Therapeutic efficacy and pharmacokinetics of liposomal-cannabidiol injection: a pilot clinical study in dogs with naturally-occurring osteoarthritis.

Introduction: Osteoarthritis is a common disease in dogs resulting in chronic pain and decreased wellbeing. Common analgesics such as non-steroidal anti-inflammatories may fail to control pain and can produce major adverse effects. Study objectives were to evaluate pharmacokinetics, therapeutic efficacy, and safety of subcutaneous liposomal-cannabidiol (CBD) as an additional analgesic therapy in dogs suffering from naturally-occurring osteoarthritis. Methods: Six such dogs were recruited following ethics approval and owner consent. Dogs were administered a single subcutaneous injection of 5 mg/kg liposomal-CBD. Plasma concentrations of CBD, blood work, activity monitoring collar data, wellbeing questionnaire (owners) and pain scoring (veterinarian) were performed at baseline and monitored up to six weeks following intervention. Data overtime were compared with baseline using linear-regression mixed-effects. P-value was set at 0.05. Results: CBD plasma concentrations were observed for 6 weeks; median (range) peak plasma concentration (Cmax) was 45.2 (17.8-72.5) ng/mL, time to Cmax was 4 (2-14) days and half-life was 12.4 (7.7-42.6) days. Median (range) collar activity score was significantly increased on weeks 5-6; from 29 (17-34) to 34 (21-38). Scores of wellbeing and pain evaluations were significantly improved at 2-3 weeks; from 69 (52-78) to 53.5 (41-68), and from 7.5 (6-8) to 5.5 (5-7), respectively. The main adverse effect was minor local swelling for several days in 5/6 dogs. Conclusion: Liposomal-CBD administered subcutaneously produced detectable CBD plasma concentrations for 6 weeks with minimal side effects and demonstrated reduced pain and increased wellbeing as part of multimodal pain management in dogs suffering from osteoarthritis. Further placebo-controlled studies are of interest.

Improving rat welfare through the development of a peribulbar anaesthesia technique for ophthalmic procedures: A preliminary study.

Rats are a commonly used animal model for the study of the pathogenesis and novel treatments of glaucoma, which is induced experimentally using invasive, painful procedures. Peribulbar anaesthesia (PBA) is frequently used in people and domestic animals prior to ophthalmic surgeries to provide excellent perioperative analgesia. Our goal was to develop a PBA technique adapted to rat anatomy, improving the welfare of animals used as a model for glaucoma. Eighteen rat cadavers (n = 36 eyes) were used to establish the optimal needle insertion location. Five injection techniques using 0.1 mL/100 g lidocaine 2% and a contrast agent (1:1 volume ratio) were compared via computed tomography (CT). CT images were scored for injectate distribution at four locations: extraconal, intraconal, around the optic nerve and at the orbital fissure (scale 0-8, where 0 = none and 8 = excellent). Median scores using the dorso-medial-75° (5; range 2-6) and medial-canthus (4.5; range 2-8) injection techniques were not different from the dorso-medial-45° (4; range 3-6) technique and were higher (better distribution) compared with mid-ventral (3; range 2-5) and ventro-lateral (2; range 1-3) techniques. The two superior techniques were used in two experimental rats (n = 4 eyes) to determine the volume of bupivacaine 0.5% necessary to affect corneal touch threshold (CTT) and periocular skin sensitivity (PSS). A volume of 0.05 mL/100 g decreased CTT and PSS for several hours, while a larger volume produced excessively long effects. Dorso-medial-75° or medial-canthus PBA using 0.05 mL/100 g bupivacaine are likely to provide ocular and periocular analgesia in rats, with minor transient adverse effects.

Anesthesia, pain management and surgical approach of ovariectomy or orchiectomy in six Egyptian fruit bats (Rousettus aegyptiacus): A case report.

