Spatial working memory in a disappearing object task is impaired in female but not male dogs with chronic osteoarthritis.

Chronic pain in humans is associated with impaired working memory but it is not known whether this is the case in long-lived companion animals, such as dogs, who are especially vulnerable to developing age-related chronic pain conditions. Pain-related impairment of cognitive function could have detrimental effects on an animal's ability to engage with its owners and environment or to respond to training or novel situations, which may in turn affect its quality of life. This study compared the performance of 20 dogs with chronic pain from osteoarthritis and 21 healthy control dogs in a disappearing object task of spatial working memory. Female neutered osteoarthritic dogs, but not male neutered osteoarthritic dogs, were found to have lower predicted probabilities of successfully performing the task compared to control dogs of the same sex. In addition, as memory retention interval in the task increased, osteoarthritic dogs showed a steeper decline in working memory performance than control dogs. This suggests that the effects of osteoarthritis, and potentially other pain-related conditions, on cognitive function are more clearly revealed in tasks that present a greater cognitive load. Our finding that chronic pain from osteoarthritis may be associated with impaired working memory in dogs parallels results from studies of human chronic pain disorders. That female dogs may be particularly prone to these effects warrants further investigation.

Awareness and Use of Canine Quality of Life Assessment Tools in UK Veterinary Practice.

The use of formal canine quality of life (QOL) assessment tools in veterinary practice has been recommended. An online survey investigated awareness, use and barriers to use of these tools in the UK. An anonymous 24-question survey was advertised through veterinary groups and social media. Ninety veterinary surgeons and twenty veterinary nurses responded. Thirty-two respondents (29.1%) were aware of the existence of formal canine QOL assessment tools. Of the three tools listed, current use was less than four per cent. No statistically significant influence of respondent age, role (veterinary surgeon or nurse) or possession of additional qualifications was found on the awareness of QOL tools (p > 0.05). Over half of respondents (55.5%) would 'certainly' or 'probably' be willing to use a QOL assessment tool. The main barrier to use was lack of time. Other barriers included a perceived resistance from owners. Although current use and awareness of canine QOL assessment tools in UK veterinary practice is low, veterinary professionals appear willing to use the tools within their daily practice. This discrepancy implies that QOL assessment tools are not well disseminated to veterinary surgeons and nurses in practice and that various barriers inhibit their use.

Influence of muscle-sparing lateral thoracotomy on postoperative pain and lameness: A randomized clinical trial.

OBJECTIVE: To assess and compare the magnitude of lameness and level of pain after muscle-sparing lateral thoracotomy (MSLT) and standard lateral thoracotomy (SLT) in dogs. STUDY DESIGN: Randomized, blinded, prospective clinical study. ANIMALS: Twenty-eight client-owned dogs. METHODS: The latissimus dorsi muscle was retracted in the MSLT group and was transected in the SLT group. Gait was analyzed with a force plate, and the peak vertical force symmetry index (SI) was calculated within 24 hours before surgery, 3 days postoperatively, and 8 to 12 weeks postoperatively. Symmetry index and pain scores as measured by the Glasgow Composite Measure Pain Scale - Short Form were assessed as primary outcome measures. RESULTS: The SI 3 days postoperatively was lower compared with the preoperative SI value in all dogs, consistent with lameness of the ipsilateral thoracic limb (P < .001). The absolute differences in preoperative and 3-day-postoperative SI provided evidence that this change was 3.1-fold greater after SLT compared with after MSLT (P = .009). Pain scores 1 day after surgery were lower after MSLT (1) compared with after SLT (2.5, P < .001). CONCLUSION: Lateral thoracotomies caused postoperative pain and ipsilateral forelimb lameness, and both were reduced by sparing the latissimus dorsi. CLINICAL SIGNIFICANCE: Sparing the latissimus dorsi should be considered to decrease immediate postoperative morbidity in dogs undergoing lateral thoracotomy.

Analgesia in pet rabbits: a survey study on how pain is assessed and ameliorated by veterinary surgeons.

