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

The Effect of a Subsequent Dose of Dexmedetomidine or Other Sedatives following an Initial Dose of Dexmedetomidine on Electrolytes, Acid-Base Balance, Creatinine, Glucose, and Cardiac Troponin I in Cats: Part II

The administered dose of dexmedetomidine may occasionally fail to produce the anticipated sedative effects. Therefore, a subsequent dose or administration of another sedative may enhance sedation; however, patient safety may be affected. The safety of seven different drugs administered at the following time point after an insufficient dose of dexmedetomidine was evaluated in a crossover, blind, experimental study that included six healthy adult cats. All cats received an initial dose of dexmedetomidine and a subsequent dose of either dexmedetomidine (Group DD), NS 0.9% (DC), tramadol (DT), butorphanol (DBT), buprenorphine (DBP), ketamine (DK), or midazolam (DM). Animal safety was assessed using repeated blood gas analysis and measurement of electrolytes, glucose, cardiac troponin I, and creatinine to evaluate cardiac, respiratory, and renal function. The median values of creatinine, cardiac troponin I, pH, partial pressure of carbon dioxide, potassium, and sodium did not change significantly throughout the study. Heart rate was significantly decreased in all groups after administration of the drug combinations, except for in the DK group. Respiratory rate decreased significantly after administration of the initial dose of dexmedetomidine and in the DBP and DM groups. The partial pressure of oxygen, although normal, decreased significantly after the administration of dexmedetomidine, whereas the median concentration of glucose increased significantly following the administration of dexmedetomidine. The results of our study suggest that the drug combinations used did not alter the blood parameters above normal limits, while cardiac and renal function were not compromised. Therefore, a safe level of sedation was achieved. However, the administration of dexmedetomidine reduced the partial pressure of oxygen; thus, oxygen supplementation during sedation may be advantageous. Additionally, the increase in glucose concentration indicates that dexmedetomidine should not be used in cats with hyperglycaemia, whereas the decrease in haematocrit suggests that dexmedetomidine is not recommended in anaemic cats.

Disposition kinetics of meloxicam in green sea turtles (Chelonia mydas) after intravenous and intramuscular administrations

The pharmacokinetics were described of meloxicam (MLX) in green sea turtles (Chelonia mydas), following a single intravenous (i.v.) and intramuscular (i.m.) administrations at one of two dosages of 0.1 or 0.2 mg/kg body weight (b.w.). The sample of 20 green sea turtles was divided into four groups (n = 5) using a randomization procedure according to a parallel study design. Blood samples were collected at pre-assigned times up to 168 h. MLX in the plasma was cleaned-up and quantified using a validated high-performance liquid chromatography method with UV detection. The concentration of MLX in the experimental green sea turtles with respect to time was pharmacokinetically analyzed using a non-compartment model. MLX plasma concentrations were quantifiable for up to 72 and 120 h after i.v. at dosages of 0.1 and 0.2 mg/kg b.w., respectively, whereas it was measurable for up to 168 h after i.m. administration at both dosages. The long elimination half-life value of MLX (28 h) obtained in green sea turtles after i.v. administration was consistent with the quite slow clearance rate for both dosages. The average maximum concentration (Cmax ) values of MLX were 1.05 μg/mL and 4.26 μg/mL at dosages of 0.1 and 0.2 mg/kg b.w., respectively, with their elimination half-life values being 37.26 h and 30.64 h, respectively, after i.m. administrations. The absolute i.m. bioavailability was approximately 110%. These results suggested that i.m. administration of MLX at a dosage of 0.2 mg/kg b.w. was likely to be effective for clinical use in green sea turtles (Chelonia mydas). However, further studies are needed to determine the pharmacodynamic properties and clinical efficacy of MLX for the treatment of inflammatory disease after single and multiple dosages.

A comparison of intra and postoperative analgesic effects of sacrococcygeal and lumbosacral epidural levobupivacaine in cats undergoing ovariohysterectomy

The aim of this study was to compare the intra and postoperative analgesic effects of sacrococcygeal epidural levobupivacaine with those of lumbosacral levobupivacaine in feline ovariohysterectomy. Thirty-six cats were premedicated with intramuscular acepromazine (0.05 mg/kg) and meperidine (6 mg/kg). Anesthesia was induced with intravenous propofol and maintained with isoflurane in oxygen. The cats were randomly assigned one of the three treatments receiving 0.33% levobupivacaine (0.3 mL/kg) into the sacrococcygeal (S-C group, n=12) or lumbosacral (L-S group, n=12) epidural space, or the same volume of 0.9% saline solution into one of the epidural approaches (Control group, n=12). Intraoperatively, cardiorespiratory variables, end-tidal isoflurane concentration (FE´ISO), and fentanyl requirements were recorded. Postoperative pain was assessed by the UNESP (Universidade Estadual Paulista)-Botucatu multidimensional composite pain scale and the Glasgow feline composite measure pain scale up to 8 hr post-extubation. Morphine was administered as rescue analgesia. Overall FE´ISO and fentanyl requirements were lower in the L-S and S-C compared to the Control (P=0.002-0.048, respectively). There was no significant difference in the cardiorespiratory variables during anesthesia, postoperative pain and rescue analgesia among groups. The time to standing after anesthesia was prolonged in the L-S and S-C groups than in the Control (P<0.001). Lumbosacral and sacrococcygeal epidural levobupivacaine resulted in similar decreases in isoflurane requirements and intraoperative fentanyl supplementation in the cats, with no postoperative benefits.

Robenacoxib versus meloxicam following ovariohysterectomy in cats: A randomised, prospective clinical trial involving owner-based assessment of pain

BACKGROUND

Injectable non-steroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed to queens undergoing ovariohysterectomy (OVH), but the requirement for postoperative administration is unclear and practices vary. Existing studies assessing efficacy rely on pain scoring by experienced clinicians. However, following OVH, most cats are discharged within hours of recovery.

METHODS

Cats undergoing OVH were randomly assigned to two treatment groups: MEL and ROB. Cats in the MEL group (n = 76) received meloxicam (0.2 mg/kg) and those in the ROB group (n = 65) received robenacoxib (2 mg/kg). Owners were contacted by a blinded assessor 3 days postoperatively and asked to identify physical or behavioural changes and to assign pain scores using a numerical rating scale.

RESULTS

More cats in the ROB group displayed abnormal behaviours than cats in the MEL group (p = 0.03). Most owners assigned a pain score of 0 (72%) (n = 101), but pain scores were significantly higher in the ROB group than in the MEL group (p = 0.005).

LIMITATION

Methods of owner assessment of pain in cats have not been validated.

CONCLUSIONS

Both meloxicam and robenacoxib are effective in controlling postoperative pain. Meloxicam may have improved efficacy in certain patient populations. Applying a blanket approach to prescribing NSAIDs to cats undergoing OVH postoperatively may not be necessary. This has safety, environmental and cost implications.