The purpose of this report is to describe the anesthetic and analgesic management and the surgical procedures of gonadectomy in six (four females and two males) healthy adult Egyptian fruit bats (Rousettus aegyptiacus). Bats were anesthetized with a combination of alfaxalone, midazolam, and morphine administered subcutaneously. Incisional line infiltration using bupivacaine was administered in all bats, and additional bilateral intratesticular injection was administered in the males. Ovariectomy was performed via a dorsal approach, by bilateral midline skin incisions at the paralumbar fossa level. Orchiectomy was performed via a ventral approach, by bilateral midline incisions of scrotal skin above the testes. Following surgery, all bats were administered flumazenil for midazolam reversal, and meloxicam for postoperative analgesia, subcutaneously. All bats recovered from anesthesia uneventfully. Bats were monitored for complications up to 10 days following surgery, when skin sutures were removed. No morbidities or mortalities occurred during this period in any of the bats. In conclusion, ventral approach orchiectomy and dorsal approach ovariectomy using the injectable combination alfaxalone-midazolam-morphine in conjunction with local anesthesia and meloxicam are feasible procedures in Egyptian fruit bats and can be performed with relative ease. However, further studies using these techniques in a larger group of bats should be performed to establish their safety.

Effect of anesthetic induction with propofol, alfaxalone or ketamine on intraocular pressure in cats: a randomized masked clinical investigation.

OBJECTIVE: To compare the effect of propofol, alfaxalone and ketamine on intraocular pressure (IOP) in cats. STUDY DESIGN: Prospective, masked, randomized clinical trial. ANIMALS: A total of 43 ophthalmologically normal cats scheduled to undergo general anesthesia for various procedures. METHODS: Following baseline IOP measurements using applanation tonometry, anesthesia was induced with propofol (n = 15), alfaxalone (n = 14) or ketamine (n = 14) administered intravenously to effect. Then, midazolam (0.3 mg kg-1) was administered intravenously and endotracheal intubation was performed without application of topical anesthesia. The IOP was measured following each intervention. Data was analyzed using one-way anova and repeated-measures mixed design with post hoc analysis. A p-value <0.05 was considered significant. RESULTS: Mean ± standard error IOP at baseline was not different among groups (propofol, 18 ± 0.6; alfaxalone, 18 ± 0.7; ketamine, 17 ± 0.5 mmHg). Following induction of anesthesia, IOP increased significantly compared with baseline in the propofol (20 ± 0.7 mmHg), but not in the alfaxalone (19 ± 0.8 mmHg) or ketamine (16 ± 0.7 mmHg) groups. Midazolam administration resulted in significant decrease from the previous measurement in the alfaxalone group (16 ± 0.7 mmHg), but not in the propofol group (19 ± 0.7 mmHg) or the ketamine (16 ± 0.8 mmHg) group. A further decrease was measured after intubation in the alfaxalone group (15 ± 0.9 mmHg). CONCLUSIONS AND CLINICAL RELEVANCE: Propofol should be used with caution in cats predisposed to perforation or glaucoma, as any increase in IOP should be avoided.

A Case Report of Subcutaneously Injected Liposomal Cannabidiol Formulation Used as a Compassion Therapy for Pain Management in a Dog.

A 14-year-old intact mixed breed dog (26 kg) was submitted for a novel cannabidiol (CBD) analgesic treatment. The dog was cachectic and had a testicular neoplasia, hip and elbow osteoarthritis and severe cervical pain. Analgesic treatment included canine osteoarthritic supplement, robencoxib and gabapentin. An additional liposomal CBD injectable formulation at 5 mg/kg was administered subcutaneously between the shoulder blades. The dog was monitored using an activity monitoring collar (PetPace), owner wellbeing questionnaire (Canine Brief Pain Inventory; CBPI), pain interactive visual analog scale (iVAS), blood work and CBD plasma concentrations. A week from the injection and up to 3 weeks afterwards the dog had improved CBPI and iVAS pain scores, and increased collar activity scores. CBD was quantified in plasma for 28 days. Due to disease progression, further difficulty to rise and walk, and relapse to pain after 3 weeks, the owners requested a second liposomal CBD injection, which was performed 4 weeks following the first injection using 3 mg/kg dose. Two days later, the dog was found dead in the yard under direct sun, while environmental temperature was 37°C. Major findings on necropsy revealed evidence of heat stroke and severe cervical disc protrusion with spinal hematoma, none related to liposomal CBD. In conclusion, subcutaneous liposomal CBD produced quantifiable CBD plasma concentrations for 28 days and may be an effective additional treatment as part of multimodal pain management in dogs.

Effect of intravenous butorphanol infusion on the minimum alveolar concentration of isoflurane in cats.