BACKGROUND: In the last 20 years, two studies on the veterinary use of perioperative analgesia in small mammals reported a limited use of analgesics in rabbits but suggested an increasing use over the years. The aim of this study was to better understand how pain is treated and ameliorated in rabbits while under veterinary care. METHODS: An online survey of 60 questions was developed and advertised at national and international veterinary conferences, in veterinary publications and on social media. RESULTS: In total 94.3 per cent of the respondents routinely administered nonsteroidal anti-inflammatory drugs (NSAIDs) to rabbits undergoing surgical procedures such as neutering, 71.4 per cent administered an opioid and 70.3 per cent routinely administered multimodal analgesia, although dosages do not always match current consensus opinion. Buprenorphine and meloxicam were the most common analgesic drugs prescribed by the respondents. The dosage of meloxicam administered both parenterally and orally varied widely. CONCLUSION: Rabbit analgesia has improved over recent years similarly to the trend seen in other companion animals. However, overall it seems that pain assessment is still limited in rabbits. The lack of multimodal composite pain scales specific for rabbits makes this task even more challenging.

Comparing paracetamol/codeine and meloxicam for postoperative analgesia in dogs: a non-inferiority trial.

BACKGROUND: There are limited published data on the analgesic efficacy of paracetamol/codeine in dogs. METHODS: Prospective, randomised, blinded, positive-controlled clinical trial with 70 dogs (paracetamol/codeine, n=46; meloxicam, n=24) undergoing surgery. Drugs were administered orally 2 hours before and for 48 hours after surgery at the licensed dose. Anaesthesia was standardised. Dogs received buprenorphine 6 hourly for the first 24 hours after surgery. Outcome assessments were made pretrial and at regular intervals up to 48 hours after extubation and comprised the Glasgow Composite Measure Pain Score-Short Form, visual analogue scale for sedation and inflammation and mechanical nociceptive threshold (MNT). Non-inferiority of paracetamol/codeine compared with meloxicam was defined using a non-inferiority margin (Δ) against the 95 per cent confidence interval of the difference between the treatment means. RESULTS: Pain scores were low in both treatment groups. With the exception of MNT all upper 95 per cent confidence intervals for the differences between outcome variable treatment means were within +Δ for each variable, establishing non-inferiority for each outcome variable. CONCLUSIONS: Paracetamol/codeine is a useful perioperative analgesic that within the context of the perioperative analgesia regimen studied (methadone premedication, buprenorphine for the first 24 hours after surgery) shows non-inferiority to the NSAID meloxicam.

Clinical measurements performed during alfaxalone total intravenous anaesthesia for radiography and neurophysiological investigations in dogs.

OBJECTIVE: To describe clinically relevant, physiological measurements collected during a 3 hour duration of alfaxalone total intravenous anaesthesia. STUDY DESIGN: Case series. ANIMALS: A total of 112 client-owned middle-aged or older dogs. METHODS: Dogs were premedicated with intramuscular acepromazine (0.03 mg kg-1). Anaesthesia was induced and subsequently maintained for up to 3 hours with alfaxalone administered intravenously. Dogs breathed 100% oxygen via an endotracheal tube. Heart rate, respiratory rate and blood pressure were evaluated 30 minutes after administration of acepromazine and used as baseline values for comparisons of intra-anaesthetic data. Blood glucose was measured 1 week prior to anaesthesia and every hour during alfaxalone anaesthesia. Quality and duration of recovery were recorded. Mean data for physiological variables were compared over three time points-before induction of anaesthesia, for the first hour of anaesthesia and from 60 minutes to discontinuation of anaesthesia. RESULTS: Mean induction dose of alfaxalone was 1.4 mg kg-1 [95% confidence interval (CI) 1.3-1.5). Post induction apnoea for >60 seconds occurred in 13 (11.6%) dogs. Mean alfaxalone infusion rate during the first 60 minutes of anaesthesia was 0.099 mg kg-1 minute-1; mean infusion rate was 0.092 mg kg-1 minute-1 from 60 minutes until discontinuation of anaesthesia. Heart rate was well maintained; hypotension (mean arterial blood pressure < 60 mmHg) was encountered in 23 (21%) dogs. Blood glucose levels did not alter during anaesthesia. Median time between discontinuation of alfaxalone infusion and extubation was 17 (7-35 minutes), time to assuming sternal recumbency was 75 (58-110 minutes), and time to standing was 109 (88-140 minutes). CONCLUSIONS AND CLINICAL RELEVANCE: Alfaxalone infusion provided effective anaesthesia in this population. In a minority of cases, respiratory and haemodynamic support of the patient was required.