Antinociceptive Effect of a Sacro-Coccygeal Epidural of Morphine and Lidocaine in Cats Undergoing Ovariohysterectomy

BACKGROUND

A commonly described analgesic protocol for ovariohysterectomy (OHE) combines systemic opioids, sedatives, and non-steroidal anti-inflammatory drugs. However, systemic analgesia does not fully prevent perioperative visceral and somatic pain triggered by the surgical stimulus.

OBJECTIVES

To compare the analgesic effects and quality of recovery of systemic analgesia with those of a sacrococcygeal epidural injection of lidocaine and morphine in cats undergoing elective OHE. Methods: Twenty domestic female cats were premedicated with dexmedetomidine (0.01 mg kg-1 IM) and alfaxalone (1.5 mg kg-1 IM) and randomly assigned to one of two analgesic protocols: methadone (0.2 mg kg-1 IM) in the control group CTR (n = 10) and methadone (0.1 mg kg-1 IM) + epidural (lidocaine 2% (0.3 mL kg-1) + morphine 1% (0.1 mg kg-1) diluted with NaCl 0.9% to a total volume of 1.5 mL in the SCC-E group (n = 10). General anaesthesia was induced with alfaxalone (1 mg kg-1 IV) and maintained with sevoflurane in 100% oxygen. Non-invasive blood arterial pressure and cardiorespiratory variables were recorded. The quality of recovery was assessed using a simple descriptive scale. Before surgery and 1, 2, 3, 4, 6, and 8 h post-op pain was assessed using the UNESP-Botucatu multidimensional composite pain scale (MCPS) and mechanical nociception thresholds (MNT). The repeated measures analysis of variance (ANOVA) was used to compare groups over time. Comparison between groups was performed using independent samples t-test if the assumption of normality was verified, or the Mann-Whitney test. The chi-square test of independence and exact Fisher's test were used to compare groups according to recovery quality.

RESULTS

Heart rate and systolic arterial pressure increased significantly from baseline values in the CTR group and did not change in the SCC-E group. In the CTR group, MNT and UNESP-Botucatu-MCPS scores increased significantly from baseline for all assessment points and the first 3 h, respectively, whereas this did not occur in the SCC-E group.

CONCLUSIONS AND CLINICAL RELEVANCE

Based on our results, the SCC-E administration of lidocaine 2% with morphine 1% is a reasonable option to provide perioperative analgesia in cats submitted to OHE, compared to a systemic protocol alone.

The ultrasound-guided funicular block in cats undergoing orchiectomy: ropivacaine injection into the spermatic cord to improve intra and postoperative analgesia

BACKGROUND

The orchiectomy in cats is a common surgical procedure with medium level of pain and for this reason requires intra and postoperative analgesia management. The aim of this study was to compare intra and postoperative pain in two groups of cats undergoing orchiectomy. Sixty healthy cats were randomly assigned in two groups (n = 30) to receive pre surgery ropivacaine hydrochloride (0.2 mL/kg at 0.5%) (R Group) or NaCl 0.9% (C group) into the spermatic cord. The intraoperative evaluation was carried out using the cardiorespiratory stability parameters and eventually administration of rescue analgesia. A rescue analgesia (fentanyl 2 µg/kg) was administered during orchiectomy in case of considerable increase of blood pressure, heart rate or respiratory rate. The postoperative evaluation was been done using scores following a UNESP-Botucatu multimodal scale for 6 h post-surgery.

RESULTS

As result, cats in R group responded better to surgical procedure, maintaining lower postoperative pain scores than C group.

CONCLUSIONS

The ultrasound-guided funicular block used in this study, as already demonstrated in dogs, is a good method to protect the cats from surgical pain and ensure a good level of surgical analgesia.

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

PRACTICAL RELEVANCE

Increases in cat ownership worldwide mean more cats are requiring veterinary care. Illness, trauma and surgery can result in acute pain, and effective management of pain is required for optimal feline welfare (ie, physical health and mental wellbeing). Validated pain assessment tools are available and pain management plans for the individual patient should incorporate pharmacological and non-pharmacological therapy. Preventive and multimodal analgesia, including local anaesthesia, are important principles of pain management, and the choice of analgesic drugs should take into account the type, severity and duration of pain, presence of comorbidities and avoidance of adverse effects. Nursing care, environmental modifications and cat friendly handling are likewise pivotal to the pain management plan, as is a team approach, involving the cat carer.

CLINICAL CHALLENGES

Pain has traditionally been under-recognised in cats. Pain assessment tools are not widely implemented, and signs of pain in this species may be subtle. The unique challenges of feline metabolism and comorbidities may lead to undertreatment of pain and the development of peripheral and central sensitisation. Lack of availability or experience with various analgesic drugs may compromise effective pain management.

EVIDENCE BASE

These Guidelines have been created by a panel of experts and the International Society of Feline Medicine (ISFM) based on the available literature and the authors' experience. They are aimed at general practitioners to assist in the assessment, prevention and management of acute pain in feline patients, and to provide a practical guide to selection and dosing of effective analgesic agents.

Stereoselective methadone disposition after administration of racemic methadone to anesthetized Shetland ponies assessed by capillary electrophoresis

The enantioselectivity of the pharmacokinetics of methadone was investigated in anesthetized Shetland ponies after a single intravenous (0.5 mg/kg methadone hydrochloride; n = 6) or constant rate infusion (0.25 mg/kg bolus followed by 0.25 mg/kg/h methadone hydrochloride; n = 3) administration of racemic methadone. Plasma concentrations of l‐methadone and d‐methadone and their major metabolites, l‐ and d‐2‐ethylidene‐1,5‐dimethyl‐3,3‐diphenylpyrrolidine (EDDP), respectively, were analyzed by CE with highly sulfated γ‐cyclodextrin as chiral selector and electrokinetic analyte injection from liquid/liquid extracts prepared at alkaline pH. In both trials, the d‐methadone concentrations were lower than those of l‐methadone and the d‐EDDP levels were lower than those of L‐EDDP. For the case of a single intravenous bolus injection, the plasma concentration versus time profile of methadone enantiomers was analyzed with a two‐compartment pharmacokinetic model. l‐methadone showed a slower elimination rate constant, a lower body clearance, and a smaller steady‐state volume of distribution than d‐methadone. d‐methadone and d‐EDDP were eliminated faster than their respective l‐enantiomers. This is the first study that outlines that the disposition of racemic methadone administered to anesthetized equines is enantioselective.