OBJECTIVE: To determine the effect of butorphanol, administered by intravenous (IV) infusion, on the minimum alveolar concentration of isoflurane (MACISO) in cats and to examine the dosage dependence of this effect. STUDY DESIGN: Randomized, placebo-controlled, crossover experimental study. ANIMALS: A group of six healthy adult male neutered cats. METHODS: Cats were anesthetized with isoflurane in oxygen. A venous catheter was placed for fluid and drug administration, and an arterial catheter was placed for measurement of arterial pressure and blood sampling. Four treatments were administered at random with at least 2 week interval between treatments: saline (control), butorphanol low dosage (treatment LD; 0.25 mg kg-1 IV bolus followed by 85 µg kg-1 minute-1 for 20 minutes, then 43 µg kg-1 minute-1 for 40 minutes, then 19 µg kg-1 minute-1), medium dosage (treatment MD, double the dosages in LD) and high dosage (treatment HD, quadruple the dosages in LD). MACISO was determined in duplicate using the bracketing technique and tail clamping. Pulse rate, arterial pressure, hemoglobin oxygen saturation, end-tidal partial pressure of carbon dioxide and arterial blood gas and pH were measured. RESULTS: Butorphanol reduced MACISO in a dosage-dependent manner, by 23 ± 8%, 37 ± 12% and 68 ± 10% (mean ± standard deviation) in treatments LD, MD and HD, respectively. The main cardiopulmonary effect observed was a decrease in pulse rate, significant in treatment HD compared with control. CONCLUSIONS AND CLINICAL RELEVANCE: Butorphanol caused a dosage-dependent MACISO reduction in cats. IV infusion of butorphanol may be of interest for partial IV anesthesia in cats.

Comparison of three regional anaesthetic techniques for infraorbital or maxillary nerve block in cats: a cadaveric study.

OBJECTIVES: The maxillary nerve courses very close to the globe, rendering cats - with their large eyes - at risk of globe penetration during infraorbital or maxillary nerve blocks. Therefore, the goals of the study were to compare the distribution and potential complications of three infraorbital or maxillary regional injection techniques. METHODS: Twenty-three bilateral maxillae of cat cadavers were used in a randomised blinded trial. Each maxilla was injected with a 0.2 ml 1:1 mixture of lidocaine 2% and a contrast medium by one of three injection techniques: infraorbital foramen (IOF; n = 14); infraorbital canal (IOC; n = 16); or maxillary foramen (MF; transpalpebral approach; n = 16) using a 25 G 1.6 cm needle. CT imaging of each cadaver head was performed before and after injections. A radiologist scored injectate distribution (none [0], mild [1], moderate [2], large [3]) in four locations: rostral, central and caudal IOC, and at the MF, for which the distribution side was also determined. Comparisons were performed with ordinal logistic mixed effects (P <0.05). RESULTS: The median (range) total distribution score of the IOC and MF technique were significantly higher compared with the IOF technique (6.5 [4-12], 4 [2-8] and 0 [0-10], respectively). The total IOC score was also significantly higher compared with the MF technique. Injectate distribution at the MF was significantly more central following IOC injection compared with MF injection, which distributed centrolaterally. None of the techniques resulted in intraocular injection. CONCLUSIONS AND RELEVANCE: The IOC and MF techniques produced a satisfactory spread of the mixture that could result in effective maxillary anaesthesia in cats. Further studies are required to determine the effectiveness and safety of these techniques.

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.

Pharmacokinetics of butorphanol in male neutered cats anesthetized with isoflurane.

This study characterized the pharmacokinetics of butorphanol in cats anesthetized with isoflurane. Six young healthy male neutered cats were used. Cats were anesthetized with isoflurane in oxygen. Catheters were placed in a jugular vein for blood sampling and in a medial saphenous vein for butorphanol and lactated Ringer's solution administration. Butorphanol tartrate (1 mg/kg over 5 min) was administered intravenously. Blood samples were collected prior to butorphanol administration and at various times up to 365 min following administration. Plasma butorphanol concentration was measured using liquid chromatography/tandem mass spectrometry. Compartment models were fitted to the time-concentration data using nonlinear mixed effect modeling. A three-compartment model best fitted the data. Typical value (% interindividual variability) for the three volumes of distribution, the metabolic clearance, and the two distribution clearances were 230 (72), 1095 (not estimated), and 2596 (not estimated) ml/kg, and 18.4 (72), 169.6 (52), and 55.0 (43), respectively. Pharmacokinetic simulation suggested that a loading dose (µg/kg) calculated as 0.287 × target plasma concentration in ng/ml (CT ) followed by intravenous infusions (µg/kg/min) of 0.098 × CT for 20 min, 0.049 × CT for 40 min, and 0.022 × CT thereafter would rapidly achieve and maintain CT  ± 10% for up to 6.5 h.

