Publications by authors named "Khursheed R Mama"

62 Publications

A COMPARISON OF A SINGLE-DART VERSUS STAGED TWO-DART ANESTHESIA INDUCTION PROTOCOL IN PRZEWALSKI'S HORSES ().

J Zoo Wildl Med 2021 Jun;52(2):453-459

Department of Veterinary Services, San Diego Zoo Safari Park, Escondido, CA 92027, USA.

Przewalski's horses () are an endangered equid species. Anesthesia administered by remote delivery is often needed to provide medical care. Behavioral and physiologic parameters were prospectively compared in 14 horses (8 females and 6 males, 3-18 yr) after a single-dart or staged two-dart anesthesia induction protocol with intramuscular medetomidine (0.06 mg/kg), butorphanol (0.05 mg/kg), thiafentanil (0.02 mg/kg), and ketamine (1 mg/kg). Seven horses were randomly assigned to receive all drugs in a single dart, and the other seven to receive medetomidine and butorphanol 10 min prior to thiafentanil and ketamine in a second dart. Induction and recovery quality were scored on a scale from 1 to 5 (worst to best), and video recordings were assessed for frequency of specific behaviors. Need for supplemental propofol was recorded. Median induction score was significantly better ( = 0.01) after two darts (4/5) compared to a single dart (3/5). Degree of muscle fasciculation (undesirable) during induction was significantly lower (= 0.006) with the two-dart protocol. During the transition to recumbency, 71% versus 14% of horses transitioned headfirst (undesirable) after a single dart versus two darts, respectively (= 0.07). Supplemental propofol administration was necessary in 43% of horses after two darts and in 100% of horses after a single dart (= 0.10) to facilitate intubation and reach a working depth of anesthesia. Physiologic and recovery parameters were not significantly different between groups. Improved induction quality was observed clinically using a staged two-dart versus a single-dart protocol and should be considered when anesthetizing captive Przewalski's horses using this drug combination.
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http://dx.doi.org/10.1638/2020-0133DOI Listing
June 2021

Comparison of sedation quality and safety of detomidine and romifidine as a continuous rate infusion for standing elective laparoscopic ovariectomy in mares.

Vet Surg 2021 Jul 1;50(5):990-998. Epub 2021 Apr 1.

Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.

Objective: To compare efficacy and safety of a continuous rate infusion of detomidine hydrochloride and romifidine hydrochloride for standing elective bilateral laparoscopic ovariectomy in mares.

Study Design: Blinded, randomized prospective clinical study.

Animals: Eighteen healthy mares presenting for elective bilateral ovariectomy METHODS: Mares were randomly assigned to one of two sedation protocols. Prior to surgery, baseline head height, heart rate, respiratory rate, and postural sway were recorded. An IV loading dose of α2-agonist (46 μg/kg romifidine or 13.9 μg/kg detomidine) was administered. Standing sedation was maintained with a continuous rate infusion of the respective α2-agonist (126 μg/kg/h romifidine or 37.8 μg/kg/h detomidine). Intraoperative measurements included respiratory rate, heart rate, head height, postural sway, and response to surgical stimulus. Postoperatively, fecal output was recorded, and pain scoring was performed using composite pain score and visual analog scales.

Results: Three of 18 horses required additional α-2 agonists: one detomidine and two romifidine and butorphanol. Head height during surgery was lower (p < .001) in mares receiving detomidine. Postural sway around the vertical axis was greater in mares sedated with detomidine rather than romifidine (p = .013). No differences were detected in intraoperative heart rate, postoperative pain scores or postoperative fecal output between sedation techniques.

Conclusion: Comparable scores for surgical stimulation and sedation were measured in both sedation groups. No differences in postoperative analgesia or manure production were identified.

Clinical Significance: Romifidine appears suitable as an alternative to detomidine and may limit ataxia and head drop in sedated horses.
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http://dx.doi.org/10.1111/vsu.13627DOI Listing
July 2021

Combined effects of dexmedetomidine and vatinoxan infusions on minimum alveolar concentration and cardiopulmonary function in sevoflurane-anesthetized dogs.

Vet Anaesth Analg 2021 May 2;48(3):314-323. Epub 2021 Feb 2.

Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.

Objective: To evaluate the effects of combined infusions of vatinoxan and dexmedetomidine on inhalant anesthetic requirement and cardiopulmonary function in dogs.

Study Design: Prospective experimental study.

Methods: A total of six Beagle dogs were anesthetized to determine sevoflurane minimum alveolar concentration (MAC) prior to and after an intravenous (IV) dose (loading, then continuous infusion) of dexmedetomidine (4.5 μg kg hour) and after two IV doses of vatinoxan in sequence (90 and 180 μg kg hour). Blood was collected for plasma dexmedetomidine and vatinoxan concentrations. During a separate anesthesia, cardiac output (CO) was measured under equivalent MAC conditions of sevoflurane and dexmedetomidine, and then with each added dose of vatinoxan. For each treatment, cardiovascular variables were measured with spontaneous and controlled ventilation. Repeated measures analyses were performed for each response variable; for all analyses, p < 0.05 was considered significant.

Results: Dexmedetomidine reduced sevoflurane MAC by 67% (0.64 ± 0.1%), mean ± standard deviation in dogs. The addition of vatinoxan attenuated this to 57% (0.81 ± 0.1%) and 43% (1.1 ± 0.1%) with low and high doses, respectively, and caused a reduction in plasma dexmedetomidine concentrations. Heart rate and CO decreased while systemic vascular resistance increased with dexmedetomidine regardless of ventilation mode. The co-administration of vatinoxan dose-dependently modified these effects such that cardiovascular variables approached baseline.

Conclusions And Clinical Relevance: IV infusions of 90 and 180 μg kg hour of vatinoxan combined with 4.5 μg kg hour dexmedetomidine provide a meaningful reduction in sevoflurane requirement in dogs. Although sevoflurane MAC-sparing properties of dexmedetomidine in dogs are attenuated by vatinoxan, the cardiovascular function is improved. Doses of vatinoxan >180 μg kg hour might improve cardiovascular function further in combination with this dose of dexmedetomidine, but beneficial effects on anesthesia plane and recovery quality may be lost.
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http://dx.doi.org/10.1016/j.vaa.2020.12.007DOI Listing
May 2021

EVALUATION OF TWO MEDETOMIDINE-AZAPERONE-ALFAXALONE COMBINATIONS IN CAPTIVE ROCKY MOUNTAIN ELK ().

