Comparison of a blind and an ultrasound-guided technique for Retrobulbar anesthesia in dogs undergoing unilateral subconjunctival enucleation.

OBJECTIVE: This study compared the quality of retrobulbar anesthesia using a blind inferior-temporal palpebral approach (ITP) with an ultrasound-guided supratemporal (ST) technique in dogs undergoing unilateral enucleation. ANIMAL STUDIED: Twenty-one client-owned dogs were undergoing enucleation. PROCEDURES: Dogs were randomly assigned to receive ITP (n = 10) or ST (n = 11) with 0.5% ropivacaine at 0.1 mL/cm of neurocranial length. The anesthetist was blinded to the technique. Intraoperative data included cardiopulmonary variables, inhalant anesthetics requirement, and requirement for rescue analgesia (intravenous fentanyl 2.5 mcg/kg). Postoperative data included pain scores, sedation scores, and need for intravenous hydromorphone (0.05 mg/kg). Treatments were compared using Wilcoxon's rank sum test or Fisher's exact test as appropriate. Comparison of variables over time were tested using a mixed effect linear model on rank. Significance was set at p = 0.05. RESULTS: Intraoperative cardiopulmonary variables and inhalant requirements were not different between groups. Dogs receiving ITP required median (interquartile range, IQR) 1.25 (0, 2.5) mcg/kg intraoperative fentanyl while those receiving ST required none (p < 0.01). Intraoperative fentanyl was required in 5/10 and 0/11 of dogs in the ITP and ST groups, respectively (p = 0.01). Postoperative analgesia requirements were not significantly different between groups; 2/10 and 1/10 dogs in the ITP and ST groups, respectively. Sedation score negatively affected pain score (p < 0.01). CONCLUSIONS: The ultrasound-guided ST technique was more effective at decreasing intraoperative opioid requirements than the blind ITP approach in dogs undergoing unilateral enucleation.

Ultrasound-guided retromammillary injections in dogs: a feasibility, descriptive and anatomical study.

OBJECTIVE: To evaluate the feasibility of an ultrasound-guided technique targeting the medial branches of the dorsal ramus of the spinal nerves (DRSN) by injecting a dye solution at the caudal aspect of the base of lumbar mammillary processes [i.e. the retromammillary (RM) space]. STUDY DESIGN: Feasibility, descriptive, anatomical study. ANIMALS: Eleven canine cadavers. METHODS: Using anatomical dissections, the relationship between the mammillary processes and the branches of the DRSN of the thoracolumbar and lumbar spine was studied in two cadavers. Subsequently, ultrasound-guided RM injections were administered in nine cadavers, randomly assigned to low volume (LV; 0.01 mL kg-1) of a dye solution at multiple points from L3 to L6 on one side, and high volume (HV; 0.4 mL kg-1) at a single L4 point on the contralateral side. Gross anatomical dissections were immediately performed after the injections. The RM injections were feasible if ultrasonographic landmarks were identifiable in at least 80% of cases, and 80% of LV injections showed medial branch staining. A one-sample binomial test was used for testing feasibility. RESULTS: The medial branches emerged shortly after the DRSN exited the intervertebral foramen and traveled towards the caudal aspect of the base of the mammillary process, which served as the target injection point. With LV, 36 out of 36 (100%) injected medial branches were stained, meeting the criteria of feasibility (p < 0.001). The median (range) number of stained medial branches per cadaver were 4 (4-4) and 2 (1-3), with LV and HV, respectively. Although no lateral branches were stained with LV, 1 (0-2) was stained with HV. Neither ventral branch staining nor epidural spread was noted in any cadaver. CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasound-guided RM injections are feasible and allow for selective staining of the medial branch of the DRSN in canine cadavers at the lumbar spine.

Greater ischiatic notch plane versus parasacral block in dogs undergoing pelvic limb surgery: a retrospective noninferiority cohort study on perioperative opioid consumption.