Use of Spinal Anaesthesia with Anaesthetic Block of Intercostal Nerves Compared to a Continuous Infusion of Sufentanyl to Improve Analgesia in Cats Undergoing Unilateral Mastectomy

Simple Summary

Postoperative analgesia is very important because pain causes various negative effects that prevent patient recovery. Our study aimed to evaluate the analgesic efficacy of subarachnoid anaesthesia combined with intercostal nerve block compared with a constant-rate infusion of sufentanyl citrate in cats undergoing unilateral mastectomy. This study demonstrated that the use of spinal anaesthesia with anaesthetic block of intercostal nerves, using levobupivacaine, guarantees long-lasting and high-quality analgesic coverage and minimises the post-surgical pain inevitably associated with invasive surgical procedures such as radical mastectomy. This study stemmed from a general trend towards increasing attention on postoperative pain after spaying procedures in cats. Since veterinarians are becoming more focused on relieving surgical pain, anaesthetists are expected to use better protocols that can minimise pain and therefore optimise surgical results. This method, considering the relative simplicity of its execution, can be used in daily clinical practice.

Abstract

Unilateral mastectomy is a common surgical procedure in feline species and requires postoperative pain management. Our study aimed to evaluate the analgesic efficacy of subarachnoid anaesthesia combined with an intercostal nerve block, in comparison with the use of sufentanyl citrate administered as a constant-rate infusion (CRI). Twenty cats were randomly divided into two groups (n = 10/group) based on the analgesic protocol used: the first received loco-regional anaesthesia with levobupivacaine (LR group), and the second received a CRI of sufentanyl (SUF group). The evaluation criteria during surgery were the need for a bolus of fentanyl in the event of an increased heart rate or increased blood pressure. In the postoperative period, the levels of comfort/discomfort and pain were used to obtain a score according to the UNESP-Botucatu multimodal scale. Subjects who scored above seven received analgesic drug supplementation. Intraoperative analgesia was satisfactory, with good haemodynamic stability in both groups. Four patients in the LR group required an extra dose of methadone after they achieved the sternal decubitus position, whereas those in the SUF group required many more doses. The analgesia achieved in the LR group was more satisfactory than that in the SUF group.

Assessment of Controlled Substance Distribution to U.S. Veterinary Teaching Institutions From 2006 to 2019

Objective: To evaluate the changing pattern of distribution of Schedule II and III opioids, barbiturates, and stimulants to veterinary educational institutions in the United States.

Design: Longitudinal study.

Sample: Veterinary teaching institutions that use Schedule II and III drugs.

Procedures: Distribution of controlled substances to veterinary teaching institutions was obtained from the Drug Enforcement Administration's Automated Reports and Consolidated Orders System (ARCOS) for opioids (e.g., methadone, fentanyl, codeine), barbiturates (pentobarbital, butalbital), and stimulants (amphetamine, methylphenidate, lisdexamfetamine) from 2006–2019. Opioids were converted to their morphine milligram equivalents (MME) for evaluation over time.

Results: Controlled substance distribution to veterinary schools exhibited dynamic, and agent specific, changes. The total MME for 11 opioids peaked in 2013 and decreased by 17.3% in 2019. Methadone accounted for two-fifths (42.3%) and fentanyl over one-third (35.4%) of the total MME in 2019. Pentobarbital distribution was greatest by weight of all substances studied and peaked in 2011 at 69.4 kg. Stimulants underwent a pronounced decline and were very modest by 2014.

Conclusions and Clinical Relevance: Opioids by total MME in veterinary teaching practice have undergone more modest changes than opioids used with humans. Hydrocodone, codeine and recently fentanyl use have declined while methadone increased. Stimulant distribution decreased to become negligible. Together, this pattern of findings warrant continued monitoring.

The use of small-bore wire-guided chest drains for the management of feline pyothorax: A retrospective case series

Background:

Pyothorax in cats is routinely managed, at least initially, with thoracic tube placement associated with systemic antimicrobial administration. Traditionally, large-bore trocar-type thoracostomy tubes have preferentially been used for the drainage of thick material from the pleural space. In recent years, the use of small-bore wire-guided thoracic drains has increased in both small animals and in humans. Few studies have highlighted the efficacy of small-bore wire-guided thoracostomy tubes.

Aim:

The purpose of this study was to describe the use of small-bore wire-guided thoracostomy tubes in feline pyothorax in terms of efficacy, safety, and outcome.

Methods:

Cats with pyothorax managed with small-bore thoracostomy tubes (SBTTs) (2015–2018) were retrospectively studied. The number of drains inserted, the need for anesthesia and analgesia for chest tube placement and maintenance, and related major and minor complications were reviewed. Clinical data, diagnostic results, treatment, and outcome were recorded.

Results:

Ten cats were enrolled. Thoracostomy tube placement was unilateral in 7/10 cats, despite the presence of bilateral effusion in 9/10 cats, and required sedation (8/10) or anesthesia (2/10). Three cats experienced minor complications during the chest tube insertion, including self-limiting pneumothorax (1/3) and malpositioning (2/3). One cat had a major complication (non-functional malposition) requiring reposition of the drain. Pain management was adequately achieved using opioids (8/10) or opioids plus nonsteroidal anti-inflammatory drugs (2/10). Partial chest tube occlusion occurred in three cases and it was resolved with lavage. In one case, the occlusion was complete, requiring drain removal. Three out of 10 cats were treated medically, combining thoracostomy tubes and antibiotics, while 7/10 cats underwent surgery. All the cats survived.

Conclusion:

SBTTs represent a safe and effective option for the initial management of feline pyothorax. In fact, mainly minor complications were reported during insertion and usage. The SBTTs were well tolerated by the cats with a satisfactory performance in terms of exudate drainage in most cases. The combined use of a small-bore thoracostomy drain together with the common practice of surgical treatment might have resulted in the successful management of the cases presented.

Pharmacokinetics of tolfenamic acid in green sea turtles (Chelonia mydas) after intravenous and intramuscular administration

The present study aimed to evaluate the pharmacokinetic features of tolfenamic acid (TA) in green sea turtles, Chelonia mydas. Green sea turtles were administered single either intravenous (i.v.) or intramuscular (i.m.) injection of TA, at a dose of 4 mg/kg body weight (b.w.). Blood samples were collected at preassigned times up to 168 hr. The plasma concentrations of TA were measured using a validated liquid chromatography tandem mass spectrometry method. Tolfenamic acid plasma concentrations were quantifiable for up to 168 hr after i.v. and i.m. administration. The concentration of TA in the experimental green sea turtles with respect to time was pharmacokinetically analyzed using a noncompartment model. The C_max values of TA were 55.01 ± 8.34 µg/ml following i.m. administration. The elimination half-life values were 32.76 ± 4.68 hr and 53.69 ± 3.38 hr after i.v. and i.m. administration, respectively. The absolute i.m. bioavailability was 72.02 ± 10.23%, and the average binding percentage of TA to plasma protein was 19.43 ± 6.75%. Based on the pharmacokinetic data, the i.m. administration of TA at a dosage of 4 mg/kg b.w. might be sufficient to produce a long-lasting anti-inflammatory effect (7 days) for green sea turtles. However, further studies are needed to determine the clinical efficacy of TA for treatment of inflammatory disease after single and multiple dosages.