Electrophysiological characterisation of central sensitisation in canine spontaneous osteoarthritis.

In man, central sensitisation (CS) contributes to the pain of osteoarthritis (OA). Dogs with spontaneous OA may also exhibit CS. Electrophysiological reflex measurements are more objective than behavioural assessments and can be used to evaluate CS in preclinical and clinical studies. It was hypothesised that dogs suffering from OA would exhibit electrophysiological characteristics indicative of CS, associated with reduced diffuse noxious inhibitory controls (DNICs). One hundred and seventeen client-owned dogs were recruited to the study. Hind limb nociceptive withdrawal reflex thresholds, stimulus response, and temporal summation characteristics were recorded, during alfaxalone anaesthesia, from 46 OA dogs, 29 OA dogs receiving nonsteroidal anti-inflammatory drugs (OANSAIDs), and 27 breed- and weight-matched control dogs. Efficacy of DNIC was evaluated in 12 control and 11 of the OA dogs, by application of a mechanical conditioning stimulus to the contralateral forelimb. Nociceptive withdrawal reflex thresholds were higher in OA compared with control dogs (P = 0.02). Stimulus response characteristics demonstrated an augmented response in OANSAID dogs compared with OA (P < 0.001) and control (P < 0.001) dogs. Temporal summation demonstrated exaggerated C-fibre-mediated responses in both OA (P < 0.001) and OANSAID (P = 0.005) groups, compared with control animals. Conditioning stimulus application resulted in inhibition of test reflex responses in both OA and control animals (P < 0.001); control animals demonstrated greater inhibition compared with OA (P = 0.0499). These data provide evidence of neurophysiological changes consistent with CS in dogs with spontaneous OA and demonstrate that canine OA is associated with reduced DNIC.

Lateralized behaviour as indicator of affective state in dairy cows.

In humans, there is evidence that sensory processing of novel or threatening stimuli is right hemisphere dominated, especially in people experiencing negative affective states. There is also evidence for similar lateralization in a number of non-human animal species. Here we investigate whether this is also the case in domestic cattle that may experience long-term negative states due to commonly occurring conditions such as lameness. Health and welfare implications associated with pain in lame cows are a major concern in dairy farming. Behavioural tests combining animal behaviour and cognition could make a meaningful contribution to our understanding of disease-related changes in sensory processing in animals, and consequently enhance their welfare. We presented 216 lactating Holstein-Friesian cows with three different unfamiliar objects which were placed either bilaterally (e.g. two yellow party balloons, two black/white checkerboards) or hung centrally (a Kong™) within a familiar area. Cows were individually exposed to the objects on three consecutive days, and their viewing preference/eye use, exploration behaviour/nostril use, and stop position during approach was assessed. Mobility (lameness) was repeatedly scored during the testing period. Overall, a bias to view the right rather than the left object was found at initial presentation of the bilateral objects. More cows also explored the right object rather than the left object with their nose. There was a trend for cows appearing hesitant in approaching the objects by stopping at a distance to them, to then explore the left object rather than the right. In contrast, cows that approached the objects directly had a greater tendency to contact the right object. No significant preference in right or left eye/nostril use was found when cows explored the centrally-located object. We found no relationship between lameness and lateralized behaviour. Nevertheless, observed trends suggesting that lateralized behaviour in response to bilaterally located unfamiliar objects may reflect an immediate affective response are discussed. Further study is needed to understand the impact of long-term affective states on hemispheric dominance and lateralized behaviour.

Species specific anaesthetics for fish anaesthesia and euthanasia.

