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This study was designed to compare the cardiovascular effects of equipotent maintenance of anesthetic doses (determined in a previous study) of propofol and propofol/ketamine, administered with and without noxious stimulation. Six healthy adult cats were anesthetized with propofol (loading dose 6.6 mg kg-1 , infusion 0.22 mg kg-1 minute-1 ), and instrumented to allow determination of blood gas and acid–base balance and measurement of blood pressures and cardiac output. The propofol infusion was continued for a further 60 minutes after which measurements were taken prior to and during application of a noxious stimulus. The propofol infusion was decreased to 0.14 mg kg-1 minute-1 , and ketamine (loading dose 2 mg kg-1 , infusion 23 µg kg minute-1 ) was administered. After a further 60 minutes, measurements were again taken prior to and during application of a noxious stimulus. The data were analyzed, using several Repeated Measures anova (first, ketamine/propofol and noxious stimulation were each treated as within-subject factors; secondly, the levels of these two factors were combined into a single within-subject factor). Mean arterial pressure, CVP, PAOP, SI, CI, SVRI, PVRI, oxygen delivery index, oxygen consumption index, oxygen utilization ratio, PvO2 , pHa, PaCO2 , bicarbonate concentration, and BD values collected during propofol administration were not changed by addition of ketamine and reduction of propofol concentration or by application of a noxious stimulus under propofol alone. Application of a noxious stimulus under propofol alone did, however, significantly increase HR and PaO2 , and these responses were not blunted by the addition of ketamine. Compared with propofol, administration of ketamine and reduction of propofol concentration significantly increased PAP and venous admixture, and significantly decreased PaO2 . Although application of a noxious stimulus to cats under propofol alone did not significantly change CVP, SI, CI, PVRI, oxygen delivery index, and oxygen consumption index, significant differences were found in these variables between propofol and propofol/ketamine. In conclusion, propofol alone provided cardiopulmonary stability; addition of ketamine did not improve hemodynamics but did decrease oxygenation. [ABSTRACT FROM AUTHOR]

Objective: To compare efficacy and duration of desensitization of oral structures with a lidocaine-bupivacaine mixture administered via a lateral percutaneous or modified infraorbital approach., Animals: 6 healthy adult hound-type female dogs., Procedures: In this crossover study, dogs were randomized for side (left or right) and maxillary nerve approach (lateral percutaneous or infraorbital), with a 2-week washout period. Dogs were anesthetized, and a 2-mL mixture of 2% lidocaine and 0.5% bupivacaine (50:50 [vol/vol]) was administered with a 22-gauge, 4.5-cm-long catheter inserted through the infraorbital canal (infraorbital approach) or with a shielded stimulating needle to the maxillary nerve (percutaneous approach). Reflex-evoked motor potentials were measured for the maxillary canine tooth, fourth premolar tooth, second molar tooth, and hard palate mucosa ipsilateral to the injected mixture and for the contralateral maxillary canine tooth (control) at three 10-minute intervals before injection (baseline) and at predetermined times after injection for up to 6.7 hours. For each oral structure, the proportion of dogs with desensitization (efficacy) and time to onset and duration of desensitization were compared between approaches., Results: The proportion of dogs with successful nerve blockade did not significantly differ between infraorbital and percutaneous approaches and among the 4 oral structures. Time to onset of desensitization did not differ between approaches, but duration was significantly longer with the infraorbital approach., Conclusions and Clinical Relevance: A modified infraorbital approach with the lidocaine-bupivacaine mixture had similar effects to a lateral percutaneous approach but provided a longer duration of desensitization. Neither approach was universally successful at desensitizing all oral structures.

Objective: To compare the efficacy and duration of desensitization of oral structures following injection of various volumes of lidocaine-bupivacaine via an infraorbital approach in dogs., Animals: 6 healthy adult hound-type dogs., Procedures: In a randomized crossover study, each dog received 1, 2, and 3 mL of a 2% lidocaine-0.5% bupivacaine mixture (50:50 vol/vol) injected within and near the caudal aspect of the infraorbital canal with a 14-day washout period between treatments. Dogs were anesthetized, and each treatment was administered through a 22-gauge, 4.5-cm-long catheter, which was fully inserted through and then withdrawn 2 cm to the caudal aspect of the infraorbital canal. The reflex-evoked motor potential was measured for the maxillary canine tooth (MC), fourth premolar tooth (MPM4), second molar tooth (MM2), and hard palate mucosa ipsilateral to the injected treatment and for the contralateral MC (control) at predetermined times before and for 6 hours after treatment administration or until the block was no longer effective. For each oral structure, the proportion of dogs with desensitization (efficacy) and time to onset and duration of desensitization were compared among the 3 treatments (injectate volumes)., Results: Treatment was not associated with efficacy, time to onset, or duration of desensitization. Regardless of treatment, MC and MPM4 were more frequently desensitized and mean durations of desensitization for MC and MPM4 were longer, compared with those for MM2 and the hard palate., Conclusions and Clinical Relevance: The volume of local anesthetic used for an infraorbital nerve block had no effect on block efficacy or duration.

Objective: To characterize the hemodynamic effects of subclinical, clinical and supraclinical plasma alfaxalone concentrations in cats., Study Design: Experimental study., Animals: A group of six adult healthy male neutered cats., Methods: Cats were anesthetized with desflurane in oxygen for instrumentation. Catheters were placed in a medial saphenous vein for drug administration and in a carotid artery for arterial blood pressure measurement and blood collection. A thermodilution catheter was placed in the pulmonary artery via an introducer placed in a jugular vein for measurement of central venous pressure, pulmonary artery pressure, pulmonary artery occlusion pressure, cardiac output and core body temperature, and for sampling mixed venous blood. A lead II electrocardiogram was connected. Desflurane administration was discontinued and a target-controlled infusion system was used to administer alfaxalone to reach six plasma alfaxalone concentrations ranging from 1.0 to 30.4 mg L -1 , with 7.6 mg L -1 considered a clinical concentration for anesthesia. Cardiovascular measurements were recorded, and arterial and mixed-venous blood samples were collected for blood-gas analysis and plasma alfaxalone concentration measurement at each target concentration. Data were analyzed using a repeated-measures analysis of variance and Dunnett's test for comparisons to the lowest target concentration. Significance was set at p < 0.05., Results: Mean ± standard deviation plasma alfaxalone concentrations were 0.73 ± 0.32, 1.42 ± 0.41, 3.44 ± 0.40, 6.56 ± 0.43, 18.88 ± 6.81 and 49.47 ± 5.50 mg L -1 for the 1, 1.9, 3.8, 7.6, 15.2, and 30.4 mg L -1 target concentrations, respectively. PaCO 2 increased with increasing target plasma alfaxalone concentrations and was 69.4 ± 14.2 mmHg (9.3 ± 1.9 kPa) at the 30.4 mg L -1 target. Some cardiovascular variables were statistically significantly affected by increasing target plasma alfaxalone concentrations., Conclusion and Clinical Relevance: Within the plasma concentration range studied, alfaxalone caused hypoventilation, but the cardiovascular effects were of small clinical significance., (Copyright © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To evaluate the effects of intrathoracic insufflation on cardiorespiratory variables and working space in cats undergoing video-assisted thoracic surgery., Study Design: Prospective randomized study., Animals: Six healthy cats., Methods: Cats were anesthetized using a standardized protocol. A Swan-Ganz catheter was positioned in the pulmonary artery under fluoroscopic guidance for measurement of cardiac output. Intrathoracic pressures (ITP) of 0 (baseline), 3, and 5 mm Hg were induced with CO 2 and maintained for 30 minutes. Statistical comparison of cardiorespiratory variables was performed. After the procedures, all cats were recovered from anesthesia. Videos of thoracic working space at each ITP level were scored in a blinded fashion by 3 board-certified surgeons using a numerical scale from 0-10., Results: All cats tolerated insufflation with 3 and 5 mm Hg for 30 minutes without oxygen desaturation, although ventilatory levels had to be increased substantially to maintain eucapnia and oxygenation. Cardiac index was not significantly different from baseline after 30 minutes at 3 mm Hg but was significantly lower after 30 minutes at 5 mm Hg compared with 3 mm Hg. Oxygen delivery was unaffected by 3 or 5 mm Hg compared with baseline. Scores for working space increased between baseline and 3 and 5 mm Hg but were not different between 3 and 5 mm Hg., Conclusion: CO 2 insufflation to 5 mm Hg seems well tolerated in healthy cats, provided ventilatory settings are substantially increased as ITP increases., Clinical Significance: Thoracic CO 2 insufflation of 3 mm Hg in cats during video-assisted thoracic surgery is associated with less hemodynamic perturbation than 5 mm Hg insufflation and may provide the benefit of improved working space compared with baseline., (© 2018 The American College of Veterinary Surgeons.)

