Construct validity, responsiveness and reliability of the Feline Grimace Scale in kittens.

OBJECTIVES: The aim of the present study was to investigate the construct validity, responsiveness and reliability of the Feline Grimace Scale (FGS) in kittens. METHODS: A total of 36 healthy female kittens (aged 10 weeks to 6 months) were included in a prospective, randomized, blinded study. Video recordings of all kittens were made before and 1 and 2 h after ovariohysterectomy using an opioid-free injectable anesthetic protocol with or without multimodal analgesia. Additional recordings were taken before and 1 h after administration of rescue analgesia (buprenorphine 0.02 mg/kg IM) to painful kittens. Screenshots of facial images were collected from the video recordings for FGS scoring. Four observers blinded to treatment groups and time points scored 111 randomized images twice with a 5-week interval using the FGS. Five action units (AUs) were scored (ear position, orbital tightening, muzzle tension, whiskers position and head position; 0-2 each). Construct validity, responsiveness, and inter- and intra-rater reliability were evaluated using linear models with Benjamini-Hochberg correction, Wilcoxon signed-rank test and single intraclass correlation coefficients (ICCsingle), respectively (P <0.05). RESULTS: FGS total ratio scores were higher at 1 and 2 h after ovariohysterectomy (median [interquartile range, IQR]: 0.30 [0.20-0.40] and 0.30 [0.20-0.40], respectively) than at baseline (median [IQR]: 0.10 [0.00-0.30]) (P <0.001). FGS total ratio scores were lower after the administration of rescue analgesia (median [IQR] before and after rescue analgesia) 0.40 [0.20-0.50] and 0.20 [0.10-0.38], respectively (P <0.001). Inter-rater ICCsingle was 0.68 for the FGS total ratio scores and 0.35-0.70 for all AUs considered individually. Intra-rater ICCsingle was 0.77-0.91 for the FGS total ratio scores and 0.55-1.00 for all AUs considered individually. CONCLUSIONS AND RELEVANCE: The FGS is a valid and responsive acute pain-scoring instrument with moderate inter-rater reliability and good to excellent intra-rater reliability in kittens.

Inter-observer reliability of three feline pain scales used in clinical practice.

OBJECTIVES: The present study aimed to evaluate the inter-observer reliability of three feline pain scales commonly used in clinical practice. METHODS: Twenty cats undergoing elective neutering surgery were assessed both pre- and postoperatively by three independent assessors (a board-certified anaesthetist, a veterinary anaesthesia nurse and a final-year veterinary student) using three different pain scales: the Glasgow Feline Composite Measure Pain Scale (CMPS - Feline), the Colorado State University Feline Acute Pain Scale (CSU - FAPS) and the Feline Grimace Scale (FGS). Reliability statistics was used to evaluate the level of agreement between assessors. RESULTS: Twenty-seven groups of paired observations were evaluated, of which 16 (59%) showed fair agreement, eight (30%) showed none to slight agreement and the remaining three (11%) showed moderate agreement based on Cohen's weighted kappa statistics. Based on Cronbach's alpha statistics, 12 (44%) of the 27 groups of observations showed moderate reliability, 12 (44%) showed poor reliability and the remaining three (11%) showed good reliability. No scale was superior to the others in terms of inter-rater reliability (P = 0.179); however, the pair composed of the final-year veterinary student and anaesthesia nurse showed better agreement than the two other pairs of assessors, both of which included the board-certified anaesthetist (P = 0.015). CONCLUSIONS AND RELEVANCE: Despite the usefulness of behavioural pain scales as clinical tools, their users should bear in mind their limitations, particularly the intrinsic subjectivity and potential variability of outcome between assessors with different backgrounds and level of expertise.

An ethogram of acute pain behaviors in cats based on expert consensus.

