Sedative and analgesic effects of buprenorphine, combined with either acepromazine or dexmedetomidine, for premedication prior to elective surgery in cats and dogs

Echocardiographic and hemodynamic effects of alfaxalone or dexmedetomidine based sedation protocols in cats with hypertrophic cardiomyopathy: a pilot study

OBJECTIVE

To report the effects of alfaxalone and dexmedetomidine based sedation protocols on echocardiographic and hemodynamic variables in cats with hypertrophic cardiomyopathy (HCM) during sedation and inhalational anesthesia.

STUDY DESIGN

Prospective, randomized, experimental study.

ANIMALS

A group of 10 client-owned cats with subclinical HCM.

METHODS

Cats were administered one of two sedative intramuscular combinations: protocol ABM (alfaxalone 2 mg kg-1, butorphanol 0.4 mg kg-1, midazolam 0.2 mg kg-1; n = 5) or protocol DBM (dexmedetomidine 8 μg kg-1, butorphanol 0.4 mg kg-1, midazolam 0.2 mg kg-1; n = 5). General anesthesia was induced with intravenous alfaxalone and maintained with isoflurane in oxygen. Echocardiographic variables and noninvasive arterial blood pressures were obtained before sedation, following sedation, and during inhalational anesthesia. Sedation scores and alfaxalone induction dose requirements were recorded. Descriptive statistics are reported for cardiovascular variables.

RESULTS

During sedation, echocardiographic and hemodynamic variables remained within normal limits with protocol ABM, whereas protocol DBM was characterized by bradycardia, low cardiac index and elevated blood pressure. During isoflurane anesthesia, both protocols demonstrated similar hemodynamic performance, with heart rates of 98 ± 12 and 89 ± 11 beats min-1, cardiac index values of 68 ± 17 and 47 ± 13 mL min-1 kg-1 and Doppler blood pressures of 72 ± 15 and 79 ± 20 mmHg with protocols ABM and DBM, respectively. A reduction in myocardial velocities were also observed during atrial and ventricular contraction with both protocols during isoflurane anesthesia.

CONCLUSIONS AND CLINICAL RELEVANCE

An alfaxalone based protocol offered hemodynamic stability during sedation in cats with HCM; however, both dexmedetomidine and alfaxalone based protocols resulted in clinically relevant hemodynamic compromise during isoflurane anesthesia. Further studies are required to determine optimal sedative and anesthetic protocols in cats with HCM.

Efficacy and Safety of Dexmedetomidine Premedication in Balanced Anesthesia: A Systematic Review and Meta-Analysis in Dogs

Simple Summary

Dexmedetomidine, on account of its potent sedative and analgesic properties, is commonly used in balanced anesthesia of small animal anesthesia; however, concerns regarding its cardiovascular effects prevent its full adoption into veterinary clinical practice. We conducted this meta-analysis to determine the effects of dexmedetomidine on sedation, analgesia, cardiovascular and adverse reactions in dogs compared to other premedications. The outcomes included sedation score, pain score, heart rate, systolic arterial blood pressure, mean arterial blood pressure and the incidence of adverse effects. Thirteen studies were included in this meta-analysis. The results showed that dexmedetomidine provides a satisfactory sedative and analgesic effect in balanced anesthesia of dogs. After dexmedetomidine premedication, dogs experienced lower heart rate and higher blood pressure within an acceptable range. The combinations in balanced anesthesia and routes of delivering drugs would affect heart rate, systolic arterial blood pressure, and mean arterial blood pressure of dogs. Before using dexmedetomidine, an animal’s cardiovascular status should be fully considered.

Abstract

Dexmedetomidine is commonly used in small animal anesthesia for its potent sedative and analgesic properties; however, concerns regarding its cardiovascular effects prevent its full adoption into veterinary clinical practice. This meta-analysis was to determine the effects of dexmedetomidine on sedation, analgesia, cardiovascular and adverse reactions in dogs compared to other premedications. Following the study protocol based on the Cochrane Review Methods, thirteen studies were included in this meta-analysis ultimately, involving a total of 576 dogs. Dexmedetomidine administration probably improved in sedation and analgesia in comparison to acepromazine, ketamine and lidocaine (MD: 1.96, 95% CI: [−0.08, 4.00], p = 0.06; MD: −0.95, 95% CI: [−1.52, −0.37] p = 0.001; respectively). Hemodynamic outcomes showed that dogs probably experienced lower heart rate and higher systolic arterial blood pressure and mean arterial blood pressure with dexmedetomidine at 30 min after premedication (MD: −13.25, 95% CI: [−19.67, −6.81], p < 0.0001; MD: 7.78, 95% CI: [1.83, 13.74], p = 0.01; MD: 8.32, 95% CI: [3.95, 12.70], p = 0.0002; respectively). The incidence of adverse effects was comparable between dexmedetomidine and other premedications (RR = 0.86, 95% CI [0.58, 1.29], p = 0.47). In summary, dexmedetomidine provides satisfactory sedative and analgesic effects, and its safety is proved despite its significant hemodynamic effects as part of balanced anesthesia of dogs.