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., (© 2018 American College of Veterinary Ophthalmologists.)

Objective: To describe a technique for video-assisted thoracoscopic (VATS) thoracic duct ligation (TDL) in normal cats with a bipolar vessel-sealing device and to assess durability of the seal., Study Design: Prospective case series., Animals: Six healthy research cats., Methods: Cats were placed under anesthesia for computed tomography lymphangiography (CTLA) to identify thoracic duct anatomy. On the basis of CTLA findings, cats were positioned in either right or left lateral recumbency for a 3-port VATS TDL. Thoracic duct branches were dissected from the aorta after subcutaneous indirect near-infrared fluorescence (NIRF) lymphography with indocyanine green was performed to optimize detection. A vessel-sealing device was used to seal each thoracic duct in 1 or more locations. Postattenuation, indirect NIRF lymphography was repeated to confirm complete occlusion of thoracic duct flow. CTLA was repeated in all cats 3 months postoperatively., Results: The thoracic duct was surgically approached from the right in 3 cats and from the left in 3 cats. A median of 2.5 (range 1-6) TDL seal sites were applied. In 2 cats, leakage of chyle was detected during dissection. At 3 months postoperatively, CTLA confirmed reestablished chylous flow in 5 of 6 cats, appearing to occur through recanalization of previously sealed sites rather than through development of de novo lymphatic vessels., Conclusion: VATS TDL is feasible in cats, although the variable and delicate nature of feline thoracic duct anatomy should be considered preoperatively., Clinical Significance: Bipolar vessel-sealing devices are not a durable modality for thoracic duct sealing in healthy cats in a seal only fashion., (© 2018 The American College of Veterinary Surgeons.)

OBJECTIVE To determine effects of 3 plasma concentrations of fentanyl on the minimum alveolar concentration of isoflurane (MAC iso ) and cardiovascular variables in Hispaniolan Amazon parrots (Amazona ventralis). ANIMALS 6 adult parrots. PROCEDURES In phase 1, anesthesia was induced and maintained with isoflurane; intermittent positive-pressure ventilation was provided. The MAC iso was determined for each bird by use of a bracketing method and supramaximal electrical stimulus. Fentanyl (20 μg/kg) was administered IV, and blood samples were collected over time to measure plasma fentanyl concentrations for pharmacokinetic calculations. In phase 2, pharmacokinetic values for individual birds were used for administration of fentanyl to achieve target plasma concentrations of 8, 16, and 32 ng/mL. At each concentration, MAC iso and cardiovascular variables were determined. Data were analyzed with mixed-effects multilevel linear regression analysis. RESULTS Mean ± SD fentanyl plasma concentrations were 0 ng/mL, 5.01 ± 1.53 ng/mL, 12.12 ± 3.58 ng/mL, and 24.93 ± 4.13 ng/mL, and MAC iso values were 2.09 ± 0.17%, 1.45 ± 0.32%, 1.34 ± 0.31%, and 0.95 ± 0.14% for fentanyl target concentrations of 0, 8, 16, and 32 ng/mL, respectively. Fentanyl significantly decreased MAC iso in a dose-dependent manner. Heart rate and blood pressure significantly decreased at all fentanyl doses, compared with values for MAC iso at 0 ng of fentanyl/mL. CONCLUSIONS AND CLINICAL RELEVANCE Fentanyl significantly decreased the MAC iso in healthy Hispaniolan Amazon parrots, but this was accompanied by a depressive effect on heart rate and blood pressure that would need to be considered for application of this technique in clinical settings.

OBJECTIVE To compare the disposition of fentanyl citrate after a single IV injection in isoflurane-anesthetized red-tailed hawks (Buteo jamaicensis) and Hispaniolan Amazon parrots (Amazona ventralis). ANIMALS 6 adult red-tailed hawks and 6 adult Hispaniolan Amazon parrots. PROCEDURES Anesthesia was induced and maintained with isoflurane; intermittent positive-pressure ventilation was provided. The minimum alveolar concentration of isoflurane was determined for each bird by use of the bracketing method and a supramaximal electrical stimulus. Fentanyl (20 μg/kg) was administered IV. Arterial (red-tailed hawks) or jugular venous (Hispaniolan Amazon parrots) blood samples were obtained immediately before and 1, 2, 4, 8, 15, 30, 60, 120, 180, 240, and 480 minutes (red-tailed hawks) and 1, 5, 10, 15, 30, 60, 120, and 180 minutes (Hispaniolan Amazon parrots) after fentanyl administration. RESULTS A 3-compartment and a 2-compartment model best described fentanyl pharmacokinetics in red-tailed hawks and Hispaniolan Amazon parrots, respectively. Median apparent volume of the central compartment and volume of distribution at steady state were 222 mL/kg and 987 mL/kg, respectively, for the red-tailed hawks and 5,108 mL/kg and 13,079 mL/kg, respectively, for the Hispaniolan Amazon parrots. Median clearance and elimination half-life were 8.9 mL/min/kg and 90.22 minutes, respectively, for the red-tailed hawks and 198.8 mL/min/kg and 51.18 minutes, respectively, for the Hispaniolan Amazon parrots. CONCLUSIONS AND CLINICAL RELEVANCE Pharmacokinetic results for fentanyl in isoflurane-anesthetized red-tailed hawks and Hispaniolan Amazon parrots indicated large differences and should strongly discourage extrapolation of doses between these 2 species.

OBJECTIVE To compare intraosseous pentobarbital treatment (IPT) and thoracic compression (TC) on time to circulatory arrest and an isoelectric electroencephalogram (EEG) in anesthetized passerine birds. ANIMALS 30 wild-caught adult birds (17 house sparrows [Passer domesticus] and 13 European starlings [Sturnus vulgaris]). PROCEDURES Birds were assigned to receive IPT or TC (n = 6/species/group). Birds were anesthetized, and carotid arterial pulses were monitored by Doppler methodology. Five subdermal braided-wire electrodes were used for EEG. Anesthetic depth was adjusted until a continuous EEG pattern was maintained, then euthanasia was performed. Times from initiation of euthanasia to cessation of carotid pulse and irreversible isoelectric EEG (indicators of death) were measured. Data (medians and first to third quartiles) were summarized and compared between groups within species. Necropsies were performed for all birds included in experiments and for another 6 birds euthanized under anesthesia by TC (4 sparrows and 1 starling) or IPT (1 sparrow). RESULTS Median time to isoelectric EEG did not differ significantly between treatment groups for sparrows (19.0 and 6.0 seconds for TC and IPT, respectively) or starlings (88.5 and 77.5 seconds for TC and IPT, respectively). Median times to cessation of pulse were significantly shorter for TC than for IPT in sparrows (0.0 vs 18.5 seconds) and starlings (9.5 vs 151.0 seconds). On necropsy, most (14/17) birds that underwent TC had grossly visible coelomic, pericardial, or perihepatic hemorrhage. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that TC might be an efficient euthanasia method for small birds. Digital pressure directly over the heart during TC obstructed venous return, causing rapid circulatory arrest, with rupture of the atria or vena cava in several birds. The authors propose that cardiac compression is a more accurate description than TC for this procedure.