An improved understanding of behaviors reflecting acute pain in cats is a priority for feline welfare. The aim of this study was to create and validate a comprehensive ethogram of acute pain behaviors in cats that can discriminate painful versus non-painful individuals. An inventory of behaviors (ethogram) with their respective descriptors was created based on a literature review of PubMed, Web of Science and CAB Abstracts databases. The ethogram was divided into ten behavior categories that could be evaluated by duration and/or frequency: position in the cage, exploratory behaviors, activity, posture and body position, affective-emotional states, vocalization, playing (with an object), feeding, post-feeding and facial expressions/features. Thirty-six behaviors were analyzed independently by four veterinarians with postgraduate qualifications in feline medicine and/or behavior as (1) not relevant, (2) somewhat relevant, (3) quite relevant or (4) highly relevant and used for content (I-CVI) and face validity. Items with I-CVI scores > 0.67 were included. Twenty-four behaviors were included in the final ethogram. Thirteen items presented full agreement (i.e., I-CVI = 1): positioned in the back of the cage, no attention to surroundings, feigned sleep, grooming, attention to wound, crouched/hunched, abnormal gait, depressed, difficulty grasping food, head shaking, eye squinting, blepharospasm and lowered head position. Seven descriptors were reworded according to expert suggestions. The final ethogram provides a detailed description of acute pain behaviors in cats after content and face validity and can be applied to the characterization of different acute painful conditions in hospitalized cats.

Sex impacts pain behaviour but not emotional reactivity of lambs following ring tail docking.

Studies in humans have shown sex differences in response to painful events, however, little is known in relation to sex differences in sheep. Understanding sex differences would enable improved experimental design and interpretation of studies of painful procedures in sheep. To examine sex differences in response to pain, 80 lambs were tested across five cohorts of 16. The lambs were penned in groups containing two male and two female lambs with their respective mothers. Lambs were randomly allocated from within each block to one of four treatment groups; FRing-Female lamb, ring tail docked without analgesia, MRing-Male lamb, ring tail docked without analgesia, FSham-Female lamb, tail manipulated and MSham-Male lamb, tail manipulated. Following treatment, lambs were returned to their pen and were video recorded for 45 mins for behavioural observations of acute pain and posture. An hour after treatment, lambs then underwent an emotional reactivity test that consisted of three phases: Isolation, Novelty and Startle. Following treatment, Ring lambs displayed more abnormal postures (mean = 2.5 ± 0.5) compared to Sham lambs (mean = 0.05 ± 0.4, P = 0.0001). There was an effect of sex on the display of acute pain-related behaviours in lambs that were tail docked (P < 0.001), with female lambs displaying more acute behaviours (mean count = +2.2). This difference in behaviour between sexes was not observed in Sham lambs. There was no effect of sex on display of postures related to pain (P = 0.99). During the Novelty and Startle phase of the emotional reactivity test, Ring lambs tended to (P = 0.084) or did (P = 0.018) show more fear related behaviours, respectively. However, no effect of sex was observed. The results of this study indicate that a pain state may alter the emotional response of lambs to novel objects and potential fearful situations. It was also demonstrated that female lambs display increased sensitivity to the acute pain caused by tail docking compared to males.

Can cat caregivers reliably assess acute pain in cats using the Feline Grimace Scale? A large bilingual global survey.

OBJECTIVES: This study aimed to investigate if cat caregivers could reliably assess acute pain using the Feline Grimace Scale (FGS), and if participant demographics could affect scores. METHODS: An online survey in English and Spanish was advertised by International Cat Care and other platforms (March-May 2021) using convenience sampling. Eligible participants were caregivers >18 years old and non-veterinary health professionals. Participants and a group of eight veterinarians scored 10 images of cats with different levels of pain. Data were analysed using linear models and intraclass correlation coefficient (ICC; α <0.05). Interpretation of the ICC was <0.2 = poor; 0.21-0.4 = reasonable; 0.41-0.60 = moderate; 0.61-0.80 = good; and 0.81-1.0 = very good. RESULTS: A total of 3039 responses were received with 1262 completed answers from 66 countries (86%, 11.1% and 2.9% identified as female, male or other, respectively). Scores for each action unit (AU; ear position, orbital tightening, muzzle tension, whiskers change and head position) and their sum (FGS score) were not significantly different between caregivers and veterinarians, except for muzzle (caregivers 0.9 ± 0.0; veterinarians 0.7 ± 0.1; P = 0.035). The ICC single (caregivers) was 0.65, 0.69, 0.58, 0.37, 0.38 and 0.65, respectively, for AU ears, eyes, muzzle, whiskers, head and sum of scores. Demographic variables did not affect FGS scores. CONCLUSIONS AND RELEVANCE: Total FGS scores had good reliability when used by cat caregivers, regardless of demographic variables, showing the potential applicability of the instrument to improve feline pain management and welfare worldwide.

Preliminary evaluation of the effects of grapiprant compared with carprofen on acute pain and inflammation following ovariohysterectomy in dogs.