Evaluation of alfaxalone and midazolam with or without flumazenil reversal in Egyptian fruit bats (Rousettus aegyptiacus).

OBJECTIVES: To evaluate alfaxalone-midazolam anesthesia in Egyptian fruit bats (Rousettus aegyptiacus) and the effect of flumazenil administration on recovery time and quality. STUDY DESIGN: Randomized, blinded, crossover and controlled, experimental trial. ANIMALS: A total of 10 male Egyptian fruit bats. METHODS: Bats were anesthetized with alfaxalone (15 mg kg-1) and midazolam (2 mg kg-1) administered subcutaneously. During anesthesia, vital signs, muscle tone and reflexes were monitored every 10 minutes. Flumazenil (0.3 mg kg-1) or saline at an equal volume was administered subcutaneously 60 minutes after anesthetic administration. Time to induction, time to first movement and recovery time (flying) were measured. Quality of induction, anesthesia and recovery were assessed on a 1-3 scale (1, poor; 2, good; 3, excellent). RESULTS: Time to induction was 4.2 ± 1.9 minutes (mean ± standard deviation), with median quality score of 2 (range, 1-3). Anesthesia quality score was 3 (1-3). During anesthesia, heart rate and respiratory frequency decreased significantly and penis relaxation, indicating muscle tone, increased significantly. Administration of flumazenil significantly reduced mean recovery time compared with saline (10 ± 5 versus 45 ± 17 minutes, respectively), and significantly improved the quality of recovery [2.5 (2-3) versus 1 (1-2), respectively]. CONCLUSIONS AND CLINICAL RELEVANCE: Alfaxalone-midazolam anesthesia resulted in good induction, muscle relaxation and sufficient anesthesia to perform routine diagnostic and therapeutic procedures for approximately 40 minutes. Reversal of midazolam with flumazenil is recommended, resulting in quicker and better recovery.

MEDETOMIDINE-KETAMINE-MIDAZOLAM VERSUS MEDETOMIDINE-KETAMINE-BUTORPHANOL FOR IMMOBILIZATION OF RED KANGAROOS (OSPHRANTER RUFUS).

The objectives of this clinical study were to compare the effectiveness and safety of medetomidine-ketamine-midazolam (MKM) versus medetomidine-ketamine-butorphanol (MKB) for immobilization of captive red kangaroos (Osphranter rufus). Twenty red kangaroos were randomly immobilized for routine treatments using intramuscular injection of MKM (0.065 ± 0.004, 2.2 ± 0.3, and 0.12 ± 0.04 mg/kg, respectively) or MKB (0.070 ± 0.015, 2.3 ± 0.5, and 0.23 ± 0.05 mg/kg, respectively) (n = 10/group). Induction, immobilization, and recovery times were recorded; vital signs monitored; and quality of induction, immobilization, and recovery scored using a single-blinded design. Oxygen was not supplemented. For reversal, atipamezole at five times the medetomidine dosage was administered intramuscularly (both groups), and flumazenil (0.020 ± 0.003 mg/kg; MKM) or naltrexone (0.23 ± 0.05 mg/kg; MKB) were administered intravenously. Induction time was significantly shorter in the MKB group versus the MKM group (7:26 ± 04:22 and 11:54 ± 04:50 minutes, respectively). Induction quality in both groups was rated "excellent" and immobilization quality was "excellent" in MKM and "very good" in MKB. Heart rate was significantly lower and hemoglobin oxygen saturation (SpO2) was significantly higher in the MKM versus the MKB group. However, SpO2 < 90% occurred with both protocols. Following antagonists administration, recovery time and quality were 17:40 ± 08:33 minutes and "very good" in the MKM group, and 14:28 ± 05:27 minutes and "excellent" in the MKB group, respectively. Both protocols provided smooth induction, good immobilization, and generally quick recovery. MKB is recommended for shorter induction time. Oxygen supplementation should be available with both protocols.