There is a need to ensure that the care and welfare for fish maintained in the laboratory are to the highest standards. This extends to the use of anaesthetics for both scientific study, humane killing and euthanasia at end of life. An anaesthetic should not induce negative behaviours and fish should not seek to avoid the anaesthetic. Surprisingly little information is available to facilitate a humane choice of anaesthetic agent for fish despite over 100 years of use and the millions of fish currently held in thousands of laboratories worldwide. Using a chemotaxic choice chamber we found different species specific behavioural responses among four closely related fish species commonly held in the laboratory, exposed to three widely used anaesthetic agents. As previously found for zebrafish (Danio rerio), the use of MS-222 and benzocaine also appears to induce avoidance behaviours in medaka (Oryzias latipes); but etomidate could provide an alternative choice. Carp (Cyprinus carpio), although closely related to zebrafish showed avoidance behaviours to etomidate, but not benzocaine or MS-222; and rainbow trout (Oncorhynchus mykiss) showed no avoidance to the three agents tested. We were unable to ascertain avoidance responses in fathead minnows (Pimephales promelas) and suggest different test paradigms are required for that species.

Effect of intramuscular methadone on pharmacokinetic data and thermal and mechanical nociceptive thresholds in the cat.

Objectives The aim of the study was to assess simultaneous pharmacokinetics and thermal and mechanical antinociception after intramuscular methadone (0.6 mg/kg) in 10 cats. Methods Thermal and mechanical threshold (TT and MT, respectively) testing and blood collection were conducted at baseline and up to 24 h after administration. Methadone plasma concentrations were determined by liquid chromatography-tandem mass spectrometry and pharmacokinetic parameters were estimated by a non-compartmental method. TT and MT were analysed using ANOVA ( P <0.05). Time of maximum plasma concentration (Tmax), time of onset of antinociception and time of reaching cut-out threshold (TT 55°C; MT 30 Newtons [N]) were determined. Results TT and MT increased above baseline from 20-240 mins and 5-40 mins, respectively, after intramuscular (IM) administration ( P <0.005). Mean maximum delta T (measured as TT minus baseline threshold) was 7.9°C (95% confidence interval [CI] 4.3-11.6) at 60 mins and mean maximum delta F (measured as MT minus baseline threshold) was 4.2 (95% CI 1.6-6.7) N at 45 mins. IM methadone concentration-time data decreased curvilinearly, and gave a clearance estimate of mean 9.1 ml/kg/min (range 5.2-15.7) with median Tmax at 20 mins (range 5-360 mins). Conclusions and relevance IM data followed classical disposition and elimination in all cats. Plasma concentrations after IM administration were associated with an antinociceptive effect, including negative hysteresis. These data can be used for devising dosing schedules for methadone in clinical feline practice.

Preliminary investigation comparing a detomidine continuous rate infusion combined with either morphine or buprenorphine for standing sedation in horses.

OBJECTIVE: To compare sedative and analgesic properties of buprenorphine or morphine for standing procedures combined with a detomidine continuous rate infusion (CRI). STUDY DESIGN: Blinded, prospective, randomized clinical pilot study. ANIMALS: Ten horses presented for dental or sinus procedures. METHODS: Horses received 0.02 mg kg(-1) acepromazine intravenously (IV), followed 30 minutes later by detomidine 10 µg kg(-1) IV. Five minutes later, buprenorphine 0.01 mg kg(-1) (n = 6) or morphine 0.1 mg kg(-1) (n = 4) was administered IV. Detomidine was administered by CRI (0.2 µg kg(-1) minute(-1)) and adjusted to maintain appropriate sedation. Heart rate, respiratory frequency, gastrointestinal motility and rectal temperature were measured; pain, ataxia and sedation were scored. Sedation, pain scores and ataxia scores were analysed using a mixed linear model. Detomidine dose and procedure success scores were compared using Wilcoxon's rank sum test. Complications between groups were analysed using Fisher's exact test. RESULTS: Two horses had incomplete data. Weights and ages were not different between groups (p = 0.15 and p = 0.42, respectively). The dose rate for detomidine was not different between groups (0.33 ± 0.02 µg kg(-1) minute(-1) in the buprenorphine group and 0.33 ± 0.05 µg kg(-1) minute(-1), in the morphine group p = 0.89). Intraoperative visual analogue scale scores were greater after buprenorphine than morphine (mean ± SD, buprenorphine 48 ± 4, morphine 40 ± 5, p = 0.0497). Procedure duration was not different between groups (buprenorphine 142 ± 33, morphine 140 ± 12 minutes). All horses treated with buprenorphine experienced complications compared with none in the morphine group (p = 0.0286). CONCLUSIONS AND CLINICAL RELEVANCE: At the doses used, buprenorphine produced greater sedation but more post-operative complications than morphine. However, Type I or Type II errors cannot be excluded and larger studies are required to confirm these findings.