Sedative effects of acepromazine in combination with nalbuphine or butorphanol, intramuscularly or intravenously, in healthy cats: a randomized, blinded clinical trial

OBJECTIVES

The aim of this study was to compare the sedative effects in cats administered acepromazine-nalbuphine and acepromazine-butorphanol, intramuscularly (IM) and intravenously (IV), and the occurrence of adverse cardiorespiratory effects.

METHODS

Forty-six cats were randomly divided into four groups and administered acepromazine (0.05 mg/kg) combined with nalbuphine (0.5 mg/kg) or butorphanol (0.4 mg/kg), IV (ACP-NALIV and ACP-BUTIV groups, respectively) or IM (ACP-NALIM and ACP-BUTIM groups, respectively). Sedation scores, ease of intravenous catheter placement (simple descriptive scale [SDS] scores), physiologic variables, venous blood gases and the propofol dose required for anesthetic induction were recorded.

RESULTS

Mild sedation was observed in all groups approximately 30 mins after treatment administration (timepoint T1, prior to propofol administration). Sedation scores at T1 increased above baseline in all groups (P <0.05), but no significant difference was observed among groups. Dynamic interactive visual analogue scale sedation scores (range 0-100 mm) recorded at T1 were (median [interquartile range]): ACP-NALIM, 12 (10-12); ACP-NALIV, 11 (6-16); ACP-BUTIM, 11 (7-14); and ACP-BUTIV, 12 (7-19). Overall, SDS scores did not change from baseline at T1 and there was no significant difference among groups. The propofol dose did not differ among groups. Blood gases remained within the reference intervals for cats. Significant decreases from baseline were detected for all groups in systolic arterial pressure (SAP). Mean ± SD values at T1 were (mmHg): ACP-NALIM, 108 ± 13; ACP-NALIV, 102 ± 10; ACP-BUTIM, 97 ± 13; and ACP-BUTIV, 98 ± 21. Arterial hypotension (SAP <90 mmHg) was recorded at T1 in 0/11, 1/13, 4/11 and 5/11 cats in groups ACP-NALIM, ACP-NALIV, ACP-BUTIM and ACP-BUTIV, respectively, and was further exacerbated after the induction of anesthesia with propofol.

CONCLUSIONS AND RELEVANCE

In healthy cats administered acepromazine-nalbuphine and acepromazine-butorphanol, IM and IV, the degree of sedation was mild regardless of the protocol and the route of administration. The main adverse effect observed was a reduction in arterial blood pressure.

Analgesia for Sheep in Commercial Production: Where to Next?

Simple Summary

Increasing societal and customer pressure to provide animals with ‘a life worth living’ continues to apply pressure on industry to alleviate pain associated with husbandry practices, injury and illness. Although a number of analgesic solutions are now available for sheep, providing some amelioration of the acute pain responses, this review has highlighted a number of potential areas for further research.

Abstract

Increasing societal and customer pressure to provide animals with ‘a life worth living’ continues to apply pressure on livestock production industries to alleviate pain associated with husbandry practices, injury and illness. Over the past 15–20 years, there has been considerable research effort to understand and develop mitigation strategies for painful husbandry procedures in sheep, leading to the successful launch of analgesic approaches specific to sheep in a number of countries. However, even with multi-modal approaches to analgesia, using both local anaesthetic and non-steroidal anti-inflammatory drugs (NSAID), pain is not obliterated, and the challenge of pain mitigation and phasing out of painful husbandry practices remains. It is timely to review and reflect on progress to date in order to strategically focus on the most important challenges, and the avenues which offer the greatest potential to be incorporated into industry practice in a process of continuous improvement. A structured, systematic literature search was carried out, incorporating peer-reviewed scientific literature in the period 2000–2019. An enormous volume of research is underway, testament to the fact that we have not solved the pain and analgesia challenge for any species, including our own. This review has highlighted a number of potential areas for further research.

Postoperative evaluation of analgesia promoted by the use of dexmedetomidine alone and associated with morphine as an intramuscular pre-anesthetic medication in bitches submitted for ovariohysterectomy

Abstract This study aimed to evaluate the postoperative analgesic efficacy of dexmedetomidine alone and when associated with morphine in patients under general inhalational anesthesia with isoflurane and undergoing elective ovariohysterectomy (OH). Twenty healthy bitches were selected via physical and laboratory examinations. Prior to the study, they underwent a 24-h period of adaptation to the environment and observers. They were then randomly divided into two groups: the dexmedetomidine group receiving a dose of 10 μg/kg, and dexmedetomidine group (10 μg/kg) associated with morphine receiving a dose of 0.3 mg/kg, administered via the intramuscular route. Thereafter, patients were induced with propofol and maintained with isoflurane diluted in 100% oxygen administered through a calibrated vaporizer. To verify postoperative analgesia, pain assessments were performed using the modified Glasgow (EGM) and Melbourne (EM) scales. For sedation assessment, the Dobbins scale was used at different times: before the administration of pre-anesthetic medication (T0) and at another six times in the postoperative period, 1 (T1), 2 (T2), 4 (T3), 8 (T4), 12 (T5), and 24 (T6) h after orotracheal extubation. No statistical differences were observed between groups in the scales according to Dunn’s Kruskal-Wallis post hoc test, and between the times a statistical difference was noticed by the Friedman test (p<0.05) for the EGM and EM scale scores, but there was no need for analgesic rescue. Therefore, we found that isolated dexmedetomidine and morphine produced adequate analgesic effects in the postoperative period of bitches submitted for OH.

