A thermal threshold testing device for evaluation of analgesics in cats

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.

The thermal antinociceptive effects of a high-concentration formulation of buprenorphine alone or followed by hydromorphone in conscious cats

OBJECTIVE

To evaluate the thermal antinociceptive effects of a high-concentration formulation of buprenorphine alone or followed by hydromorphone in conscious cats.

STUDY DESIGN

Randomized, blinded, placebo-controlled crossover study design.

ANIMALS

A total of six purpose-bred, adult female ovariohysterectomized Domestic Short Hair cats.

METHODS

Cats were allocated into three treatments each consisting of two injections, subcutaneous then intravenous (IV) administration, 2 hours apart: treatment SS, two injections of 0.9% saline; treatment BS, buprenorphine (0.24 mg kg^-1, 1.8 mg mL^-1) and saline; and treatment BH, buprenorphine (0.24 mg kg^-1) and hydromorphone (0.1 mg kg^-1). Skin temperature (ST) and thermal threshold (TT) were recorded before (baseline) and for 24 hours following first injection. TT data were analyzed using mixed linear models and a Benjamini-Hochberg sequential adjustment procedure (p < 0.05).

RESULTS

There were no significant differences among treatments for baseline ST and TT values, treatment SS over time and between treatments BS and BH. Compared with baseline, TT was significantly increased at all time points in treatments BH and BS except at 2 hours in treatment BS. TT was significantly higher than SS at 3-18 hours and 4-12 hours for treatments BS and BH, respectively. Maximal increases in TT were 47.5 °C at 2 hours, 53.9 °C at 3 hours and 52.4 °C at 6 hours in treatments SS, BS and BH, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of IV hydromorphone following high-concentration buprenorphine provided no additional antinociception and decreased the duration of effect when compared with high-concentration buprenorphine alone. Alternative analgesics should be considered if additional analgesia is required after administration of high-concentration buprenorphine.

Remote Controlled Nociceptive Threshold Testing Systems in Large Animals

Simple Summary

Measurement of the nociceptive threshold (NT) is widely used in the study of pain and its alleviation. This records the intensity of a stimulus that causes pain to the test subject. The end point of the test that indicates when the subject experiences pain, the NT, is a behavioural escape response. Detection of a reliable and repeatable response depends on the animal behaving normally throughout testing. Restraint and an unfamiliar environment may prevent the animal from displaying normal behaviour and impede acquisition of robust NTs. Remotely controlled testing enables NT data to be collected from unrestrained animals behaving normally. Development of a remote controlled system for measurement of thermal and mechanical NTs in a range of large animal species is described. Normal “baseline” thermal and mechanical NTs from untreated animals are reported. This information can be used to improve both the welfare of the animals under investigation and the quality of the data collected. Remote controlled systems are now in use worldwide in both the study of pain physiology and in developing new pharmaceutical and non-drug-based methods of pain relief.

Abstract

Nociceptive threshold (NT) testing is widely used for the study of pain and its alleviation. The end point is a normal behavioural response, which may be affected by restraint or unfamiliar surroundings, leading to erroneous data. Remotely controlled thermal and mechanical NT testing systems were developed to allow free movement during testing and were evaluated in cats, dogs, sheep, horses and camels. Thermal threshold (TT) testing incorporated a heater and temperature sensor held against the animal’s shaved skin. Mechanical threshold (MT) testing incorporated a pneumatic actuator attached to a limb containing a 1–2 mm radiused pin pushed against the skin. Both stimuli were driven from battery powered control units attached on the animal’s back, controlled remotely via infra-red radiation from a handheld component. Threshold reading was held automatically and displayed digitally on the unit. The system was failsafe with a safety cut-out at a preset temperature or force as appropriate. The animals accepted the equipment and behaved normally in their home environment, enabling recording of reproducible TT (38.5–49.8 °C) and MT (2.7–10.1 N); precise values depended on the species, the individual and the stimulus characteristics. Remote controlled NT threshold testing appears to be a viable refinement for pain research.

Use of nociceptive threshold testing in cats in experimental and clinical settings: a qualitative review

OBJECTIVE

The objective of this study was to review the scientific articles on the use of nociceptive threshold testing (NTT) in cats and to summarize the clinical and experimental applications in this species.

DATABASES USED

Pertinent literature was searched with PubMed, Scopus, Web of Science, Universitätsbibliothek Basel (swissbib Basel Bern) and Google Scholar. The search was then refined manually based first on article titles and abstracts, and subsequently on full texts.

CONCLUSIONS

Of the four classical acute nociceptive models used for NTT, thermal and mechanical are most commonly used in cats. Thermal stimulation is applicable in experimental settings and has been used in pharmacodynamics studies assessing feline antinociception. Although mechanical stimulation is currently less used in cats, in the future it might play a role in the evaluation of clinical feline pain. However, the low response reliability after stimulus repetition within a narrow time interval represents a major limitation for the clinical use of mechanical thresholds in this species. Challenges remain when thermal thresholds are used to investigate analgesics that have the potential to affect skin temperature, such as opioids and α2-adrenergic agonists, and when a model of inflammatory pain is reproduced in experimental cats with the purpose of evaluating non-steroidal anti-inflammatory drugs as analgesics.

Thermal, mechanical and electrical stimuli in antinociceptive studies in standing horses: an update

OBJECTIVE

To perform a literature review of the thermal and mechanical antinociceptive devices used in pharmacological studies in standing horses published after 2011 (2012-2019). To complete a full literature review about electrical stimulation used for evaluation in similar studies.

DATABASES USED

PubMed, Google Scholar and Web of Science.

CONCLUSIONS

A high level of standardization has been reached in antinociceptive studies in standing horses using thermal and mechanical stimuli in most recent years. Commercially available testing devices to deliver thermal, mechanical and electrical stimuli, with observation of aversive responses to these stimuli, are reliable, sensitive and specific. For electrical stimulus testing, there is evidence that the resistance between the electrodes should be measured and should not exceed 3 kΩ to guarantee consistent and reproducible stimuli. The specific analysis of electromyographic activity after an electrical stimulus provides more detailed information about the neurons stimulated.

The antinociceptive effects of intravenous administration of three doses of butorphanol tartrate or naloxone hydrochloride following hydromorphone hydrochloride to healthy conscious cats

OBJECTIVE

To evaluate thermal antinociception from intravenous (IV) administration of hydromorphone alone or followed by butorphanol or naloxone in cats.