Analgesic effects of intraorbital insertion of an absorbable gelatin hemostatic sponge soaked with 1% ropivacaine solution following enucleation in dogs.

OBJECTIVE: To evaluate analgesic effects and complications associated with intraorbital insertion of an absorbable gelatin hemostatic sponge (AGHS) soaked with 1% ropivacaine solution following enucleation in dogs. ANIMALS: 20 client-owned dogs undergoing enucleation. PROCEDURES: Dogs were randomly assigned to receive an AGHS soaked with 1% ropivacaine solution (n = 10) or saline (0.9% NaCl) solution (control group; 10) inserted intraorbitally prior to skin closure following enucleation. Carprofen (2 mg/kg [0.9 mg/lb]) was administered SC once after orotracheal extubation and then PO twice a day for 5 days. During the postoperative recovery period, apparent pain level was scored at various points with a modified short-form Glasgow Composite Pain Scale (score range, 0 to 19), and methadone was administered for rescue analgesia if any score was ≥ 5. After dogs returned home, owners recorded their behavior and apparent pain level for the first 3 days following enucleation. RESULTS: At extubation, the median (range) pain score was significantly higher in the control group (8 [2 to 14]) versus the ropivacaine group (3 [1 to 7]). A greater proportion of dogs in the control group received methadone (7/10 vs 1/10) and had crying or attention-seeking behavior on the first day following enucleation (7/10 vs 1/10). No complications were observed in either group. CONCLUSIONS AND CLINICAL RELEVANCE: Addition of intraorbital insertion of a ropivacaine-soaked AGHS to the analgesic protocol for dogs undergoing enucleation provided better analgesia than was achieved without this treatment as measured immediately and the first day after surgery, with no noted adverse effects.

Immobilization of captive Persian fallow deer (Dama dama mesopotamica) using medetomidine-ketamine or medetomidine-midazolam.

OBJECTIVE: To establish and compare the effectiveness of two medetomidine-based immobilization protocols in Persian fallow deer (Dama dama mesopotamica). STUDY DESIGN: Prospective, randomized, blinded clinical study. ANIMALS: A group of 31 captive Persian fallow deer. METHODS: Deer scheduled for translocation were immobilized with a combination of medetomidine (76 ± 11 µg kg-1) and ketamine (1.0 ± 0.2 mg kg-1) (MK; n = 15) or medetomidine (77 ± 11 µg kg-1) and midazolam (0.10 ± 0.01 mg kg-1) (MM; n = 16) administered intramuscularly. An observer unaware of group assignments recorded times to immobilization and recovery, monitored physiologic variables and scored the quality of induction, immobilization and recovery (scale 1-5: 1, poor; 5, excellent). Atipamezole was administered for reversal. Data analysis was performed using the t test, the Mann-Whitney U test, the chi-square test and the Fisher's exact test. Significance was set at p < 0.05. RESULTS: Data are presented as mean ± standard deviation or median (range). Time to induce immobilization was 9 ± 4 and 10 ± 4 minutes in the MK and MM groups, respectively. Immobilization quality score was 5 (1-5) following both combinations. Hemoglobin oxygen saturation (SpO2) was significantly lower in the MK (80 ± 8%) than in the MM group (87 ± 8%) although respiratory frequency did not differ between MK and MM (11 ± 5 and 10 ± 2 breaths minute-1, respectively). Recovery times were 13 ± 6 (MK) and 14 ± 7 minutes (MM) and did not differ between groups. No morbidities or mortalities were recorded during 1 month after immobilization. CONCLUSIONS AND CLINICAL RELEVANCE: The MK and MM combinations produced sufficient immobilization in captive Persian fallow deer for short nonpainful procedures. Based on the SpO2 values, the MM combination may be associated with less respiratory depression; nevertheless, both combinations may result in a decrease in SpO2.

Retrobulbar vs peribulbar regional anesthesia techniques using bupivacaine in dogs.