OBJECTIVE: To compare perioperative opioid consumption in dogs undergoing pelvic limb surgeries and receiving a lumbosacral plexus block by combining a lumbar [lateral pre-iliac (LPI)] block with a lumbosacral trunk [i.e. parasacral (PS group) or greater ischiatic notch plane (GIN group)] block. Study design Retrospective, descriptive, exploratory, noninferiority cohort study. METHODS: Medical records of 37 client-owned dogs were analyzed. Intraoperative (primary outcome) and postoperative (24 hours) opioid use, 24 hour cumulative pain scores and prevalence of complications were compared between the two groups. Opioid use was quantified in morphine equivalents (ME, mg kg-1 ). The noninferiority limit for intraoperative opioid consumption was set at 0.05 ME kg-1 hour-1. Demographic data, procedure duration, surgery type and perioperative dexmedetomidine and ketamine use were also collected. A t-test or Wilcoxon rank-sum test, a Fisher's exact test and multivariable linear regression were used. Significance was set at p < 0.05. RESULTS: The GIN and PS groups comprised 17 and 20 dogs, respectively. Total intraoperative ME consumption was 0.17 (0.11-0.21) and 0.22 (0.16-0.30) mg kg-1 hour-1 for the GIN and PS groups, respectively (p = 0.077). The noninferiority analysis adjusted by surgery type and body mass revealed that the mean difference between the groups (GIN - PS) was -0.039 (95% CI -0.11-0.03, p = 0.247) ME mg kg-1 hour-1, indicating that the GIN group was not inferior to the PS group regarding intraoperative ME consumption. Dexmedetomidine and ketamine use, postoperative ME consumption and pain scores were similar between groups. CONCLUSIONS AND CLINICAL RELEVANCE: This retrospective study and preliminary observations support the clinical use of the GIN plane block, demonstrating its noninferiority to the PS block when combined with the LPI block for multimodal perioperative analgesia in dogs undergoing pelvic limb surgeries.

Cardiovascular changes, laboratory findings and pain scores in calves undergoing ultrasonography-guided bilateral rectus sheath block before herniorrhaphy: a prospective randomized clinical trial.

BACKGROUND: The study aimed to assess the clinical utility of a multiparametric approach to measure the impact of bilateral ultrasound-guided rectus sheath blocks (RSB) on heart rate, serum cortisol concentrations, and pain in calves undergoing herniorraphy. Fourteen calves were randomly assigned to receive either the RSB (RSB group, n = 7, injected with 0.3 mL/kg of bupivacaine 0.25% and 0.15 µg/kg of dexmedetomidine per side) or a sham injection (CG group, n = 7, injected with an equivalent volume of sterile saline solution). Monitoring included (i) continuous Holter recording from 120 min pre-surgery to 120 min post-surgery; (ii) serum cortisol concentration (SC) at -150 min pre-surgery (baseline), induction time, skin incision, end of surgical procedure (EP-t), and then 30 min, 45 min, 60 min, 120 min, 360 min after recovery; (iii) UNESP-Botucatu pain evaluation at -150 min pre-surgery and 30 min, 45 min, 60 min, 120 min, 240 min, 360 min after recovery. RESULTS: A significant difference in the heart rate was observed within the RSB group, in the time frame between 120 min to induction compared to the time frame between induction to EP-t period. The SC concentration was significantly higher in the CG at the skin incision. Calves in the RSB group recorded significantly lower pain scores at 45 min, 60 min, 120 and 240 min after recovery. CONCLUSIONS: The study demonstrated that monitoring heart rate and serum cortisol concentrations effectively quantified the effects of RSB during surgery. At the same time, the UNESP-Botucatu pain scale identified effects post-surgery when the calves regained consciousness. Overall, ultrasound-guided RSB appeared to enhance the well-being of calves undergoing herniorrhaphy.

A single-cohort retrospective analysis of factors associated with morbidity and mortality in 193 anesthetized domestic goats.