OBJECTIVE: To compare the analgesic efficacy of grapiprant to carprofen for the treatment of postoperative pain and inflammation in dogs following ovariohysterectomy. ANIMALS: 12 purpose-bred adult sexually intact female Beagles. PROCEDURES: Dogs were randomly assigned to 1 of 2 treatment groups: grapiprant (2 mg/kg, PO; n = 6) or carprofen (4.4 mg/kg, PO; n = 6), 1.5 hours prior to ovariohysterectomy (OVH) and every 24 hours afterward for 3 total doses. An ultrafiltration probe was placed within the OVH incision to collect interstitial fluid (ISF). Pain and inflammation were assessed by masked investigators via mechanical nociceptive threshold testing and the short form of the Glasgow Composite Pain Scale before drug administration and at multiple time points for 72 hours following dosing and surgery. ISF samples were collected at the same time points to assess prostaglandin E2 concentrations at the site of inflammation. RESULTS: In both groups, pain scale scores were highest in the immediate postoperative period and decreased over time. In both treatment groups, there were significant (P = 0.003) differences in mechanical nociceptive threshold results over time when compared with baseline, but there was no difference between groups. Prostaglandin E2 concentrations in ISF were higher in dogs receiving grapiprant compared with carprofen (P < 0.001). One dog in the carprofen group required rescue analgesia. CLINICAL RELEVANCE: Results of this preliminary study suggested both carprofen and grapiprant may be effective for postoperative pain following OVH in dogs; however, additional studies are warranted to determine grapiprant's effectiveness in a larger and more diverse population of dogs.

Use of mechanical thresholds in a model of feline clinical acute pain and their correlation with the Glasgow Feline Composite Measure Pain Scale scores.

OBJECTIVES: The aim of this study was to evaluate the use of mechanical thresholds (MT), measured with the SMALGO (Small Animal ALGOmeter), and to determine whether there was a correlation between MT and Glasgow Feline Composite Measure Pain Scale (CMPS-Feline) scores in cats undergoing ovariohysterectomy. METHODS: Client-owned cats undergoing flank ovariohysterectomy were recruited. Pain scores for the pre- and postoperative periods were obtained using the CMPS-Feline in each cat by two independent investigators (A and B). Following CMPS-Feline scoring, MT were measured with the SMALGO, in the surgical area, pre- and postoperatively, only by investigator A. Each cat served as its own control for the comparison of pre- and postoperative variables. Reliability statistics were used to assess the level of inter-observer agreement (A vs B) with respect to pre- and postoperative CMPS-Feline scores, while Spearman's correlation statistics were used to analyse the relationship between MT and CMPS-Feline scores. RESULTS: Twenty-nine cats completed the study. Preoperative MT (340 g [range 108-691]) were significantly higher than postoperatively (233 g [range 19-549]; P = 0.001). CMPS-Feline scores were not found to differ significantly between the preoperative period (2 [range 0-7] for investigator A and 3.2 ± 2.3 for investigator B) and postoperative period (2 [range 0-10] for investigator A and 3 [range 0-8] for investigator B) for either investigator. Reliability statistics revealed that the level of inter-observer agreement with respect to CMPS-Feline was fair for the preoperative assessments but poor for the postoperative evaluations. There was no correlation between MT and CMPS-Feline scores. CONCLUSIONS AND RELEVANCE: Although there was no correlation with CMPS-Feline scores performed at the same timepoint, MT increased postoperatively vs baseline. Assuming that, despite analgesia, susceptibility of the surgical area to mechanical stimulation would increase after surgery, this finding suggests that MT might be useful to assess feline surgical pain. The poor level of inter-observer agreement with respect to postoperative CMPS-Feline scores highlights the potential limitations of this scale.

Surgical Castration Changes Struggle Behavior and Vocalizations in Male Piglets.

This study assessed acute pain in piglets during castration through behavioral indicators. Piglets (n=88) were randomly allocated to one of two treatments: surgical castration and sham-castration. Within 24 hours after birth, identical castration procedures were followed for both treatment groups, except sham piglets were not castrated. Struggle behavior (curl ups, leg kicks, and body flailing) and vocalization (duration and peak frequency) were analyzed during the castration procedure. Castrated piglets kicked more frequently than sham piglets (28.8 vs. 21.3 kicks/min, SE = 0.09; P = 0.02). Additionally, 51.2% of castrated piglets displayed body flailing, whereas only 4.4% of sham piglets displayed the same behavior (P = 0.03). Castrated piglets responded with more high frequency (≥1,000 Hz) calls than sham piglets (23.6 vs. 18.6 calls/min, SE = 0.26; P = 0.04) and high frequency calls tended to be of longer duration for castrated piglets (0.45 vs. 0.27 sec/call, SE = 0.04; P = 0.08). Results indicate that surgical castration increased the frequency of leg kicks, body flailing, and high frequency calls compared to sham-castration, suggesting these may be useful behavioral indicators of acute pain in piglets.