STUDY DESIGN

Randomized, controlled, masked, crossover design.

ANIMALS

A group of eight adult female cats.

METHODS

Cats were administered six treatments of two IV injections 30 minutes apart: treatments S-S, two 0.9% saline; H-S, hydromorphone (0.1 mg kg^-1) and saline; H-LB, hydromorphone and butorphanol (0.02 mg kg^-1); H-MB, hydromorphone and butorphanol (0.1 mg kg^-1); H-HB, hydromorphone and butorphanol (0.2 mg kg^-1); H-N, hydromorphone and naloxone (0.04 mg kg^-1). Skin temperature (ST), thermal threshold (TT) and sedation score (SS) were recorded before (baseline) and for 8 hours after the first injection. Percentage maximum possible effect (%MPE), thermal excursion (TE), TT, SS and ST were compared using two-way repeated measures anova or Friedman test followed by Tukey's or Dunn's multiple comparisons test when appropriate. Significance was set at p ≤ 0.05.

RESULTS

Data from seven cats were analyzed. There were no significant differences among treatments in baseline values, SS and within S-S over time. Compared with respective 0.5 hour values following hydromorphone administration, %MPE was significantly lower at 4-8 hours for H-S; at 3-8 hours for H-LB; at 4-8 hours for H-MB; at 6-8 hours for H-HB and at 1-8 hours for H-N. Compared with respective 0.5 hour values, TE was significantly lower at 4-8 hours for H-S; at 3-8 hours for H-LB; at 2 and 4-8 hours for H-MB; at 6 and 8 hours for H-HB and at 1-8 hours for H-N.

CONCLUSIONS AND CLINICAL RELEVANCE

Butorphanol and naloxone reduced hydromorphone-induced thermal antinociception. Butorphanol preserved hydromorphone antinociceptive properties better than naloxone. Butorphanol is recommended during non-life-threatening scenarios as a partial reversal agent for hydromorphone in cats.

Thermal antinociceptive, sedative and cardiovascular effects of Governing Vessel 1 dexmedetomidine pharmacopuncture in healthy cats

OBJECTIVE

To compare the antinociceptive, sedative and cardiovascular effects of dexmedetomidine pharmacopuncture at Governing Vessel 1 (GV 1) with dexmedetomidine intramuscular (IM) administration.

STUDY DESIGN

Randomized, masked crossover design.

ANIMALS

A group of eight healthy female cats.

METHODS

Cats were randomly administered either dexmedetomidine (0.005 mg kg^-1; Dex-IM) IM or at acupuncture point GV 1 (Dex-P) separated by 1 week. Prior to and up to 120 minutes posttreatment, skin temperature (ST), thermal threshold (TT), heart rate (HR), respiratory rate (f_R), sedation, muscle relaxation and auditory response scores were recorded. Parametric data were analyzed using a two-way repeated measures anova followed by Tukey's test for multiple comparisons. Nonparametric data were analyzed using a Friedman test followed by Dunn's multiple comparisons test, and Wilcoxon signed-rank test with Bonferroni correction for multiple comparisons. Significance was set at p ≤ 0.05.

RESULTS

There were no differences within or between treatments for ST, f_R and auditory response. TT was significantly higher at 30-90 minutes in Dex-P (p ≤ 0.0285) than baseline. TT was significantly higher at 60-90 minutes for Dex-P than for Dex-IM (p ≤ 0.0252). HR was significantly lower at 10-75 minutes in Dex-P (p ≤ 0.0378) and at 5-75 minutes in Dex-IM (p ≤ 0.0132) than baseline. Compared with baseline, sedation scores were higher at 25 minutes (p = 0.0327) and 30 minutes (p = 0.0327), and muscle relaxation scores were higher at 25 minutes (p = 0.0151) and 35 minutes (p = 0.0151) in Dex-P. There were no differences in HR, sedation and muscle relaxation scores between treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Dex-P increased thermal antinociception compared with Dex-IM at the same dose of dexmedetomidine in cats. This antinociceptive effect must be evaluated under clinical situations.

The effects of aging on hydromorphone-induced thermal antinociception in healthy female cats

Introduction:

This study aimed to evaluate the effects of aging on hydromorphone-induced thermal antinociception in cats.

Methods:

In a prospective, randomized, blinded, controlled design, 10 healthy female cats received each of the following treatments intramuscularly: hydromorphone (0.1 mg/kg) and 0.9% saline (0.05 mL/kg) with a 1-week washout between treatments at 6, 9, and 12 months of age. Skin temperature and thermal thresholds (TTs) were recorded before and up to 12 hours after injection. Data were analyzed using a repeated-measures linear mixed model (α = 0.05).

Results:

After saline treatment, TT was not significantly different from baseline at any time point for any age group. After hydromorphone treatment, TT was significantly higher than baseline at 6 months for up to 1 hour, and at 9 and 12 months for up to 4 hours. Peak TT at 6, 9, and 12 months were 50.4 ± 2.7, 50.9 ± 2.0, and 53.6 ± 2.0°C at 0.5, 1, and 1 hours, respectively. Mean TT was significantly higher after hydromorphone treatment when compared with saline treatment at 9 and 12 months for up to 4 hours but not at 6 months. Magnitude of antinociception was consistently larger at 12 months when compared with 6 months of age. Hydromorphone provided a shorter duration and smaller magnitude of antinociception at 6 months when compared with 9 and 12 months.

Conclusion:

Pediatric cats may require more frequent dosing of hydromorphone than adults.

Pharmacokinetics of low-dose and high-dose buprenorphine in cats after rectal administration of different formulations

OBJECTIVES

A prospective experimental study was performed in nine young healthy cats to investigate a pharmacokinetic profile and the clinical relevance of rectally administered buprenorphine. Rectal pH value was measured in all nine cats.

METHODS

Blood was collected 15, 30, 60, 90, 120, 240 and 480 mins and 24 h after the rectal administration of a suppository and a gel at doses between 0.02 mg/kg and 0.1 mg/kg buprenorphine to determine the plasma concentration of buprenorphine. Rectal pH was measured with pH paper.