An analysis of the relative frequencies of reported adverse events associated with NSAID administration in dogs and cats in the United Kingdom.

This study aimed to analyse UK pharmacovigilance data to quantify adverse events (AEs) associated with the non-steroidal anti-inflammatory drug (NSAID) molecules found in veterinary medicines authorised for use in dogs and cats. It was hypothesised that the frequency of AEs would be lower when associated with cyclo-oxygenase-2 selective (coxib), compared to non-selective (non-coxib) NSAIDs. The UK Veterinary Medicines Directorate (VMD) supplied frequencies of AEs derived from Periodic Safety Update Reports subdivided by formulation and species for each NSAID molecule. Frequencies of AEs were similar between species. The five most reported AEs were emesis, death, anorexia, lethargy, and diarrhoea. Reported frequency of emesis, renal insufficiency and death was higher with injectable compared to oral NSAIDs (P = 0.043). Reported frequency of emesis, lethargy and death was higher with coxib, compared to non-coxib NSAIDs (P = 0.029). Median (range) interval since authorisation was shorter for coxibs at 5 (2.5-9) years compared to non-coxibs at 15 (12-25) years. A negative correlation between time elapsed since authorisation and the frequency of AEs was identified (rs = -0.11 to -0.94). Higher frequency of reported AEs with injectable NSAIDs may be related to perioperative administration. The AE frequency associated with coxib and non-coxib NSAIDs may be confounded by changes in reporting habits over time. This study highlights the value of interrogating passive surveillance data to identify low frequency AEs and the need to facilitate improvement in recording and collecting AEs in small animal practice.

Refinement and partial validation of the UNESP-Botucatu multidimensional composite pain scale for assessing postoperative pain in horses.

BACKGROUND: Quantification of pain plays a vital role in the diagnosis and management of pain in animals. In order to refine and validate an acute pain scale for horses a prospective, randomized, blinded study was conducted. Twenty-four client owned adult horses were recruited and allocated to one of four following groups: anaesthesia only (GA); pre-emptive analgesia and anaesthesia (GAA,); anaesthesia, castration and postoperative analgesia (GC); or pre-emptive analgesia, anaesthesia and castration (GCA). One investigator, unaware of the treatment group, assessed all horses at time-points before and after intervention and completed the pain scale. Videos were also obtained at these time-points and were evaluated by a further four blinded evaluators who also completed the scale. The data were used to investigate the relevance, specificity, criterion validity and inter- and intra-observer reliability of each item on the pain scale, and to evaluate construct validity and responsiveness of the scale. RESULTS: Construct validity was demonstrated by the observed differences in scores between the groups, four hours after anaesthetic recovery and before administration of systemic analgesia in the GC group. Inter- and intra-observer reliability for the items was only satisfactory. Subsequently the pain scale was refined, based on results for relevance, specificity and total item correlation. CONCLUSIONS: Scale refinement and exclusion of items that did not meet predefined requirements generated a selection of relevant pain behaviours in horses. After further validation for reliability, these may be used to evaluate pain under clinical and experimental conditions.

Challenges of thermal nociceptive threshold testing in the donkey.