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., (Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To determine plasma bupivacaine concentrations after retrobulbar or peribulbar injection of bupivacaine in cats., Study Design: Randomized, crossover, experimental trial with a 2 week washout period., Animals: Six adult healthy cats, aged 1-2 years, weighing 4.6 ± 0.7 kg., Methods: Cats were sedated by intramuscular injection of dexmedetomidine (36-56 μg kg -1 ) and were administered a retrobulbar injection of bupivacaine (0.75 mL, 0.5%; 3.75 mg) and iopamidol (0.25 mL), or a peribulbar injection of bupivacaine (1.5 mL, 0.5%; 7.5 mg), iopamidol (0.5 mL) and 0.9% saline (1 mL) via a dorsomedial approach. Blood (2 mL) was collected before and at 5, 10, 15, 22, 30, 45, 60, 120, 240 and 480 minutes after bupivacaine injection. Atipamezole was administered approximately 30 minutes after bupivacaine injection. Plasma bupivacaine and 3-hydroxybupivacaine concentrations were determined using liquid chromatography-mass spectrometry. Bupivacaine maximum plasma concentration (C max ) and time to C max (T max ) were determined from the data., Results: The bupivacaine median (range) C max and T max were 1.4 (0.9-2.5) μg mL -1 and 17 (4-60) minutes, and 1.7 (1.0-2.4) μg mL -1 , and 28 (8-49) minutes, for retrobulbar and peribulbar injections, respectively. In both treatments the 3-hydroxybupivacaine peak concentration was 0.05-0.21 μg mL -1 ., Conclusions and Clinical Relevance: In healthy cats, at doses up to 2 mg kg -1 , bupivacaine peak plasma concentrations were approximately half that reported to cause arrhythmias or convulsive electroencephalogram (EEG) activity in cats, and about one-sixth of that required to produce hypotension., (Copyright © 2016 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Hypertrophic cardiomyopathy (HCM) is an inherited disease of the heart muscle characterized by otherwise unexplained thickening of the left ventricle. Left ventricular outflow tract (LVOT) obstruction is present in approximately two-thirds of patients and substantially increases the risk of disease complications. Invasive treatment with septal myectomy or alcohol septal ablation can improve symptoms and functional status, but currently available drugs for reducing obstruction have pleiotropic effects and variable therapeutic responses. New medical treatments with more targeted pharmacology are needed, but the lack of preclinical animal models for HCM with LVOT obstruction has limited their development. HCM is a common cause of heart failure in cats, and a subset exhibit systolic anterior motion of the mitral valve leading to LVOT obstruction. MYK-461 is a recently-described, mechanistically novel small molecule that acts at the sarcomere to specifically inhibit contractility that has been proposed as a treatment for HCM. Here, we use MYK-461 to test whether direct reduction in contractility is sufficient to relieve LVOT obstruction in feline HCM. We evaluated mixed-breed cats in a research colony derived from a Maine Coon/mixed-breed founder with naturally-occurring HCM. By echocardiography, we identified five cats that developed systolic anterior motion of the mitral valve and LVOT obstruction both at rest and under anesthesia when provoked with an adrenergic agonist. An IV MYK-461 infusion and echocardiography protocol was developed to serially assess contractility and LVOT gradient at multiple MYK-461 concentrations. Treatment with MYK-461 reduced contractility, eliminated systolic anterior motion of the mitral valve and relieved LVOT pressure gradients in an exposure-dependent manner. Our findings provide proof of principle that acute reduction in contractility with MYK-461 is sufficient to relieve LVOT obstruction. Further, these studies suggest that feline HCM will be a valuable translational model for the study of disease pathology, particularly LVOT obstruction., Competing Interests: This work was supported in part by an unrestricted research grant from MyoKardia, Inc. to SPH, SM, MJE and EMG are employees and own shares of, and JBK is a former employee and owns shares of, MyoKardia, Inc., a biotechnology company developing small molecules that target the sarcomere for treatment of inherited cardiomyopathy. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

OBJECTIVE To determine the locomotor response to the administration of fentanyl in horses with and without the G57C polymorphism of the μ-opioid receptor. ANIMALS 20 horses of various breeds and ages (10 horses heterozygous for the G57C polymorphism and 10 age-, breed-, and sex-matched horses that did not have the G57C polymorphism). PROCEDURES The number of steps each horse took was counted over consecutive 2-minute periods for 20 minutes to determine a baseline value. The horse then received a bolus of fentanyl (20 μg/kg, IV), and the number of steps was again counted during consecutive 2-minute periods for 60 minutes. The mean baseline value was subtracted from each 2-minute period after fentanyl administration; step counts with negative values were assigned a value of 0. Data were analyzed by use of a repeated-measures ANOVA. RESULTS Data for 19 of 20 horses (10 horses with the G57C polymorphism and 9 control horses without the G57C polymorphism) were included in the analysis. Horses with the G57C polymorphism had a significant increase in locomotor activity, compared with results for horses without the polymorphism. There was a significant group-by-time interaction. CONCLUSIONS AND CLINICAL RELEVANCE Horses heterozygous for the G57C polymorphism of the μ-opioid receptor had an increased locomotor response to fentanyl administration, compared with the response for horses without this polymorphism. The clinical impact of this finding should be investigated.

OBJECTIVE To determine the onset, duration, and extent of regional nerve blocks performed by administration of lidocaine or lidocaine-bupivacaine into the infraorbital canal in dogs. ANIMALS 6 healthy hound-type dogs. PROCEDURES Under general anesthesia, stimulating needles were inserted into the gingiva dorsolateral to both maxillary canine (MC) teeth and the maxillary fourth premolar (MPM4) and second molar (MM2) teeth on the treatment side. A reflex-evoked muscle potential (REMP) was recorded from the digastricus muscle after noxious electrical stimulation at each site. After baseline measurements, 1 mL of 2% lidocaine solution or a 2% lidocaine-0.5% bupivacaine mixture (0.5 mL each) was injected into the infraorbital canal (at approx two-thirds of the canal length measured rostrocaudally). The REMPs were recorded for up to 7 hours. The REMP data for the contralateral (untreated control) canine tooth were used to normalize results for all stimulation sites. RESULTS With both treatments, nerve block for MC teeth on the treated side was achieved by 5 (n = 5 dogs) or 10 (1) minutes after injection, but nerve block for ipsilateral MPM4 and MM2 teeth was successful for only 3 dogs and 1 dog, respectively. Mean duration of nerve blocks for MC teeth was 120 and 277 minutes following injection of lidocaine and lidocaine-bupivacaine, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Local anesthesia, as performed in this study, successfully blocked innervation of MC teeth, but results for MPM4 and MM2 teeth were inconsistent. This specific technique should not be used during tooth extractions caudal to the MC teeth.

Objectives: To systematically review published studies evaluating pain associated with onychectomy in cats, and to assess the efficacy of the analgesic therapies applied., Databases Used: Four sources were used to identify manuscripts for review. Databases searched were those of the National Library of Medicine, EMBASE and CAB International. In addition, pertinent references in the bibliographies of included articles were retrieved., Results: Twenty manuscripts published in refereed journals were reviewed. These included papers reporting 18 clinical trials and two studies conducted in conditioned research cats. Twelve analgesics were evaluated, including seven opioids, four non-steroidal anti-inflammatory drugs and one local anesthetic. Nine studies involved a direct comparison of analgesic agents. Limb use was abnormal when measured at 2 and 12 days following onychectomy, and neither fentanyl patch nor butorphanol administration resulted in normal use of the surgical limb. In another study, cats evaluated at 6 months after this surgery were not lame. Differing surgical techniques were compared in six studies; the results indicated that pain scores were lower after laser surgery than after scalpel surgery. The difficulties associated with assessing pain in cats and the lack of sensitivity of the evaluation systems utilized were highlighted in many of the studies. Huge variations in dose and dosing strategies had significant impacts on drug efficacy. Statistically significant differences among treatments were found in most studies; however, no clearly superior analgesic treatment was identified. A combination of meloxicam or robenacoxib with an opioid may provide more effective analgesia and should be evaluated., (© 2015 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.)