RESULTS

Upon pharmacokinetic non-compartment analysis of high-dose buprenorphine (0.1 mg/kg), average maximal plasma concentration was found to be 1.13 ng/ml, time to maximal plasma concentration was 45 mins and area under the plasma concentration-time curve was 94.19 ng*min/ml, representing low but potential bioavailability. Mean residual time was 152.2 mins and the half-life was 92.6 mins. A wide range of plasma concentrations within the cohort was measured and two of the cats had to be excluded from statistical analysis owing to incomplete uptake. Vital parameters of all cats were considered to be normal but three of the cats showed mydriasis up to 8 h after application. After the administration of a low-dose suppository or a rectal gel (0.02 mg/kg) within pilot studies, no buprenorphine was detected in cat plasma. Rectal pH in all cats was between 7.7 and 8.

CONCLUSIONS AND RELEVANCE

The rectal application of buprenorphine at a dose of 0.1 mg/kg revealed a potential but weak uptake in cats. Regarding effective concentrations in previous pharmacokinetic investigations, rectal administration is currently not recommended for good provision of opioid analgesia in cats. Pharmacological investigations of formulation and galenics in order to improve the rectal bioavailability of buprenorphine remain to be clarified before further dose-finding and pharmacokinetic/pharmacodynamic studies are performed.

Translational pain assessment: could natural animal models be the missing link?

Failure of analgesic drugs in clinical development is common. Along with the current "reproducibility crisis" in pain research, this has led some to question the use of animal models. Experimental models tend to comprise genetically homogeneous groups of young, male rodents in restricted and unvarying environments, and pain-producing assays that may not closely mimic the natural condition of interest. In addition, typical experimental outcome measures using thresholds or latencies for withdrawal may not adequately reflect clinical pain phenomena pertinent to human patients. It has been suggested that naturally occurring disease in veterinary patients may provide more valid models for the study of painful disease. Many painful conditions in animals resemble those in people. Like humans, veterinary patients are genetically diverse, often live to old age, and enjoy a complex environment, often the same as their owners. There is increasing interest in the development and validation of outcome measures for detecting pain in veterinary patients; these include objective (eg, locomotor activity monitoring, kinetic evaluation, quantitative sensory testing, and bioimaging) and subjective (eg, pain scales and quality of life scales) measures. Veterinary subject diversity, pathophysiological similarities to humans, and diverse outcome measures could yield better generalizability of findings and improved translation potential, potentially benefiting both humans and animals. The Comparative Oncology Trial Consortium in dogs has pawed the way for translational research, surmounting the challenges inherent in veterinary clinical trials. This review describes numerous conditions similarly applicable to pain research, with potential mutual benefits for human and veterinary clinicians, and their respective patients.

Pharmacokinetic and pharmacodynamic modelling after subcutaneous, intravenous and buccal administration of a high-concentration formulation of buprenorphine in conscious cats

Background

The aim of this study was to describe the joint pharmacokinetic-pharmacodynamic model and evaluate thermal antinociception of a high-concentration formulation of buprenorphine (Simbadol^™) in cats.

Methods

Six healthy cats (4.9 ± 0.7 kg) were included in a prospective, randomized, blinded, crossover study. Simbadol^™ (1.8 mg mL^-1) was administered by the subcutaneous (SC; 0.24 mg kg^-1), intravenous (IV; 0.12 mg kg^-1) or buccal (OTM; 0.12 mg kg^-1) route of administration and thermal thresholds (TT) were compared with a saline group (SAL). Thermal threshold testing and blood sampling were performed at predetermined time points up to 72 hours including a placebo group. Plasma buprenorphine and norbuprenorphine concentrations were measured using liquid chromatography mass spectrometry. A bespoke bicompartmental pharmacokinetic model simultaneously fitted data from two analytes/three routes of administration. Temporal changes in TT were analyzed using one-way ANOVA followed by Dunnett’s test and treatment comparisons using two-way ANOVA with Bonferroni’s correction (P < 0.05).

Results

Thermal thresholds were significantly increased after SC, IV and OTM from 1–24 hours (except 2 hours), 0.5–8 hours (except 6 hours), and 1–8 hours (except 6 hours), respectively, when compared with baseline. Thermal thresholds were significantly increased after SC (1–30 hours), IV (1–8 hours) and OTM (1–12 hours) when compared with SAL, but not different among buprenorphine-treated cats. The absolute buprenorphine clearance was 0.98 L kg^-1 hour^-1, volume of distribution at steady state was 7.9 L kg^-1 and the elimination-half-life was 12.3 hours. Bioavailability for SC and OTM was 94% and 24%, respectively. Subcutaneous absorption was biphasic. An initial peak (0.08 hours) was followed by a slow (half-life 11.2 hours) and progressive (peak acceleration at 2.8 hours) uptake.

Conclusion

The SC administration of Simbadol^™ was characterized by prolonged absorption half-life and sustained plasma concentrations yielding long-lasting antinociception (≥ 24 hours) when compared with the IV and OTM routes.

Sciatic and femoral nerve blockade using bupivacaine alone, or in combination with dexmedetomidine or buprenorphine in cats

The aim of this study was to determine the onset and offset of antinociception after sciatic (ScN) and femoral (FN) nerve blocks. Six healthy adult cats (4.8±1.3years; 4.3±0.4 kg) were included in a randomised, crossover, blinded and controlled study. Following sedation with dexmedetomidine (25 µg/kg, intramuscular), each ScN and FN injection was performed using 0.1 ml/kg of saline (CONTROL), bupivacaine (0.46 per cent, 0.46 mg/kg; BUPI), bupivacaine and dexmedetomidine (1 µg/kg; BUPI-DEX) or bupivacaine and buprenorphine (2.5 µg/kg; BUPI-BUPRE). Atipamezole (250 µg/kg) was administered after injections. Paw withdrawal thresholds (PWT) and motor blockade were evaluated before sedation and up to 24 hours. The PWT were significantly increased at half an hour in CONTROL, from two to four hours in BUPI and BUPI-DEX when compared with baseline. Motor blockade was observed between one and three hours in treatments using bupivacaine. Ability to walk was significantly impaired in BUPI at half an hour to two hours, BUPI-DEX at one to two hours and BUPI-BUPRE at two hours. Antinociception was observed in BUPI between one and eight hours, and in BUPI-DEX and BUPI-BUPRE between one and four hours. This study could not demonstrate a benefit of administering bupivacaine with dexmedetomidine or buprenorphine in cats. Results in BUPI-DEX may have been biased by the administration of atipamezole.