Clinical applicability of the Feline Grimace Scale: real-time versus image scoring and the influence of sedation and surgery

Background

The Feline Grimace Scale (FGS) is a facial expression-based scoring system for acute pain assessment in cats with reported validity using image assessment. The aims of this study were to investigate the clinical applicability of the FGS in real-time when compared with image assessment, and to evaluate the influence of sedation and surgery on FGS scores in cats.

Methods

Sixty-five female cats (age: 1.37 ± 0.9 years and body weight: 2.85 ± 0.76 kg) were included in a prospective, randomized, clinical trial. Cats were sedated with intramuscular acepromazine and buprenorphine. Following induction with propofol, anesthesia was maintained with isoflurane and cats underwent ovariohysterectomy (OVH). Pain was evaluated at baseline, 15 min after sedation, and at 0.5, 1, 2, 3, 4, 6, 8, 12 and 24 h after extubation using the FGS in real-time (FGS-RT). Cats were video-recorded simultaneously at baseline, 15 min after sedation, and at 2, 6, 12, and 24 h after extubation for subsequent image assessment (FGS-IMG), which was performed six months later by the same observer. The agreement between FGS-RT and FGS-IMG scores was calculated using the Bland & Altman method for repeated measures. The effects of sedation (baseline versus 15 min) and OVH (baseline versus 24 h) were assessed using linear mixed models. Responsiveness to the administration of rescue analgesia (FGS scores before versus one hour after) was assessed using paired t-tests.

Results

Minimal bias (-0.057) and narrow limits of agreement (-0.351 to 0.237) were observed between the FGS-IMG and FGS-RT. Scores at baseline (FGS-RT: 0.16 ± 0.13 and FGS-IMG: 0.14 ± 0.13) were not different after sedation (FGS-RT: 0.2 ± 0.15, p = 0.39 and FGS-IMG: 0.16 ± 0.15, p = 0.99) nor at 24 h after extubation (FGS-RT: 0.16 ± 0.12, p = 0.99 and FGS-IMG: 0.12 ± 0.12, p = 0.96). Thirteen cats required rescue analgesia; their FGS scores were lower one hour after analgesic administration (FGS-RT: 0.21 ± 0.18 and FGS-IMG: 0.18 ± 0.17) than before (FGS-RT: 0.47 ± 0.24, p = 0.0005 and FGS-IMG: 0.45 ± 0.19, p = 0.015).

Conclusions

Real-time assessment slightly overestimates image scoring; however, with minimal clinical impact. Sedation with acepromazine-buprenorphine and ovariohysterectomy using a balanced anesthetic protocol did not influence the FGS scores. Responsiveness to analgesic administration was observed with both the FGS-RT and FGS-IMG.

The effect of intravenous maropitant on blood pressure in healthy awake and anesthetized dogs

OBJECTIVE

To evaluate the effects of intravenous maropitant on arterial blood pressure in healthy dogs while awake and under general anesthesia.

DESIGN

Experimental crossover study.

ANIMALS

Eight healthy adult Beagle dogs.

PROCEDURE

All dogs received maropitant (1 mg kg-1) intravenously under the following conditions: 1) awake with non-invasive blood pressure monitoring (AwNIBP), 2) awake with invasive blood pressure monitoring (AwIBP), 3) premedication with acepromazine (0.005 mg kg-1) and butorphanol (0.2 mg kg-1) intramuscularly followed by propofol induction and isoflurane anesthesia (GaAB), and 4) premedication with dexmedetomidine (0.005 mg kg-1) and butorphanol (0.2 mg kg-1) intramuscularly followed by propofol induction and isoflurane anesthesia (GaDB). Heart rate (HR), systolic (SAP), diastolic (DAP), and mean blood pressures (MAP) were recorded before injection of maropitant (baseline), during the first 60 seconds of injection, during the second 60 seconds of injection, at the completion of injection and every 2 minutes post injection for 18 minutes. The data were compared over time using a Generalized Linear Model with mixed effects and then with simple effect comparison with Bonferroni adjustments (p <0.05).

RESULTS

There were significant decreases from baseline in SAP in the GaAB group (p < 0.01) and in MAP and DAP in the AwIBP and GaAB (p < 0.001) groups during injection. A significant decrease in SAP (p < 0.05), DAP (p < 0.05), and MAP (p < 0.05) occurred at 16 minutes post injection in GaDB group. There was also a significant increase in HR in the AwIBP group (p < 0.01) during injection. Clinically significant hypotension occurred in the GaAB group with a mean MAP at 54 ± 6 mmHg during injection.