OBJECTIVE: To define the morbidity and mortality rates in goats undergoing general anesthesia at a large animal teaching hospital. STUDY DESIGN: Retrospective, single-cohort, observational study. ANIMALS: Records of 193 client-owned goats. METHODS: Data were collected from 218 medical records on 193 goats undergoing general anesthesia between January 2017 and December 2021. Demographic data, anesthetic management, recovery period and perianesthetic complications were recorded. Perianesthetic death was defined as anesthesia-related or anesthesia-contributory death occurring within 72 hours after recovery. Records of goats that were euthanized were reviewed to ascertain the cause of euthanasia. Each explanatory variable was individually investigated by univariable penalized maximum likelihood logistic regression, followed by multivariable analysis. Statistical significance was set at p < 0.05. RESULTS: Perianesthetic mortality was 7.3%, but was 3.4% when considering only goats undergoing elective procedures. Multivariable analysis showed that gastrointestinal surgeries [odds ratio (OR) 19.17, standard error (SE) 12.99, 95% confidence interval (CI) 5.08-72.33; p < 0.01] and requirement for perianesthetic norepinephrine infusion (OR 10.85, SE 8.82, 95% CI 2.21-53.33; p < 0.01) were associated with increased mortality. Maintaining other variables equal, the use of perianesthetic ketamine infusion was associated with decreased mortality (OR 0.09, SE 0.09, 95% CI 0.01-0.73; p = 0.02). Anesthesia-related or anesthesia-contributory complications included hypothermia (52.4%), bradycardia (38.1%), hypotension (35.3%), hypoxemia (14.8%), regurgitation/aspiration (7.3%), azotemia/acute renal failure (4.6%), myopathies/neuropathies (4.1%) and fever of unknown origin (2.7%). CONCLUSIONS AND CLINICAL RELEVANCE: In this population, gastrointestinal surgeries and the requirement for perianesthetic norepinephrine infusion were associated with increased mortality in goats undergoing general anesthesia, while ketamine infusion may have a protective effect.

A non-inferiority study comparing the ultrasound-guided parasacral with a novel greater ischiatic notch plane approach in canine cadavers.

OBJECTIVE: To describe the gross and ultrasound anatomy of the parasacral region and an ultrasound-guided greater ischiatic notch (GIN) plane approach aimed at staining the lumbosacral trunk (LST) in canine cadavers. To evaluate if the ultrasound-guided GIN plane approach is non-inferior to the previously described ultrasound-guided parasacral approach at staining the LST. STUDY DESIGN: Prospective, randomized, non-inferiority experimental anatomic study. ANIMALS: A total of 17 (23.9 ± 5.2 kg) mesocephalic canine cadavers. METHODS: Anatomic and echographic landmarks, and the feasibility of performing a GIN plane technique were evaluated using two canine cadavers. The remaining 15 cadavers had each hemipelvis randomly assigned to be administered either parasacral or GIN plane injection of 0.15 mL kg-1 dye solution. The parasacral region was dissected after injections to assess the staining of LST, cranial gluteal nerve, pararectal fossa and pelvic cavity. The stained LST were removed and processed for histological evaluation of intraneural injections. A one-sided z-test for non-inferiority (non-inferiority margin -14%) was used to statistically evaluate the success of the GIN plane versus the parasacral approach. Data were considered statistically significant when p < 0.05. RESULTS: The GIN plane and parasacral approach stained the LST in 100% and 93.3% of the injections, respectively. The success rate difference between treatments was 6.7% [95% confidence interval, -0.6 to 19.0%; p < 0.001 for non-inferiority]. The GIN plane and parasacral injections stained the LST for 32.7 ± 16.8 mm and 43.1 ± 24.3 mm, respectively (p = 0.18). No evidence of intraneural injection was found. CONCLUSIONS AND CLINICAL RELEVANCE: The ultrasound-guided GIN plane technique resulted in nerve staining that was non-inferior to the parasacral technique and may be considered an alternative to the parasacral approach to block the LST in dogs.

Effect of end-inspiratory pause on airway and physiological dead space in anesthetized horses.

OBJECTIVE: To evaluate the impact of a 30% end-inspiratory pause (EIP) on alveolar tidal volume (VTalv), airway (VDaw) and physiological (VDphys) dead spaces in mechanically ventilated horses using volumetric capnography, and to evaluate the effect of EIP on carbon dioxide (CO2) elimination per breath (Vco2br-1), PaCO2, and the ratio of PaO2-to-fractional inspired oxygen (PaO2:FiO2). STUDY DESIGN: Prospective research study. ANIMALS: A group of eight healthy research horses undergoing laparotomy. METHODS: Anesthetized horses were mechanically ventilated as follows: 6 breaths minute-1, tidal volume (VT) 13 mL kg-1, inspiratory-to-expiratory time ratio 1:2, positive end-expiratory pressure 5 cmH2O and EIP 0%. Vco2br-1 and expired tidal volume (VTE) of 10 consecutive breaths were recorded 30 minutes after induction, after adding 30% EIP and upon EIP removal to construct volumetric capnograms. A stabilization period of 15 minutes was allowed between phases. Data were analyzed using a mixed-effect linear model. Significance was set at p < 0.05. RESULTS: The EIP decreased VDaw from 6.6 (6.1-6.7) to 5.5 (5.3-6.1) mL kg-1 (p < 0.001) and increased VTalv from 7.7 ± 0.7 to 8.6 ± 0.6 mL kg-1 (p = 0.002) without changing the VTE. The VDphys to VTE ratio decreased from 51.0% to 45.5% (p < 0.001) with EIP. The EIP also increased PaO2:FiO2 from 393.3 ± 160.7 to 450.5 ± 182.5 mmHg (52.5 ± 21.4 to 60.0 ± 24.3 kPa; p < 0.001) and Vco2br-1 from 0.49 (0.45-0.50) to 0.59 (0.45-0.61) mL kg-1 (p = 0.008) without reducing PaCO2. CONCLUSIONS AND CLINICAL RELEVANCE: The EIP improved oxygenation and reduced VDaw and VDphys, without reductions in PaCO2. Future studies should evaluate the impact of different EIP in healthy and pathological equine populations under anesthesia.