Development and initial validation of a sensory threshold examination protocol (STEP) for phenotyping canine pain syndromes

OBJECTIVE

To study the feasibility and test-retest repeatability of a sensory threshold examination protocol (STEP) and report the quantitative sensory threshold distributions in healthy dogs.

STUDY DESIGN

Prospective, observational, cohort study.

ANIMALS

Twenty-five healthy client-owned dogs.

METHODS

Tactile sensitivity test (TST) (von Frey filaments), mechanical thresholds (MT with 2, 4 and 8 mm probes), heat thresholds (HT) and responsiveness to cold stimulus (CT at 0 °C) were quantitatively assessed for five body areas (BAs; tibias, humeri, neck, thoracolumbar region and abdomen) in a randomized order on three different occasions. Linear mixed model and generalized linear mixed models were used to evaluate the effects of body weight category, age, sex, BA, occasion, feasibility score and investigator experience. Test-retest repeatability was evaluated with the intra-class correlation coefficient.

RESULTS

The STEP lasted 90 minutes without side effects. The BA affected most tests (p ≤ 0.001). Higher thresholds and longer cold latencies were scored in the neck (p ≤ 0.024) compared to other BAs. Weight category affected all thresholds (p ≤ 0.037). Small dogs had lower MT (∼1.4 N mean difference) and HT (1.1 °C mean difference) than other dogs (p ≤ 0.029). Young dogs had higher HT than adults (2.2 °C mean difference) (p = 0.035). Gender also affected TST, MT and HT (p < 0.05) (females versus males: TST odds ratio = 0.5, MT = 1.3 N mean difference, HT = 2.2 °C mean difference). Repeatability was substantial to moderate for all tests, but poor for TST. There was no difference in thresholds between occasions, except for CT. Test-retest repeatability was slightly better with the 2 mm MT probe compared to other diameters and improved with operator experience.

CONCLUSIONS AND CLINICAL RELEVANCE

The STEP was feasible, was well tolerated and showed substantial test-retest repeatability in healthy dogs. Further validation is needed in dogs suffering pain.

Evaluation of the use of thermal thresholds to investigate NSAID analgesia in a model of inflammatory pain in cats

This study evaluated thermal threshold (TT) testing for investigation into NSAID analgesia in cats. Seven cats participated in two crossover studies. TTs were measured on thoracic skin using a device developed specifically for cats. Skin temperature was recorded, then the heater activated. At the behavioural end point heating was stopped and temperature (=TT) recorded. In part 1, TTs were measured following subcutaneous (SC) ketoprofen or saline. In part 2, the process was repeated after intradermal kaolin induced mild inflammation at the test site. TTs were measured before treatment and two hourly for 24 h. In part 1, skin temperature did not change but in part 2 it increased more after saline than ketoprofen. TT did not change significantly after any treatment. However, after ketoprofen TT fell below the 95% confidence interval (CI) in part 1 and increased above it in part 2. The method detected some NSAID effects but is unlikely to be sufficiently sensitive for study of NSAID analgesia.

Mechanical nociceptive threshold testing in Bos indicus bull calves

The aim of this prospective, controlled, randomised trial was to develop a technique for mechanical nociceptive threshold testing (NTT) to assess pain in Bos indicus bull calves undergoing surgical castration. Analgesia was provided by 0.5 mg/kg subcutaneous (SC) meloxicam (M) and/or 2 mg/kg of intra-testicular and SC (at the surgery sites) lidocaine (L). Forty-eight Brahman bull calves at 6–8 months of age were divided into six study groups, each with eight animals: no surgery control; surgical castration (C) without analgesia; C and Mpre-op; C and Mpost-op; C, L and Mpost-op; C and L. Mechanical NTT was performed the day before surgery (Day –1) and on Days 1, 2, 6, 10 and 13 after surgery. A handheld manual pneumatic device with a 1-mm (diameter) blunt pin was used to deliver a mechanical stimulus to a maximum of 27 Newtons either side of the most dorsal aspect of the sacrum. The most frequent responses to the mechanical stimulus were lifting or kicking of the leg on the same side as the stimulus (31%) and stepping away from the stimulus (24.9%). Data were analysed with a mixed effect linear model with the nociceptive threshold (NT) as the response variable and day and analgesic treatment as predictors (P < 0.05 was considered significant). For all groups, there was a trend towards decreasing NT over the study period but there were no significant differences between groups. Step down model selection with day, batch and treatment terms revealed a significant effect of day (P < 0.001) and batch (P = 0.007). Mechanical NTT for assessment of pain in Bos indicus bull calves requires further refinement to determine if this is a useful method of pain assessment.

Antinociceptive effects of intravenous administration of hydromorphone hydrochloride alone or followed by buprenorphine hydrochloride or butorphanol tartrate to healthy conscious cats

OBJECTIVE

To evaluate antinociceptive effects of IV administration of hydromorphone alone or followed by buprenorphine or butorphanol to cats.

ANIMALS

6 healthy adult cats.

PROCEDURES

In a randomized, blinded crossover design, cats received each of 4 treatments in which 2 IV injections were given 30 minutes apart: 2 of saline (0.9% NaCl) solution (Sal-Sal) or 1 each of hydromorphone HCl and saline solution (H-Sal), hydromorphone and buprenorphine HCl (H-Bupre), or hydromorphone and butorphanol tartrate (H-Butor). Skin temperature and thermal threshold were recorded before (baseline) and for 12 hours after the first injection. Percentage of maximum possible effect (%MPE) and thermal excursion (TE) were compared among treatments and measurement points.

RESULTS

Compared with baseline values, skin temperature was higher from 0.75 to 2 hours after the first injection for H-Sal; at 0.5, 1, 3, and 4 hours for H-Bupre; from 0.5 to 3 hours for H-Butor; and from 0.5 to 1 hours for Sal-Sal. Thermal excursion was higher than at baseline from 0.25 to 2 hours for H-Sal and H-Bupre and 0.25 to 0.75 hours for H-Butor; %MPE increased from 0.25 to 2 hours for H-Sal, 0.25 to 3 hours for H-Bupre, and 0.25 to 0.75 hours for H-Butor. Results were similar for comparisons with Sal-Sal, except TE was greater for H-Sal versus Sal-Sal and TE and %MPE were greater for H-Bupre versus Sal-Sal from 0.25 to 1 hours after the first injection.