Separation of anaesthetic ketamine and its derivates in PAMAPTAC coated capillaries with tuneable counter-current electroosmotic flow

Capillary electrophoretic separation of ketamine, norketamine, hydroxynorketamine, and dehydronorketamine was performed in the counter-current regime under the influence of oppositely-directed electroosmotic flow. For this purpose, the fused silica capillaries were covalently coated with the poly(acrylamide-co-3-acrylamidopropyl trimethylammonium chloride) copolymer (PAMAPTAC). The content of the cationic monomer APTAC in the polymerization mixture varied in the range 0-6 mol. % and the generated electroosmotic flow increased continuously in the 0-20 · 10^-9 m²V^-1s^-1 interval. Importantly, it resulted in improved electrophoretic resolution of ketamine/norketamine, which increased from 0.8 for neutral PAM coating (i.e. 0% PAMAPTAC) to 3.0 for 6% PAMAPTAC. The determination of ketamine and its derivates in rat serum was performed in a 4% PAMAPTAC capillary with an inner diameter of 25 μm. The separation was performed in a 500 mM aqueous solution of acetic acid (pH 2.3). The clinical sample was deproteinized by the addition of acetonitrile to the serum and a large volume of the treated sample was injected directly into the capillary. The achieved limit of detection ranged from 2.2 ng/mL for dehydronorketamine to 4.1 ng/mL for hydroxynorketamine; the intra-day repeatability was 1.0-1.5% for the migration time and 2.8-3.3% for the peak area. The developed methodology was employed for time monitoring of ketamines in rat serum after intra venous administration of low doses of anaesthetic at a level of 2 μg per g of body weight.

Determining priority welfare issues for cats in the United Kingdom using expert consensus

Background

Cats are the most popular pets in the UK, yet relatively little research has been conducted into the welfare of cats living in a home environment. The purpose of this study was to determine and prioritise welfare issues for cats using a Delphi method.

Methods

Cat welfare experts (n=14) were asked to identify and rank welfare issues for cats in the UK. An initial list of 118 welfare issues was generated by an anonymous online discussion board of experts and thematic analysis using NVivo. Subsequently experts ranked the list of welfare issues according to severity, duration and prevalence using a 6-point Likert scale. All issues with a median score of 3 or above (n=43) were included in the second survey to determine agreement on the rankings of issues. Finally, a subsection of experts attended a two-day workshop to discuss the welfare rankings and determine the final prioritised list of welfare issues.

Results

The issues considered to be the most severe and/or likely to cause prolonged cat suffering included social behaviour issues, diseases of old age, obesity, owners not seeking veterinary care and poor pain management. The welfare issues perceived to be most prevalent included neglect/hoarding, delayed euthanasia, inherited conformational defects/diseases, social or environmental restriction, and poor pain management.

Conclusions

The outcomes suggested that, although issues such as cat behaviour required further research, owner education was an important factor in improving cat welfare.

Pharmacokinetics of tolfenamic acid in Hawksbill turtles (Eretmochelys imbricata) after single intravenous and intramuscular administration

To the best of our knowledge, limited pharmacokinetic information to establish suitable therapeutic plans is available for Hawksbill turtles. Therefore, the present study aimed to assess the pharmacokinetic features of tolfenamic acid (TA) in Hawksbill turtles, Eretmochelys imbricata, after single intravenous (i.v.) and intramuscular (i.m.) administration at dosage 4 mg/kg body weight (b.w.). The study (parallel design) used 10 Hawksbill turtles randomly divided into equal groups. Blood samples were collected at assigned times up to 144 hr. The concentrations of TA in plasma were quantified by a validated liquid chromatography tandem mass spectrometry (LC-ESI-MS/MS). The concentration of TA in the experimental turtles with respect to time was pharmacokinetically analyzed using a noncompartment model. The C_max values of TA were 89.33 ± 6.99 µg/ml following i.m. administration. The elimination half-life values were 38.92 ± 6.31 hr and 41.09 ± 9.32 hr after i.v. and i.m. administration, respectively. The absolute i.m. bioavailability was 94.46%, and the average binding percentage of TA to plasma protein was 31.39%. TA demonstrated a long half-life and high bioavailability following i.m. administration. Therefore, the i.m. administration is recommended for use in clinical practice because it is both easier to perform and provides similar plasma concentrations to the i.v. administration. However, further studies are needed to determine the clinical efficacy of TA for treatment of inflammatory disease after single and multiple dosages.

Determining priority welfare issues for cats in the United Kingdom using expert consensus

BACKGROUND

Cats are the most popular pets in the UK, yet relatively little research has been conducted into the welfare of cats living in a home environment. The purpose of this study was to determine and prioritise welfare issues for cats using a Delphi method.

METHODS

Cat welfare experts (n=14) were asked to identify and rank welfare issues for cats in the UK. An initial list of 118 welfare issues was generated by an anonymous online discussion board of experts and thematic analysis using NVivo. Subsequently experts ranked the list of welfare issues according to severity, duration and prevalence using a 6-point Likert scale. All issues with a median score of 3 or above (n=43) were included in the second survey to determine agreement on the rankings of issues. Finally, a subsection of experts attended a two-day workshop to discuss the welfare rankings and determine the final prioritised list of welfare issues.

RESULTS

The issues considered to be the most severe and/or likely to cause prolonged cat suffering included social behaviour issues, diseases of old age, obesity, owners not seeking veterinary care and poor pain management. The welfare issues perceived to be most prevalent included neglect/hoarding, delayed euthanasia, inherited conformational defects/diseases, social or environmental restriction, and poor pain management.

CONCLUSIONS

The outcomes suggested that, although issues such as cat behaviour required further research, owner education was an important factor in improving cat welfare.

Comparison of two high doses of subcutaneous buprenorphine in cats undergoing ovariohysterectomy

Objectives:

The aim of the study was to evaluate the analgesia and recovery effects of two doses (0.12 mg/kg and 0.24 mg/kg) of subcutaneous buprenorphine in cats undergoing ovariohysterectomy.

Methods:

This was an assessor-blinded, randomised, clinical study. A total of 83 cats were recruited and randomly allocated to receive 0.12 mg/kg buprenorphine or 0.24 mg/kg buprenorphine subcutaneously, followed 30 minutes later by 40 μg/kg medetomidine intramuscularly. Anaesthesia was induced with intravenous alfaxalone to effect and maintained with isoflurane in oxygen. All cats received meloxicam before surgery. Temperament score, quality of sedation, induction of anaesthesia, dose of alfaxalone and recovery were scored using simple descriptive scales. Atipamazole was administered following surgery. Physiological variables during anaesthesia were recorded. Cats were assessed postoperatively by the same blinded observer at 2, 4 and 24 hours using a modified Colorado Feline Acute Pain scale. The presence or absence of mydriasis was noted.

Results:

No significant differences were identified between groups. Three cats in the 0.12 mg/kg group and four in the 0.24 mg/kg group required rescue analgesia. Mydriasis persisting for at least 24 hours was evident in 75 cats.