Lumbosacral plexus block using a combination of ultrasound-guided lateral pre-iliac and parasacral approaches in cats.

OBJECTIVE: To describe an ultrasound-guided lateral pre-iliac (LPI) and parasacral (PS) approach in feline cadavers (phase I) and compare the perioperative analgesic use and complications in cats administered LPI and PS blocks (group PNB) or epidural anesthesia (group EPI) for pelvic limb surgery (phase II). STUDY DESIGN: Experimental uncontrolled, anatomic and retrospective cohort study. ANIMALS: A group of eight feline cadavers and 52 medical records. METHODS: Bilateral LPI and PS approaches with 0.1 mL kg-1 of dye to stain the femoral and obturator nerves and the lumbosacral trunk, respectively, were performed on each cadaver. Nerve staining effect was evaluated upon dissections (phase I). Perioperative analgesics use, and complication rates were retrospectively compared between groups PNB and EPI (phase II). Continuous data were compared using the Mann-Whitney U test and the prevalence of events with Fisher's exact test. Differences were considered significant when p < 0.05. RESULTS: Dissections revealed that the LPI approach stained 94% and 75% of the femoral and obturator nerves, respectively. The PS approach stained 100% of the lumbosacral trunks. Cats enrolled in group PNB (n = 23) were administered lower doses of intraoperative opioids than those in group EPI (n = 25) (p = 0.006). Intraoperative rescue analgesia was required in 60% and 17.4% of cats enrolled in groups EPI and PNB, respectively (p = 0.003). Group PNB required more intraoperative anticholinergics than group EPI (p = 0.02). There were no differences in postoperative pain scores, analgesic use and complication rates. CONCLUSIONS AND CLINICAL RELEVANCE: The ultrasound-guided LPI and PS approach stained the femoral/obturator nerves and the lumbosacral trunk, respectively, in feline cadavers. Furthermore, PNB was associated with lower intraoperative opioid use and similar postoperative pain and analgesic use compared with epidural anesthesia in a cohort of cats undergoing surgery of the pelvic limb.

Development of an ultrasound-guided transgluteal injection of the pudendal nerve in cats: a cadaveric study.

OBJECTIVE: To develop an ultrasound-guided interfascial plane technique for injection of the pudendal nerve near its sacral origin in cats. STUDY DESIGN: Prospective, randomized, anatomical study. ANIMALS: A group of 12 feline cadavers. METHODS: Gross and ultrasound anatomy of the ischiorectal fossa, the pudendal nerve relationship with parasacral structures, and the interfascial plane were described. Computed tomography was employed to describe a cranial transgluteal approach to the pudendal nerve. Bilateral ultrasound-guided injections were performed in eight cadavers using low [(LV) 0.1 mL kg-1] or high volume [(HV) 0.2 mL kg-1] of ropivacaine-dye solution. Dissections were performed to determine successful staining of the pudendal nerve (>1 cm) and inadvertent staining of the sciatic nerve, and any rectal, urethral, or intravascular puncture. Pudendal nerve staining in groups LV and HV were compared using Fisher's exact and Wilcoxon rank-sum test as appropriate (p = 0.05). RESULTS: The pudendal nerve and its rectal perineal and sensory branches coursed through the ischiorectal fossa, dorsomedial to the ischiatic spine. The pudendal nerve was not identified ultrasonographically, but the target plane was identified between the sacral transverse process, the ischiatic spine, the pelvic fascia and the rectum, and it was filled with dye solution. Both branches of the pudendal nerve were completely stained 75% and 87.5% in groups LV and HV, respectively (p = 1.00). The dorsal aspect of the sciatic nerve was partially stained in 37% of injections in group HV. Rectal or urethral puncture and intravascular injection were not observed. CONCLUSIONS AND CLINICAL RELEVANCE: In cats, ultrasound-guided cranial transgluteal injection successfully stained the pudendal nerve in at least 75% of attempts, regardless of injectate volume. Group HV had a greater probability of sciatic nerve staining.