OBJECTIVE: To evaluate a thermal nociceptive threshold (TNT) testing device in the donkey, and the influence of potential confounding factors on TNTs. ANIMALS: Two groups (Group 1 and Group 2) of eight castrated male donkeys aged 4-9 years, weighing 105-170 kg. METHODS: TNTs were measured by heating a thermal probe on skin until an end-point behaviour (threshold temperature) or a cut-out temperature (51 °C) was reached. The withers and the dorsal aspect of the distal limb were used as sites for TNT testing. The effects on TNT of different confounding factors: the limb tested; rate of heating; and ambient temperature were evaluated. Data were analyzed using general linear models, and Mann-Whitney tests, p < 0.05 was considered significant. RESULTS: End-point behaviours (skin twitch or donkey looking at test device) when the thermal probe heated the withers were observed in approximately half of tests. TNT was (mean ± SD) 46.8 ± 2.85 °C. Subsequently the limb was evaluated as the test site in Group 1 followed by Group 2 donkeys; end-point behaviour being a foot-lift. In Group 1, 72% of tests ended in an end-point behaviour but the response rate was lower in Group 2 (20%), although TNTs were similar [(47.6 ± 3.3) and (47.3 ± 3.0) °C respectively] for responding animals. Rate of heating, ambient temperature and laterality (right or left) did not affect thresholds, but mean TNT was significantly higher in the forelimb (48.5 ± 2.8 °C) than the hind limb (47.4 ± 2.8 °C) (p = 0.012). CONCLUSIONS: When a thermal probe cut-out temperature of 51 °C was used in TNT testing in the donkey a high proportion of tests did not produce an identifiable end point behaviour. Higher cut-out temperatures damaged the skin. Under these conditions, thermal nociceptive threshold testing appears not be an appropriate analgesiometry technique in the donkey. CLINICAL RELEVANCE: TNT testing under these conditions is not suitable form of analgesiometry for donkeys.

The effects of two non-steroidal anti-inflammatory drugs on the mobility of laying hens with keel bone fractures.

OBJECTIVE: Investigate the effects of administration of meloxicam and carprofen on the mobility of hens with and without keel fractures. STUDY DESIGN: Within each of two experiments a 'blinded' randomised cross over design whereby birds received either the test drug (carprofen or meloxicam) or saline. ANIMALS: Two groups of Lohman Brown hens with and without keel bone fractures. METHODS: The first group (n = 63) was treated with carprofen 25 mg kg(-1) and saline subcutaneously, twice. The second group (n = 40) was treated with meloxicam (5 mg kg(-1) ) and saline subcutaneously. The latency of birds to fly down from perches 50, 100 and 150 cm above the ground was measured after each treatment. Data from experiment 1 and 2 were analysed separately; the effects of drug treatment compared with saline on landing time for birds with and without keel bone fractures were evaluated using MLwiN. RESULTS: In both experiments latency to fly down from perches was longer in hens with keel fractures and there was a significant interaction between perch height and fracture status. For carprofen, at the 50 cm, 100 cm and 150 cm perch heights, birds with fractures took (mean ± SD) 2.5 ± 2.9, 6.8 ± 9.7 and 11.5 ± 13.2 seconds respectively to fly down compared with 1.3 ± 0.5, 2.3 ± 1.2 and 4.2 ± 3.1 seconds for birds without fractures. For meloxicam, at the 50 cm, 100 cm and 150 cm perch heights, birds with fractures took 2.9 ± 2.5, 49.8 ± 85.4 and 100.3 ± 123.6 seconds respectively compared with 0.7 ± 0.5, 2.5 ± 7.1 and 3.0 ± 4.6 seconds to fly down for birds without fractures. There was no significant effect of carprofen or meloxicam treatment. CONCLUSION AND CLINICAL RELEVANCE: These data provide further confirmation that keel fractures reduce the willingness of birds to move from perches.

Pharmacokinetic-pharmacodynamic modelling of intravenous buprenorphine in conscious horses.