CONCLUSION

Intravenous maropitant administration significantly decreases arterial blood pressure during inhalant anesthesia. Patients premedicated with acepromazine prior to isoflurane anesthesia may develop clinically significant hypotension.

Effect of premedication on dose requirement, cardiovascular effects and recovery quality of alfaxalone total intravenous anaesthesia in dogs

OBJECTIVE

To investigate alfaxalone total intravenous anaesthesia (TIVA) following premedication with methadone combined with acepromazine (ACP) or dexmedetomidine in bitches undergoing ovariohysterectomy.

STUDY DESIGN

Prospective, blinded, randomized, experimental study.

ANIMALS

A group of 12 female Beagles.

METHODS

Dogs were premedicated intravenously with methadone (0.2 mg kg^-1) combined with ACP (20 μg kg^-1, group AM) or dexmedetomidine (5 μg kg^-1, group DM). Anaesthesia was induced with alfaxalone (2 mg kg^-1). Anaesthetic maintenance was obtained with an alfaxalone variable rate infusion (VRI) started at 0.15 mg kg^-1 minute^-1 and adjusted every 5 minutes based on clinical assessment. Mechanical ventilation was initiated when necessary to maintain normocapnia. Anaesthetic monitoring included electrocardiogram, heart rate (HR), invasive diastolic (DAP), systolic (SAP) and mean arterial blood pressure, arterial haemoglobin oxygen saturation, respiratory variables and oesophageal temperature. Data were recorded every 5 minutes. A mixed model statistical approach was used to compare cardiovascular variables within and between groups (α = 0.05). A Wilcoxon rank-sum test was used to compare body temperature, VRI alfaxalone rate, administered rescue analgesia, sedation, induction, intubation, recovery scores and recovery times between treatments.

RESULTS

Overall HR, SAP and DAP differed between groups (p = 0.001, 0.016, 0.019, respectively). The mean VRI dose rate of alfaxalone differed between groups DM [0.13 (0.11-0.14) mg kg^-1 minute^-1] and AM [0.18 (0.13-0.19) mg kg^-1 minute^-1; p = 0.030]. Rescue analgesia was administered more in group AM (p = 0.019). No significant difference in recovery times and scores was observed between protocols.

CONCLUSIONS AND CLINICAL RELEVANCE

Alfaxalone TIVA following dexmedetomidine/methadone premedication produced a more stable plane of anaesthesia to perform ovariohysterectomy than ACP/methadone. A dose reduction of alfaxalone of 27.7% was obtained in group DM compared with group AM. Recovery quality and recovery times were comparable between both groups.

Effects of sedation with dexmedetomidine and buprenorphine on echocardiographic variables, blood pressure and heart rate in healthy cats

Objectives Sedative agents are occasionally used to enable echocardiographic examination when screening cats for heart disease, such as hypertrophic cardiomyopathy (HCM). Owing to their haemodynamic effects, sedative agents may alter echocardiographic measurements. The aim of the study was to evaluate the effects of the sedative combination dexmedetomidine and buprenorphine on echocardiographic variables, blood pressure (BP) and heart rate (HR) in healthy cats. Methods Fifty healthy, client-owned cats were prospectively recruited and included after physical examination. Cats were sedated intramuscularly with dexmedetomidine and buprenorphine, according to body weight. Blood pressure and HR measurements, echocardiographic and Doppler examinations were performed prior to sedation and repeated once cats had achieved acceptable sedation. Results Left ventricular internal diameter at end-diastole and systole, right ventricular internal diameter at end-diastole, left atrium (LA), pulmonary artery (PA) deceleration time, and systolic, diastolic and mean arterial blood pressure increased after sedation ( P ⩽0.022). Aortic and PA maximum velocity, fractional shortening, PA acceleration/deceleration time and HR decreased after sedation ( P <0.0001). Interventricular septum at end-diastole and systole, left ventricular posterior wall at end-diastole and systole, aortic diameter (Ao), left atrial/aortic diameter (LA/Ao) and pulmonic acceleration time did not change. Conclusions and relevance Blood pressure increased and HR decreased post-sedation. While wall thickness and LA/Ao were not affected by sedation, indices of LA and left ventricular size increased. Further studies are needed using cats with HCM to assess the effect of this sedative combination on HCM screening results.

A comparison between methadone and buprenorphine for perioperative analgesia in dogs undergoing ovariohysterectomy

OBJECTIVE

To investigate whether preoperative methadone provides superior perioperative analgesia compared to buprenorphine in dogs undergoing ovariohysterectomy.