Intravenous dexmedetomidine, morphine, or a combination can result in gallbladder wall thickening; with no significant association with plasma histamine concentrations.

The gallbladder is routinely evaluated during ultrasonographic examinations in dogs. However, published studies describing the effects of sedative agents on gallbladder wall thickness are currently lacking. The aims of this prospective, blinded, randomized crossover pilot study were to test hypotheses that IV morphine would result in gallbladder wall thickening, that morphine administration would increase plasma histamine concentrations, and that combining IV morphine with dexmedetomidine would potentiate gallbladder wall thickening. Six healthy Beagle dogs were sedated with intravenous (IV) morphine 0.4 mg/kg (group M), dexmedetomidine 7 µg/kg (group D), or a combination of the two (group MD). Physiologic parameters were measured at baseline and at regular intervals until the last ultrasonographic scan. Ultrasonographic scans were performed at baseline, 90 s, and at 5, 15, 30, 45, 60, 90, and 120 min. Plasma histamine samples were taken at baseline, 90 s, and 5 and 60 min. Cochran's Q-test was used to compare gallbladder wall thickening between groups, while the association between histamine plasma concentration and gallbladder wall thickness was compared with a mixed-effects model. Baseline gallbladder wall thickness was not significantly different between groups. Six of 18 treatments/dogs (33%) developed gallbladder thickening, with no difference between groups. There was no significant difference in baseline plasma histamine concentrations between groups, and no association between plasma histamine concentration and gallbladder wall thickness. Gallbladder wall thickening was observed in at least one dog in each group, therefore caution is recommended for gallbladder wall thickness ultrasonographic interpretation in dogs when these drugs have been administered.

An ultrasound-guided subparaneural approach to the sciatic nerve in the dog: a cadaver study.

OBJECTIVE: To describe the gross and microscopic anatomy of the sciatic nerve paraneural sheath and to report an ultrasound (US)-guided subparaneural approach to the sciatic nerve in dogs, comparing two different volumes of injectate. STUDY DESIGN: Prospective, randomized, anatomical study. ANIMALS: A group of nine middle-sized adult Mongrel canine cadavers (18 limbs). METHODS: The sciatic nerves of three pelvic limbs of two canine cadavers were identified, exposed and isolated between the greater trochanter and the popliteal fossa for gross anatomical and microscopic examination. An additional three pelvic limbs were surgically dissected on the lateral surface of the limb; the sciatic nerves were isolated, and a 26 gauge over-the-needle catheter was inserted through the paraneural sheath under direct visualization. A methylene blue solution was then slowly injected into the subparaneural compartment through the catheter under US visualization using an 8-13 MHz linear-array transducer. Subsequently, 12 pelvic limbs (six cadavers) were randomly allocated to one of two groups; using US-guided percutaneous subparaneural approach, either 0.1 or 0.05 mL kg-1of a 1:1 solution of methylene blue and 0.5% bupivacaine was injected. The spread of the dye solution and the amount of nerve staining were macroscopically scored. The stained sciatic nerves with their sheaths were then harvested for microscopic examination. RESULTS: The paraneural sciatic nerve sheath was easily identified distinct from the nerve trunk both macroscopically and with US visualization, and microscopically. Complete staining was achieved in five of six (83.3%) sciatic nerves in each group; no difference was found in the amount of staining between the two groups. Microscopically, no signs of sciatic nerve intraneural injection were observed. CONCLUSIONS AND CLINICAL RELEVANCE: The US-guided subparaneural injection of 0.05 mL kg-1 of a dye injectate resulted in satisfactory nerve staining without evidence of sciatic nerve intraneural injection.

A computed tomography-based method for the assessment of canine retrobulbar cone volume for ophthalmic anaesthesia.