OBJECTIVE: To compare the effectiveness of retrobulbar anesthesia (RBA) and peribulbar anesthesia (PBA) in dogs. ANIMAL STUDIED: Six adult mixed-breed dogs (18-24 kg). PROCEDURES: In a randomized, masked, crossover trial with a 10-day washout period, each dog was sedated with intravenously administered dexmedetomidine and administered 0.5% bupivacaine:iopamidol (4:1) as RBA (2 mL via a ventrolateral site) or PBA (5 mL divided equally between ventrolateral and dorsomedial sites). The contralateral eye acted as control. Injectate distribution was evaluated by computed tomography. Following intramuscularly administered atipamezole, corneal and periocular skin sensation, intraocular pressure (IOP), and ocular reflexes, and appearance were evaluated for 24 hours. Comparisons were performed with mixed-effects linear regression (IOP) or the exact Wilcoxon signed rank test (scores). Significance was set at P ≤ .05. RESULTS: Injectate distribution was intraconal in 2/6 RBA- and 4/6 PBA-injected eyes. Eyes undergoing PBA had significantly reduced lateral, ventral, and dorsal periocular skin sensation for 2-3 hours, and significantly reduced corneal sensitivity for 4 hours, relative to control eyes. Chemosis and exophthalmos occurred in 33%-40% of eyes undergoing RBA and 83%-100% eyes undergoing PBA but resolved within 14 hours. Anterior uveitis developed in 2/6 and 1/6 eyes of RBA and PBA, respectively, of them corneal ulcer developed in one eye of each treatment. Both resolved 1-3 days following medical treatment. CONCLUSIONS: Peribulbar injection produced notable anesthesia more reliably than did retrobulbar injection. Both techniques may produce adverse effects, although the uveitis/ulcer could have resulted from the contrast agent used.

A review of ophthalmic local and regional anesthesia in dogs and cats.

OBJECTIVE: Orbital and globe surgeries are commonly performed in companion animals and are considered to cause moderate to severe pain. Regional anesthesia techniques can provide complete sensory blockade, analgesia for painful procedures and improve surgical conditions. The purpose of this review is to summarize local and regional anesthesia techniques for ophthalmic surgery in dogs and cats with emphasis on veterinary publications in the past 12 years. DATABASES USED: Review of the literature was conducted using PubMed and Google Scholar. The search terms were 'ophthalmic regional anesthesia', 'retrobulbar anesthesia', 'peribulbar anesthesia', 'sub-Tenon's anesthesia', 'intracameral anesthesia', 'eye infiltration', 'dogs' and 'cats'. Further studies and reports were obtained from the reference lists of the retrieved papers. In addition, related veterinary anatomy, ophthalmology and regional anesthesia books were reviewed. CONCLUSIONS: Reported techniques include regional techniques such as retrobulbar anesthesia, peribulbar anesthesia and sub-Tenon's anesthesia, and local techniques such as eyelid and conjunctival infiltration, intracameral anesthesia, splash block and insertion of intraorbital absorbable gelatin sponge infused with local anesthetic. Administration guidelines, indications and contraindications, and complications of each technique are discussed. Regional anesthesia techniques were reported to be effective during ophthalmic surgeries and are recommended for use as part of the anesthetic regimen and pain management in animals. However, the veterinary literature is still lacking controlled clinical trials and adverse events reports; therefore, there is very little evidence for choosing one technique over another.

Description of a regional anaesthesia technique for the dorsal cranium in the dog: a cadaveric study.

OBJECTIVE: To identify landmarks and to describe a technique for nerve blockade of the dorsal cranium in dogs. STUDY DESIGN: Anatomic cadaveric study. ANIMALS: A total of 39 dog cadavers, weighing 18.0 ± 9.7 kg (mean ± standard deviation). METHODS: The study was performed in three parts. In the initial part, cadavers were dissected to determine the location of the frontal, zygomaticotemporal, and major occipital nerves, and to identify prominent landmarks for their blockade. In the second part, one technique was developed to block each of the frontal and zygomaticotemporal nerves, and two techniques, rostral and caudal, were developed to block the major occipital nerve. Injection solution was 0.05% methylene blue in 0.5% bupivacaine. In the third part, cadavers were used to test the techniques developed in the second part with 0.04 mL kg-1 of the same injectate administered at each site (maximal volume 0.5 mL per site). The length of nerve stained was measured, with a length ≥6 mm considered successful. Confidence intervals were calculated using Fisher's exact test. RESULTS: Success rates (95% confidence interval) for the frontal, zygomaticotemporal, and rostral and caudal locations for the major occipital nerve were 94% (80-99%), 91% (76-98%), 74% (58-86%) and 77% (59-89%), respectively. With a combination of both locations, the success rate for the major occipital nerve was 100% (90-100%). CONCLUSION AND CLINICAL RELEVANCE: This study describes a simple regional anaesthesia technique using palpable anatomical landmarks that may provide analgesia for dogs undergoing craniotomy.