J Zoo Wildl Med 2021 Jan;51(4):825-833

Colorado Parks and Wildlife, Fort Collins, CO 80526, USA.

Alfaxalone has been successfully used intramuscularly (im) combined with medetomidine and azaperone for immobilization of small ungulates. An experimental 40 mg/ml alfaxalone solution (RD0387) was recently formulated for reduced injection volume. The objective of this study was to assess the efficacy and cardiopulmonary effects of high-concentration alfaxalone combined with medetomidine and azaperone for the intramuscular immobilization of captive Rocky Mountain elk (). Seven adult female elk were used in a crossover design in which they were administered alfaxalone 1 mg/kg, medetomidine 0.05 mg/kg, and azaperone 0.1 mg/kg or alfaxalone 0.5 mg/kg, medetomidine 0.1 mg/kg, and azaperone 0.1 mg/kg im approximately 3 wk apart. Drugs were delivered to each elk in a chute by hand injection. Once recumbent, elk were placed in sternal recumbency for a period of 30 min, during which time level of sedation, response to minor procedures, heart rate, respiratory rate, rectal temperature, oxygen saturation, and direct arterial blood pressures were recorded every 5 min. Arterial blood gases were performed every 15 min. At 30 min, elk were administered atipamezole 0.25 or 0.5 mg/kg im and recovery quality and times were recorded. Statistical comparisons were made by test, Wilcoxon signed rank test, and repeated measures analysis (significance level < 0.05). Both drug combinations provided effective immobilization for 30 min, with induction and recovery time and quality similar to other medetomidine-based combinations used in elk. Cardiopulmonary effects included bradycardia, hypertension, and hypoxemia that resolved with oxygen supplementation. The average injection volume in the low-dose alfaxalone combination was approximately 5 ml. These combinations provided deep sedation and the ability to perform minor procedures in captive elk, with acceptable cardiopulmonary parameters as long as supplemental oxygen was provided.
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http://dx.doi.org/10.1638/2020-0028DOI Listing
January 2021

Evaluation of the Element point-of-care blood gas analyzer for use in horses.

J Vet Emerg Crit Care (San Antonio) 2020 May 18;30(3):279-285. Epub 2020 Mar 18.

Department of Clinical Sciences, Colorado State University, Fort Collins, CO.

Objective: To compare the Element point-of-care (POC) portable blood gas analyzer with a laboratory-based bench-top reference analyzer using whole blood samples obtained from horses presenting to a referral center with various disorders in order to determine agreement between these analyzers.

Design: Prospective clinical study.

Setting: The study was conducted at a university teaching hospital at moderate altitude.

Animals: One hundred paired samples from 80 horses >1 year of age were collected after obtaining informed client consent. Fifty paired samples were from patients admitted for elective procedures and considered to be healthy, and 50 paired samples were emergency admissions and considered to be critically ill.

Measurements And Main Results: Paired whole blood samples were evaluated on both the Element POC and Radiometer ABL 800 FLEX analyzers simultaneously, and results were compared. Pearson correlation coefficients between analyzers were calculated. To assess agreement, scatter and Bland-Altman plots were evaluated, and mean difference and 95% limits of agreement were calculated for each analyte. Correlation was either good (0.8-0.92) or excellent (>0.93) for the majority of analytes. All analytes apart from hemoglobin had acceptable agreement, with ≥80% of individual results within agreement targets. Precision targets were acceptable for most analytes, with partial pressure of carbon dioxide (pCO ) and calcium (Ca ) exceeding precision targets.

Conclusions: The portable Element POC system had acceptable agreement with the ABL 800 FLEX bench-top analyzer currently in use at the study center when evaluating the majority of analytes from equine whole blood samples.
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http://dx.doi.org/10.1111/vec.12950DOI Listing
May 2020

Recovery quality following a single post-anaesthetic dose of dexmedetomidine or romifidine in sevoflurane anaesthetised horses.

Equine Vet J 2020 Sep 21;52(5):685-691. Epub 2020 Feb 21.

Department of Statistics, College of Natural Sciences, Colorado State University, Fort Collins, CO, USA.

Background: Post-anaesthetic sedation is administered to horses to improve recovery quality from inhalant anaesthesia and reduce the risk of catastrophic injury. A single dose of dexmedetomidine for this purpose has not been evaluated clinically.

Objectives: To determine whether dexmedetomidine improves recovery quality from sevoflurane anaesthesia compared to a previously studied dose of romifidine.

Study Design: Prospective, randomised, masked clinical trial.

Methods: Ninety-nine, adult, client-owned horses anaesthetised for elective procedures completed the trial. Anaesthetic protocol was standardised. Horses were randomly assigned to receive either dexmedetomidine 1 mcg/kg bwt (D) or romifidine 20 mcg/kg bwt (R) intravenously at their first spontaneous breath in recovery. Recoveries were reviewed and independently assigned subjective visual analogue scale (VAS) scores (0-100 mm, worst to best) for overall quality and standing ataxia scores (1-4, none to severe) by two anaesthesiologists blinded to treatment group. Objective anaesthesia and recovery data were also recorded. Comparisons were made using the Chi-square, Wilcoxon rank sum, linear models or Welch-Satterthwaite two-sample t-test (P ≤ .05). Predictors of VAS score were analysed independent of treatment group.

Results: There were no significant differences between groups except end-tidal sevoflurane (FE´Sevo) concentration and post-induction extra ketamine dosing. Including FE´Sevo and additional ketamine in the analysis as covariates, VAS scores and time to standing were not significantly different between groups. Increased age, not receiving a nerve block, increased duration of hypotension, and having a nervous temperament were significant predictors of VAS score.

Main Limitations: No universal recovery scale exists for inter-study comparisons.

Conclusions: After sevoflurane anaesthesia, sedation with dexmedetomidine or romifidine provides clinically similar recovery time and quality.
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http://dx.doi.org/10.1111/evj.13238DOI Listing
September 2020

REPEATED USE OF A THIAFENTANIL-BASED ANESTHESIA PROTOCOL IN AN OKAPI ().

J Zoo Wildl Med 2020 Jan;50(4):993-996

Harter Veterinary Medical Center, San Diego Zoo Safari Park, Escondido, CA 92027, USA.