METHODS

Eighty female dogs were recruited to an assessor-blinded, randomised, clinical trial. Dogs received a premedication dose of 0·05 mg/kg acepromazine or 10 μg/kg medetomidine combined with either 0·3 mg/kg methadone or 20 μg/kg buprenorphine intramuscularly. Anaesthesia was induced with propofol and maintained with isoflurane. Pain was assessed using two scoring schemes (a dynamic interactive visual analogue scale and the short form of the Glasgow Composite Pain Scale) before premedication, 30 minutes later and every hour for 8 hours after premedication. If indicated, rescue analgesia was provided with methadone. Meloxicam was administered after the final assessment. The area under the curve for change in pain scores over time and the requirement for rescue analgesia were compared between groups.

RESULTS

Groups premedicated with buprenorphine had significantly higher pain scores than those premedicated with methadone. There was no interaction between opioid and sedative for any outcome measure. Rescue analgesia was required by significantly more dogs premedicated with buprenorphine (45%) than that of methadone (20%).

CLINICAL SIGNIFICANCE

At the doses investigated, methadone produced superior postoperative analgesia compared to buprenorphine in dogs undergoing ovariohysterectomy.

State of the art analgesia-Recent developments pharmacological approaches to acute pain management in dogs and cats: Part 2

There has been considerable interest in the area of acute pain management over recent years, focusing on pain assessment, pharmacological and non-pharmacological interventions. The evidence base for our clinical decision making and treatment of patients is ever increasing and becoming more robust. There is still a tendency to base some aspects of pain management on poor quality evidence and this requires further input in years to come. With new literature come new ideas and this review will detail the current knowledge base behind pharmacological management of acute pain in dogs and cats. The known mechanisms of action of each analgesic and its evidence will be considered. The second part of this review will consider the non-traditional analgesics, describing their component drugs individually, thereby focusing on their mechanisms of action and the current evidence for their use in acute pain management.

Comparison of the postoperative analgesic effects of cimicoxib, buprenorphine and their combination in healthy dogs undergoing ovariohysterectomy

OBJECTIVE

To determine the noninferior postoperative analgesic efficacy of cimicoxib compared to buprenorphine following elective ovariohysterectomy in healthy bitches.

STUDY DESIGN

Prospective, randomized, blinded, controlled clinical trial.

ANIMALS

A total of 63 healthy dogs.

METHODS

To provide perioperative analgesia, cimicoxib 2 mg kg^-1 (orally), buprenorphine 0.02 mg kg^-1 (two doses, intramuscularly), or both drugs combined, were administered. Dogs were sedated with acepromazine and anaesthetized with propofol and isoflurane. Pain was assessed with the short form of the Glasgow Composite Pain Scale (GCPS), a pain numerical rating scale (NRS) and mechanical nociceptive thresholds (MNT), preoperatively and at 1, 2, 4, 6, 20 and 23 hours after extubation. Sedation was also scored at the same time points. A noninferiority approach was employed to determine the efficacy of cimicoxib compared to buprenorphine. Treatment groups were compared with parametric [analysis of variance (anova), t test] and nonparametric test as appropriate (Kruskal-Wallis, chi-square).

RESULTS

The GCPS, pain NRS and MNT tests demonstrated noninferiority of cimicoxib compared to buprenorphine (rejection of inferiority: p < 0.001, all). Furthermore, cimicoxib provided better analgesia compared to buprenorphine alone according to the GCPS (p < 0.01) and NRS (p < 0.05), but not the MNT. Conversely, an increase in the analgesic effect when cimicoxib was combined with buprenorphine was only observed with the MNT (p < 0.01). There were no differences in rescue analgesia requirements both intra- and postoperatively between treatments. Gastrointestinal side effects were increased in dogs administered cimicoxib, whereas dogs treated with buprenorphine had higher sedation scores 1-hour postoperatively and required lower doses of propofol for the induction of anaesthesia.

CONCLUSIONS AND CLINICAL RELEVANCE

Cimicoxib has noninferior postoperative analgesic efficacy compared to buprenorphine, and both drugs have comparable analgesic effects for the control of postoperative pain in bitches undergoing ovariohysterectomy.

An investigation of mechanical nociceptive thresholds in dogs with hind limb joint pain compared to healthy control dogs

This study investigated the effects of osteoarthritis (OA) on somatosensory processing in dogs using mechanical threshold testing. A pressure algometer was used to measure mechanical thresholds in 27 dogs with presumed hind limb osteoarthritis and 28 healthy dogs. Mechanical thresholds were measured at the stifles, radii and sternum, and were correlated with scores from an owner questionnaire and a clinical checklist, a scoring system that quantified clinical signs of osteoarthritis. The effects of age and bodyweight on mechanical thresholds were also investigated. Multiple regression models indicated that, when bodyweight was taken into account, dogs with presumed osteoarthritis had lower mechanical thresholds at the stifles than control dogs, but not at other sites. Non-parametric correlations showed that clinical checklist scores and questionnaire scores were negatively correlated with mechanical thresholds at the stifles. The results suggest that mechanical threshold testing using a pressure algometer can detect primary, and possibly secondary, hyperalgesia in dogs with presumed osteoarthritis. This suggests that the mechanical threshold testing protocol used in this study might facilitate assessment of somatosensory changes associated with disease progression or response to treatment.