Evaluation of injectable anaesthesia with five medetomidine-midazolam based combinations in Egyptian fruit bats ( Rousettus aegyptiacus).

Egyptian fruit bats are increasingly used as model animals in neuroscience research. Our aim was to characterize suitable injectable anaesthesia for this species, possibly replacing inhalant anaesthesia, thus minimizing occupational health hazards. Eight bats were randomly assigned by a crossover design for subcutaneously administered combinations of medetomidine-midazolam with: saline (MM-Sal), ketamine (MM-Ket), fentanyl (MM-Fen), morphine (MM-Mor), or butorphanol (MM-But). The anaesthetic depth and vital signs were monitored at baseline and every 10 min until bats recovered. If after 180 min the bats did not recover, atipamezole was administered. Mean induction times were 7-11.5 min with all combinations. Twitching during induction was common. All combinations produced anaesthesia, with significantly decreased heart rate (from 400 to 200 bpm) and respiratory rate (from 120-140 to 36-65 rpm). Arrhythmia and irregular breathing patterns occurred. MM-Fen, MM-Mor, and MM-But depressed respiration significantly more than MM-Sal. Time to first movement with MM-Ket and MM-But lasted significantly longer than with MM-Sal. Recovery time was significantly shorter in the MM-Sal (88 min) in comparison to all other treatments, and it was significantly longer in the MM-But (159 min), with atipamezole administered to four of the eight bats. In conclusion, all five anaesthetic protocols are suitable for Egyptian fruit bats; MM-Ket produces long anaesthesia and minimal respiratory depression, but cannot be antagonized completely. MM-Fen, MM-Mor, and MM-But depress respiration, but are known to produce good analgesia, and can be fully antagonized. Administration of atipamezole following the use of MM-But in Egyptian fruit bats is recommended.

A RETROSPECTIVE COMPARISON OF CHEMICAL IMMOBILIZATION WITH THIAFENTANIL, THIAFENTANIL-AZAPERONE, OR ETORPHINE-ACEPROMAZINE IN CAPTIVE PERSIAN FALLOW DEER (DAMA DAMA MESOPOTAMICA).

Records of 56 Persian fallow deer (Dama dama mesopotamica) immobilized for translocation were reviewed. Twenty-three were administered 0.05 ± 0.01 (mean ± SD) mg/kg thiafentanil (THIA), 20 were administered 0.045 ± 0.008 mg/kg thiafentanil combined with 0.19 ± 0.03 mg/kg azaperone (THIA-AZP), and 13 were administered 0.032 ± 0.04 mg/kg etorphine-acepromazine (ETOR-ACP) by intramuscular remote injection. Parameters recorded and compared between groups included induction and recovery times, heart rate, respiratory rate, rectal temperature, oxygen saturation, blood pressure, reflexes, quality of immobilization, and blood concentrations of lactate and glucose. Naltrexone (THIA groups) or diprenorphine (ETOR-ACP) were administered for reversal. Mean induction time was significantly shorter in the THIA group versus the ETOR-ACP group (2.0 ± 1.3 and 4.8 ± 2.8 min, respectively), but not significantly shorter than the THIA-AZP group (2.8 ± 3.1 min). Respiratory rate was significantly higher in the THIA group in comparison to the two other groups. None of the protocols provided excellent immobilization quality, which was significantly poorer in the THIA group. Following antagonist administration, all deer from the THIA and ETOR-ACP groups recovered quickly, while there were five perianesthetic morbidity and mortality cases in the THIA-AZP group. Mean recovery time was significantly shorter in the THIA group versus the THIA-AZP and ETOR-ACP groups (0.5 ± 0.3, 1.1 ± 0.8, and 2.3 ± 1.1 min, respectively). In conclusion, the use of THIA provided faster induction and recovery, with less respiratory depression, but poorer immobilization. The THIA-AZP combination should be used with caution in Persian fallow deer until further investigation.