Seven anesthesia events were performed over 6 wk on a 1.5-yr-old female okapi () being managed for a fetlock injury. A combination of butorphanol (B) (median; range) (0.045; 0.031-0.046 mg/kg), medetomidine (M) (0.037; 0.031-0.037 mg/kg), ketamine (K) (0.553; 0.536-1.071 mg/kg), and thiafentanil (T) (0.0045; 0.0040-0.0046 mg/kg) was administered in a padded stall. One dart containing all drugs was used for the first two anesthesias. Subsequently, BM was administered 10 min prior to KT using two darts. Time (median; range) from initial injection to first effects (6; 3-7 min) and recumbency (14; 4-20 min) were recorded. Induction quality with the one-dart protocol was poor or fair and was good or excellent with the two-dart protocol. Following recumbency, the okapi was intubated and ventilated, and physiological parameters were recorded. Anesthesia was consistently achieved with BMKT, but induction was smoother with the staged two-dart approach. Neither resedation nor renarcotization was observed post-reversal.
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http://dx.doi.org/10.1638/2019-0037DOI Listing
January 2020

Comparison of intravenous anesthetic induction doses and physiologic effects of ketamine or alfaxalone in goats undergoing surgery with isoflurane anesthesia.

Am J Vet Res 2019 Sep;80(9):819-824

Objective: To compare IV doses of alfaxalone and ketamine needed to facilitate orotracheal intubation and assess effects of each treatment on selected physiologic variables in goats undergoing orthopedic surgery with isoflurane anesthesia.

Animals: 18 healthy adult goats.

Procedures: Behavior was assessed before and after sedation with midazolam (0.1 mg/kg, IV) for IV catheter placement. Anesthesia was induced with additional midazolam (0.1 mg/kg, IV) and alfaxalone (n = 9) or ketamine (9) at 2 mg/kg, IV, over 30 seconds. An additional dose of alfaxalone or ketamine (1 mg/kg) was given IV if needed for intubation; anesthesia was maintained with isoflurane in oxygen and IV fluids with ketamine (0.5 to 1 mg/kg/h). Direct systolic (SAP), diastolic (DAP), and mean (MAP) arterial blood pressures; heart rate; and respiratory rate were recorded before induction, immediately after intubation, and during surgery. Qualitative anesthetic induction and recovery characteristics were assessed. Variables were compared within and between groups by statistical methods.

Results: No preinduction variables differed significantly between groups. Postintubation and 30-minute intraoperative SAP, DAP, and MAP were higher for the ketamine group than for the alfaxalone group; within the alfaxalone group, postintubation SAP, MAP, and respiratory rate prior to mechanical ventilation were lower than respective preinduction values. All alfaxalone-group goats were intubated after 1 dose of the induction agent; 5 of 9 ketamine-group goats required an additional (1-mg/kg) dose. Postoperative recovery was good to excellent for all animals.

Conclusions And Clinical Relevance: Both drugs were suitable for induction of anesthesia after sedation with midazolam, but most goats required higher doses of ketamine to allow intubation. For situations in which alfaxalone administration is appropriate, the potential for decreased arterial blood pressures and respiratory rate should be considered.
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http://dx.doi.org/10.2460/ajvr.80.9.819DOI Listing
September 2019

COMPARISON OF ANESTHESIA OF ADULT GIRAFFE () USING MEDETOMIDINE-KETAMINE WITH AND WITHOUT A POTENT OPIOID.

J Zoo Wildl Med 2019 Jun 13;50(2):457-460. Epub 2019 Jun 13.

San Diego Zoo Global, Escondido, CA 92027, USA.

Two anesthetic protocols in adult giraffe were compared by retrospective study. Thirteen anesthesia records for medetomidine-ketamine (MK) and seven for medetomidine-ketamine with a potent opioid (MKO) were evaluated for differences in demographic, behavioral, drug, and respiratory parameters. Giraffe stood significantly more quickly with MKO vs MK though MK animals were physically restrained to preclude premature standing as part of normal recovery practices (5.5 min vs 21.4 min, = 0.01). Regurgitation was recorded in 5/13 and resedation in 4/13 MK animals. The range of values for blood lactate was higher in MKO (5.18-11.25 mM/L) than in MK giraffe (0.78-6.08 mM/L). Despite limitations of a retrospective study, both MK and MKO giraffe anesthesia protocols exhibit benefits and side effects. Awareness and management of these factors will improve outcomes until standardized, prospective studies of giraffe immobilization offer more comprehensive guidance on protocol selection.
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http://dx.doi.org/10.1638/2018-0119DOI Listing
June 2019

A COMPARISON OF OPIOID-BASED PROTOCOLS FOR IMMOBILIZATION OF CAPTIVE GREVY'S ZEBRA ().

J Zoo Wildl Med 2019 03;50(1):258-261

Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.

Grevy's zebra () is an endangered species often found in zoological collections. Veterinary care for this species often requires immobilization. This study retrospectively evaluated behavioral and physiological parameters from Grevy's zebra records after three immobilization protocols: etorphine and alpha-2 agonist (EA2; = 11); etorphine, alpha-2 agonist, and ketamine (EA2K; = 16); and thiafentanil, alpha-2 agonist, and ketamine (TA2K; = 6). Median time to working depth was statistically different ( = 0.03; EA2 = 6.5 min, EA2K = 6.3 min, TA2K = 14.5 min) by the Kruskal-Wallis test. When EA2 + EA2K were combined and compared with TA2K (Wilcoxon rank sum test), median recumbency time ( = 0.02) was also significantly longer (15 min compared with 6 min) for TA2K. There were no significant differences between the groups for physiological parameters or recovery time after reversal. Although all protocols produced anesthesia in Grevy's zebra, increased time to achieve working depth was observed with the alpha-2 and thiafentanil combinations.
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http://dx.doi.org/10.1638/2018-0108DOI Listing
March 2019

Hyperkalemia during general anesthesia in two Greyhounds.

J Am Vet Med Assoc 2019 Jun;254(11):1329-1334

Case Description: A 36-kg (79-lb) castrated male Greyhound (dog 1) and a 25-kg (55 lb) spayed female Greyhound (dog 2) underwent general anesthesia for dental care with similar perianesthetic protocols on multiple occasions from 2013 to 2016. Both dogs had periodontal disease but were otherwise deemed healthy. Both dogs developed clinically relevant hyperkalemia, with signs including loss of P waves on ECG tracings, during multiple anesthetic events.