Case Description: A 1.5-year-old spayed female Bernese Mountain Dog was examined for a 6-month history of intermittent vomiting, regurgitation, wheezing, and coughing. Initially, a diagnosis of gastroesophageal reflux disease with secondary aspiration pneumonitis was made but clinical signs did not resolve with treatment., Clinical Findings: Thoracic and cervical radiography and CT revealed a sessile, irregularly marginated soft tissue opacity at the level of the fourth rib. Results of a CBC, serum biochemical analysis, and urinalysis were within reference limits. Results of abdominal ultrasonography were normal., Treatment and Outcome: Tracheoscopy revealed a firm, irregularly marginated mass apparently originating from the ventral aspect of the trachea, occluding approximately one-half of the tracheal lumen, and located 2 cm cranial to the carina. Cytologic and histopathologic examination of fine-needle aspirate and biopsy samples suggested a benign etiology; therefore, endoscopic minimally invasive laser and electrocautery resection of the mass was scheduled. A total IV anesthetic protocol was administered with an oxygen-air mixture used to decrease the risk of fire during tracheal surgery. The mass was successfully resected, and histopathologic examination confirmed a diagnosis of osteochondroma. Clinical signs resolved, and at follow-up 32 months later, no regrowth of the mass was evident., Clinical Relevance: Tracheoscopy-guided electrocautery and surgical diode laser resection was successful in removing an obstructive tracheal mass that was not resectable by means of a conventional open surgical approach. Minimally invasive procedures may decrease morbidity and mortality and improve outcome in appropriately selected small animal patients.

Vascular-based interventional radiology (IR) procedures are being more regularly performed in veterinary patients for both diagnostic and therapeutic purposes. A complete description of the fluoroscopic arterial anatomy of the canine abdominal cavity has not been published. This information is essential for performance of IR procedures to allow for improved preparation before and during a particular procedure. The primary purpose of this study was to provide a fluoroscopic description of the vascular branching from the abdominal aorta in a ventro-dorsal projection with a secondary goal of producing pictorial reference images of the major abdominal arterial blood vessels. Five healthy female hound type dogs were enrolled and underwent fluoroscopic arteriography. During fluoroscopy, both nonselective and selective arteriography were performed. The nonselective arteriograms were obtained in the aorta at four locations: cranial to the celiac artery, cranial to the renal arteries, cranial to the caudal mesenteric artery, and cranial to the branching of the external iliac arteries. Selective arteriography was conducted by performing injections into the following arteries: celiac, splenic, common hepatic, cranial mesenteric, left and right renal, and caudal mesenteric. Fluoroscopic arteriography allowed for excellent characterization of the aortic ostia and the location of the lower order vascular branches. Future evaluation of vascular-based treatment options will likely increase as the understanding of the normal and pathologic anatomy improves., (© 2015 American College of Veterinary Radiology.)

Objectives: To document a technique for one-lung ventilation (OLV) in cats and evaluate the effect of low-pressure carbon dioxide insufflation and OLV (OLV-CDI) on cardiorespiratory variables in cats., Study Design: Prospective randomized study., Animals: Cats (n = 6)., Methods: General anesthesia was induced using a standardized anesthetic protocol. A thermodilution catheter was placed into the pulmonary artery using fluoroscopic guidance. Two 6 mm thoracoscopic cannulae were placed at a subxiphoid and intercostal location, respectively, to allow direct observation of all lung lobes. OLV was induced using an endobronchial blocker, which was placed into the right and left main stem bronchi in randomized order using bronchoscopic guidance. Cardiorespiratory variables were measured at 5 and 30 minutes after induction of OLV and subsequently at 5 and 30 minutes after initiation of OLV-CDI at intra-thoracic pressures of 3 mmHg., Results: Left-sided OLV was successful in 5 cats, right-sided OLV was successful in 2 cats, and neither was successful in 1 cat. No significant effects on hemodynamic variables or oxygen delivery were observed after right or left-sided OLV alone. Hemodynamic variables were also well-preserved after OLV-CDI; however, oxygen delivery was significantly lower after left OLV-CDI compared with right OLV-CDI, and in 2 cats, severe desaturation occurred after L-OLV-CDI before the 30 minute time point., Conclusions: OLV can be used in cats for thoracoscopic interventions. Although right OLV-CDI was tolerated better than left OLV-CDI, the technique requires further investigation before it can be recommended for widespread clinical use., (© Copyright 2014 by The American College of Veterinary Surgeons.)

Objective: To determine the cardiopulmonary changes associated with intravenous (IV) infusions of dexmedetomidine at equipotent isoflurane-dexmedetomidine concentrations compared with isoflurane alone., Study Design: Prospective, randomized, crossover experiment., Animals: Six adult intact female mixed-breed dogs weighing (mean ± SD [range]) 23.3 ± 3.8 (17.8-29.4) kg., Methods: Anesthesia was induced and maintained with isoflurane in oxygen. Measurements of respiratory rate (fR), heart rate (HR), systemic and pulmonary arterial pressures (SAP, DAP, MAP, MPAP), central venous pressure (CVP), pulmonary arterial occlusion pressure (PAOP), cardiac index (CI), left and right ventricular stroke work index (LVSWI, RVSWI), systemic and pulmonary vascular resistance index (SVRI, PVRI), arteriovenous shunt (Q˙s/Q˙t), oxygen delivery (D˙O2), oxygen extraction ratio (O2 ER), oxygen consumption, arterial and mixed venous blood gases, and arterial packed cell volume (PCV) were obtained 30 minutes after instrumentation at an end-tidal isoflurane concentration (Fe'Iso) of 1.73 ± 0.02% (1.3 MAC). Dexmedetomidine was administered IV at 0.5 or 3 μg kg(-1) over 6 minutes followed by an infusion at 0.5 (LD) or 3 μg kg(-1) hour(-1) (HD), respectively, with Fe'Iso at 1.41 ± 0.02 (LD) or 0.72 ± 0.09% (HD). Measurements were taken at 10, 30, 60, 90, 120, 150 and 180 minutes after the start of the infusion., Results: The low dose produced significant decreases in HR, increases in SAP, DAP, CVP, MPAP, PAOP and LVSWI, but no change in CI. HD produced significant increases in SAP, MAP, DAP, CVP, PAOP, SVRI, LVSWI, O2 ER and PCV and significant decreases in CI and D˙O2. There were significant differences between treatments in HR, MAP, DAP, CVP, MPAP, PAOP, CI, SVRI, HCO3-, SBE, D˙O2, O2 ER and Q˙s/Q˙t., Conclusions and Clinical Relevance: Cardiopulmonary changes associated with LD were within clinically accepted normal ranges whereas HD produced clinically significant changes. The LD may be useful as an anesthetic adjunct in healthy dogs., (© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.)

Objective: To compare effectiveness and complications associated with peribulbar and retrobulbar anesthesia with bupivacaine in cats., Animals: 6 healthy adult cats., Procedures: Cats were sedated with dexmedetomidine and received a peribulbar injection of 0.5% bupivacaine (1.5 mL), iopamidol (0.5 mL), and saline (0.9% NaCl) solution (1 mL) or retrobulbar injection of 0.5% bupivacaine (0.75 mL) and iopamidol (0.25 mL) in a crossover study with ≥ 2 weeks between treatments. The contralateral eye was the control. Injectate distribution was evaluated with CT. After atipamezole administration, periocular and corneal sensations, intraocular pressure (IOP), and ocular reflexes and appearance were evaluated for 24 hours., Results: All peribulbar and 3 of 6 retrobulbar injections resulted in CT evidence of intraconal injectate. Corneal sensation and periocular skin sensation were absent or significantly reduced relative to that for control eyes for 3 hours after peribulbar injection. Mean ± SD IOP immediately after injection was significantly higher for eyes with peribulbar injections (33 ± 12 mm Hg) than for control eyes or eyes with retrobulbar injections (both 14 ± 4 mm Hg) but 10 minutes later decreased to 18 ± 3 mm Hg. Exophthalmos, chemosis, and ptosis were evident in most injected eyes, and irritation was evident in 3 of 6 peribulbar-injected and 1 of 6 retrobulbar-injected eyes. All conditions resolved within 14 hours., Conclusions and Clinical Relevance: Peribulbar injection resulted in intraconal deposition of bupivicaine in a higher percentage of cats than did retrobulbar injection and induced notable anesthesia relative to that for the control eye; however, IOP increased temporarily.