Sedative and physiological effects of brimonidine tartrate ophthalmic solution in healthy cats

OBJECTIVE

To determine the effects of brimonidine tartrate ophthalmic solution on sedation, heart rate (HR), respiratory frequency (f_R), rectal temperature (RT) and noninvasive mean arterial pressure (MAP) in healthy cats.

STUDY DESIGN

Randomized, blinded crossover study, with 1 week washout between treatments.

ANIMALS

Six healthy purpose-bred cats.

METHODS

Brimonidine tartrate ophthalmic solution 0.1% (one or two drops; 58.6 ± 3.3 μg per drop) or a control solution (artificial tear solution) was administered to six healthy cats. Behavioural observations and measurements of HR, f_R, RT and MAP were recorded before and at 30, 60, 90, 120, 180, 240, 300 and 360 minutes after topical administration. Behavioural scores were analysed using Friedman's test for repeated measures to evaluate the time effect in each treatment and treatment effect at each time point. Physiological variables (HR, f_R, RT and MAP) were analysed using two-way analysis of variance for repeated measures to evaluate the time and treatment effects. The level of significance was set at p < 0.05.

RESULTS

Dose-dependent behavioural and physiological responses were noted. A dose of two drops of brimonidine resulted in sedation in the cats and decreased HR and MAP. Significant sedative effects occurred between 30 and 120 minutes and for physiological responses up to 360 minutes. The most frequent adverse reaction was vomiting, occurring within 40 minutes in all six cats administered two drops and five of the six cats administered one drop of brimonidine.

CONCLUSIONS AND CLINICAL RELEVANCE

The results demonstrated that ocular administration of brimonidine 0.1% ophthalmic solution induced sedation in cats and some cardiovascular effects usually associated with α₂-adrenoceptor agonists. Further studies should be performed to determine clinical applications for this agent in cats.

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.

Intraoperative end-tidal concentration of isoflurane in cats undergoing ovariectomy that received tramadol, buprenorphine or a combination of both

Objectives The aim of the study was to evaluate the end-tidal concentration of isoflurane required to maintain heart and respiratory rate within ± 20% of basal measurement in cats undergoing ovariectomy that received buprenorphine, tramadol or a combination of both. Methods Thirty cats, divided into three groups, were enrolled in a simple operator-blinded, randomised study. Cats received acepromazine (0.03 mg/kg) and one of the following treatments: buprenorphine (0.02 mg/kg), tramadol (2 mg/kg) or a combination of both. Anaesthesia was induced with propofol and maintained with isoflurane titrated in order to maintain heart and respiratory rate within the target values recorded before premedication. Results Groups were similar for age, weight, dose of propofol administered, sedation and recovery scores. Cats receiving tramadol with buprenorphine were extubated earlier after isoflurane discontinuation. No statistical differences were detected in end-tidal fraction of isoflurane between buprenorphine alone or with tramadol. In cats that received tramadol or buprenorphine alone, ovarian pedicle traction caused a statistical increase in end-tidal isoflurane concentration compared with that measured during incision and suture of the skin. In cats that received the combination of tramadol plus buprenorphine no differences among surgical time points were observed. Conclusions and relevance Tramadol added to buprenorphine did not provide any advantage in decreasing the end-tidal fraction of isoflurane compared with buprenorphine alone, although it is speculated there may be an infra-additive interaction between tramadol and buprenorphine in cats.

Physiologic and biochemical effects of electroacupuncture combined with intramuscular administration of dexmedetomidine to provide analgesia in goats

OBJECTIVE

To investigate physiologic and biochemical effects of electroacupuncture and dexmedetomidine administration to goats.

ANIMALS

30 healthy adult goats.

PROCEDURES

Goats were allotted to 5 groups (6 goats/group) and received electroacupuncture, dexmedetomidine (5 or 20 μg/kg, IM), electroacupuncture plus dexmedetomidine (5 μg/kg, IM), or saline (0.9% NaCl) solution (IM [control treatment]). Pain threshold, cardiorespiratory effects, rectal temperature, and hematologic and biochemical variables were assessed.

RESULTS

Dexmedetomidine (20 μg/kg) increased pain threshold and decreased heart rate, respiratory rate, and rectal temperature. Pain threshold of goats receiving electroacupuncture plus dexmedetomidine (5 μg/kg) was higher than that of goats receiving electroacupuncture or of goats receiving dexmedetomidine at 5 μg/kg at 30 minutes, but did not differ from that of goats receiving dexmedetomidine at 20 μg/kg. Compared with goats administered dexmedetomidine at 20 μg/kg, goats receiving electroacupuncture plus dexmedetomidine at 5 μg/kg had a higher heart rate from 30 to 60 minutes and a higher respiratory rate from 5 to 60 minutes. Electroacupuncture plus dexmedetomidine (5 μg/kg) did not affect rectal temperature. Serum glucose concentrations of goats receiving electroacupuncture plus dexmedetomidine (5 μg/kg) were higher than for goats receiving dexmedetomidine at 5 μg/kg at 30 minutes but not for goats receiving dexmedetomidine at 20 μg/kg. Creatinine and BUN concentrations, alanine or aspartate aminotransferase activities, and hematologic variables of treated goats did not change.