Clinical Findings: Dog 1 developed hyperkalemia during 2 of 2 anesthetic events, with ECG changes noted during the first event. Dog 2 developed hyperkalemia during 3 of 4 anesthetic events, with ECG changes identified during the second and third events. Serum potassium concentration for both dogs was within the reference range prior to and between anesthetic events. No underlying etiopathogenesis for hyperkalemia was identified for either dog.

Treatment And Outcome: In each hyperkalemic event, the clinician stopped the dental procedure and continued to provide supportive care and monitoring while the dog recovered from anesthesia. The ECG changes resolved, and serum potassium concentration returned to the reference range rapidly after inhalant anesthetic administration was discontinued. The dogs were discharged from the hospital without further complications.

Clinical Relevance: Hyperkalemia in anesthetized Greyhounds resulted in serious cardiac conduction abnormalities, which could be potentially fatal if not recognized and promptly treated. Further investigation into the etiopathogenesis, prevention and treatment strategies, and genetic or familial components of this condition is indicated.
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http://dx.doi.org/10.2460/javma.254.11.1329DOI Listing
June 2019

Therapeutic developments in equine pain management.

Vet J 2019 May 28;247:50-56. Epub 2019 Feb 28.

Department of Clinical Sciences, Colorado State University, Fort Collins, CO 80523, USA.

Many drugs and non-drug modalities are used to manage pain in horses, but evidence regarding efficacy and safety remains limited. This manuscript will first briefly review tried and tested techniques, e.g. the use of non-steroidal anti-inflammatory drugs, in the management of pain. Newer approaches to administering medications such as oral use of detomidine, which was previously only administered by injection, will also be discussed. Finally, introductory information on newer therapies, for example acupuncture and chiropractic manipulation, that the veterinarian may consider for the management of equine pain will be presented.
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http://dx.doi.org/10.1016/j.tvjl.2019.02.010DOI Listing
May 2019

Influence of changing lateral recumbency and mode of ventilation on the alveolar-arterial oxygen tension gradient and selected laboratory analytes in adult isoflurane anesthetized horses.

J Vet Med Sci 2018 Nov 3;80(10):1584-1589. Epub 2018 Sep 3.

Department of Statistics, Colorado State University, Fort Collins, CO 80523, U.S.A.

This study investigated the influence of changing recumbency and mode of ventilation over repeated anesthesias on the alveolar to arterial oxygen tension gradient (PO) and laboratory analytes in eight horses during a year-long imaging study. Anesthesia was induced with xylazine, diazepam or guaifenesin, and ketamine and maintained with isoflurane. Horses were positioned in right or left lateral recumbency for computed tomography. Ventilation was controlled during 47% of the anesthetics. Blood was sampled from an arterial catheter prior to (30 ± 5 min from connection to anesthetic circuit), within 5 min of changing lateral recumbency, and prior to circuit disconnection (24 ± 6 min after second sample) for measurement of pH, partial pressure of arterial oxygen (PaO) and partial pressure of arterial carbon dioxide, blood glucose and electrolytes. PO was calculated. Data from five anesthetic episodes for each horse were summarized as mean ± standard error and analyzed using a mixed-model ANOVA. t tests were used for pairwise comparisons (P<0.05). PaO decreased after turning (198 vs. 347 mmHg), then increased to 291 mmHg prior to disconnection. Correspondingly, PO was wider (252 vs.120 mmHg), and improved before disconnection (190 mmHg). Body temperature, ionized-Ca and blood glucose were lower, and Na was higher at the last time point. In conclusion, turning anesthetized horses decreases PaO and results in a widening PO suggesting a cautious approach in animals with pre-existing hypoxemia.
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http://dx.doi.org/10.1292/jvms.18-0032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6207512PMC
November 2018

EVALUATION OF BLOOD GAS VALUES IN ANESTHETIZED SOUTHERN WHITE RHINOCEROS ( CERATOTHERIUM SIMUM) VENTILATED WITH A NOVEL DEMAND VENTILATOR IN A ZOOLOGICAL PARK SETTING.

J Zoo Wildl Med 2017 12;48(4):1016-1025

Rhinoceros conservation efforts are essential to the survival of the species. One such effort is focused on using advanced reproductive technologies to produce viable northern white rhinoceros ( Ceratotherium simum cottoni) embryos for implantation into southern white rhinoceros ( Ceratotherium simum simum) surrogates. Anesthesia may be required to facilitate necessary procedures in these surrogate rhinoceros, but commonly reported side effects including hypercapnia and hypoxemia limit anesthetic recumbency time due to animal safety concerns. Although many interventions have been attempted, success in improving these physiologic parameters to date is mixed. The objective of this report is to describe arterial pH (pHa), blood gas (PaO and PaCO), bicarbonate, base excess, lactate, and cardiovascular (heart rate, direct arterial blood pressure) values recorded in seven intubated and ventilated female southern white rhinoceros anesthetized for reproductive examinations in a zoological park setting. Anesthetic induction was accomplished using etorphine, medetomidine, butorphanol, and midazolam. The primary hypotheses were that PaO and PaCO would improve after intubation and mechanical ventilation. Induction and recovery observations were also summarized. Physiologic and laboratory data were analyzed using a mixed linear regression model using ranks. Statistical significance was set at P < 0.05. The PaO increased significantly ( P < 0.001) following ventilation from a median value of 58 (range, 38-67) to 123 (range, 42-184) mm Hg. The PaCO significantly ( P = 0.003) decreased from 63 (range, 55-73) to 52 (range, 30-75) mm Hg, with a corresponding improvement ( P = 0.068) in pHa from 7.33 (7.25-7.34) to 7.37 (7.24-7.58) units. Intubation and ventilation improve respiratory parameters and may facilitate safe prolongation of anesthetic duration in white rhinoceros.
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http://dx.doi.org/10.1638/2017-0048R1.1DOI Listing
December 2017

Pharmacokinetics and selected pharmacodynamics of trazodone following intravenous and oral administration to horses undergoing fitness training.