Objective: To evaluate the exposure obtained for minimally invasive abdominal organ biopsy (MIOB) from 3 access incisions in cats., Design: Prospective experimental study and clinical case series., Animals: 6 purpose-bred research cats and 6 feline clinical patients with indications for abdominal organ biopsy., Procedures: Three 3-cm incisions into the peritoneal cavity were created at different locations along the linea alba in research cats in randomized order. A wound retraction device was inserted in each incision. Ability to exteriorize various abdominal organs to the extent required to reasonably perform a surgical biopsy was recorded, and results were compared among incision sites. On the basis of results obtained, the access incision that provided exposure of the most frequently biopsied abdominal organs was used to perform MIOB in 6 feline clinical patients with various underlying pathological conditions., Results: On the basis of experiments with research cats, a 3-cm access incision centered midway between the caudal margin of the xiphoid cartilage and the umbilicus was found to provide access for MIOB for most organs. In 5 of 6 clinical patients, all of the organs of interest were biopsied successfully via this incision location, although access to all hepatic lobes and all parts of the pancreas was inconsistent. In 1 cat, conversion to an open approach was performed because a palpable mass was detected in the area of the duodenocolic ligament., Conclusions and Clinical Relevance: Optimization of access incision location for MIOB allowed biopsy specimen collection from organs of interest to be performed in a minimally invasive manner in cats.

Background. Our objective was to test the effectiveness of a local anesthetic line block administered before surgery in reducing postoperative pain scores in dogs undergoing ovariohysterectomy (OVHX). Methods. This study is a prospective, randomized, blinded, clinical trial involving 59 healthy female dogs. An algometric pressure-measuring device was used to determine nociceptive threshold, and compared to three subjective pain scales. Group L/B received a line block of lidocaine (4 mg/kg) and bupivacaine (1 mg/kg) subcutaneously in the area of the incision site and saline subcutaneously as premedication; group L/BM (positive control) received a similar block and morphine (0.5 mg/kg) subcutaneously for premedication; and group SS (negative control) received a saline line block and saline premedication. Criteria for rescue analgesia were defined before the study. Dogs were assessed prior to surgery, at extubation (time 0) and at 2, 4, 6, 8 and 24 h post-recovery. The data were analyzed with one-way ANOVA, and a Split Plot Repeated Measures ANOVA with one grouping factor and one repeat factor (time). P < 0.05 was considered statistically significant. Results. Approximately 33% of dogs required rescue analgesia at some point during the study, with no significant difference between groups. There was no significant difference between treatment groups with any assessment method. Conclusions. As there were no statistically significant differences between positive and negative controls, the outcome of this technique cannot be proven.

Objective: To compare injectate distribution and potential complications of retrobulbar and peribulbar injections in cat cadavers., Study Design: Prospective randomized masked study., Animals: Ten cat cadavers (20 eyes)., Methods: A dorsomedial retrobulbar injection (RB) of 1 mL of 0.5% bupivacaine and iopamidol (1:1) was performed in seven eyes. A dorsomedial peribulbar injection (PB-1) of 4 mL of the same injectate was performed in seven eyes, and two peribulbar injections (PB-2) of the same injectate, divided equally between the dorsomedial and ventrolateral regions (2 mL each) were performed in six eyes. Intraocular pressure (IOP) was measured before, immediately and 15 minutes after injection. Cadavers underwent computed tomography before and following injections. A radiologist scored injectate distribution within the intraconal space (none, moderate, or large) and around the optic nerve (degrees). An injection was defined as likely to provide adequate regional anesthesia if the volume of distribution of intraconal injectate was 'large' and it contacted over 270° of the optic nerve circumference., Results: The success rate (95% confidence interval) of RB, PB-1, and PB-2 injections was 71% (29.0-96.3%), 86% (42.1-99.6%), and 67% (22.3-95.7%), respectively. With all three techniques, IOP increased significantly after injection, but returned to baseline by 15 minutes following RB injection. No intraocular, intravascular, intrathecal, or intraneural injectate was observed., Conclusion and Clinical Relevance: The single-peribulbar injection technique may be superior to retrobulbar or double-peribulbar injections, however, all techniques require further studies in live cats to determine safety and efficacy prior to clinical use., (© 2013 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.)

Objective: To evaluate the effect of pneumoperitoneum on cardiorespiratory variables and working space during experimental induction of 3 intra-abdominal pressures (IAPs) in cats., Animals: 6 healthy young adult neutered male domestic shorthair cats., Procedures: All cats were anesthetized through use of a standardized protocol. A catheter was placed in the right femoral artery for blood pressure and blood gas monitoring. A thermodilution catheter was placed in the right jugular vein via fluoroscopic guidance. Cardiopulmonary variables were measured before (baseline) and 2 and 30 minutes after initiation of pneumoperitoneum at IAPs of 4, 8, and 15 mm Hg; these were created through the use of a mechanical insufflator. At each IAP, abdominal dimensions (height, width, and circumference) were measured at a standardized location., Results: At 4 mm Hg and 8 mm Hg IAP, no clinically important changes were identified in cardiorespiratory values. Heart rate, cardiac index, and stroke volume index remained unchanged throughout the study at all IAPs. Mean arterial blood pressure began to increase at 8 mm Hg and was significantly higher, compared with baseline, at both time points at 15 mm Hg. At 15 mm Hg, Paco2 was significantly higher and cats were more acidotic than at baseline. Working space was subjectively greater at 8 mm Hg than at 4 mm Hg IAP; however, at 15 mm Hg, no clinically important enlargement of the working space was identified, compared with at 8 mm Hg., Conclusions and Clinical Relevance: Values of cardiopulmonary variables were largely unchanged by induction of pneumoperitoneum in healthy cats up to an IAP of 8 mm Hg, and no clinically important increases in working space were evident at an IAP of 15 versus 8 mm Hg. These findings provide little justification for use of IAPs > 8 mm Hg in healthy cats undergoing laparoscopic procedures; however, whether the situation is similar in diseased or elderly cats remains to be determined.

Objective: To describe clinicopathologic features of dogs that underwent lung lobectomy for resection of primary lung tumors via video-assisted thoracoscopic surgery (VATS) or open thoracotomy (OT) and to compare short-term outcomes for dogs following these procedures., Design: Retrospective cohort study., Animals: 46 medium- to large-breed dogs with primary lung tumors., Procedures: Medical records of dogs that underwent a lung lobectomy via VATS (n = 22) or OT (24) for resection of primary lung tumors between 2004 and 2012 were reviewed. Dogs were included if they weighed > 10 kg (22 lb) and resection of a primary lung tumor was confirmed histologically. Tumor volumes were calculated from preoperative CT scans where available. Surgical time, completeness of excision, time in the ICU, indwelling thoracic drain time, postoperative and total hospitalization time, incidence of major complications, and short-term survival rate were evaluated., Results: VATS was performed with a 3-port (n = 12) or 4-port (10) technique and 1-lung ventilation (22). In 2 of 22 (9%) dogs, VATS was converted to OT. All dogs survived to discharge from the hospital. There were no significant differences between the VATS and OT groups with regard to most variables. Surgery time was significantly longer for VATS than for OT (median, 120 vs 95 minutes, respectively)., Conclusions and Clinical Relevance: In medium- to large-breed dogs, short-term outcomes for dogs that underwent VATS for lung lobectomy were comparable to those of dogs that underwent OT. Further studies are required to evaluate the effects of surgical approach on indices of postoperative pain and long-term outcomes.

Objective: To evaluate the effects of dorsal versus lateral recumbency on the cardiopulmonary system during isoflurane anesthesia in red-tailed hawks (Buteo jamaicensis)., Animals: 6 adult 1.1- to 1.6-kg red-tailed hawks., Procedures: A randomized, crossover study was used to evaluate changes in respiratory rate, tidal volume, minute ventilation, heart rate, mean arterial and indirect blood pressures, and end-tidal Pco(2) measured every 5 minutes plus Paco(2) and Pao(2) and arterial pH measured every 15 minutes throughout a 75-minute study period., Results: Respiratory rate was higher, tidal volume lower, and minute ventilation not different in lateral versus dorsal recumbency. Position did not affect heart rate, mean arterial blood pressure, or indirect blood pressure, although heart rate decreased during the anesthetic period. Birds hypoventilated in both positions and Paco(2) differed with time and position × time interaction. The Petco(2) position × time interaction was significant and Petco(2) was a mean of 7 Torr higher than Paco(2). The Paco(2) in dorsal recumbency was a mean of 32 Torr higher than in lateral recumbency. Birds in both positions developed respiratory acidosis., Conclusions and Clinical Relevance: Differences in tidal volume with similar minute ventilation suggested red-tailed hawks in dorsal recumbency might have lower dead space ventilation. Despite similar minute ventilation in both positions, birds in dorsal recumbency hypoventilated more yet maintained higher Pao(2), suggesting parabronchial ventilatory or pulmonary blood flow distribution changes with position. The results refute the hypothesis that dorsal recumbency compromises ventilation and O(2) transport more than lateral recumbency in red-tailed hawks.