CONCLUSIONS AND CLINICAL RELEVANCE

Butorphanol administration decreased the duration of antinociception achieved with hydromorphone administration in cats. This opioid interaction and its impact on pain management require additional investigation.

Effect of pretreatment with hydromorphone or buprenorphine on thermal antinociception induced by fentanyl in awake cats

Objectives

The aim of this study was to determine the effect of pretreatment with hydromorphone or buprenorphine on thermal antinociception induced by fentanyl in cats.

Methods

Seven healthy cats received five different treatments consisting of two drugs. Drug 1 was administered intravenously 1 h before drug 2. Drug 2 was given as an intravenous loading dose followed by an infusion for 4 h. The drug combinations used were: buprenorphine 20 µg/kg followed by fentanyl (BF; 7 μg/kg, 7 μg/kg/h), buprenorphine 20 µg/kg followed by 0.9% saline solution (B), hydromorphone 0.07 mg/kg followed by 0.9% saline solution (H), hydromorphone 0.07 mg/kg followed by fentanyl (HF; 7 μg/kg, 7 μg/kg/h) and 0.9% saline solution followed by fentanyl (F; 7 μg/kg, 7 μg/kg/h). Thermal thresholds were obtained prior to treatment and at predetermined times up to 7 h after drug 1.

Results

Thermal thresholds were significantly higher than baseline in all treatment groups as follows: H from 0.25 to 2.50 h; B from 0.25 to 2.50 h; F from 1.25 to 5.50 h; HF from 0.25 to 5.50 h and BF from 0.25 to 5.25 h. Thermal thresholds were significantly higher in HF and BF than in F treatment before the fentanyl infusion was commenced (from 0.25 to 1.00 h). During the fentanyl infusion thermal thresholds in BF compared with F were lower at 1.75 h and from 2.50 to 3.50 h. After the constant rate infusion of fentanyl was started, thermal thresholds were significantly lower in HF compared with F at one time point (3 h).

Conclusions and relevance

Pretreatment with buprenorphine did partially inhibit the antinociceptive action of fentanyl. Hydromorphone did inhibit the antinociceptive action of fentanyl at one single time point in cats.

Pain management in cats—past, present and future. Part 2. Treatment of pain—clinical pharmacology

Opioids have an unjustified reputation for causing mania in cats, but with refinements in dosing they are now used successfully in this species. The mu-opioid agonists are generally considered the best analgesics. Morphine (0.1–0.3 mg/kg) is effective in a clinical setting. Methadone (up to 0.5 mg/kg) has a similar profile to morphine. Pethidine (Demerol, meperidine; 2–5 mg/kg) is a useful analgesic with a faster onset but shorter duration of action than morphine. Oxymorphone and hydromorphone (0.05–0.1 mg/kg) are widely used in the USA. These opioids are more potent (up to 10 times), and longer acting than morphine in cats. Butorphanol (0.1–0.4 mg/kg) is a mu-opioid antagonist that produces its analgesic actions through kappa agonist activity. It rapidly reaches a ceiling effect, is short acting and is a weaker analgesic than pure mu opioids. Buprenorphine (0.01–0.02 mg/kg), a partial mu-agonist, is the most popular opioid used in small animal practice in the UK, other parts of Europe, Australia and South Africa. In clinical studies it has produced better analgesia than several other opioids and appears to be highly suitable for perioperative pain management in cats. NSAIDs are also used in cats for pain management, although cats metabolise these differently from other species. With appropriate dosing, carprofen (1–4 mg/kg) and meloxicam (0.3 mg/kg) have proved highly effective with few side effects. The use of ketoprofen (2 mg/kg), tolfenamic acid (4 mg/kg) and vedaprofen (0.5 mg/kg) has been reported in cats. Other less traditional analgesics such as ketamine, medetomidine and local anaesthetics are also used for clinical pain management. The transmucosal, transdermal and epidural routes offer novel methods for administration of analgesic drugs and have considerable potential for improving techniques in feline pain management.

Systematic review of the behavioural assessment of pain in cats

Objectives

The objectives were to review systematically the range of assessment tools used in cats to detect the behavioural expression of pain and the evidence of their quality; and to examine behavioural metrics (considering both the sensory and affective domains) used to assess pain.

Methods

A search of PubMed and ScienceDirect, alongside articles known to the authors, from 2000 onwards, for papers in English was performed. This was followed by a manual search of the references within the primary data sources. Only peer-reviewed publications that provided information on the assessment tool used to evaluate the behavioural expression of pain in cats, in conscious animals (not anaesthetised cats), were included.

Results

No previous systematic reviews were identified. One hundred papers were included in the final assessment. Studies were primarily related to the assessment of pain in relation to surgical procedures, and no clear distinction was made concerning the onset of acute and chronic pain. Ten broad types of instrument to assess pain were identified, and generally the quality of evidence to support the use of the various instruments was poor. Only one specific instrument (UNESP-Botucatu scale) had published evidence of validity, reliability and sensitivity at the level of a randomised control trial, but with a positive rather than placebo control, and limited to its use in the ovariohysterectomy situation. The metrics used within the tools appeared to focus primarily on the sensory aspect of pain, with no study clearly discriminating between the sensory and affective components of pain.

Conclusions and relevance

Further studies are required to provide a higher quality of evidence for methods used to assess pain in cats. Furthermore, a consistent definition for acute and chronic pain is needed. Tools need to be validated that can detect pain in a range of conditions and by different evaluators (veterinary surgeons and owners), which consider both the sensory and emotional aspects of pain.

Pharmacokinetic and pharmacodynamic evaluation of high doses of buprenorphine delivered via high-concentration formulations in cats

OBJECTIVES

To evaluate the potential benefits of high-dose buprenorphine formulations for analgesia in cats, serial and crossover studies were undertaken to investigate their pharmacokinetics and thermal antinociceptive effects.

METHODS

Twelve healthy adult domestic shorthair cats (6.0 ± 1.1 kg body weight) were studied. Aqueous solutions of buprenorphine hydrochloride at 0, 0.02, 0.06, 0.12 and 0.24 mg/kg body weight and formulations containing 0, 0.3, 0.6 and 1.2 mg/ml with and without preservatives were given subcutaneously. Blood samples were taken and thermal threshold (TT) measured prior to and at regular time points up to 72 h after dosing. Descriptive statistics and analyses of variance were applied as appropriate.