Am J Vet Res 2017 Oct;78(10):1182-1192

OBJECTIVE To measure concentrations of trazodone and its major metabolite in plasma and urine after administration to healthy horses and concurrently assess selected physiologic and behavioral effects of the drug. ANIMALS 11 Thoroughbred horses enrolled in a fitness training program. PROCEDURES In a pilot investigation, 4 horses received trazodone IV (n = 2) or orally (2) to select a dose for the full study; 1 horse received a vehicle control treatment IV. For the full study, trazodone was initially administered IV (1.5 mg/kg) to 6 horses and subsequently given orally (4 mg/kg), with a 5-week washout period between treatments. Blood and urine samples were collected prior to drug administration and at multiple time points up to 48 hours afterward. Samples were analyzed for trazodone and metabolite concentrations, and pharmacokinetic parameters were determined; plasma drug concentrations following IV administration best fit a 3-compartment model. Behavioral and physiologic effects were assessed. RESULTS After IV administration, total clearance of trazodone was 6.85 ± 2.80 mL/min/kg, volume of distribution at steady state was 1.06 ± 0.07 L/kg, and elimination half-life was 8.58 ± 1.88 hours. Terminal phase half-life was 7.11 ± 1.70 hours after oral administration. Horses had signs of aggression and excitation, tremors, and ataxia at the highest IV dose (2 mg/kg) in the pilot investigation. After IV drug administration in the full study (1.5 mg/kg), horses were ataxic and had tremors; sedation was evident after oral administration. CONCLUSIONS AND CLINICAL RELEVANCE Administration of trazodone to horses elicited a wide range of effects. Additional study is warranted before clinical use of trazodone in horses can be recommended.
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http://dx.doi.org/10.2460/ajvr.78.10.1182DOI Listing
October 2017

Effects of constant rate infusions of dexmedetomidine or MK-467 on the minimum alveolar concentration of sevoflurane in dogs.

Vet Anaesth Analg 2017 Jul 4;44(4):755-765. Epub 2017 Mar 4.

Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.

Objective: To determine the effects of low and high dose infusions of dexmedetomidine and a peripheral α-adrenoceptor antagonist, MK-467, on sevoflurane minimum alveolar concentration (MAC) in dogs.

Study Design: Crossover experimental study.

Animals: Six healthy, adult Beagle dogs weighing 12.6±0.9 kg (mean±standard deviation).

Methods: Dogs were anesthetized with sevoflurane in oxygen. After a 60-minute instrumentation and equilibration period, the MAC of sevoflurane was determined in triplicate using the tail clamp technique. PaCO and temperature were maintained at 40±5 mmHg (5.3±0.7 kPa) and 38±0.5 ºC, respectively. After baseline MAC determination, dogs were administered two incremental loading and infusion doses of either dexmedetomidine (1.5 μg kg then 1.5 μg kg hour and 4.5 μg kg then 4.5 μg kg hour) or MK-467 (90 μg kg then 90 μg kg hour and 180 μg kg then 180 μg kg hour); loading doses were administered over 10 minutes. MAC was redetermined in duplicate starting 30 minutes after the start of drug administration at each dose. End-tidal sevoflurane concentrations were corrected for calibration and adjusted to sea level. A repeated-measures analysis was performed and comparisons between doses were conducted using Tukey's method. Statistical significance was considered at p<0.05.

Results: Sevoflurane MAC decreased significantly from 1.86±0.3% to 1.04±0.1% and 0.57±0.1% with incremental doses of dexmedetomidine. Sevoflurane MAC significantly increased with high dose MK-467, from 1.93±0.3% to 2.29±0.5%.

Conclusions And Clinical Relevance: Dexmedetomidine caused a dose-dependent decrease in sevoflurane MAC, whereas MK-467 caused an increase in MAC at the higher infusion dose. Further studies evaluating the combined effects of dexmedetomidine and MK-467 on MAC and cardiovascular function may elucidate potential benefits of the addition of a peripheral α-adrenergic antagonist to inhalation anesthesia in dogs.
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http://dx.doi.org/10.1016/j.vaa.2016.12.058DOI Listing
July 2017

Assessment of agreement among diplomates of the American College of Veterinary Anesthesia and Analgesia for scoring the recovery of horses from anesthesia by use of subjective grading scales and development of a system for evaluation of the recovery of horses from anesthesia by use of accelerometry.

Am J Vet Res 2017 Jun;78(6):668-676

OBJECTIVE To evaluate agreement among diplomates of the American College of Veterinary Anesthesia and Analgesia for scores determined by use of a simple descriptive scale (SDS) or a composite grading scale (CGS) for quality of recovery of horses from anesthesia and to investigate use of 3-axis accelerometry (3AA) for objective evaluation of recovery. ANIMALS 12 healthy adult horses. PROCEDURES Horses were fitted with a 3AA device and then were anesthetized. Eight diplomates evaluated recovery by use of an SDS, and 7 other diplomates evaluated recovery by use of a CGS. Agreement was tested with κ and AC1 statistics for the SDS and an ANOVA for the CGS. A library of mathematical models was used to map 3AA data against CGS scores. RESULTS Agreement among diplomates using the SDS was slight (κ = 0.19; AC1 = 0.22). The CGS scores differed significantly among diplomates. Best fit of 3AA data against CGS scores yielded the following equation: RS = 9.998 × SG × ∑UG, where RS is a horse's recovery score determined with 3AA, SG is acceleration of the successful attempt to stand, and ∑UG is the sum of accelerations of unsuccessful attempts to stand. CONCLUSIONS AND CLINICAL RELEVANCE Subjective scoring of recovery of horses from anesthesia resulted in poor agreement among diplomates. Subjective scoring may lead to differences in conclusions about recovery quality; thus, there is a need for an objective scoring method. The 3AA system removed subjective bias in evaluations of recovery of horses and warrants further study.
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http://dx.doi.org/10.2460/ajvr.78.6.668DOI Listing
June 2017

Pain: Its Diagnosis and Management in the Rehabilitation of Horses.

Vet Clin North Am Equine Pract 2016 Apr;32(1):13-29

Veterinary, Anesthesiology, Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA. Electronic address:

This article provides a brief overview of pain physiology and its relevance to equine patients. Objective and subjective techniques for assessing pain in the horse are described in depth. Pharmacologic and interventional pain modulation treatments are discussed with a focus on the rehabilitating horse.
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http://dx.doi.org/10.1016/j.cveq.2015.12.005DOI Listing
April 2016

Pharmacokinetics and pharmacodynamics of propofol with or without 2% benzyl alcohol following a single induction dose administered intravenously in cats.

Vet Anaesth Analg 2015 Sep 20;42(5):472-83. Epub 2014 Oct 20.

Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.