Objective: To evaluate the physiological effect and response to noxious stimulation at five concentrations of MS-222 in koi (Cyprinus carpio)., Study Design: Prospective experimental study., Animals: Twenty-one healthy adult unknown sex koi fish weighing mean 450±SD 120 g., Methods: Each fish was exposed to five different concentrations of MS-222 (50, 70, 110, 150 and 190 mg L(-1) ) in a random sequence during the same anaesthetic event. For each concentration of MS-222, vital functions such as heart rate (HR) (via Doppler) and opercular rate (OpR) were recorded after a standardized induction period. Response to two noxious stimuli in the form of haemostat clamp pressure applied on the tail and the lip was evaluated, and blood was drawn to measure biochemical and blood gas values., Results: Decrease in response to noxious stimulation with an increase of MS-222 concentration both for the lip (p=0.0027) and the tail (p<0.0001) stimulus was observed. Biochemical values were unaffected by the concentration of MS-222 with the exception of lactate concentration which was weakly correlated with the duration of anaesthesia (r=0.31, p<0.001) and the number of times the fish was clamped or bled prior to sampling (r=0.23, p<0.001). Opercular rate decreased with the increase in anaesthetic concentration, and HR was not affected., Conclusions and Clinical Relevance: Our results indicated a decrease in response to stimulus and a decrease in OpR that were associated with increased concentrations of MS-222. This may assist in establishing anaesthetic protocols using MS-222 in fish and supports the use of supramaximal pressure stimuli to teleost fish under variable MS-222 concentrations as a model for future studies., (© 2012 The Authors. Veterinary Anaesthesia and Analgesia. © 2012 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.)

Objective: To describe a technique for blind thoracoscopic-assisted double-lumen endobronchial tube (DLT) placement for achieving one-lung ventilation (OLV) using 3 different DLT designs and to evaluate whether thoracic auscultation could reliably confirm OLV in dogs., Study Design: Prospective randomized study., Animals: Mature female hound dogs (n = 6)., Methods: Physical examination, baseline blood work and thoracic radiography confirmed the absence of preexisting disease in all dogs. Thoracoscopic observation was established through a subxiphoid portal and used for evaluation of differential lung lobe ventilation. Each dog was sequentially intubated using 1 of 3 DLT designs in random order; Robertshaw left-sided tube (RS-L), Carlens left-sided tube (C-L), Dr. White right-sided tube (DW-R). Incidence of initial and overall (after a maximum of 3 DLT manipulations) correct and complete OLV (CC-OLV) was recorded. After each blind thoracoscopic-assisted DLT placement, bronchoscopic evaluation was performed to document correct DLT position., Result: Blind DLT placement achieved overall CC-OLV in all dogs using RS-L, 66% using C-L, and all using DW-R. Successful initial left-sided OLV (L-OLV) was statistically more likely when RS-L DLTs were used compared to C-L or DW-R. Of cases where overall CC-OLV was achieved, correct DLT position was present in only 44% of intubations., Conclusions: Blind DLT placement produced successful CC-OLV in all dogs using at least one DLT design evaluated. Use of thoracoscopic assistance may obviate the need for bronchoscopic observation during DLT placement in dogs. However, bronchoscopic observation may still refine DLT positioning in dogs after blind thoracoscopic-assisted DLT placement., (© Copyright 2012 by The American College of Veterinary Surgeons.)

Objective: To evaluate the use of a bipolar vessel-sealing device for peripheral lung lobe biopsy in healthy dogs., Study Design: Experimental study., Animals: Mature female hound dogs (n = 6)., Methods: Thoracoscopic access was obtained by placement of a subxiphoid telescope portal with instrument portals at the right 4-6th intercostal spaces and the left 10th intercostal space. The 10-mm Ligasure Atlas device was used to collect a biopsy specimen from the periphery of the left cranial lung lobe. Dogs were recovered from anesthesia. Histologic evaluation was used to characterize the effect of biopsy technique on pulmonary tissue. Thoracic radiography was performed at 1, 2, 4, and ∼180 days to evaluate for air leakage or other postoperative complications., Results: Lung specimens were collected without complications. Postoperatively, 1 dog had some residual pneumothorax thought to be secondary to incomplete thoracic evacuation of air postoperatively. No evidence of air leakage was detected at any time point. Histologically, specimens had 3 distinct zones: a crush zone representing the tissue within the jaws of the device, a transition zone of thermally damaged parenchyma, and beyond that a viable zone of normal parenchyma., Conclusion: From these limited data, it appears that the Ligasure Atlas vessel-sealing device can be used for peripheral lung biopsy in healthy dogs. Further studies are required to evaluate the efficacy of the device in dogs with parenchymal disease., (Copyright 2012 by The American College of Veterinary Surgeons.)

Objective: To determine the impact of three different target plasma concentrations of fentanyl on the minimum anaesthetic concentration (MAC) for isoflurane in the red-tailed hawk and the effects on the haemodynamic profile., Study Design: Experimental study., Animal Population: Six healthy adult red-tailed hawks (Buteo jamaicensis) of unknown sex with body weights (mean ± SD) of 1.21 ± 0.15 kg., Methods: This study was undertaken in two phases. In the first phase anaesthesia was induced with isoflurane in oxygen via facemask and maintained with isoflurane delivered in oxygen via a Bain circuit. Following instrumentation baseline determination of the MAC for isoflurane was made for each animal using the bracketing method and a supramaximal electrical stimulus. End-tidal isoflurane concentration (E'Iso) was then set at 0.75 × MAC and after an appropriate equilibration period a bolus of fentanyl (20 μg kg(-1)) was administered intravenously (IV) in order to determine the pharmacokinetics of fentanyl in the isoflurane-anaesthetized red-tailed hawk. During the second phase anaesthesia was induced in a similar manner and E'Iso was set at 0.75 × MAC for each individual. Fentanyl was infused IV to achieve target plasma concentrations between 8 and 32 ng mL(-1). At each fentanyl plasma concentration, the MAC for isoflurane and cardiovascular variables were determined. Data were analyzed by use of repeated-measures anova., Results: Mean ± SD fentanyl plasma concentrations and isoflurane MACs were 0 ± 0, 8.51 ± 4, 14.85 ± 4.82 and 29.25 ± 11.52 ng mL(-1), and 2.05 ± 0.45%, 1.42 ± 0.53%, 1.14 ± 0.31% and 0.93 ± 0.32% for the target concentrations of 0, 8, 16 and 32 ng mL(-1), respectively. At these concentrations fentanyl significantly (p = 0.0016) decreased isoflurane MAC by 31%, 44% and 55%, respectively. Dose had no significant effect on heart rate, systolic, diastolic or mean arterial blood pressure., Conclusions and Clinical Relevance: Fentanyl produced a dose-related decrease of isoflurane MAC with minimal effects on measured cardiovascular parameters in red-tailed hawks., (© 2011 The Authors. Veterinary Anaesthesia and Analgesia. © 2011 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.)

Objectives: To evaluate the efficacy of ultrasound-guidance in nerve blockade of the sciatic and saphenous nerves in dogs and to determine if this technique could allow lower anaesthetic doses to be used with predictable onset and duration of effect., Study Design: Prospective randomized (for dose and leg) blinded experimental crossover trial with 10 day washout period., Animals: Six healthy female Hound dogs aged 12.3 +/- 0.5 (mean +/- SD) months and weighing 18.7 +/- 0.8 (mean +/- SD) kg., Methods: An ultrasound-guided, perineural injection was used with saline at 0.2 mL kg(-1) (Sal) or bupivacaine 0.5% at 0.05 (low dose; LD), 0.1 (medium dose; MD), or 0.2 (high dose; HD) mL kg(-1), divided 2/3 at the sciatic nerve and 1/3 at the saphenous nerve. Blocks were performed using dexmedetomidine sedation with atipamezole reversal immediately after completion of the injections. Motor/proprioceptive and sensory functions were scored using a 0-8 and a 0-2 scale, respectively. Clinically relevant blocks were defined as a motor score > or =2 and sensory score > or =1. Nonparametric methods were used for statistical analysis., Results: No adverse effects were noted. There was a significant difference between the treatments with bupivacaine and the saline control, but not between the three bupivacaine treatments. Success rates of clinically relevant sciatic and saphenous blocks were both 67% (CI 95% 0.22-0.96). Onset and duration of the blocks were variable; 20-160 and 20-540 minutes, respectively., Conclusion and Clinical Relevance: None of the bupivacaine doses was significantly superior, though there was a tendency for a better block with the high bupivacaine dose. Either the technique or the doses used need further modification before this method will be useful in clinical practice.