RESULTS

Baseline TT was 47.6 ± 4.1°C, which increased in all groups treated with all buprenorphine dosages and formulations. After doses of 0.12 mg/kg and above, TT was significantly higher than baseline at most time points from 1-30 h post-treatment. The time to maximum effect (Tmax) ranged between 0.25 and 2.00 h; and plasma concentrations associated with maximum antinociceptive effect (Cmax) were 1.01-1.72 ng/ml after the 0.02 mg/kg dose, 1.4-4.9 ng/ml after the 0.06 mg/kg dose, 4.6-51.4 ng/ml after the 0.12 mg/kg dose and 5.3-22.3 ng/ml after the 0.24 mg/kg dose. The range of estimates for the buprenorphine elimination half-life were as follows: 0.02 mg/kg = 1.35-5.33 h; 0.06 mg/kg = 16.1-31.2 h; 0.12 mg/kg = 10.1-34.0 h; and 0.24 = mg/kg 16.1-31.6 h. The mean 'plasma concentration for the offset of analgesia' was 2.3 ± 2.0 ng/ml. No adverse effects were seen. The addition of preservatives to a high-concentration buprenorphine formulation had no impact on antinociception nor any side effects.

CONCLUSIONS AND RELEVANCE

Aqueous high-concentration buprenorphine formulations administered at 0.12 or 0.24 mg/kg have potential for clinical use in cats, providing prolonged antinociception in a single subcutaneous injection of minimal dose volume.

Practical use of opioids in cats: a state-of-the-art, evidence-based review

Rationale

Recent recognition of the need to improve pain management in cats has led to the investigation of the pharmacokinetics and efficacy of opioid analgesic drugs in this species. The results of these studies may be difficult to interpret because the effect of these drugs varies with dose, route of administration and the method used to assess them. As equipotency of different opioids is not known, it is hard to compare their effects. Animals do not verbalise the pain they feel and, in cats, it may be more difficult to recognise signs of pain in comparison with other species such as dogs.

Aim

This article reviews the use of opioid analgesics in cats. It must be remembered that not all drugs are licensed for use in cats, and that marketing authorisations vary between different countries.

Refinement of a thermal threshold probe to prevent burns

Thermal threshold testing is commonly used for pain research. The stimulus may cause burning and merits prevention. Thermal probe modifications hypothesized to reduce burning were evaluated for practicality and effect. Studies were conducted on two humans and eight cats. Unmodified probe 0 was tested on two humans and promising modifications were also evaluated on cats. Probe 1 incorporated rapid cooling after threshold was reached: probe 1a used a Peltier system and probe 1b used water cooling. Probe 2 released skin contact immediately after threshold. Probe 3 (developed in the light of evidence of 'hot spots' in probe 0) incorporated reduced thermal mass and even heating across the skin contact area. Human skin was heated to 48℃ (6℃ above threshold) and the resulting burn was evaluated using area of injury and a simple descriptive scale (SDS). Probe 1a cooled the skin but required further heat dissipation, excessive power, was not 'fail-safe' and was inappropriate for animal mounting. Probe 1b caused less damage than no cooling (27 ± 13 and 38 ± 11 mm(2) respectively, P = 0.0266; median SDS 1.5 and 4 respectively, P = 0.0317) but was cumbersome. Probe 2 was unwieldy and was not evaluated further. Probe 3 produced even heating without blistering in humans. With probe 3 in cats, after opioid treatment, thermal threshold reached cut-out (55℃) on 24 occasions, exceeded 50℃ in a further 32 tests and exceeded 48℃ in the remainder. No skin damage was evident immediately after testing and mild hyperaemia in three cats at 2-3 days resolved rapidly. Probe 3 appeared to be suitable for thermal threshold testing.

Preliminary investigation of the thermal antinociceptive effects of codeine in cats

Objectives

The aim of this study was to evaluate the potential thermal antinociceptive effects of oral administration of a single dose of codeine in cats compared with positive (buprenorphine) and negative (saline 0.9%) controls.

Methods

Six adult healthy cats weighing 5.14 ± 0.6 kg were used. Skin temperature and thermal thresholds (TTs) were evaluated using a wireless device (Topcat Metrology) at baseline, 0.5, 1, 3, 6 and 10 h after treatment. In period 1, TTs were evaluated after subcutaneous administration of saline 0.9%. In period 2, cats were administered either oral codeine (10 mg total, 2.0 ± 0.2 mg/kg) or buccal buprenorphine (0.04 mg/kg) in a cross-over, blinded study design. Half of the volume of buprenorphine was administered into each cheek pouch. Δ TT (difference between TTs after and before treatment) was used for data comparison. Mean ± SD data were analyzed using one-way ANOVA followed by Dunnett’s or Tukey’s test when appropriate ( P <0.05).

Results

Adverse effects did not occur in any group. Skin temperature was not different between groups nor over time. Temporal changes in TTs were not observed after saline or codeine. Buprenorphine increased Δ TT at 3 h (2.7 ± 3.3°C) when compared with baseline or saline ( P <0.05). For buprenorphine, TTs were not >47.6°C at any time point in four cats. The mean highest temperature recorded in the two other cats in that group was 54.5 and 52.8°C at 3 h.

Conclusions and clinical relevance

At the dose administered, codeine did not produce thermal antinociception. Mild increases in TT after buccal buprenorphine might be related to the first-pass effect after drug swallowing, drug spillage during administration and/or individual variability. These factors should be taken in to consideration when administering buprenorphine by this route in the clinical setting.

Relationship between plasma dexmedetomidine concentration and sedation score and thermal threshold in cats

OBJECTIVE

To characterize the relationship between plasma dexmedetomidine concentration and the temperature difference between the thermal threshold and skin temperature (ΔT) and between plasma dexmedetomidine concentration and sedation score in healthy cats.

ANIMALS

5 healthy adult spayed female cats.

PROCEDURES

Cats received IV administrations of saline (0.9% NaCl) solution, dexmedetomidine (5, 20, or 50 μg/kg), or acepromazine (0.1 mg/kg). Blood samples were collected and thermal threshold and sedation score were determined before and at various times up to 8 hours after drug administration. In addition, cats received an IV infusion of dexmedetomidine that targeted a concentration achieving 99% of the maximum effect on ΔT.