Objective: To compare the pharmacokinetics and pharmacodynamics of propofol with or without 2% benzyl alcohol administered intravenously (IV) as a single induction dose in cats.

Study Design: Prospective experimental study.

Animals: Six healthy adult cats, three female intact, three male castrated, weighing 4.8 ± 1.8 kg.

Methods: Cats received 8 mg kg(-1) IV of propofol (P) or propofol with 2% benzyl alcohol (P28) using a randomized crossover design. Venous blood samples were collected at predetermined time points to 24 hours after drug administration to determine drug plasma concentrations. Physiologic and behavioral variables were also recorded. Propofol and benzyl alcohol concentrations were determined using high pressure liquid chromatography with fluorescence detection. Pharmacokinetic parameters were described using a 2-compartment model. Pharmacokinetic and pharmacodynamic parameters were analyzed using repeated measures anova (p < 0.05).

Results: Plasma concentrations of benzyl alcohol were below the lower limits of quantification (LLOQ) at all time points for two of the six cats (33%), and by 30 minutes for the remaining four cats. Propofol pharmacokinetics, with or without 2% benzyl alcohol, were characterized by rapid distribution, a long elimination phase, and a large volume of distribution. No differences were noted between treatments with the exception of clearance from the second compartment (CLD2), which was 23.6 and 38.8 mL kg(-1)  minute(-1) in the P and P28 treatments, respectively. Physiologic and behavioral variables were not different between treatments with the exception of heart rate at 4 hours post administration.

Conclusions And Clinical Relevance: The addition of 2% benzyl alcohol as a preservative minimally altered the pharmacokinetics and pharmacodynamics of propofol 1% emulsion when administered as a single IV bolus in this group of cats. These data support the cautious use of propofol with 2% benzyl alcohol for induction of anesthesia in healthy cats.
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http://dx.doi.org/10.1111/vaa.12233DOI Listing
September 2015

Multicenter clinical evaluation of a multi-dose formulation of propofol in the dog.

BMC Vet Res 2013 Dec 23;9:261. Epub 2013 Dec 23.

Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.

Background: Propofol is a widely used injectable anesthetic agent for induction and short-term maintenance in dogs. A multi-dose formulation of propofol (MDP) has been developed which includes 2% benzyl alcohol as a preservative. In order to document the use of the product under clinical conditions, MDP was tested in a prospective clinical trial conducted at six sites within the United States. One hundred thirty-eight healthy, client-owned dogs were assigned to one of six treatment groups based on premedicants (none, acepromazine/buprenorphine, midazolam/buprenorphine, medetomidine/buprenorphine) and maintenance agents (MDP, inhaled anesthetic). Anesthesia was induced by the intravenous administration of MDP given to effect. Physiological indices including heart rate, respiratory rate and blood pressure were monitored prior to and during anesthesia induction, maintenance and recovery. Adverse events, defined for severity by pre-established limits of these physiological values, as well as side effects, defined as any observation outside the normal range, were noted.

Results: The mean intubation dose was 7.6 ± 2.1 mg/kg for MDP alone and 4.7 ± 1.3, 4.0 ± 1.0 mg/kg and 3.2 ± 1.4 mg/kg when buprenorphine was used in combination with midazolam, acepromazine and medetomidine, respectively. Of the 32 adverse events, apnea (12 incidents), bradycardia (9 incidents) and hypotension (7 incidents) were most frequently recorded. Emesis, cyanosis and second degree heart block were each noted once and successfully resolved. The cause of a single death 2 days post-anesthesia was assessed as a surgical complication.

Conclusions: MDP was found to be acceptable for use in healthy dogs for induction and short term maintenance of anesthesia when used alone and in combination with premedicants and inhaled anesthetics.
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http://dx.doi.org/10.1186/1746-6148-9-261DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901023PMC
December 2013

Cardiorespiratory and antinociceptive effects of two different doses of lidocaine administered to horses during a constant intravenous infusion of xylazine and ketamine.

BMC Vet Res 2013 Oct 9;9:199. Epub 2013 Oct 9.

Department of Veterinary Surgery and Anesthesiology, School of Veterinary Medicine and Animal Science, UNESP-Univ Estadual Paulista, Botucatu, Botucatu, São Paulo 18618970, Brazil.

Background: This study investigated the antinociceptive effects of a constant rate infusion (CRI) of lidocaine during xylazine and ketamine anesthesia in horses and aimed to correlate these effects with cardiorespiratory variables, bispectral index (BIS) and plasma lidocaine concentrations. Six adult crossbred mares weighing 320-400 kg were anesthetized on three different occasions. Sedation was performed with xylazine (0.75 mg/kg IV) and anesthetic induction with guaifenesin (75 mg/kg IV) and ketamine (2 mg/kg IV). Anesthesia was maintained with 37.5 μg/kg/min of xylazine and 87.5 μg/kg/min of ketamine both administered intravenously for 75 min. The three treatments consisted of: lidocaine (loading dose: 5 mg/kg, CRI: 100 μg/kg/min; THL); lidocaine (loading dose: 2.5 mg/kg; CRI: 50 μg/kg/min: TLL); and saline (TS); all given 15 min after induction and maintained for 1 h. Antinociception was measured by response to electrical stimulation and bispectral index (BIS) was recorded during anesthesia. Parametric and non-parametric data were compared using ANOVA followed by Student-Newman-Keuls and Friedman tests, respectively.

Results: Plasma lidocaine concentrations peaked at the end of lidocaine loading dose and was greater in THL (9.61 ± 2.75 μg/mL) vs TLL (4.50 ± 3.34 μg/mL). Electrical noxious stimulation caused purposeful movement in all horses from TS, but no response in THL. The BIS was decreased in THL only and was less when compared to the other treatments throughout anesthesia. Blood pressure, PaO2 and PaCO2 increased and heart rate (HR), respiratory rate (RR), pH, total plasma protein and temperature decreased during anesthesia in all treatments. PaCO2 and HR were greater and RR and pH less in THL compared to TLL and TS at 30 min during anesthesia. All recoveries were considered excellent. Time to standing was longer after THL (60 ± 20 min) than following TLL and TS (32 ± 17 and 30 ± 15 min, respectively).