OBJECTIVE: To develop a comprehensive formula for calculating the volume of local anaesthetic solution used for retrobulbar anaesthesia in dogs with different skull morphologies. STUDY DESIGN: Retrospective cohort imaging study. ANIMALS: Skull computed tomography (CT) images of 188 dogs of different breeds collected between January 2009 and December 2017. METHODS: Anatomical integrity of the orbit and adjacent structures, presenting complaint, clinical signs and CT findings were verified to exclude ocular abnormalities. The volume of the retrobulbar cone of 376 eyes was calculated using CT scans of the dogs' skulls. Additional data recorded included morphology of the skull, body weight, sex and size of the dogs, all of which were matched for possible association to the retrobulbar cone volume through univariable and multivariable linear regression models. Results of linear regression models were expressed as estimated beta coefficients with the corresponding 95% confidence intervals (95% CIs). RESULTS: Using univariate analysis, the retrobulbar cone volume was positively associated with weight and male sex. In addition, brachycephalic and dolichocephalic dogs showed a larger retrobulbar cone volume than mesocephalic dogs, while sex was no longer significantly associated with the retrobulbar cone volume. In multivariate analysis, when considering all variables in the model, weight emerged as the strongest predictor (beta coefficient: 0.062 mL kg-1, 95% CI: 0.056-0.067 mL kg-1, p < 0.001). CONCLUSIONS: and clinical relevance In the veterinary literature, there is no agreement on the precise volume of local anaesthetic solution that should be used to achieve intraconal retrobulbar anaesthesia in dogs. Here we suggest a formula to calculate the retrobulbar cone volume and, accordingly, the injection volume of local anaesthetic solution for effective retrobulbar anaesthesia.

Impact of epidural bupivacaine on perioperative opioid requirements, recovery characteristics, and duration of hospitalization in dogs undergoing cystotomy: A retrospective study of 56 cases.

OBJECTIVE: To compare perioperative opioid consumption and duration of hospitalization (DOH) in anesthetized dogs receiving opioid-based analgesia (OBA) vs those receiving bupivacaine epidural-based analgesia (EPID) during cystotomy. STUDY DESIGN: Retrospective cross-sectional study. ANIMALS: Fifty-six client-owned dogs undergoing cystotomy. METHODS: Clinical records of dogs undergoing cystotomy between January 2015 and December 2017 were reviewed. Demographic data, duration of anesthesia and surgery, anesthetic management, perioperative opioid consumption expressed in morphine equivalents (ME), perioperative use of adjuvant analgesics, time to first micturition, time to eat, time to ambulate, and DOH were recorded. Opioid consumption and DOH were compared with a Wilcoxon rank-sum test, followed by linear regression analysis as appropriate. Time to first micturition, time to eat, and time to walk unassisted were modeled with Cox-proportional hazard models. RESULTS: Dogs treated with EPID during surgery required 1.5 mg/kg ME less compared with those treated with OBA (P = .04) during surgery. Three of 19 dogs treated with EPID vs 15 of 37 dogs receiving OBA required intraoperative adjuvant analgesics (P = .06). Dogs treated with EPID regained motor function slower than dogs treated with OBA (P = .01); however, there was no difference in time to urinate, time to eat, or DOH between treatments. CONCLUSION: Perioperative lumbosacral epidural with bupivacaine reduced intraoperative opioid consumption in dogs anesthetized for cystotomy. CLINICAL SIGNIFICANCE: The use of epidural bupivacaine in dogs undergoing cystotomy may reduce intraoperative opioid requirements without affecting return of bladder function or DOH.

Comparison of the sedative effects of alfaxalone and methadone with or without midazolam in dogs.

This blinded, randomized, prospective study evaluated the sedative and physiologic effects of a combination of alfaxalone and methadone with or without midazolam in adult dogs. Sixteen dogs received methadone (0.5 mg/kg body weight) and alfaxalone (1 mg/kg body weight), either with or without midazolam (0.5 mg/kg body weight), by intramuscular injection. Quality of sedation, heart rate, respiratory rate, systolic arterial pressure, rectal temperature, arterial oxygen saturation of hemoglobin, and dose of alfaxalone required for endotracheal intubation were recorded. Sedation score increased over time in both groups; however, dogs premedicated with methadone and alfaxalone appeared significantly less sedated than dogs premedicated with midazolam at 15, 20, and 25 minutes post-injection (P = 0.04). Dogs receiving methadone and alfaxalone were almost 5 times more likely to show excitement than those receiving midazolam (P = 0.03). We concluded that adding midazolam to an intramuscular combination of methadone and alfaxalone cannot be recommended in healthy dogs.

