible, used by the same individual each time pain is assessed in a single patient in order to mini-mize variation in scores, which can occur when several observers are involved.

3. Used in conjunction with the patient’s behavioral his-tory in order to identify the cat’s “normal” behavior and changes in behavior that may indicate pain.

4. An integral and consistent part of the postoperative record.

table 1. characteristics of an optimal Pain scoring system for cats

• simple and easy to use• identifies type, source, cause, and duration of pain• clearly defines assessment criteria for all observers,

including owners and veterinary team• sensitive to small changes in pain over time• Describes where assessment should take place—

homes versus veterinary clinic• Guides the user toward a treatment plan• Analyzes the system’s strengths and weaknesses• Validated for use in cats

Figure 2. Prior to surgery, the cat is in a fearful position (A), while postsurgery, the cat’s position indicates pain due to its hunched, arched back and facial expression of squinting, slanted eyes and pulled back whiskers (B).

A

B

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5. Applied both pre- and postoperatively—comparison of the cat’s behavior before and after surgery, and noting changes, is the best indicator of pain.

6. Part of the follow-up after injury or surgery; assessments should be repeated often to ensure the cat is recovering comfortably and appropriately, and responding to inter-vention.

ROLE OF BEHAVIOR IN ASSESSMENT A trip to a veterinary clinic and interaction with veterinary staff can be very stressful for some cats; this stress results in changes in physiologic parameters that are also seen with pain.14 In addition, differentiating pain from fear and anxiety can be challenging because some behaviors and postures associated with pain and fear/anxiety are similar (Figure 2). The more familiar you become with observ-ing animal posture and behavior, the easier this process becomes.

To assess behavior in cats:• Identify the presence or absence of normal behavior and

new or abnormal behaviors • For cats presented due to injury, ask the owner about the

cat’s normal behavior• For cats presented for a surgical procedure, observe and

document preoperative, “normal” behavior, which can then be compared to postoperative behavior

•Remember that it is not always the behavior itself, but rather the changes in behavior (Figure 3) that help deter-mine whether a cat is in pain and requires an analgesic. Table 2 provides a comprehensive list of key categories

and clinical signs that should be assessed when determin-ing whether a cat is in pain.

Behavioral domains, along with additional indicators, such as blood pressure, have been used to create the UNE-SP-Botucatu Multidimensional Composite Pain Scale for Assessing Postoperative Pain in Cats, available at animalpain.com.br/en-us/. The scale, complemented by videos demonstrating specific pain behaviors, results in a numerical pain score, and the website provides videos that can be used to assess a veterinary professional’s abil-ity to use the scale. Initially, this system may take consid-erable time to complete but, with experience, it can be done rapidly.

ASSESSMENT OF EFFECTIVE PAIN MANAGEMENTPain assessment tools should help you develop a treatment plan, and should also indicate whether or not the interven-tion is effective. If, after an intervention, the pain score decreases, then treatment was effective, but continued monitoring is needed to ensure the patient remains com-fortable. Treatment of acute pain in cats will be discussed in the next issue of Today’s Veterinary Practice.

table 2. A List of categories & clinical signs for Recognizing Acute Pain in cats

CATEGORY NO PAIN IN PAIN

Posture Relaxedslightly curled upcomfortable

tense, stiff, rigidstretched out or tucked upcrouched and/or hunched

Behavior Bright and alertHead upAt front of cageGroomingActive and/or playinginteractive with

people

Licking lips and/or salivating

Head downHiding and/or at back of

cagecannot get comfortableLicking at woundsAggressive

Vocalization Purrs when petted normal, chirpy meow

Growl and/or hissLong deep meowPurring

Palpation of Wound

no response to pressure

Quick turning, flinchingBiting, aggressionVocalization

Demeanor interactive with people

enjoys being petted

Avoids peopleAvoids petting

Facial Expression8,15

open and relaxed eyes

Head up

squinting, slanted, or closed eyes

Head downWhiskers pulled back

Figure 3. Facial expression is an important indicator of pain: a comfortable cat will be bright and alert (A), while a painful cat may keep its head down and demonstrate squint-ing, slanted, and/or closed eyes; pushed back ears; and pulled back whiskers (B).