CONCLUSIONS AND CLINICAL RELEVANCE

Electroacupuncture in combination with a low dose of dexmedetomidine (5 μg/kg, IM) administered to goats provided antinociception.

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.

Effects of intramuscular sedation with alfaxalone and butorphanol on echocardiographic measurements in healthy cats

OBJECTIVES

The aim of the study was to evaluate the effects of intramuscular (IM) injections of alfaxalone combined with butorphanol on echocardiographic (ECG) measurements in cats.

METHODS

Client-owned adult domestic shorthair cats younger than 5 years of age were recruited. All cats that were considered healthy on the basis of physical examination, blood work, urinalysis, blood pressure measurement and baseline ECG underwent a second ECG under sedation. Cats were sedated with two separate IM injections of butorphanol at 0.2 mg/kg and alfaxalone at 2 mg/kg. ECG variables were analysed using a linear mixed model, and sedation scores were analysed using an ordinal mixed logistic model. The significance level was set at α = 0.05 and adjusted at α = 0.0017 for multiple comparisons of the ECG measurements.

RESULTS

Ten healthy cats were included. Sedation was uneventful, and recovery was smooth and quick for all cats. The mean duration of lateral recumbency was 36.3 ± 4.37 mins. Reduction in heart rate following sedation approached statistical significance (P = 0.002). The thickness of the interventricular septum, the thickness of the left ventricular free wall, and the left ventricular internal dimensions in diastole and systole were not affected by the sedation. The changes in left atrium/aortic ratio and shortening fraction were statistically significant. Although the peak velocity of early diastolic transmitral flow (E) and late diastolic transmitral flow (A), the peak early diastolic (Ea) mitral valve annulus velocity, and the peak late diastolic (Aa) mitral valve annulus velocity changed after sedation, the ratios E/A, E/Ea and Ea/Aa were not significantly different after sedation.

CONCLUSIONS AND RELEVANCE

IM injections of alfaxalone and butorphanol induced rapid, deep and short-lasting sedation. The mean differences after sedation were not clinically significant for most echocardiographic measurements.

Prepubertal gonadectomy in cats: different injectable anaesthetic combinations and comparison with gonadectomy at traditional age

Anaesthetic and analgesic effects of three different injectable anaesthetic combinations for prepubertal gonadectomy (PPG) in cats were studied. One anaesthetic protocol was compared with a similar one for gonadectomy at traditional age (TAG). Kittens were randomly assigned to PPG or TAG. For PPG, three different protocols were compared: (1) intramuscular (IM) administration of 60 μg/kg dexmedetomidine plus 20 μg/kg buprenorphine followed by an IM injection of the anaesthetic agent (20 mg/kg ketamine) (DB-IM protocol); (2) oral transmucosal (OTM) administration of 80 μg/kg dexmedetomidine plus 20 μg/kg buprenorphine followed by an IM injection of 20 mg/kg ketamine combined with 20 µg/kg dexmedetomidine (DB-OTM protocol); (3) IM injection of a 40 μg/kg medetomidine-20 μg/kg buprenorphine-20 mg/kg ketamine combination (MBK-IM protocol). For TAG, a DB-IM protocol was used, but with different doses for dexmedetomidine (40 μg/kg) and ketamine (5 mg/kg). All cats (PPG and TAG) received a non-steroidal anti-inflammatory before surgery. Anaesthetic and analgesic effects were assessed pre- and postoperatively (until 6 h). Cumulative logit, linear and logistic regression models were used for statistical analysis. Compared with the DB-OTM protocol, the DB-IM and MBK-IM protocols provided better anaesthesia with fewer adverse effects in PPG cats. Postoperative pain was not significantly different between anaesthetic protocols. PPG and TAG cats anaesthetised with the two DB-IM protocols differed significantly only for sedation and pain scores, but sedation and pain scores were generally low. Although there were no anaesthesia-related mortalities in the present study and all anaesthetic protocols for PPG in cats provided a surgical plane of anaesthesia and analgesia up to 6 h postoperatively, our findings were in favour of the intramuscular (DB-IM and MBK-IM) protocols.

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.

Evaluation of the perioperative analgesic efficacy of buprenorphine, compared with butorphanol, in cats

OBJECTIVE

To compare the analgesic effects of buprenorphine and butorphanol in domestic cats.

DESIGN

2-phase positive-controlled randomized masked clinical trial.

ANIMALS

39 healthy female cats (10 in phase 1 and 29 in phase 2).