RESULTS

No change in ΔT over time was found for the saline solution and acepromazine treatments; ΔT increased for 45 minutes when cats received dexmedetomidine at 5 and 20 μg/kg and for 180 minutes when cats received dexmedetomidine at 50 μg/kg. No change in sedation score over time was found for saline solution. Sedation score increased for 120 minutes after cats received acepromazine and for 60, 120, and 180 minutes after cats received dexmedetomidine at 5, 20, and 50 μg/kg, respectively. The plasma dexmedetomidine concentration-effect relationships for the effect on ΔT and sedation score were almost identical. The plasma dexmedetomidine concentration after infusion was lower than targeted, and ΔT was not significantly affected.

CONCLUSIONS AND CLINICAL RELEVANCE

Dexmedetomidine administration to cats resulted in thermal analgesia and also profound sedation. These data may be useful for predicting the course of thermal analgesia and sedation after dexmedetomidine administration to cats.

Comparison of preoperative tramadol and pethidine on postoperative pain in cats undergoing ovariohysterectomy

Background

A variety of analgesic agents are available, and which one can be used in dogs and cats is a highly controversial issue, existing however a fear in the use of opiates due to possible adverse effects that these drugs can cause. The aim of this study was to compare the analgesic effect provided by the administration of tramadol or pethidine on early postoperative pain of cats undergoing ovariohysterectomy in a double-blind prospective study. Fourty-two animals were randomly assigned into three groups. Pet received pethidine (6 mg/kg), Tra 2 received tramadol (2 mg/kg) and Tra 4 received tramadol (4 mg/kg); all intramuscularly and associated with acepromazine (0.1 mg/kg). The efficacy of each analgesic regimen was evaluated prior to surgery (baseline - T_BL), during surgery and 1, 3 and 6 hours after extubation with subjective pain scale, physiologic parameters, serum concentrations of glucose, cortisol and IL-6.

Results

Changes in cardiovascular system were not clinically relevant. There were no significant differences in pain scores (P > 0.05) during the study, although the number of rescue analgesia was significantly higher (P < 0.05) at Pet group (5/14) than Tra 4 group (0/14), whereas in Tra 2, two animals (2/14) required additional analgesia. The serum cortisol values of Pet group were significantly higher at T_1h T_3h (P < 0.05) and T_6h (P < 0.01) when compared to baseline (induction), also it was noticed a significant difference among the groups at T_6h (Pet values were higher than Tra 2 and Tra 4; P < 0.05).

Conclusions

Tramadol provided adequate analgesia and it was more effective than pethidine to at least six hours for the studied animals. At the higher dose (4 mg/kg) tramadol is probably more effective, since rescue analgesia was not necessary. No significant changes were observed physiological parameter that could contraindicate the use of these opioid in described doses, for the feline species.

Pharmacokinetics and pharmacodynamics of a constant rate infusion of fentanyl (5 μg/kg/h) in awake cats

OBJECTIVE

To evaluate the pharmacokinetics and thermal and mechanical antinociceptive effects of a fentanyl constant rate infusion (CRI) in conscious cats.

ANIMALS

8 healthy adult cats.

PROCEDURES

At a ≥ 14-day interval, 7 cats received a loading dose (LD) of fentanyl (5 μg/kg, IV [administered at 0 hours]) followed by fentanyl infusion (5 μg/kg/h, IV) for 2 hours or similar administrations of equivalent volumes of 0.9% saline (NaCl) solution. One cat received only the fentanyl treatment. For both treatments, sedation and adverse events were evaluated and mechanical threshold (MT) and thermal threshold (TT) testing was performed prior to (baseline) and at predetermined times up to 26 hours after LD administration; plasma fentanyl concentrations were determined at similar times when the cats received fentanyl.

RESULTS

Fentanyl induced mild sedation during the infusion. The only adverse effect associated with fentanyl LD administration was profuse salivation (1 cat). Saline solution administration did not significantly change MT or TT over time. For the duration of the CRI, MT and TT differed significantly between treatments, except for TT 1 hour after LD administration. For the fentanyl treatment, MT and TT were significantly higher than baseline at 0.25 to 0.75 hours and at 0.25 to 1 hour, respectively. During the fentanyl CRI, mean ± SD plasma fentanyl concentration decreased from 4.41 ± 1.86 ng/mL to 2.99 ± 1.28 ng/mL and was correlated with antinociception; plasma concentrations < 1.33 ± 0.30 ng/mL were not associated with antinociception.

CONCLUSIONS AND CLINICAL RELEVANCE

Fentanyl CRI (5 μg/kg/h) induced mechanical and thermal antinociception in cats.

A review of the studies using buprenorphine in cats

Pain management is a crucial component of feline medicine and surgery. This review critically evaluates studies using buprenorphine in cats and highlights the clinical application of the opioid in this species. The pharmacokinetic-pharmacodynamic (PK-PD) modeling of IV buprenorphine has been best described by a combined effect compartmental/receptor association-dissociation model with negative hysteresis. Therefore, plasma concentrations of the drug are not correlated with analgesia, and clinicians should not expect to observe pain relief immediately after drug administration. In addition, a ceiling effect has not been demonstrated after administration of clinical doses of buprenorphine in cats; dosages of up to 0.04 mg/kg have been reported. The route of administration influences the onset, duration, and magnitude of antinociception and analgesia when using this drug in cats. At clinical dosages, the SC route of administration does not appear to provide adequate antinociception and analgesia whereas the buccal route has produced inconsistent results. Intravenous or IM administration at a dosage of 0.02-0.04 mg/kg is the preferred for treatment of pain in the acute setting. A literature search found 14 clinical trials evaluating buprenorphine sedation, analgesia, or both in cats. There were 22 original research studies reporting the antinociceptive effects of buprenorphine by means of thermal threshold, mechanical threshold, or both, minimal alveolar concentration, or PK-PD. Individual variability in response to buprenorphine administration has been reported, indicating that buprenorphine may not provide sufficient analgesia in some cats. Pain assessment is important when evaluating the efficacy of buprenorphine and determining whether additional analgesic treatment is needed.