Conclusions and relevance:

No differences in analgesia were detected between groups with these protocols; mydriasis was common in both groups.

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.

Rapid electrophoretic monitoring of the anaesthetic ketamine and its metabolite norketamine in rat blood using a contactless conductivity detector to study the pharmacokinetics

A method of capillary electrophoresis with contactless conductivity detection has been developed for non-enantioselective monitoring the anaesthetic ketamine and its main metabolite norketamine. The separation is performed in a 15 μm capillary with an overall length of 31.5 cm and length to detector of 18 cm; inner surface of the capillary is covered with a commercial coating solution to reduce the electroosmotic flow. In an optimised background electrolyte with composition 2 M acetic acid + 1% v/v coating solution under application of a high voltage of 30 kV, the migration time is 97.1 s for ketamine and 95.8 s for norketamine, with an electrophoretic resolution of 1.2. The attained detection limit was 83 ng/mL (0.3 μmol/L) for ketamine and 75 ng/mL (0.3 μmol/L) for norketamine; the number of theoretic plates for separation of an equimolar model mixture with a concentration of 2 μg/mL was 683 500 plates/m for ketamine and 695 400 plates/m for norketamine. Laboratory preparation of rat blood plasma is based on mixing 10 μL of plasma with 30 μL of acidified acetonitrile, followed by centrifugation. A pharmacokinetic study demonstrated an exponential decrease in the plasma concentration of ketamine after intravenous application and much slower kinetics for intraperitoneal application.

Anaesthetics and analgesics used in adult fish for research: A review

The number of fish used in research has increased in the last decades. Anaesthesia is required when fish must be held immobile and it is crucial to promote fish welfare, because these vertebrates can show signs of stress and/or pain during handling, transport, tagging, sampling and invasive procedures. The use of an inadequate anaesthetic protocol can compromise not only the welfare of the fish, but also the reliability of the research results. Thus, the development of suitable anaesthetic regimes for each fish species is important. This article reviews the main anaesthetic and analgesic agents used in adult fish in a research setting.

Evaluation of intraoperative analgesia provided by incisional lidocaine and bupivacaine in cats undergoing ovariohysterectomy

Objectives The objective of this study was to assess the intraoperative analgesic effect of preoperative infiltration of the incision site with lidocaine or a mixture of lidocaine with bupivacaine in cats undergoing ovariohysterectomy (OHE). Methods This was a prospective, randomised clinical study. Healthy female intact cats (n = 75) undergoing OHE under medetomidine-ketamine-buprenorphine anaesthesia were assigned randomly into three treatment groups (n = 25 per group) to receive one of two local anaesthesia protocols or placebo preoperatively in the midline incision: lidocaine 1.5 mg/kg (group GL) or mixture of lidocaine 1 mg/kg and bupivacaine 1 mg/kg (group GLB) or sodium chloride 0.9% (control group). Blood pressure, heart and respiratory rate, temperature, muscle tonus and pupillary reflex were registered during surgery. During recovery, the cats were observed for side effects. Postoperative analgesia was provided with meloxicam (0.2 mg/kg). Most cats were rechecked 2 weeks postoperatively to remove skin sutures. Results There was no significant difference between groups regarding breed, age, body weight, surgical time and postoperative complication rate. The majority of the cats (60%) included in the control group received a supplemental bolus of propofol during surgery, when compared with 43% and 44% of the cats included in the GL and GLB groups, respectively. Heart rate was significantly higher ( P <0.05) in the control group at the time of excision of the second ovary and the uterine body. Mean arterial pressure (MAP) was stable in both treatment groups; in contrast, it tended to increase in the control group. Heart rate and MAP were similar between treatment groups. Conclusions and relevance Preoperative incisional block with only lidocaine or combined with bupivacaine seems to produce a similar intraoperative analgesia in cats undergoing OHE. Despite the similar intraoperative analgesic effect between treatment groups, the combination of lidocaine and bupivacaine reduced the required doses, and had a faster onset of action and prolonged effect.

Tolfenamic Acid

Tolfenamic acid (TA) is a nonsteroidal antiinflammatory drug and belongs to the group of fenamates. It is used as a potent pain reliever in the treatment of acute migraine attacks, and disorders like dysmenorrhea, rheumatoid, and osteoarthritis. TA has shown excellent in vitro antibacterial activity against certain ATCC strains of bacteria when complexed with bismuth(III). It has also been reported to block pathological processes associated with Alzheimer's disease. In the recent past, TA has also been used as a novel anticancer agent for the treatment of various cancers. In view of the clinical importance of TA, a comprehensive review of the physical and pharmaceutical properties and details of the various analytical methods used for the assay of the drug in pharmaceutical and biological systems has been made. The methods reviewed include identification tests and titrimetric, spectrophotometric, chromatographic, electrochemical, thermal, microscopic, enzymatic, and solid-state techniques. Along with the analytical profile, the stability and degradation of TA, its pharmacology and pharmacokinetics, dosage forms and dose, adverse effects and toxicity, and interactions have been discussed.

Prevalence of spondylosis deformans in the feline spine and correlation with owner-perceived behavioural changes

Objectives: The primary objective was to determine the prevalence, spinal distribution, and association with the signalment of cats suffering from different grades of feline spondylosis deformans (spondylosis). The secondary objective was to document behavioural changes associated with spondylosis by owner observation.

Methods: A cross-sectional study was performed to determine the prevalence of feline spondylosis (group 1). A prospective study was performed to determine the association between radiographic abnormalities of the lumbosacral region (L3-S1) and owner perceived behavioural changes based on a completed questionnaire (group 2). The radiographs were reviewed using a grading system (0–3) for spondylosis.

Results: The prevalence of spondylosis in group 1 was 39.4% (158/402). Cats with spondylosis were significantly older than cats without spondylosis (p <0.001). The thoracic (T) vertebrae T4-T10 were most often affected by spondylosis, but spondylosis was most severe in the T10-S1 vertebrae. In group 2, spondylosis of the lumbosacral region was significantly correlated with owner-reported behavioural changes, such as a decreased willingness to greet people and to being petted, increased aggressiveness, and a poor perceived quality of life (p = 0.037).

Clinical significance: This study found that feline spondylosis is common and that spondylosis of the lumbosacral region may be accompanied by behavioural changes.