OBJECTIVE: Describe the pharmacokinetics of buprenorphine and norbuprenorphine in horses and to relate the plasma buprenorphine concentration to the pharmacodynamic effects. STUDY DESIGN: Single phase non-blinded study. ANIMALS: Six dedicated research horses, aged 3-10 years and weighing 480-515 kg. METHODS: Thermal and mechanical nociceptive thresholds, heart and respiratory rates and locomotor activity were measured before and 15, 30, 45 & 60 minutes and 2, 4, 6, 8, 12 & 24 hours post-administration of 10 µg kg(-1) buprenorphine IV. Intestinal motility was measured 1, 6, 12 & 24 hours after buprenorphine administration. Venous blood samples were obtained before administration of buprenorphine 10 µg kg(-1) IV and 1, 2, 4, 6, 10, 15, 30, 45 & 60 minutes, and 2, 4, 6, 8, 12 & 24 hours afterwards. Plasma buprenorphine and norbuprenorphine concentrations were measured using a liquid chromatography-tandem mass spectroscopy (LC-MS/MS) assay with solid-phase extraction. A non-compartmental method was used for analysis of the plasma concentration-time data and plasma buprenorphine concentrations were modelled against two dynamic effects (change in thermal threshold and mechanical threshold) using a simple Emax model. RESULTS: Plasma buprenorphine concentrations were detectable to 480 minutes in all horses and to 720 minutes in two out of six horses. Norbuprenorphine was not detected. Thermal thresholds increased from 15 minutes post-buprenorphine administration until the 8-12 hour time points. The increase in mechanical threshold ranged from 3.5 to 6.0 Newtons (median: 4.4 N); and was associated with plasma buprenorphine concentrations in the range 0.34-2.45 ng mL(-1) . CONCLUSIONS AND CLINICAL RELEVANCE: The suitability of the use of buprenorphine for peri-operative analgesia in the horse is supported by the present study.

Methadone in combination with medetomidine as premedication prior to ovariohysterectomy and castration in the cat.

OBJECTIVES: The aim of the study was to evaluate the tolerability, sedative and analgesic effects of methadone in combination with medetomidine for premedication prior to neutering in healthy cats. METHODS: This was an assessor-blinded, randomised, clinical research study. Forty-five cats were recruited and divided into three treatment groups of 15. Following premedication with medetomidine (20 µg/kg) and one of the three test drugs - methadone 0.5 mg/kg, buprenorphine 20 µg/kg or butorphanol 0.4 mg/kg intramuscularly - anaesthesia was induced with propofol and maintained with isoflurane, and neutering was carried out. Sedation and physiological parameters were assessed before premedication, after premedication before induction of anaesthesia, and at 90 mins and 2, 3, 4, 6, 7, 8 and 24 h after premedication. Pain and mechanical nociceptive threshold were assessed at similar time points. RESULTS: There were no differences between groups with respect to age, sex, duration of anaesthesia or surgery. Most cats had low pain scores in the postoperative period, with small differences in pain scores between groups at individual time points only. Five, two and no cats required additional rescue analgesia in the postoperative period in the butorphanol, methadone and buprenorphine groups, respectively, representing no significant difference between groups. CONCLUSIONS AND RELEVANCE: Medetomidine combined with methadone for premedication prior to neutering in healthy cats provided adequate analgesia for the first 6 h after administration with no adverse effects; effects overall were comparable with medetomidine combined with buprenorphine or butorphanol. Administration of further analgesia with methadone at 6 h and a non-steroidal anti-inflammatory drug at 8 h provided adequate analgesia for the first 24 h after surgery.

Thermal nociceptive threshold testing detects altered sensory processing in broiler chickens with spontaneous lameness.

Lameness is common in commercially reared broiler chickens but relationships between lameness and pain (and thus bird welfare) have proved complex, partly because lameness is often partially confounded with factors such as bodyweight, sex and pathology. Thermal nociceptive threshold (TNT) testing explores the neural processing of noxious stimuli, and so can contribute to our understanding of pain. Using an acute model of experimentally induced articular pain, we recently demonstrated that TNT was reduced in lame broiler chickens, and was subsequently attenuated by administration of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs). This study extended these findings to a large sample of commercial broilers. It examined factors affecting thermal threshold (Part 1) and the effect of an NSAID drug (meloxicam, 5 mg/kg) and of an opioid (butorphanol; 4 mg/kg) (Part 2). Spontaneously lame and matched non-lame birds (n=167) from commercial farms were exposed to ramped thermal stimulations via a probe attached to the lateral aspect of the tarsometatarsus. Baseline skin temperature and temperature at which a behavioural avoidance response occurred (threshold) were recorded. In Part 1 bird characteristics influencing threshold were modelled; In Part 2 the effect of subcutaneous administration of meloxicam or butorphanol was investigated. Unexpectedly, after accounting for other influences, lameness increased threshold significantly (Part 1). In Part 2, meloxicam affected threshold differentially: it increased further in lame birds and decreased in non-lame birds. No effect of butorphanol was detected. Baseline skin temperature was also consistently a significant predictor of threshold. Overall, lameness significantly influenced threshold after other bird characteristics were taken into account. This, and a differential effect of meloxicam on lame birds, suggests that nociceptive processing may be altered in lame birds, though mechanisms for this require further investigation.