2022 ISFM Consensus Guidelines on the Management of Acute Pain in Cats.

PRACTICAL RELEVANCE: Increases in cat ownership worldwide mean more cats are requiring veterinary care. Illness, trauma and surgery can result in acute pain, and effective management of pain is required for optimal feline welfare (ie, physical health and mental wellbeing). Validated pain assessment tools are available and pain management plans for the individual patient should incorporate pharmacological and non-pharmacological therapy. Preventive and multimodal analgesia, including local anaesthesia, are important principles of pain management, and the choice of analgesic drugs should take into account the type, severity and duration of pain, presence of comorbidities and avoidance of adverse effects. Nursing care, environmental modifications and cat friendly handling are likewise pivotal to the pain management plan, as is a team approach, involving the cat carer. CLINICAL CHALLENGES: Pain has traditionally been under-recognised in cats. Pain assessment tools are not widely implemented, and signs of pain in this species may be subtle. The unique challenges of feline metabolism and comorbidities may lead to undertreatment of pain and the development of peripheral and central sensitisation. Lack of availability or experience with various analgesic drugs may compromise effective pain management. EVIDENCE BASE: These Guidelines have been created by a panel of experts and the International Society of Feline Medicine (ISFM) based on the available literature and the authors' experience. They are aimed at general practitioners to assist in the assessment, prevention and management of acute pain in feline patients, and to provide a practical guide to selection and dosing of effective analgesic agents.

Towards an improved pain assessment in castrated horses using facial expressions (HGS) and circulating miRNAs.

BACKGROUND: Pain in horses is an emergent welfare concern, and its assessment represents a challenge for equine clinicians. This study aimed at improving pain assessment in horses through a convergent validation of existing tools: we investigated whether an effective analgesic treatment influences the horse grimace scale (HGS) and the concentration of specific circulating microRNAs (miRNAs). METHODS: Eleven stallions underwent routine surgical castration under general anaesthesia. They were divided into two analgesic treatment groups: castration with the administration of preoperative flunixin and castration with preoperative flunixin plus a local injection of mepivacaine into the spermatic cords. HGS and levels of seven circulating miRNAs were evaluated pre-, 8 and 20 hours post-procedure. RESULTS: Compared to pre-castration, HGS, miR-126-5p, miR-145 and miR-let7e increased significantly in horses receiving flunixin at 8 hours post-castration (Friedman test, p < 0.05). Both behavioural and molecular changes occurred in horses receiving flunixin only, confirming that the addition of local mepivacaine is an effective analgesic treatment. CONCLUSIONS: Combining the use of HGS and circulating miRNAs, particularly miR-145, could be meaningful to monitor acute pain conditions in horses. Our results further validate the HGS as a method to assess acute pain in horses and point out miR-145 as a promising biomarker to identify pain.

Randomized control trial assessing the efficacy of pain control strategies for caustic paste disbudding in dairy calves younger than 9 days of age.

Disbudding is a common procedure practiced in the dairy industry and is known to cause pain when performed without pain control. Dairy producers who disbud calves with caustic paste are less likely to provide pain control than those using cautery. Little research has been conducted on pain control for caustic paste disbudding and no studies have specifically examined calves under 9 d of age. The objective of this study was to evaluate the efficacy of local anesthesia and nonsteroidal anti-inflammatory drug analgesia on indicators of pain and inflammation in dairy calves disbudded using caustic paste. One hundred forty Holstein heifer calves 1 to 9 d of age were enrolled in 28 blocks and randomly allocated to 1 of 5 treatments: sham control (SH); positive control (POS); lidocaine cornual nerve block (LC); meloxicam (MEL); and lidocaine cornual nerve block plus meloxicam (LCM). We measured outcomes including serum cortisol and haptoglobin, pressure sensitivity, and lying behavior. Data were analyzed using mixed linear regression models with treatment as a fixed effect, baseline values as a covariate, and trial block as a random effect. Compared with the POS group, the LCM group had reduced serum cortisol at 15, 30, 45, and 60 min post-disbudding; cortisol values were not different between LC, LCM, and SH calves at these time points. At 60, 90, 120, and 180 min post-disbudding, LCM calves had reduced cortisol compared with LC calves, whereas, values did not differ between LCM and SH calves at these time points. At 3 to 4 d post-disbudding, the LCM group tended to have reduced haptoglobin, but no differences were found between groups at 180 min and 7 d post-disbudding. At 60, 90, and 120 min post-disbudding, LC and LCM treated calves had decreased pressure sensitivity compared with other groups. No differences were seen in pressure sensitivity between groups at 180 min, 3 to 4 or 7 d post-disbudding. No differences in lying behavior were found between treatment groups on any of the 7 d following disbudding. These findings demonstrate that the combination of a local anesthetic with a nonsteroidal anti-inflammatory drug is beneficial for reducing indicators of pain and inflammation in young calves disbudded with caustic paste.