Surgical procedures of the wing are commonly performed in companion, captive, and wild avian species. To develop a clinically applicable brachial plexus nerve block technique for perioperative analgesia in birds, 8 adult female mallard ducks (Anas platyrhynchos) were anesthetized and used in several local anesthetic trials with bupivacaine (2 or 8 mg/kg) or a combination of lidocaine (15 mg/kg) and epinephrine (3.8 microg/kg) perineurally; equal volumes of saline were administered as control treatments. Both axillary and dorsal approaches to the brachial plexus were evaluated. With the axillary approach, radial and ulnar compound nerve action potentials (CNAP), sensory nerve conduction velocities (SNCVs), and cord dorsum potentials (CDPs) were recorded after distal sensory nerve stimulation. Values were recorded before and at 5, 30, and 60 minutes after injection of local anesthetic or saline. Birds were monitored for the presence of a wing droop and a change in motor function on recovery from anesthesia. Results were highly variable for all techniques. No technique significantly decreased CDPs or resulted in consistent wing droop. Radial and ulnar CNAPs, SNCVs, and CDPs were consistently recorded in all birds. Variable results might indicate that the treatment, concentration, or volume of local anesthetic used was ineffective in producing local anesthesia. Electrodiagnostic methods used in these ducks to assess loss of sensory nerve conduction might not be sensitive enough to assess the effects of local anesthesia. Further research is needed to identify methods for assessing the efficacy of brachial plexus nerve blockade in birds.

Objective: To compare Doppler and oscillometric methods of indirect arterial blood pressure (IBP) with direct arterial measurements in anesthetized and awake red-tailed hawks., Study Design: Prospective, randomized, blinded study., Animals: Six, sex unknown, adult red-tailed hawks., Methods: Birds were anesthetized and IBP measurements were obtained by oscillometry (IBP-O) and Doppler (IBP-D) on the pectoral and pelvic limbs using three cuffs of different width based on limb circumference: cuff 1 (20-30% of circumference), cuff 2 (30-40%), and cuff 3 (40-50%). Direct arterial pressure measurements were obtained from the contralateral superficial ulnar artery. Indirect blood pressure measurements were compared to direct systolic arterial pressure (SAP) and mean arterial pressure (MAP) during normotension and induced states of hypotension and hypertension. Measurements were also obtained in awake, restrained birds. Three-way anova, linear regression and Bland-Altman analyses were used to evaluate the IBP-D data. Results are reported as mean bias (95% confidence intervals)., Results: The IBP-O monitor reported errors during 54% of the measurements. Indirect blood pressure Doppler measurements were most accurate with cuff 3 and were comparable to MAP with a bias of 2 (-9, 13 mmHg). However, this cuff consistently underestimated SAP with a bias of 33 (19, 48 mmHg). Variability in the readings within and among birds was high. There was no significant difference between sites of cuff placement. Awake birds had SAP, MAP and diastolic arterial pressure that were 56, 43, and 38 mmHg higher than anesthetized birds., Conclusions and Clinical Relevance: Indirect blood pressure (oscillometric) measurements were unreliable in red-tailed hawks. Indirect blood pressure (Doppler) measurements were closer to MAP measurements than SAP measurements. There was slightly better agreement with the use of cuff 3 on either the pectoral or pelvic limbs. Awake, restrained birds have significantly higher arterial pressures than those under sevoflurane anesthesia.

Objective: To determine the effects of body position on lung and air-sac volumes in anesthetized and spontaneously breathing red-tailed hawks (Buteo jamaicensis)., Animals: 6 adult red-tailed hawks (sex unknown)., Procedures: A crossover study design was used for quantitative estimation of lung and air-sac volumes in anesthetized hawks in 3 body positions: dorsal, right lateral, and sternal recumbency. Lung volume, lung density, and air-sac volume were calculated from helical computed tomographic (CT) images by use of software designed for volumetric analysis of CT data. Effects of body position were compared by use of repeated-measures ANOVA and a paired Student t test., Results: Results for all pairs of body positions were significantly different from each other. Mean +/- SD lung density was lowest when hawks were in sternal recumbency (-677 +/- 28 CT units), followed by right lateral (-647 +/- 23 CT units) and dorsal (-630 +/- 19 CT units) recumbency. Mean lung volume was largest in sternal recumbency (28.6 +/- 1.5 mL), followed by right lateral (27.6 +/- 1.7 mL) and dorsal (27.0 +/- 1.5 mL) recumbency. Mean partial air-sac volume was largest in sternal recumbency (27.0 +/- 19.3 mL), followed by right lateral (21.9 +/- 16.1 mL) and dorsal (19.3 +/- 16.9 mL) recumbency., Conclusions and Clinical Relevance: In anesthetized red-tailed hawks, positioning in sternal recumbency resulted in the greatest lung and air-sac volumes and lowest lung density, compared with positioning in right lateral and dorsal recumbency. Additional studies are necessary to determine the physiologic effects of body position on the avian respiratory system.

Background: Some studies in dogs undergoing adrenalectomy for pheochromocytoma suggest that anesthetic complications and perioperative mortality are common. In humans, surgical outcome has improved with the use of phenoxybenzamine (PBZ) before adrenalectomy., Hypothesis: Dogs treated with PBZ before adrenalectomy have increased survival compared with untreated dogs., Animals: Forty-eight dogs that underwent adrenalectomy for pheochromocytoma., Methods: A retrospective medical record review for dogs that underwent adrenalectomy for pheochromocytoma at a veterinary medical teaching hospital over the period from January 1986 through December 2005., Results: Twenty-three of 48 dogs were pretreated with PBZ (median dosage: 0.6 mg/kg PO q12h) for a median duration of 20 days before adrenalectomy. Duration of anesthesia and surgery, percentage of dogs with pheochromocytoma involving the right versus left adrenal gland, size of tumor, and presence of vascular invasion were similar for PBZ-treated and untreated dogs. Thirty-three (69%) of 48 dogs survived adrenalectomy in the perioperative period. PBZ-treated dogs had a significantly (P = .014) decreased mortality rate compared with untreated dogs (13 versus 48%, respectively). Additional significant prognostic factors for improved survival included younger age (P = .028), lack of intraoperative arrhythmias (P = .0075), and decreased surgical time (P = .0089)., Conclusions and Clinical Importance: Results from this retrospective study support treatment with PBZ before surgical removal of pheochromocytoma in dogs.

Objective: To develop a clinically applicable technique for recording cord dorsum potentials (CDPs) following stimulation of the radial and ulnar nerves and establish reference values for radial and ulnar sensory nerve conduction velocities (SNCVs) in the wings of ducks., Animals: 8 clinically normal adult female mallard ducks (Anas platyrhynchos)., Procedures: Radial and ulnar compound nerve action potentials (CNAPs) and CDPs were recorded following distal sensory nerve stimulation. The CDPs were recorded from the interarcuate space between the last cervical vertebra and the first thoracic vertebra. Surgical dissection and transection of the brachial plexus in 1 anesthetized duck were performed to identify nerve root location and confirm functional loss of nerve conduction assessed by loss of the CDP., Results: Radial and ulnar CNAPs and CDPs were consistently recorded in all birds. Median radial SNCV was 38.3 m/s (range, 36.0 to 49.0 m/s), and ulnar SNCV was 35.3 m/s (range, 28.0 to 40.0 m/s). Surgical transection of the brachial plexus resulted in complete loss of the CDP., Conclusions and Clinical Relevance: Measurement of radial and ulnar SNCV or CDP is feasible in isoflurane-anesthetized mallard ducks. The CDP accurately reflects sensory nerve conduction through the brachial plexus. Assessment of brachial plexus function in mallard ducks via evaluations of SNCVs and CDPs may have application for diagnosis of traumatic injuries to the brachial plexus, evaluation of neuropathies associated with exposure to toxic chemicals, and assessment of the efficacy of interventions such as brachial plexus nerve blockade.