Conclusions: At the highest dose administered (THL) lidocaine CRI during xylazine/ketamine anesthesia decreased BIS and motor response to noxious stimulation, and prolonged recovery time without significant added cardiorespiratory depression.
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http://dx.doi.org/10.1186/1746-6148-9-199DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3852357PMC
October 2013

Evaluation of antioxidant capacity and inflammatory cytokine gene expression in horses fed silibinin complexed with phospholipid.

Am J Vet Res 2013 Oct;74(10):1333-9

Department of Clinical Sciences, College of Veterinary Medicine and Biological Sciences, Colorado State University, Fort Collins, CO. 80523.

Objective: To evaluate antioxidant capacity and inflammatory cytokine gene expression in horses fed silibinin complexed with phospholipid.

Animals: 5 healthy horses.

Procedures: Horses consumed increasing orally administered doses of silibinin phospholipid during 4 nonconsecutive weeks (0 mg/kg, 6.5 mg/kg, 13 mg/kg, and 26 mg/kg of body weight, twice daily for 7 days each week). Dose-related changes in plasma antioxidant capacity, peripheral blood cell glutathione concentration and antioxidant enzyme activities, and blood cytokine gene expression were evaluated.

Results: Plasma antioxidant capacity increased throughout the study period with increasing dose. Red blood cell nicotinamide adenine dinucleotide phosphate:quinone oxidoreductase I activity decreased significantly with increasing doses of silibinin phospholipid. No significant differences were identified in glutathione peroxidase activity, reduced glutathione or oxidized glutathione concentrations, or expression of tumor necrosis factor α, interleukin-1, or interleukin-2.

Conclusions And Clinical Relevance: Minor alterations in antioxidant capacity of healthy horses that consumed silibinin phospholipid occurred and suggest that further study in horses with liver disease is indicated.
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http://dx.doi.org/10.2460/ajvr.74.10.1333DOI Listing
October 2013

Pharmacokinetics and safety of silibinin in horses.

Am J Vet Res 2013 Oct;74(10):1327-32

Department of Clinical Sciences, College of Veterinary Medicine and Biological Sciences, Colorado State University, Fort Collins, CO, 80523.

Objective: To determine the oral bioavailability, single and multidose pharmacokinetics, and safety of silibinin, a milk thistle derivative, in healthy horses.

Animals: 9 healthy horses.

Procedures: Horses were initially administered silibinin IV and silibinin phospholipid orally in feed and via nasogastric tube. Five horses then consumed increasing orally administered doses of silibinin phospholipid during 4 nonconsecutive weeks (0 mg/kg, 6.5 mg/kg, 13 mg/kg, and 26 mg/kg of body weight, twice daily for 7 days each week).

Results: Bioavailability of orally administered silibinin phospholipid was 0.6% PO in feed and 2.9% via nasogastric tube. During the multidose phase, silibinin had nonlinear pharmacokinetics. Despite this, silibinin did not accumulate when given twice daily for 7 days at the evaluated doses. Dose-limiting toxicosis was not observed.

Conclusions And Clinical Relevance: Silibinin phospholipid was safe, although poorly bio-available, in horses. Further study is indicated in horses with hepatic disease.
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http://dx.doi.org/10.2460/ajvr.74.10.1327DOI Listing
October 2013

Validation of the English version of the UNESP-Botucatu multidimensional composite pain scale for assessing postoperative pain in cats.

BMC Vet Res 2013 Jul 17;9:143. Epub 2013 Jul 17.

Department of Veterinary Surgery and Anesthesiology, School of Veterinary Medicine and Animal Science, UNESP Univ Estadual Paulista, Botucatu, SP 18618-970, Brazil.

Background: A scale validated in one language is not automatically valid in another language or culture. The purpose of this study was to validate the English version of the UNESP-Botucatu multidimensional composite pain scale (MCPS) to assess postoperative pain in cats. The English version was developed using translation, back-translation, and review by individuals with expertise in feline pain management. In sequence, validity and reliability tests were performed.

Results: Of the three domains identified by factor analysis, the internal consistency was excellent for 'pain expression' and 'psychomotor change' (0.86 and 0.87) but not for 'physiological variables' (0.28). Relevant changes in pain scores at clinically distinct time points (e.g., post-surgery, post-analgesic therapy), confirmed the construct validity and responsiveness (Wilcoxon test, p < 0.001). Favorable correlation with the IVAS scores (p < 0.001) and moderate to very good agreement between blinded observers and 'gold standard' evaluations, supported criterion validity. The cut-off point for rescue analgesia was > 7 (range 0-30 points) with 96.5% sensitivity and 99.5% specificity.

Conclusions: The English version of the UNESP-Botucatu-MCPS is a valid, reliable and responsive instrument for assessing acute pain in cats undergoing ovariohysterectomy, when used by anesthesiologists or anesthesia technicians. The cut-off point for rescue analgesia provides an additional tool for guiding analgesic therapy.
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http://dx.doi.org/10.1186/1746-6148-9-143DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3722032PMC
July 2013

Prevalence of dysphoria after fentanyl in dogs undergoing stifle surgery.

Vet Surg 2013 Apr 11;42(3):302-7. Epub 2012 Dec 11.

Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.

Objective: To describe the prevalence of dysphoria after intraoperative administration of fentanyl by infusion and identify other risk factors influencing this in dogs undergoing stifle surgery.

Study Design: Prospective, randomized clinical study.

Animals: Dogs (n = 92) that had tibial plateau leveling osteotomy (TPLO) or tibial tuberosity advancement (TTA).

Methods: Dogs were anesthetized using a standardized anesthetic protocol, and randomly assigned to receive a loading dose followed by 1 of 3 infusions of fentanyl perioperatively: 2 μg/kg/h, 10 μg/kg/h, or 20 μg/kg/h. Dog characteristics and all additional medications were recorded and included as part of the statistical analysis. Dog behavior was scored before anesthesia and during recovery using a scale of 1-4 (Appendices A and B). If no improvement in behavior was seen in 3-5 minutes postextubation, dogs with a score of 3 or 4 during recovery were administered fentanyl (2 μg/kg intravenously [IV]) in the event that the behaviors associated with the higher scores were related to pain. If they did not respond favorably to the administration of additional fentanyl and wound palpation did not elicit a response, but the untoward behaviors continued, dogs were administered either a tranquilizer, sedative, or opioid antagonist, and were considered dysphoric.

Results: Of 92 dogs, 22 (23.9%) were considered dysphoric using aforementioned criteria.