Facial expressions of pain in cats: the development and validation of a Feline Grimace Scale.

Grimace scales have been used for pain assessment in different species. This study aimed to develop and validate the Feline Grimace Scale (FGS) to detect naturally-occurring acute pain. Thirty-five client-owned and twenty control cats were video-recorded undisturbed in their cages in a prospective, case-control study. Painful cats received analgesic treatment and videos were repeated one hour later. Five action units (AU) were identified: ear position, orbital tightening, muzzle tension, whiskers change and head position. Four observers independently scored (0-2 for each AU) 110 images of control and painful cats. The FGS scores were higher in painful than in control cats; a very strong correlation with another validated instrument for pain assessment in cats was observed (rho = 0.86, p < 0.001) as well as good overall inter-rater reliability [ICC = 0.89 (95% CI: 0.85-0.92)], excellent intra-rater reliability (ICC > 0.91), and excellent internal consistency (Cronbach's alpha = 0.89). The FGS detected response to analgesic treatment (scores after analgesia were lower than before) and a cut-off score was determined (total pain score > 0.39 out of 1.0). The FGS is a valid and reliable tool for acute pain assessment in cats.

Comparison of three acute colic pain scales: Reliability, validity and usability.

A valid, reliable and usable scale is needed for assessing severity of acute abdominal pain in horses. The study aim was to compare three different scales: (1) the equine acute abdominal pain scale (EAAPS); (2) a scale described by Mair and Smith (2005; M and S); and (3) a numerical rating scale (NRS). Forty brief films of horses (35 of colic cases and five of control horses) were randomly presented to 46 equine veterinarians from different countries. Participants, randomly divided into three groups, each used one scale. Five randomly selected films were shown twice for determining intra-observer reliability. Speed, ease of use and face validity of the scales were evaluated based on expert opinion. Response rate was excellent: 89% for the EAAPS (16/18), and 100% for the M and S (18/18) and NRS groups (10/10). The intraclass correlation (ICC) of 0.86 [95% confidence interval (CI); 0.80-0.92] for EAAPS indicated significantly better inter-observer reliability compared to 0.68 for the M and S and 0.71 for the NRS. Moreover, intra-observer reliability of EAAPS (weighted κ 0.95 [95%CI; 0.92-0.98]) was superior to the other scales (weighted κ 0.78, 0.77, for the M and S and NRS, respectively). Other validity measures (convergent, extreme group, predictive validities), usability (time taken to score the films-speed) and the ease of use of the scales were not significantly different. Face validity (endorsement by experts) was better for the M and S scale than for the EAAPS. The EAAPS showed superior reliability, the M and S scale better face validity, with comparable usability and other tests of validity.

Acute pain responses in dairy calves undergoing cornual nerve blocks with or without topical anesthetic.

Dairy calves are routinely administered medicines, vaccines, and anesthesia via injection. Although injections are painful, little is known about methods to alleviate this pain. The aim of this study was to determine whether lidocaine-prilocaine cream, a topical anesthetic, reduced calves' pain response to a subcutaneous injection around the cornual nerve. Calves were assigned 1 of 2 treatments: lidocaine-prilocaine cream at the sites of injection (n = 10) or no cream (n = 9). Thirty minutes after treatment, calves received a subcutaneous injection of 2% buffered lidocaine hydrochloride around the left and right cornual nerves. Contrary to our hypothesis, calves that received anesthetic cream beforehand displayed more escape behaviors during the injections than control calves. Both treatments had similarly low amounts of head-related behaviors afterward. Maximum eye temperature did not differ between the calves that received anesthetic cream and control calves, although eye temperature increased over time for both treatments. Heart rate increased during the 30 s following the first injection in both treatments. There were no treatment differences for any heart rate measures over the 5-min period after the first injection (mean heart rate, root mean square of successive differences, high-frequency power, and the ratio of low-frequency power to high-frequency power). These results suggest that cornual nerve blocks with buffered lidocaine are painful and that a lidocaine-prilocaine cream was not only ineffective in reducing this pain but that it may also worsen it.

