The effect of neuraxial morphine on postoperative pain in dogs after extrahepatic portosystemic shunt attenuation.

OBJECTIVE: To investigate the analgesic effect of epidural morphine after surgical extrahepatic portosystemic shunt (EHPSS) attenuation. STUDY DESIGN: Randomized clinical trial. ANIMALS: A total of 20 dogs with a congenital EHPSS. METHODS: Dogs were randomly allocated to be given either a single epidural dose of 0.2 mg kg-1 preservative-free morphine (group M) or not (group C) before surgery. All dogs were administered 0.3 mg kg-1 methadone intravenously (IV) as preanaesthetic medication. Pain scores were determined every 2 hours for the first 24 hours postoperatively using the short-form Glasgow Composite Measure Pain Scale (GCMPS-SF). Dogs with a GCMPS-SF pain score >4/20 or >5/24 received 0.1 mg kg-1 methadone IV as rescue analgesia and were reassessed 30 minutes later. If more than three doses of methadone were administered in a 2 hour period, alternative pain relief was provided and a treatment failure recorded. The GCMPS-SF pain scores and number of rescue analgesia injections were analysed over 24 hours. The last observation carried forward method was applied in case of treatment failure. Food consumption and time to first urination were recorded. Data were analysed using a Mann-Whitney U test and presented as median (minimum-maximum range), with significance set at p < 0.05. RESULTS: Group M showed lower GCMPS-SF pain scores [15 (11-41) versus 31 (11-86); p = 0.023] and lower postoperative methadone requirements [0 (0-0.2) versus 0.25 (0-0.5) mg kg-1; p = 0.029] than group C. There were three treatment failures in group C only. Food consumption and time to first urination did not differ between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Epidural morphine reduced the requirement for postoperative analgesia in this study population.

Effect of predosing versus slow administration of propofol on the dose required for anaesthetic induction and on physiologic variables in healthy dogs.

OBJECTIVE: To investigate the effects of the timing of propofol administration on the dose required for induction of anaesthesia and commonly measured physiological effects. STUDY DESIGN: Randomized, investigator-blinded clinical study. ANIMALS: A group of 32 healthy dogs aged 6-144 months and weighing 3.5-47.2 kg. METHODS: Premedication was intramuscular acepromazine (0.025 mg kg-1) and methadone (0.25 mg kg-1). After 30 minutes, one of three treatments was administered to the dogs: propofol (0.5 mg kg-1; group PP), an equivalent volume of saline (group CP) or a propofol infusion (1.3 mg kg-1 minute-1; group SI). Two minutes later, a propofol infusion (4 mg kg-1 minute-1) was started in PP and CP, whereas the propofol infusion was continued in SI. At this stage an investigator, blinded to the group assignments, entered the room and decided when each animal was ready for intubation and stopped the propofol infusion. After intubation, management of anaesthesia was standardized. Pulse rate (PR), respiratory rate (fR) and mean arterial pressure (MAP) were recorded before induction, 2 minutes later and 0, 2 and 5 minutes after intubation. Apnoea >30 seconds was recorded and managed. Sedation, quality of induction and endotracheal intubation were scored using simple descriptive scales. Data are presented as mean±standard deviation. RESULTS: Propofol dose requirement was lower in SI (3.5±1.2 mg kg-1) compared with PP and CP (5.0±0.9 and 4.8±0.6 mg kg-1; p=0.002 and 0.012), respectively. No statistically significant differences were found among groups for PR, fR, MAP or incidence of apnoea. Sedation score and quality of induction were similar among groups. CONCLUSIONS: Slow administration of propofol reduced the anaesthetic induction dose required compared with predosing and control groups. Effects on PR, fR, MAP and apnoea were similar among groups. CLINICAL RELEVANCE: Slower injection of propofol reduces the dose required for induction of anaesthesia.

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

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

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

RATIONALE: Recent recognition of the need to improve pain management in cats has led to the investigation of the pharmacokinetics and efficacy of opioid analgesic drugs in this species. The results of these studies may be difficult to interpret because the effect of these drugs varies with dose, route of administration and the method used to assess them. As equipotency of different opioids is not known, it is hard to compare their effects. Animals do not verbalise the pain they feel and, in cats, it may be more difficult to recognise signs of pain in comparison with other species such as dogs. AIM: This article reviews the use of opioid analgesics in cats. It must be remembered that not all drugs are licensed for use in cats, and that marketing authorisations vary between different countries.