Defining local nerve blocks for feline distal pelvic limb surgery: a cadaveric study

Objectives Anatomical and methodological detail is lacking regarding local anesthetic peripheral nerve block techniques for distal pelvic limb surgery in cats. The aim of this study was to develop, describe and test nerve block methods based on cadaveric dissections and dye injections. Methods Ten pairs of feline pelvic limbs (n = 20) were dissected and the tibial nerve (T n.), common fibular (peroneal) nerve (CF n., and its two branches, the superficial fibular [peroneal] nerve [SpF n.] and the deep fibular [peroneal] nerve [DpF n.]) and the saphenous nerve (Sa n.) were identified. Based on these dissections, a 'distal crus block' (selective blockade of the CF n., T n. and Sa n.) and a 'distal pes block' (selective blockade of the SpF n., DpF n., T n. and Sa n.) were developed for surgical procedures in two different regions of the distal pelvic limb. Techniques were tested using new methylene blue (NMB) dye injections in feline pelvic limbs (n = 12). Using a 25 G × 5/8 inch needle and 1 ml syringe, 0.1 ml/kg of NMB dye solution was injected at the site of the CF n., and 0.05 ml/kg was injected at the sites of the SpF n., DpF n., Sa n. and T n. The length and circumference (fully or partially stained) of each stained nerve were measured. Results Positive staining of nerves was observed in 12/12 limbs. The lengths stained for the CF n., DpF n., SpF n., Sa n. and T n. were 27.19 ± 7.13, 20.39 ± 5.57, 22.82 ± 7.13, 30.89 ± 6.99 and 25.16 ± 8.09 mm, respectively. The nerves were fully stained in 12, 12, 10, 11 and 11 out of 12 limbs, respectively. Conclusions and relevance These two, three-point injection methods may be an effective perioperative analgesia technique for feline distal pelvic limb procedures.

Dexmedetomidine-methadone-ketamine versus dexmedetomidine-methadone-alfaxalone for cats undergoing ovariectomy

OBJECTIVE

To compare the duration, quality of anaesthesia and analgesia, and quality of recovery of dexmedetomidine and methadone combined with either ketamine or alfaxalone.

STUDY DESIGN

Randomized, prospective clinical trial.

ANIMALS

A group of 44 healthy client-owned cats presenting for ovariectomy.

METHODS

Cats were randomly assigned to one of the two treatment groups: DAM (n=22), which was administered intramuscularly (IM) dexmedetomidine (15 μg kg^-1), methadone (0.3 mg kg^-1) and alfaxalone (3 mg kg^-1), and DKM (n=22), which was administered IM dexmedetomidine (15 μg kg^-1), methadone (0.3 mg kg^-1) and ketamine (3 mg kg^-1). During anaesthesia, heart rate, respiratory rate and systolic arterial pressure were measured every 5 minutes. Cats that moved or had poor muscle relaxation were administered an additional 1 mg kg^-1 of either alfaxalone (DAM) or ketamine (DKM) intravenously (IV). In cases of increased autonomic responses to surgical stimulation, fentanyl (2 μg kg^-1) was administered IV. At the end of the surgery, atipamezole (75 μg kg^-1) was administered IM, and the times to both sternal recumbency and active interaction were recorded. Quality of recovery was evaluated with a simple descriptive scale. The UNESP-Botucatu multidimensional composite pain scale and a visual analogue scale were used to evaluate postoperative analgesia at the return of active interaction and 1, 2 and 3 hours later.

RESULTS

The additional anaesthesia and rescue fentanyl requirements were similar between groups. The quality of recovery was better in the DAM group than in the DKM group [simple descriptive scale scores: 0 (0-1) and 1 (0-3), respectively; p=0.002]. Postoperative pain scores decreased progressively over time in both groups, with no significant differences (p=0.08) between them.

CONCLUSIONS AND CLINICAL RELEVANCE

Both protocols provided comparable quality of anaesthesia and analgesia and were suitable for cats undergoing ovariectomy. In combination with methadone and dexmedetomidine, alfaxalone and ketamine showed comfortable and reliable recoveries.

Evaluation of an ultrasound-guided technique for axillary brachial plexus blockade in cats

Objectives The aim of this study was to evaluate and refine an ultrasound (US)-guided technique to block the brachial plexus (BP) at the level of the axillary space in live cats. Methods Eight adult experimental cats were enrolled into the study. The animals were sedated and positioned in dorsal recumbency with the limb to be blocked abducted 90º. The US transducer was placed in the axillary region and a non-traumatic peripheral nerve block needle was inserted in-plane with respect to the transducer, medial to the BP up to the level of the axillary artery. Lidocaine 1% (0.4 ml/kg) was injected as the needle was being progressively withdrawn in a caudal-to-cranial direction. The efficacy of the block was confirmed by evaluation of the motor and sensory functions of the blocked forelimb. Motor blockade was assessed observing the position of the blocked leg on standing and walking patterns. Sensory blockade was evaluated by the stimulation of mechanical nociceptors in the dermatomes supplied by the four major sensory nerves of the distal thoracic limb. Results The BP was successfully located by US in all cases. The achieved BP block was complete in six cats (75%) and partial in the remaining two cats (25%). All animals recovered uneventfully from the sedation and the BP blocks. Conclusions and relevance The US-guided block at the axillary space evaluated in this study is a feasible, reproducible and safe technique to block the BP plexus in experimental live cats.

Pilot evaluation of a novel unilateral onychectomy model and efficacy of an extended release buprenorphine product

Background

Non-steroidal anti-inflammatory drugs (NSAIDs), transdermal fentanyl patches, and transmucosal buprenorphine are probably the most commonly used options for providing post-operative analgesia in the early at-home period. However, these require daily administration or are associated with abuse concerns. One of the significant unmet needs in veterinary surgery and pain management is for longer acting opioids for cats to effectively bridge the gap between the in-hospital and at-home recovery periods.

A proof of concept study of an extended release formulation of buprenorphine HCL (ER-Bup) was conducted using objective kinetic measures and a unilateral onychectomy model. Using a blinded, randomized, two period crossover design, four cats were allocated to control (saline) or ER-Bup (0.6 mg/kg, subcutaneously [SC]) treatment groups. All animals underwent a unilateral forelimb onychectomy per period with a washout/recovery period in between. Observational pain scores and kinetic data (using a pressure sensitive walkway [PSW]) were collected prior to (baseline) and at intervals for 72 h following surgery. Symmetry indices were derived for kinetic variables (peak vertical force [PVF]; vertical impulse [VI]) of each forelimb for landing following a jump and for walking. A rescue analgesic protocol was in place. Effect of surgery and treatment were evaluated using a mixed model statistical approach.

Results

No cats required rescue analgesics based on subjective pain score. ER-Bup had a positive influence on subjective pain scores during the 72 h postsurgery (p = 0.0473). PVF and VI of the operated limb were significantly decreased for both landing (p < 0.0001 and p < 0.0001) and walking (p < 0.0001 and p < 0.0001 respectively) compared to control. ER-Bup resulted in significantly decreased asymmetry in limb use during landing (PVF, p < 0.0001; VI, p < 0.0001) and walking (PVF, p = 0.0002, VI, p < 0.0001). The novel use of data collected following a jump from an elevated platform appeared to provide all desired information and was easier to collect than walking data.