Preliminary appraisal of the reliability and validity of the Colorado State University Feline Acute Pain Scale.

OBJECTIVES: The objective of this study was to determine the inter-rater reliability and convergent validity of the Colorado State University Feline Acute Pain Scale (CSU-FAPS) in a preliminary appraisal of its performance in a clinical teaching setting. METHODS: Sixty-eight female cats were assessed for pain after ovariohysterectomy. A cohort of 21 cats was examined independently by four raters (two board-certified anesthesiologists and two anesthesia residents) with the CSU-FAPS, and intra-class correlation coefficient (ICC) was used to determine inter-rater reliability. Weighted Cohen's kappa was used to determine inter-rater reliability centered on the 'need to reassess analgesic plan' (dichotomous scale). A separate cohort of 47 cats was evaluated independently by two raters (one board-certified anesthesiologist and one veterinary small animal rotating intern) using the CSU-FAPS and the Glasgow Composite Measure Pain Scale (CMPS-Feline), and Spearman rank-order correlation was determined to assess convergent validity. Reliability was interpreted using Altman's classification as very good, good, moderate, fair and poor. Validity was considered adequate if correlation coefficients were between 0.4 and 0.8. RESULTS: The ICC was 0.61 for anesthesiologists and 0.67 for residents, indicating good reliability. Weighted Cohen's kappa was 0.79 for anesthesiologists and 0.44 for residents, indicating moderate to good reliability. The Spearman rank correlation indicated a statistically significant ( P = 0.0003) positive correlation (0.31; 95% confidence interval 0.14-0.46) between the CSU-FAPS and the CMPS-Feline. CONCLUSIONS AND RELEVANCE: The CSU-FAPS showed moderate-to-good inter-rater reliability when used by veterinarians to assess pain level or need to reassess analgesic plan after ovariohysterectomy in cats. The validity fell short of current guidelines for correlation coefficients and further refinement and testing are warranted to improve its performance.

Acute pain in cats: Recent advances in clinical assessment.

PRACTICAL RELEVANCE: Pain assessment has gained much attention in recent years as a means of improving pain management and treatment standards. It has become an elemental part of feline practice with ultimate benefit to feline health and welfare. Currently pain assessment involves mostly the investigation of sensory-discriminative (intensity, location and duration) and affective-motivational (emotional) domains of pain. Specific behaviors associated with acute pain have been identified and constitute the basis for its assessment in cats. RECENT ADVANCES: The publication of pain scales with reported validation - the UNESP-Botucatu multidimensional composite pain scale and the Glasgow feline composite measure pain scale - and species-specific studies have advanced our knowledge on the subject. Facial expressions have also been shown to be different between painful and non-painful cats, and very recently the Feline Grimace Scale has been validated as a tool for acute pain assessment. CLINICAL CHALLENGES: Despite recent advances, several challenges still exist. For instance, the effects of disease and sedation on pain scoring/ assessment are unknown. Also, specific painful conditions (eg, dental pain) have not been systematically investigated. The development and validation of instruments for pain assessment by cat owners is warranted, as these tools are currently lacking. AIMS: This article reviews the use, advantages, disadvantages and limitations of the two validated pain scales, and presents a practical, stepwise approach to feline pain recognition and assessment using a dynamic and interactive process. The authors also offer perspectives regarding current challenges and future directions.

The neurobiology of acute pain.

The mechanisms by which noxious stimuli produce the sensation of pain in animals are complex. Noxious stimuli are transduced at the periphery and transmitted to the CNS, where this information is subject to considerable modulation. Finally, the information is projected to the brain where it is perceived as pain. Additionally, plasticity can develop in the pain pathway and hyperalgesia and allodynia may develop through sensitisation both peripherally and centrally. A large number of different ion channels, receptors, and cell types are involved in pain perception, and it is hoped that through a better understanding of these, new and refined treatments for pain will result.