Objective: To determine the incidence and type of alterations in heart rate (HR), peak systolic blood pressure (PSBP), and serum biochemical variables (serum total bilirubin, BUN, and creatinine concentrations) associated with IV administration of ionic-iodinated contrast (IIC), nonionic-iodinated contrast (NIC), and gadolinium (GD) contrast media in anesthetized cats., Animals: 220 anesthetized cats undergoing cross-sectional imaging., Procedures: HR and PSBP were recorded at 5-minute intervals for 20 minutes for untreated control cats and cats that received IIC, NIC, or GD contrast medium. The development of HR < 100 beats/min or > 200 beats/min that included a > or = 20% change from baseline was considered a response. The development of PSBP of < 90 mm Hg or > 170 mm Hg that included a > or = 20% change from baseline was considered a response. Pre- and postcontrast serum biochemical values were recorded. Results-Of cats receiving IIC medium, 2% (1/60) had a response in HR at > or = 1 time point. Of cats receiving IIC medium, 7% (4/60) had a response in PSBP. None of the cats receiving NIC medium had a response in HR; 2 of 12 had a response in PSBP. Of cats receiving GD contrast medium, 6% (5/83) had a response in HR and 8% (7/83) had a response in PSBP. None of the control cats had a response in HR or PSBP. No serum biochemical alterations were observed., Conclusions and Clinical Relevance: IV administration of iodine and GD contrast media in anesthetized cats was associated with changes in HR and PSBP.

Objective: To determine the incidence and type of alterations in heart rate (HR), peak systolic blood pressure (PSBP), and serum biochemical variables (total bilirubin, BUN, and creatinine concentrations) associated with IV administration of ionic-iodinated contrast (IIC), nonionic-iodinated contrast (NIC), and gadolinium dimeglumine (GD) contrast media in anesthetized dogs., Animals: 280 anesthetized dogs undergoing cross-sectional imaging., Procedures: HR and PSBP were recorded at 5-minute intervals for 20 minutes for untreated control dogs and dogs that received IIC, NIC, or GD contrast medium. The development of an HR of < 60 beats/min or > 130 beats/min that included a > or = 20% change from baseline was considered a response. The development of PSBP of < 90 mm Hg or > 160 mm Hg that included a > or = 20% change from baseline was considered a response. Pre- and postcontrast serum biochemical values were recorded. Results-Of dogs receiving IIC medium, 3% (3/91) had a response in HR and 4% (4/91) had a response in PSBP at > or = 1 time points. None of the dogs receiving NIC medium had a response in HR; 1 of 16 had a response in PSBP. Of dogs receiving GD contrast medium, 1% (1/92) had a response in HR and 4% (4/92) had a response in PSBP. Of control dogs, 2% (2/81) had a response in HR and 4% (3/81) had a response in PSBP. No serum biochemical alterations were observed., Conclusions and Clinical Relevance: IV administration of contrast media in anesthetized dogs caused moderate bradycardia, tachycardia, hypotension, or hypertension.

Objective: To determine the antinociceptive effects of epidural administration of morphine or buprenorphine in cats by use of a thermal threshold model., Animals: 6 healthy adult cats., Procedures: Baseline thermal threshold was determined in duplicate. Cats were anesthetized with isoflurane in oxygen. Morphine (100 microg/kg diluted with saline [0.9% NaCl] solution to a total volume of 0.3 mL/kg), buprenorphine (12.5 microg/kg diluted with saline solution to a total volume of 0.3 mL/kg), or saline solution (0.3 mL/kg) was administered into the epidural space according to a Latin square design. Thermal threshold was determined at various times up to 24 hours after epidural injection., Results: Epidural administration of saline solution did not affect thermal threshold. Thermal threshold was significantly higher after epidural administration of morphine and buprenorphine, compared with the effect of saline solution, from 1 to 16 hours and 1 to 10 hours, respectively. Maximum (cutout) temperature was reached without the cat reacting in 0, 74, and 11 occasions in the saline solution, morphine, and buprenorphine groups, respectively., Conclusions and Clinical Relevance: Epidural administration of morphine and buprenorphine induced thermal antinociception in cats. At the doses used in this study, the effect of morphine lasted longer and was more intense than that of buprenorphine.

Case Description: Acute severe systemic reactions developed during i.v. administration of an ionic iodinated contrast agent (iothalamate meglumine) in 2 dogs undergoing contrast-enhanced computed tomography., Clinical Findings: Both dogs developed marked changes in heart rate and systolic arterial blood pressure during or immediately after i.v. administration of the contrast agent. The first dog became profoundly hypertensive and bradycardic with poor oxygenation, apparent bronchospasm, and prolonged diarrhea. The second dog became hypotensive and tachycardic with erythema on the ventral aspect of the abdomen and pelvic limbs, periocular edema, and diarrhea., Treatment and Outcome: Both dogs were treated for shock by means of i.v. fluid administration, and anesthesia was discontinued. The first dog was placed on a ventilator to improve oxygenation but was hypertensive and unresponsive for 6.5 hours following contrast agent administration. Bloody diarrhea persisted once consciousness was regained. The dog was discharged 3 days after contrast agent administration, and diarrhea resolved 15 days later. The second dog responded to phenylephrine administration, but urine output appeared low immediately following recovery from anesthesia. Urine output was normal the following day, and the dog was released 36 hours after contrast administration with no residual adverse effects., Clinical Relevance: Findings highlighted the potential risk for severe reactions associated with i.v. administration of ionic iodinated contrast agents in dogs. Both hypertensive and hypotensive responses were seen. Supportive care for systemic manifestations was effective in these 2 dogs, and extended hospitalization was not necessary.

Objectives: To determine the minimum alveolar concentration (MAC) of isoflurane during the infusion of ketamine., Study Design: Prospective, experimental trial., Animals: Twelve adult spayed female cats weighing 5.1 +/- 0.9 kg., Methods: Six cats were anesthetized with isoflurane in oxygen, intubated and attached to a circle-breathing system with mechanical ventilation. Catheters were placed in a peripheral vein for the infusion of fluids and ketamine, and the jugular vein for blood sampling for the measurement of ketamine concentrations. An arterial catheter was placed to allow blood pressure measurement and sampling for the measurement of PaCO2, PaO2 and pH. PaCO2 was maintained between 29 and 41 mmHg (3.9-5.5 kPa) and body temperature was kept between 37.8 and 39.3 degrees C. Following instrumentation, the MAC of isoflurane was determined in triplicate using a tail clamp method. A loading dose (2 mg kg(-1) over 5 minutes) and an infusion (23 microg kg(-1) minute(-1)) of ketamine was started and MAC was redetermined starting 30 minutes later. Two further loading doses and infusions were used, 2 mg kg(-1) and 6 mg kg(-1) with 46 and 115 microg kg(-1) minute(-1), respectively and MAC was redetermined. Cardiopulmonary measurements were taken before application of the noxious stimulus. The second group of six cats was used for the measurement of steady state plasma ketamine concentrations at each of the three infusion rates used in the initial study and the appropriate MAC value determined from the first study., Results: The MAC decreased by 45 +/- 17%, 63 +/- 18%, and 75 +/- 17% at the infusion rates of 23, 46, and 115 microg kg(-1) minute(-1). These infusion rates corresponded to ketamine plasma concentrations of 1.75 +/- 0.21, 2.69 +/- 0.40, and 5.36 +/- 1.19 microg mL(-1). Arterial blood pressure and heart rate increased significantly with ketamine. Recovery was protracted., Conclusions and Clinical Relevance: The MAC of isoflurane was significantly decreased by an infusion of ketamine and this was accompanied by an increase in heart rate and blood pressure. Because of the prolonged recovery in our cats, further work needs to be performed before using this in patients.