PROCEDURES

Cats admitted for ovariohysterectomy received buprenorphine (4 in phase 1; 14 in phase 2) or butorphanol (6 in phase 1; 15 in phase 2). In phase 1, cats were premedicated with buprenorphine (0.02 mg/kg [0.009 mg/lb], IM) or butorphanol (0.4 mg/kg [0.18 mg/lb], IM), in combination with medetomidine. Anesthesia was induced with propofol (IV) and maintained with isoflurane in oxygen. After extubation, medetomidine was antagonized with atipamezole. A validated multidimensional composite scale was used to assess signs of pain after surgery starting 20 minutes after extubation and continuing for up to 360 minutes, and pain score comparisons were made between the 2 groups. Phase 2 proceeded similar to phase 1 with the following addition: during wound closure, cats from the butorphanol and buprenorphine groups received butorphanol (0.4 mg/kg, IM) or buprenorphine (0.02 mg/kg, IM), respectively.

RESULTS

Phase 1 of the study was stopped after 10 cats were ovariohysterectomized because 9 of 10 cats required rescue analgesia at the first evaluation. In phase 2, at the first pain evaluation, pain scores from the buprenorphine group were lower, and all cats from the butorphanol group required rescue analgesia. None of the cats from the buprenorphine group required rescue analgesia at any time.

CONCLUSIONS AND CLINICAL RELEVANCE

Buprenorphine (0.02 mg/kg, IM) given before surgery and during wound closure provided adequate analgesia for 6 hours following ovariohysterectomy in cats, whereas butorphanol did not.

Influence of experimental protocol on response rate and repeatability of mechanical threshold testing in dogs

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Mechanical nociceptive thresholds were obtained from healthy dogs.

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Effect of protocol on success rate, repeatability and threshold was examined.

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Stimulus area, position of dog and anatomical site affected success rate.

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Wider stimulus areas were associated with higher thresholds.

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Between dog variation had a greater effect than protocol on all three outcomes.

Mechanical threshold (MT) testing is widely used to measure nociceptive thresholds. However, there has been little research into factors that contribute to the response rate and repeatability (collectively termed ‘efficacy’) of MT testing protocols. The aim of this study was to investigate whether the efficacy of a protocol using a hand-held algometer to measure MTs (N) in healthy dogs (n = 12) was affected by varying (1) the area over which force was applied (tip diameter), (2) rate of force application, (3) position of dog during testing, and (4) anatomical site of testing. The effect of these factors on MT and the impact of individual dog effects on both efficacy and MT were also investigated.

Overall, 3175/3888 tests (82%) resulted in a measurable response. The response rate was reduced by using wider tip diameters, testing at the tibia, and testing when the dog was lying down (compared to sitting upright). Wider tips were associated with higher, more variable MTs (mean ± standard deviation) with values of 4.18 ± 2.55 N for 2 mm diameter tips, 5.54 ± 3.33 for those of 4 mm, and 7.59 ± 4.73 for 8 mm tips. Individual dog effects had the most significant impact on efficacy and MT. The findings indicate that tip diameter, dog position, and anatomical site may affect both protocol efficacy and MTs, and should be taken into account when comparing different studies and in designing protocols to measure MTs in dogs. The predominant effect of the individual dog over other factors indicates that between-subject differences should always be accounted for in future studies.

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.

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.

Robenacoxib versus meloxicam for the management of pain and inflammation associated with soft tissue surgery in dogs: a randomized, non-inferiority clinical trial

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) are used routinely to control pain and inflammation after surgery in dogs. Robenacoxib is a new NSAID with high selectivity for the cyclo-oxygenase (COX)-2 isoform of COX. The objective of this study was to evaluate the efficacy and tolerability of robenacoxib for the management of peri-operative pain and inflammation associated with soft tissue surgery in dogs. The study was a prospective, randomized, blinded, positive-controlled, non-inferiority, multi-center clinical trial. A total of 174 dogs undergoing major soft tissue surgery were included and randomly allocated in a 2:1 ratio to receive either robenacoxib (n = 118) or the positive control, meloxicam (n = 56). Each dog received an initial dose subcutaneously prior to surgery (robenacoxib 2 mg/kg, meloxicam 0.2 mg/kg), followed by daily oral doses (robenacoxib 1-2 mg/kg, meloxicam 0.1 mg/kg) for 12 days (range 10-14) after surgery. Pain and inflammation were assessed subjectively using the Glasgow Composite Pain Scale (GCPS) by clinicians as the primary end point and additional evaluations by the clinicians and animal owners as secondary endpoints.

RESULTS

Both treatments provided similar pain control, with no significant differences between groups for any efficacy variable using non-parametric analyses (Mann-Whitney U test). In no dog was analgesic rescue therapy administered. Non-inferior efficacy of robenacoxib compared to meloxicam was demonstrated statistically for the primary and all secondary endpoints using parametric analysis of variance, although the data were not normally distributed even after log transformation. For the primary endpoint (reciprocal of the modified GCPS score), the relative efficacy of robenacoxib/meloxicam was 1.12 with a 95% confidence interval of 0.97-1.29.

CONCLUSION

A treatment regimen of robenacoxib by subcutaneous injection followed by oral tablets had good tolerability and non-inferior efficacy compared to meloxicam for the management of peri-operative pain and inflammation associated with soft tissue surgery in dogs.