Comparaison des effets sédatifs de l'alfaxalone et de la méthadone avec ou sans midazolam chez le chien. Cette étude prospective randomisée à l'aveugle a évalué les effets sédatifs et physiologiques d'une association d'alfaxalone et de méthadone avec ou sans midazolam chez le chien adulte. Seize chiens ont reçu par voie intramusculaire (IM) méthadone (0,5 mg/kg) et alfaxalone (1 mg/kg) (MA) ou méthadone et alfaxalone à les même dosages plus midazolam (0,5 mg/kg) (MMA). La qualité de la sédation, la fréquence cardiaque, la fréquence respiratoire, la pression artérielle systolique, la température rectale, la saturation artérielle en oxygène de l'hémoglobine et la dose d'alfaxalone requise pour l'intubation endotrachéale ont été enregistrées. Le score de sédation augmentait avec le temps dans les deux groupes, cependant, les chiens ayant reçu la combinaison MMA semblaient significativement moins sous sédation que les chiens ayant reçu la combinaison MA 15, 20, et 25 minutes après l'injection (P = 0,04). Les chiens recevant MMA étaient presque cinq fois plus susceptibles de montrer de l'excitation que ceux recevant du MA (P = 0,03). Nous avons conclu que l'ajout de midazolam à une combinaison IM de méthadone et d'alfaxalone ne peut pas être recommandé chez les chiens en santé.(Traduit par les auteurs).

Comparison of intraocular pressure and pupil diameter after sedation with either acepromazine or dexmedetomidine in healthy dogs.

OBJECTIVE: To compare intraocular pressure (IOP) and pupillary diameter (PD) following intravenous (IV) administration of dexmedetomidine and acepromazine in dogs. STUDY DESIGN: Prospective, randomized experimental trial. ANIMALS: A group of 16 healthy adult dogs aged (mean ± standard deviation) 4.9 ± 3.3 years and weighing 15.7 ± 9.6 kg, without pre-existing ophthalmic disease. METHODS: IV dexmedetomidine hydrochloride (0.002 mg kg-1; DEX) or acepromazine maleate (0.015 mg kg-1; ACE) was administered randomly to 16 dogs (eight per group). The IOP and PD, measured using applanation tonometry and Schirmer's strips mm scale, respectively, and the heart rate (HR), systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures and respiratory rate (fR) were recorded at baseline, at time of injection, and then 5, 10, 15, 20 and 25 minutes after injection. A single ophthalmologist, unaware of treatment, performed all measurements under consistent light conditions. Values were compared with baseline and among treatments using a multivariate mixed-effects model (p ≤ 0.05). RESULTS: The IOP was significantly lower in the DEX group compared with the ACE group at 10 (p < 0.01) and 15 minutes (p < 0.01) after drug injection. PD was significantly smaller compared to baseline for the entire duration of the study (p < 0.01) in both groups. Dogs in the DEX group had significant lower HR (p < 0.01) and fR (p < 0.01), higher SAP (p < 0.01) and DAP (p < 0.01) at all time points, and higher MAP (p < 0.01) during the first 15 minutes following drug injection in comparison with the ACE group. CONCLUSIONS AND CLINICAL RELEVANCE: Our results suggest that premedication with IV dexmedetomidine temporarily decreases IOP when compared with IV acepromazine. Both drugs cause miosis.

Preclinical imaging anesthesia in rodents.

Despite the outstanding progress achieved by preclinical imaging science, laboratory animal anesthesia remains quite stationary. Ninety percent of preclinical imaging studies are carried on small rodents (mice and rats) anesthetized by outdated injectable and/or inhalation agents. A need for imaging awake (conscious) animals is questionably registered mainly for brain research, for phMRI and for accomplishing pain and analgesia studies. A need for improving current rodent anesthesia protocols and for enforcing the 3Rs paradigm is sought. Patient monitoring throughout the procedure and recovery phases, as well as vital parameter's data must be recorded in basic consciousness states and during imaging sessions. A multidrug approach is suggested to overcome the limits of monoanesthesia and well-timed physiological data are required to ground findings and to interpret imaging data.