Pharmacokinetic-pharmacodynamic modelling of intravenous buprenorphine in conscious horses.

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

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

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

Thermal and mechanical nociceptive threshold testing in horses: a review.

OBJECTIVE: This review evaluates the thermal and mechanical nociceptive threshold testing techniques that have been used in horses and discusses them with reference to their applications, limitations and the factors which can influence both the testing procedure itself and the animal's responses. Methods to optimise the reliability and repeatability of the testing procedures are suggested and the potential clinical applications discussed. DATABASES USED: Web of Science and Medline. CONCLUSIONS: Thermal and mechanical nociceptive threshold testing techniques have valuable roles in both the identification of altered nociceptive function and the pre-clinical evaluation of analgesics in horses.

Validity and client use of information from the World Wide Web regarding veterinary anesthesia in dogs.

OBJECTIVE: To determine the validity of the information on the World Wide Web concerning veterinary anesthesia in dogs and to determine the methods dog owners use to obtain that information. DESIGN: Web-based search and client survey. SUBJECTS: 73 Web sites and 92 clients. PROCEDURES: Web sites were scored on a 5-point scale for completeness and accuracy of information about veterinary anesthesia by 3 board-certified anesthesiologists. A search for anesthetic information regarding 49 specific breeds of dogs was also performed. A survey was distributed to the clients who visited the University of Georgia Veterinary Teaching Hospital during a 4-month period to solicit data about sources used by clients to obtain veterinary medical information and the manner in which information obtained from Web sites was used. RESULTS: The general search identified 73 Web sites that included information on veterinary anesthesia; these sites received a mean score of 3.4 for accuracy and 2.5 for completeness. Of 178 Web sites identified through the breed-specific search, 57 (32%) indicated that a particular breed was sensitive to anesthesia. Of 83 usable, completed surveys, 72 (87%) indicated the client used the Web for veterinary medical information. Fifteen clients (18%) indicated they believed their animal was sensitive to anesthesia because of its breed. CONCLUSIONS AND CLINICAL RELEVANCE: Information available on the internet regarding anesthesia in dogs is generally not complete and may be misleading with respect to risks to specific breeds. Consequently, veterinarians should appropriately educate clients regarding anesthetic risk to their particular dog.

Morphine administration in horses anaesthetized for upper respiratory tract surgery.

OBJECTIVE: To determine the effect of morphine administration on commonly monitored cardio-respiratory variables and recovery quality in horses undergoing anaesthesia and surgery. STUDY DESIGN: Prospective, randomized clinical study. ANIMALS: Thirty-eight thoroughbred horses, 32 geldings and six mares, 3-13 years old, weighing 411-600 kg. MATERIALS AND METHODS: A standard anaesthetic technique was used. Twenty minutes after induction of anaesthesia horses received 0.1 mg kg(-1) (0.1 m) or 0.2 mg kg(-1) (0.2 m) morphine by intravenous injection. A control group did not receive morphine. Heart rate, respiratory rate (fr), mean arterial pressure (MAP) and blood gases were measured before morphine administration and every 10 minutes thereafter. Horses were positioned for 35 minutes in right lateral recumbency for tension palatoplasty by cautery and were then moved into dorsal recumbency for additional intraluminal surgery comprising one or more of aryepiglottic fold resection, sub-epiglottal mucosal resection, ventriculectomy and cordectomy. A subjective recovery score from 0 (worst) to 5 (best) was assigned by a single observer who was unaware of treatment group. Two-way repeated measures anova, one-way anova, Kruskal-Wallis test, Mann-Whitney test, Pearson and Spearman correlation coefficients, and chi-squared tests were used to analyse the data where appropriate. RESULTS: Arterial partial pressure of oxygen (PaO(2)) decreased significantly over time and was significantly lower in horses that received morphine. One horse in the control group and two horses in each of the morphine groups had a PaO(2) <13 kPa. No other significant cardiopulmonary effects were detected. Recovery scores [median (range)] were higher in morphine recipients: 4 (2-5) in 0.1 m, 4 (3-5) in 0.2 m compared with 3 (2-4) in the control group. CONCLUSIONS AND CLINICAL RELEVANCE: The lower PaO(2) in morphine recipients did not appear to be of clinical significance in healthy horses because the number of horses with a low PaO(2) was similar between groups. The quality of recovery was significantly better in morphine recipients. These results indicate that morphine may be considered for use in clinical cases although further work is required to assess the analgesic properties of the drug in this species.