The influence of various confounding factors on mechanical nociceptive thresholds in the donkey.

OBJECTIVE: To evaluate a mechanical nociceptive threshold (MNT) testing device in the donkey, and to investigate the influence of potential confounders on MNTs generated. STUDY DESIGN: Prospective, randomised. ANIMALS: Sixteen castrated male donkeys aged 4-9 years, weighing 105-170 kg. METHODS: Mechanical nociceptive thresholds were measured using an actuator with three pins placed on the dorsal aspect of the distal limb, connected to a force meter. The pins (surface area 15 mm(2) ) were extruded onto the limb by pressurising an air-filled syringe, until the MNT force (when foot-lift was observed) or 25 N (cut-off force) was reached. Effect on MNT of presence of a companion donkey, the limb tested, rate of application of force, testing location, level of distraction, ambient temperature and hair cover at the test site was evaluated. Long and short-term repeatability of MNT was assessed. Data were analysed using general linear models and Mann-Whitney U tests, p < 0.05 was considered significant. RESULTS: Increasing the rate of force application significantly increased the mean ± SD MNT from 9.2 ± 2.0 N when applied at 0.4 N sec(-1) to 10.6 ± 2.1 N when applied at 1.2 N sec(-1) (p = 0.001). No other factors significantly influenced MNT. Mean MNT remained stable over a 3 week period, however MNTs were significantly (p = 0.006) higher (12.8 ± 3.0 N cf 10.3 ± 1.9 N) after a 12 month interval. CONCLUSIONS AND CLINICAL RELEVANCE: When designing studies measuring MNT in donkeys, rate of application of force must be standardised. Donkeys' MNTs have good short-term stability suggesting this technique is appropriate for short-term analgesiometry studies; however variability of MNTs over the long-term is greater.

The effects of an intravenous bolus of dexmedetomidine following extubation in a mixed population of dogs undergoing general anaesthesia and surgery.

An observer blinded, placebo controlled study evaluated the effects of 62.5 µg/m(2) dexmedetomidine administered IV on recovery from isoflurane anaesthesia in dogs. Forty-four healthy dogs, weighing 1.8-19.95 kg, presented for surgery that was expected to cause mild to moderate pain were studied. All were premedicated with 125 µg/m(2) dexmedetomidine and 20 µg/kg buprenorphine IM. Anaesthesia was induced with propofol and maintained with isoflurane. Non-steroidal anti-inflammatory drugs and local anaesthetics were administered as appropriate. Immediately prior to extubation dogs were treated with dexmedetomidine 62.5 µg/m(2) (group D) or an equivalent volume of heparinised saline (S). Assessments of heart rate, respiratory rate, pain (short form Glasgow composite pain scale [SF-GCPS], dynamic interactive visual analogue scale [DIVAS]), sedation (simple descriptive scale [SDS], DIVAS) and mechanical nociceptive threshold (MNT) were performed immediately before premedication, 20 min later, at the time of test drug administration (T0) and at 15-30 min intervals for four hours (T240 min). Recovery quality was scored 0 - 3 (SDS). Data were analysed with Student's t and Mann-Whitney U tests, two-way ANOVA and Fisher's exact test. Significantly fewer poor quality recoveries were observed in group D (D 2 [1-3]; S 2 [0-3]; P=0.02), however, sedation was increased in group D compared to group S from T15 to T150 min (P=0.0001). Pain scores were lower in group D compared to group S from T15 to T120 min (P=0.001), but the requirement for additional analgesia in the first 4h following extubation was not different between groups. Dexmedetomidine may decrease the incidence of poor quality anaesthetic recoveries in dogs.