Nociceptive thermal threshold testing in horses - effect of neuroleptic sedation and neuroleptanalgesia at different stimulation sites

Background

Aim of the study was to compare the effect of neuroleptic sedation with acepromazine and neuroleptanalgesia with acepromazine and buprenorphine on thermal thresholds (TT) obtained at the nostrils and at the withers. The study was carried out as a randomized, blinded, controlled trial with cross-over design. Thermal thresholds were determined by incremental contact heat applied to the skin above the nostril (N) or the withers (W). Eleven horses were treated with saline (S), acepromazine (0.05 mg/kg) (ACE) or acepromazine and buprenorphine (0.0075 mg/kg) (AB) intravenously (IV). Single stimulations were performed 15 minutes prior and 15, 45, 75, 105, 165, 225, 285, 405 and 525 minutes after treatment. Sedation score, gastrointestinal auscultation score and occurrence of skin lesions were recorded. Data were analysed with analysis of variance for repeated measurements.

Results

There were no significant differences in TT between N and W with all treatments. The TT remained constant after S and there was no difference in TT between S and ACE. After AB there was a significant increase above baseline in TT until 405 minutes after treatment. Restlessness occurred 30–90 minutes after AB in 7 horses. All horses had reduced to absent borborygmi after AB administration for 165 to 495 minutes.

Conclusion

Thermal stimulation at both described body areas gives comparable results in the assessment of cutaneous anti-nociception in horses. There is no differential influence of neuroleptic sedation or neuroleptanalgesia on TTs obtained at N or W. Buprenorphine combined with acepromazine has a long lasting anti-nociceptive effect associated with the typical opioid induced side effects in horses.

Evaluation of contact heat thermal threshold testing for standardized assessment of cutaneous nociception in horses - comparison of different locations and environmental conditions

Background

The aim of the study was to evaluate the performance of contact heat thermal stimulation in horses at different body sites and under different environmental conditions and different test situations. Five warm-blood horses were equipped with the thermal probe located on the skin of nostril (N), withers (W) or coronary band (C). Skin temperature and reaction temperature (thermal threshold) at each location were measured and percent thermal excursion (% TE = 100 * (threshold temperature - skin temperature)/(cut-out temperature - skin temperature) was calculated. Environmental conditions were changed in partial random order for all locations, so each horse was tested in its familiar box stall and stocks, in the morning and evening and at warm and cold ambient temperatures. Type of reaction to the stimulus and horse’s general behaviour during stimulation were recorded. The stimulation sites were examined for the occurrence of possible skin lesions.

Results

Skin temperatures were significantly different during warm and cold ambient temperatures at all three locations, but remained constant over repeated stimulation. An obvious response to stimulation before reaching cut-out temperature could be detected most frequently at N and W in boxes during warm ambient temperatures. The most frequent type of reaction to thermal stimulation at the nostril was headshaking (64.6%), skin twitching at the withers (82.9%) and hoof withdrawal at the coronary band (79.2%).

Conclusion

The outcome of thermal threshold testing depended on ambient temperature, stimulation site and environment. Best results with the WTT2 in horses were obtained at the nostrils or withers in a familiar environment at warm ambient temperatures.

Contact heat thermal threshold testing in beagle dogs: baseline reproducibility and the effect of acepromazine, levomethadone and fenpipramide

BACKGROUND

In this methodology article a thermal threshold testing device designed to test nociception in cats was assessed in six dogs. The purpose of this study was to investigate baseline reproducibility of thermal thresholds obtained by the contact heat testing device, to assess the influence of acepromazine and levomethadone and fenpipramide in dogs. The relationship between change in nociceptive thermal threshold and the opioid's plasma concentration was determined. Six adult beagle dogs received levomethadone (0.2 mg/kg), acepromazine (0.02 mg/kg) or saline placebo by intramuscular injection (IM) in a randomized cross-over design. Three baseline nociceptive thermal threshold readings were taken at 15 minutes intervals prior to treatment. Further readings were made at 15, 30, 45, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, 360, 420 and 480 minutes after injection. A sedation score was assigned at every reading. Four saline placebo treatments were performed to assess baseline reproducibility. Levomethadone serum concentrations were measured prior and 0.5, 1, 2, 4, 8, 12 and 24 hours after drug dosing in a separate occasion.

RESULTS

Acepromazine did not seem to increase the thermal threshold at any time. After levomethadone there was a significant rise of the thermal threshold between 15 to 120 minutes at serum concentrations between 22.6-46.3 ng/mL. Baseline reproducibility was stable in adult beagle dogs.

CONCLUSION

The thermal threshold testing system is a suitable device for nociceptive threshold testing in dogs.

A comparison of thermographic imaging, physical examination and modified questionnaire as an instrument to assess painful conditions in cats

Pain recognition in cats is difficult and requires a multidisciplinary approach for diagnosis. A total of 103 client-owned cats were enrolled in this prospective, blinded clinical trial. Cats were invited to the clinic, or presented for annual rechecks/vaccinations, or gastrointestinal, dental or locomotor problems. The cats were of different breeds; both shorthaired and longhaired cats were included. Those cats that tolerated it were palpated and all cats were examined with the non-invasive method of thermographic imaging. Owners filled out a questionnaire about their cat’s behaviour and estimated whether the cat was in any pain. The agreement between a questionnaire and thermographic imaging or palpation was low. Also, the agreement between the owner’s estimation of pain and thermographic imaging or palpation was low. The agreement between palpation and thermographic imaging was moderate, suggesting that thermographic imaging is a potential tool in clinical practice for detecting and screening cats that are, potentially, in pain.

Comparison of two formulations of buprenorphine in cats administered by the oral transmucosal route

This randomised, blinded, cross-over study investigated the ease of oral transmucosal administration of two formulations of buprenorphine using glucose as a control in 12 cats. The cats received three treatments: buprenorphine multi-dose, buprenorphine and the equivalent volume of glucose 5%. Ease of treatment administration, observation of swallowing, changes in pupil size, sedation, salivation, vomiting, behaviour and food intake were assessed. The data were analysed using MLwiN and multi-level modelling. Ease of administration of buprenorphine multi-dose was statistically different from glucose (P <0.001), and the administration of all treatments became easier over the study periods. Swallowing was not statistically different between groups (P >0.05). Mydriasis was evident after the administration of both formulations of buprenorphine. Sedation, salivation, vomiting, behavioural changes or in-appetence were not observed after any treatment. Cats tolerated oral transmucosal administration of glucose better than buprenorphine multi-dose, while buprenorphine administration was tolerated as well as glucose.