Conclusion

This study demonstrates that SC administration of ER-Bup may be an effective analgesic for a 72 h period postoperatively. Furthermore, landing onto a PSW from an elevated perch may be a useful and efficient way to assess analgesics in cats using a unilateral model of limb pain.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-0943-5) contains supplementary material, which is available to authorized users.

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.

Anaesthetic and cardiopulmonary effects of intramuscular morphine, medetomidine and ketamine administered to telemetered cats

The quality and duration of anaesthesia, cardiorespiratory effects and recovery characteristics of a morphine, medetomidine, ketamine (MMK) drug combination were determined in cats. Six healthy, adult female cats were administered 0.2 mg/kg morphine sulphate, 60 μg/kg medetomidine hydrochloride, and 5 mg/kg ketamine hydrochloride intramuscularly. Atipamezole was administered intramuscularly at 120 min after MMK administration. Time to lateral recumbency, intubation, extubation and sternal recumbency were recorded. Cardiorespiratory variables and response to a noxious stimulus were recorded before and at 3 min and 10 min increments after drug administration until sternal recumbency. The time to lateral recumbency and intubation were 1.9±1.2 and 4.3±1.2 min, respectively. Body temperature and haemoglobin saturation with oxygen remained unchanged compared to baseline values throughout anaesthesia. Respiratory rate, tidal volume, minute volume, heart rate, and blood pressure were significantly decreased during anaesthesia compared to baseline values. One cat met criteria for hypotension (systolic blood pressure <90 mmHg). End tidal carbon dioxide increased during anaesthesia compared to baseline values. All but one cat remained non-responsive to noxious stimuli from 3 to 120 min. Time to extubation and sternal recumbency following atipamezole were 2.9±1.1 and 4.7±1.0 min, respectively. MMK drug combination produced excellent short-term anaesthesia and analgesia with minimal cardiopulmonary depression. Anaesthesia lasted for at least 120 min in all but one cat and was effectively reversed by atipamezole.

Postoperative pain control in cats: clinical trials with pre-emptive lidocaine epidural co-administered with morphine or methadone

Objectives The aim of the study was to evaluate the effectiveness of epidural lidocaine in combination with either methadone or morphine for postoperative analgesia in cats undergoing ovariohysterectomy. Methods Under general anesthesia, 24 cats that underwent ovariohysterectomy were randomly allocated into three treatment groups of eight each. Treatment 1 included 2% lidocaine (4.0 mg/kg); treatment 2 included lidocaine and methadone (4.0 mg/kg and 0.3 mg/kg, respectively); and treatment 3 included lidocaine and morphine (4.0 mg/kg and 0.1 mg/kg, respectively). All drugs were injected in a total volume of 0.25 ml/kg via the lumbosacral route in all cats. During the anesthetic and surgical periods, the physiologic variables (respiratory and heart rate, arterial blood pressure and rectal temperature) were measured at intervals of time zero, 10 mins, 20 mins, 30 mins, 60 mins and 120 mins. After cats had recovered from anesthesia, a multidimensional composite pain scale was used to assess postoperative analgesia 2, 4, 8, 12, 18 and 24 h after epidural. Results The time to first rescue analgesic was significantly ( P <0.05) prolonged in cats that received both lidocaine and methadone or lidocaine and morphine treatments compared with those that received lidocaine treatment alone. All cats that received lidocaine treatment alone required rescue analgesic within 2 h of epidural injections. All treatments produced significant cardiovascular and respiratory changes but they were within an acceptable range for healthy animals during the surgical period. Conclusions and relevance The two combinations administered via epidural allowed ovariohysterectomy with sufficient analgesia in cats, and both induced prolonged postoperative analgesia.

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.

Validation of the dorsal approach for the blockade of the femoral nerve using ultrasound and nerve electrolocation in cats

OBJECTIVES

This study was conducted to validate the dorsal approach for femoral nerve (FN) blockade in cats and to verify the efficacy of the sole use of peripheral nerve electrolocation (PNE) or ultrasound (US)-guided technique to achieve the block.

METHODS

This study was carried out in two phases. In phase 1, five adult experimental cats were used to validate the approach. In each cat, one FN was located by US and the accuracy of this location confirmed by PNE. Then, 2 mg/kg lidocaine 2% (diluted in saline to a final volume of 1 ml) was injected around the target nerve and the success of the blockade was evaluated. In phase 2, four adult experimental cats were included in two groups to verify the reliability of this approach to block eight FNs by the sole use of PNE (group 1) or US-guided technique (group 2). Evidence of motor blockade, time required to perform the blockade, onset time and duration of the blockades were determined.

RESULTS

The FN was successfully located by US in all cats enrolled in phase 1, as confirmed by PNE in all cases. The success rate was clinically higher in group 2 (87.5%) than in group 1 (75.0%). The US-guided technique required less time to perform and produced blocks of longer duration. Recovery was uneventful in all cases.

CONCLUSIONS AND RELEVANCE

The combined use of PNE and US-guided technique enabled validation of the dorsal approach for the FN blockade as it provided a successful FN blockade in all cases. The sole use of a US-guided technique may offer some advantages over the use of a sole PNE-guided technique to perform these blocks.

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.

Defining the local nerve blocks for feline distal thoracic limb surgery: a cadaveric study

Objectives

Though controversial, onychectomy remains a commonly performed distal thoracic limb surgical procedure in cats. Peripheral nerve block techniques have been proposed in cats undergoing onychectomy but evidence of efficacy is lacking. Preliminary tests of the described technique using cadavers resulted in incomplete staining of nerves. The aim of this study was to develop nerve block methods based on cadaveric dissections and test these methods with cadaveric dye injections.

Methods

Ten pairs of feline thoracic limbs (n = 20) were dissected and superficial branches of the radial nerve (RSbr nn.), median nerve (M n.), dorsal branch of ulnar nerve (UDbr n.), superficial branch of palmar branch of ulnar nerve (UPbrS n.) and deep branch of palmar branch of ulnar nerve (UPbrDp n.) were identified. Based on these dissections, a four-point block was developed and tested using dye injections in another six pairs of feline thoracic limbs (n = 12). Using a 25 G × 5/8 inch needle and 1 ml syringe, 0.07 ml/kg methylene blue was injected at the site of the RSbr nn., 0.04 ml/kg at the injection site of the UDbr n., 0.08 ml/kg at the injection site of the M n. and UPbrS n., and 0.01 ml/kg at the injection site of the UPbrDp n. The length and circumference of each nerve that was stained was measured.

Results

Positive staining of all nerves was observed in 12/12 limbs. The lengths stained for RSbr nn., M n., UDbr n., UPbrS n. and UPbrDp n. were 34.9 ± 5.3, 26.4 ± 4.8, 29.2 ± 4.0, 39.1 ± 4.3 and 17.5 ± 3.3 mm, respectively. The nerve circumferences stained were 93.8 ± 15.5, 95.8 ± 9.7, 100 ± 0.0, 100 ± 0.0 and 93.8 ± 15.5%, respectively.