A

B

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Role of AnalgesicsMechanistically, tissue damage from surgery or injury causes release of inflammatory mediators at the site of the wound. Inflammatory mediators sensitize the nerve end-ings around the wound, a process known as transduction. This information is then transmitted along the peripheral nerves to the central nervous system and then to higher centers where, in the conscious animal, it is perceived as pain. Pain medications alter the pain pathway to reduce pain perception.

Analgesic Requirements Quite often it is difficult to determine how much and what type of pain medication should be administered to control pain in cats. Pain can be perceived differently in individual cats and the same degree of inflammation can cause vary-ing amounts of pain. Pain medications also have unique effects on different animals due to metabolism, tissue specificity, and individual variation.5,6,16,17

To properly assess the effectiveness of pain management:1. Perform frequent assessments by identifying whether

clinical signs associated with acute pain in cats (Table 2) are present.

2. If, after analgesic administration, the cat is still display-ing signs of discomfort and pain, treat again and reas-sess. Treatment may involve using the same opioid as originally administered, changing the dose, switching to

another opioid or a different class of drug, or using a com-bination of drugs.

3. After additional pain medica-tion is administered, improve-ment in behavior should be observed (Figure 4).

4. Remember, veterinarians have a responsibility to adminis-ter enough pain medication to keep the cat comfortable.1

Duration of TreatmentThe duration of treatment of acute pain depends on the degree of inflammation, which is related to the amount of tissue trauma. It is critical to manage pain for the duration of active inflammation.18 For example, postsurgical inflammation can cause pain for days (eg, ovar-iohysterectomy) or weeks (eg, major orthopedic surgery).

If uncertainty exists about whether a cat still requires pain intervention, use pain assessment and response to treatment as diagnostic tools. One of the big-gest mistakes in veterinary pain management is providing good

pain control for a short time after tissue damage; then with-drawing analgesics before inflammation has started to sub-side. If sufficient inflammation is present, sensitizing the nerve endings, it causes re-initiation of the pain pathway and results in ongoing pain for the cat. There should be analgesic coverage for the entire healing process.

SUMMARYAccurate pain assessment is essential for appropriate pain management. Key components to pain assessment include:•Behavior and the cat’s interaction with humans • Posture and facial expression •Observation of the cat pre- and postoperatively •Discussion with the owner about the cat’s usual behav-

ior, if observation is not possible before injury/surgery •Treatment and re-evaluation, if there is uncertainty about

whether the cat is in pain. Can pain be appropriately assessed and treated in cats?

Yes. The more attentive the health care provider is to sub-tle changes in animal behavior, the more accurate pain recognition will be. There are excellent pain medications available for cats, which ultimately allow for the delivery of compassionate and humane care.

Read the next article in this series—Management of Acute Pain in Cats—in the March/April 2014 issue of Today’s Veterinary Practice. n

(Continued on page 83.)

Figure 4. Cat with optimal pain management (A)—at the cage front, alert, and inter-acting with the staff—and in pain (B)—at the back of the cage and hunched up, with eyes squinted shut.

A B

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(Feline Pain continued from page 35.)

VAs = visual analog scale; DiVAs = dynamic interactive visual analog scale;

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13. Polson S, Taylor PM, Yates D. Effects of age and reproductive status on postoperative pain after routine ovariohysterectomy in cats. J Feline Med Surg 2013; Epub ahead of print.

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Sheilah Robertson, BVMS (Hons), PhD, MRCVS, Diplomate ECVAA, ACVA, ECAWBM (Wel-fare Science, Ethics and Law), & ACAW, is an associate professor in the Michigan State University College of Veterinary Medicine’s

Department of Small Animal Clinical Sciences. She is co-author of the AAFP/AAHA Pain Man-agement Guidelines and ISFM/AAFP Consensus Guidelines: Long-Term Use of NSAIDs in Cats.