A comparison of retrobulbar and two peribulbar regional anesthetic techniques in dog cadavers.

OBJECTIVE: To compare injectate distribution and likelihood of regional anesthesia to the orbit following retrobulbar (RB) or peribulbar (PB) injections in dog cadavers. STUDY DESIGN: Randomized, masked study. ANIMALS: Twenty-four dog cadavers (aged 5.5-17 years, 2.0-36.3 kg). METHODS: Orbits underwent one of three injection techniques with bupivacaine 0.5% and iohexol (1:1): ventrolateral RB injection (1-2 mL; 15 orbits), medial canthal PB injection (2-8 mL; PB-1; 16 orbits), or dorsomedial and ventrolateral PB injections (each 1-4 mL; PB-2; 16 orbits). The likelihood of successful regional anesthesia was estimated based on computed tomographic images scored for injectate volume of distribution at the base and within the extraocular muscle cone (EOMC), and injectate distribution around the optic nerve. Intraocular pressure (IOP) was measured before and after injections. Mixed-effects linear regression with post hoc Bonferroni contrast adjustments was performed. Significance was set at 0.05. RESULTS: A difference in injectate volume of distribution within or at the base of the EOMC was not detected among groups. The median optic nerve circumference of injectate distribution was significantly higher in the RB injected group than in the PB-2 group. Injectate distribution following RB, PB-1 and PB-2 injections was graded as likely to provide regional anesthesia within the EOMC in 40%, 19% and 31% of eyes, and at the EOMC base in 60%, 63% and 50% of eyes, respectively. The probability of likelihood to provide regional anesthesia was lower in dogs of higher body weights. The IOP was significantly higher than baseline following PB-1 (18 ± 14 mmHg) and in comparison with RB (2 ± 3 mmHg), but not different from PB-2 injection (10 ± 11 mmHg). CONCLUSIONS AND CLINICAL RELEVANCE: None of the techniques reliably produced 'successful' injectate distribution based on this study's definitions; however, clinical assessment of anesthetic success is required.

Intratesticular and incisional line infiltration with ropivacaine for castration in medetomidine-butorphanol-midazolam sedated dogs.

OBJECTIVE: To evaluate whether intratesticular and incisional ropivacaine infiltration produces sufficient intra- and postoperative analgesia for castrating dogs under sedation. STUDY DESIGN: Randomized, blinded, controlled clinical study. ANIMALS: Twenty-three healthy dogs weighing 5.8-35.6 kg admitted for castration. METHODS: Dogs were sedated with medetomidine (0.01 mg kg-1), butorphanol (0.2 mg kg-1) and midazolam (0.2 mg kg-1) intramuscularly, and were randomly assigned to group R, 0.2-0.4 mL kg-1 of ropivacaine 0.5%, or group S, an equivalent volume of saline injected intratesticularly and along the incision line. If persistent motion was observed during surgery, sedation was considered to be insufficient and general anaesthesia was induced. Carprofen 2.2 mg kg-1 was administered postoperatively. Pain was evaluated in all dogs before sedation and postoperatively following atipamezole administration at 1, 2, 4, 8 and 24 hours using an interactive visual analogue scale (IVAS; 0-100), the Glasgow composite pain scale-short form (CMPS-SF; 0-24), and a mechanical algometer. Methadone 0.3 mg kg-1 was administered intravenously to dogs if IVAS >30 or CMPS-SF >4. RESULTS: There was no significant difference between groups for the number of dogs administered general anaesthesia. The time from the beginning of surgery to induction of general anaesthesia was significantly shorter [median (range)] in group S [6 (3-25) minutes] than in group R [56 (36-76) minutes]. At 8 hours IVAS was significantly higher in group S (14 ± 10) than in group R (6 ± 4). CONCLUSIONS AND CLINICAL RELEVANCE: Intratesticular and incisional ropivacaine infiltration delayed the time to anaesthesia induction, and provided analgesia after castration performed under deep sedation in dogs. Intratesticular local anaesthesia can be an important part of the anaesthetic plan for castration.