Conclusions and relevance

This described four-point injection method may be an effective perioperative analgesia technique for feline distal thoracic limb procedures.

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.

The safety of high-dose buprenorphine administered subcutaneously in cats

The safety of a proprietary formulation of buprenorphine hydrochloride administered subcutaneously (SC) to young cats was investigated in a blinded, randomized study. Four cohorts of eight cats aged approximately 4 months were administered saline, 0.24, 0.72 or 1.20 mg/kg/day buprenorphine SC for nine consecutive days, representing 0×, 1×, 3× and 5× of the intended dose. Cats were monitored daily for evidence of clinical reactions, food and water intake and adverse events (AEs). Physical examinations, clinical pathology, vital signs and electrocardiograms (ECGs) were evaluated at protocol-specified time points. Complete necropsy and histopathologic examinations were performed following humane euthanasia. Four buprenorphine-treated cats experienced AEs during the study, two unrelated and two related to study drug administration. The two cats with AEs considered related to drug administration had clinical signs of hyperactivity, difficulty in handling, disorientation, agitation and dilated pupils in one 0.24 mg/kg/day cat and one 0.72 mg/kg/day cat. All of these clinical signs were observed simultaneously. There were no drug-related effects on survival, injection response, injection site inspections, body weight, food or water consumption, bleeding time, urinalysis, respiration rate, heart rate, ECGs, blood pressures, body temperatures, macroscopic examinations or organ weights. Once daily buprenorphine s.c. injections at doses of 0.24, 0.72 and 1.20 mg/kg/day for 9 consecutive days were well tolerated in young domestic cats.

Effects of surgical wound infiltration with bupivacaine on postoperative analgesia in cats undergoing bilateral mastectomy

The analgesic effect of wound infiltration with bupivacaine was evaluated in cats undergoing bilateral mastectomy. Twenty-one female cats with mammary gland tumors were anesthetized with propofol and oxygen-isoflurane anesthesia following premedication with atropine. In the trial group (Group I; n=11), 30 ml of saline containing 2 mg/kg of bupivacaine was infiltrated topically into the surgical wound right after removal of the mammary glands, whereas only saline solution was infiltrated in the control group (Group II; n=10). At the same time, carprofen (4 mg/kg) was also administered subcutaneously in both groups. Behavioral signs of pain were monitored during the recovery period after general anesthesia. In order to examine the behavioral changes associated with acute pain, a questionnaire was prepared and given to the owners to be completed 4 hr and then 10 hr after the operation. According to the owners' anwers to the questionnaire, a pain score was specified using a "numerical rating scale" for each cat. Although some cats showed mild to moderate pain, the pain score recorded at 4 hr after the operation was significantly lower in Group I (P<0.001). No significant difference was found at 10 hr after the operation between the groups. The incidence of vocalization, aggression and convulsion within 2 hr after the operation was also lower in Group I. In conclusion, wound infiltration with bupivacaine before incisional closure provided reliable analgesia at least 4 hr after bilateral radical mastectomy in cats.

The pharmacokinetics and in vitro/ex vivo cyclooxygenase selectivity of parecoxib and its active metabolite valdecoxib in cats

Parecoxib (PX) is an injectable prodrug of valdecoxib (VX, which is a selective cyclo-oxyganase-2 (COX-2)) inhibitor licensed for humans. The aim of the present study was to evaluate pharmacokinetics and in vitro/ex vivo cyclooxygenase selectivity of PX and VX in cats. In a whole blood in vitro study, PX did not affect either COX enzymes whereas VX revealed a COX-2 selective inhibitory effect in feline whole blood. The IC50 values of VX for COX-2 and COX-1 were 0.45 and 38.6 µM, respectively. Six male cats were treated with 2.5 mg/kg of PX by intramuscular injection. PX was rapidly converted to VX with a relatively short half-life of 0.4 h. VX achieved peak plasma concentration (2.79 ± 1.59 µg/mL) at 7 h following PX injection. The mean residence times for PX and VX were 0.43 ± 0.15 and 5.94 ± 0.88 h, respectively. In the ex vivo study, PX showed a COX-2 inhibition rate of about 70% in samples taken at 1, 2, 4 and 10 h after injection, with a significant difference compared to the control. In contrast, COX-1 was slightly inhibited, ranging from 0.7% to 9.7% of the control inhibition rate without any significant difference for 24 h after PX administration. The preliminary findings of the present research appear promising and encourage further studies to investigate whether PX can be successfully used in feline medicine.

Perceived efficacy of analgesic drug regimens used for koalas (Phascolarctos cinereus) in Australia

Recent publications report that some therapeutic drugs used in koalas (Phascolarctos cinereus) have poor oral absorption and are rapidly eliminated. Therefore, information on both the analgesic drug dosage regimens used to treat koalas in Australia and koala caretakers' perceptions of the efficacy of these drugs to control pain was collected for the purpose of identifying the most popular analgesics to prioritize future analgesic pharmacokinetic studies for this species. A one-page, double-sided questionnaire was distributed both electronically and by mail to Australian koala care facilities such as zoos and wildlife hospitals. Information was received from 13 respondents. Nonsteroidal anti-inflammatory drugs (NSAIDs) were the most frequently used analgesics, followed by full micro- and partial opioid receptor agonists and acetaminophen with or without codeine. The full micro-opioid receptor agonists and acetaminophen with or without codeine were most consistently considered efficacious, with wider variation in perceived efficacy of the NSAIDs. Analgesic drug combinations were generally thought efficacious.

Pharmacokinetic profiles of the analgesic drug flupirtine in cats

Flupirtine (FLU) is a non-opioid analgesic drug with no antipyretic or antiphlogistic effects, used in the treatment of a wide range of pain states in human beings. There is a substantial body of evidence on the efficacy of FLU in humans but this is inadequate to recommend its off-label use in veterinary clinical practice. The aim of this study was to evaluate the pharmacokinetic profiles of FLU after IV and PO administration in healthy cats. Six mixed breed adult cats were randomly assigned to two treatment groups using an open, single-dose, two-treatment, two-phase, paired, cross-over design (2 × 2 Latin-square). Group 1 (n  =  3) received a single dose of 5 mg/kg of FLU injected IV into the jugular vein. Group 2 (n  =  3) received the same dose via PO route. The wash out period was 1 week. Blood samples (1 mL) were collected at assigned times and plasma was then analysed by a validated HPLC method. No adverse effects at the point of injection and no behavioural changes or alterations in health parameters were observed in the animals during or after the study (up to 7 days after the full study). After IV administration, FLU was detectable in plasma up to 36 h. After PO administration, FLU plasma concentrations were lower than those following IV administration, but they were detectable over the same time range. The terminal part of both mean pharmacokinetic curves showed a similar trend of elimination. The oral bioavailability was approximately 40%. This is the first study of FLU in an animal species of veterinary interest and it could pave the way for the use of this active ingredient in the veterinary field.

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.