Conclusions: About one-fourth of dogs enrolled in this study were dysphoric based on study criteria.
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http://dx.doi.org/10.1111/j.1532-950X.2012.01080.xDOI Listing
April 2013

Occupational per-patient radiation dose from a conservative protocol for veterinary (18) F-fluorodeoxyglucose positron emission tomography.

Vet Radiol Ultrasound 2012 Sep-Oct;53(5):591-7. Epub 2012 Jun 15.

Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO 80526, USA.

The occupational external radiation dose to human medical personnel from positron emission tomography (PET) radiopharmaceuticals has been documented, but to date no corresponding veterinary staff dose data are available. Electronic personal dosimeters (EPDs) were used in this study to measure the per-patient external radiation doses to veterinary staff using a PET/CT (PET combined with computed tomography) protocol in which the patient radiopharmaceutical dose was injected after anesthetic induction. Radiation doses were recorded for the nuclear medicine technologists, the on-duty anesthesiology technologist, and an occasional observer from 19 veterinary (18) F-fluorodeoxyglucose PET/CT studies. Patient mass range was 2.8 to 61.0 kg (22.3 kg mean) and injected activity averaged 6 MBq kg(-1) . The dose range received by nuclear medicine technologists per procedure was 0-30 μSv (9.1 μSv mean), by anesthetists 1-22 μSv (8.2 μSv mean), and by the observer 0-2 μSv (0.5 μSv mean). In both feline and canine studies, placement of the EPD on staff was a significant predictor of radiation dose. Additional significant predictors of staff radiation dose from canine studies included job position and injected activity. The per-patient occupational radiation doses to veterinary PET/CT technologists were slightly greater than those reported for human nuclear medicine PET/CT technologists, but were comparable to estimated radiation doses for nurses caring for nonambulatory human PET/CT patients. Efforts toward maintaining staff radiation doses as low as reasonably achievable (ALARA) will be important as veterinary PET/CT caseload increases.
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http://dx.doi.org/10.1111/j.1740-8261.2012.01958.xDOI Listing
October 2012

Comparison of the analgesic efficacy of oral ABT-116 administration with that of transmucosal buprenorphine administration in dogs.

Am J Vet Res 2012 Apr;73(4):476-81

Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.

Objective: To evaluate the analgesic efficacy of ABT-116, a transient receptor potential cation channel vanilloid subfamily V member 1 antagonist, and compare it with that of buprenorphine by measurement of mechanical and thermal nociceptive thresholds in dogs.

Animals: Six 7- to 8-month-old dogs (3 males and 3 females).

Procedures: In a crossover study design, all dogs received ABT-116 (30 mg/kg, PO) and buprenorphine (0.03 mg/kg, orotransmucosally), with each treatment separated by 1 week. Physiologic variables were recorded prior to and 1, 6, and 24 hours after drug administration. Thermal (thoracic) and mechanical (dorsolateral aspect of the radius [proximal] and dorsopalmar aspect of the forefoot [distal]) nociceptive thresholds were assessed prior to (baseline) and 15 minutes and 1, 2, 4, 6, 12, 18, and 24 hours after treatment.

Results: Buprenorphine administration resulted in higher overall thermal and proximal mechanical nociceptive thresholds, compared with ABT-116. Distal mechanical nociceptive thresholds after treatment were higher than baseline values for both treatments, but the magnitude of change was greater for buprenorphine at 1 hour after administration. Whereas HR and RR sporadically differed from baseline values after ABT-116 administration, rectal temperature increased from a baseline value of 39 ± 0.2°C (mean ± SD) to a peak of 40.6 ± 0.2°C at 6 hours.

Conclusions And Clinical Relevance: In dogs without inflammation or nerve injury, PO administration of ABT-116 did not consistently result in an increase in nociceptive thresholds. However, clinically relevant increases in rectal temperature were identified after ABT-116 administration.
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http://dx.doi.org/10.2460/ajvr.73.4.476DOI Listing
April 2012

Evaluation of infusions of xylazine with ketamine or propofol to modulate recovery following sevoflurane anesthesia in horses.

Am J Vet Res 2012 Mar;73(3):346-52

Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.

Objective: To determine whether infusion of xylazine and ketamine or xylazine and propofol after sevoflurane administration in horses would improve the quality of recovery from anesthesia.

Animals: 6 healthy adult horses.

Procedures: For each horse, anesthesia was induced by administration of xylazine, diazepam, and ketamine and maintained with sevoflurane for approximately 90 minutes (of which the last 60 minutes were under steady-state conditions) 3 times at 1-week intervals. For 1 anesthetic episode, each horse was allowed to recover from sevoflurane anesthesia; for the other 2 episodes, xylazine and ketamine or xylazine and propofol were infused for 30 or 15 minutes, respectively, after termination of sevoflurane administration. Selected cardiopulmonary variables were measured during anesthesia and recovery. Recovery events were monitored and subjectively scored.

Results: Cardiopulmonary variables differed minimally among treatments, although the xylazine-propofol infusion was associated with greater respiratory depression than was the xylazine-ketamine infusion. Interval from discontinuation of sevoflurane or infusion administration to standing did not differ significantly among treatments, but the number of attempts required to stand successfully was significantly lower after xylazine-propofol infusion, compared with the number of attempts after sevoflurane alone. Scores for recovery from anesthesia were significantly lower (ie, better recovery) after either infusion, compared with scores for sevoflurane administration alone.

Conclusions And Clinical Relevance: Xylazine-ketamine or xylazine-propofol infusion significantly improved quality of recovery from sevoflurane anesthesia in horses. Xylazine-ketamine or xylazine-propofol infusions may be of benefit during recovery from sevoflurane anesthesia in horses for which a smooth recovery is particularly critical. However, oxygenation and ventilation should be monitored carefully.
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http://dx.doi.org/10.2460/ajvr.73.3.346DOI Listing
March 2012

Effect of epidural and intravenous use of the neurokinin-1 (NK-1) receptor antagonist maropitant on the sevoflurane minimum alveolar concentration (MAC) in dogs.

Vet Anaesth Analg 2012 Mar 22;39(2):201-5. Epub 2011 Nov 22.

College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.

Objective: To determine the effect of maropitant, an NK-1 receptor antagonist on the minimum alveolar concentration (MAC) of sevoflurane after intravenous and epidural administration to dogs.

Study Design: Prospective experimental study.

Animals: Seven, adult, spayed-female dogs (24.8 ± 1.9 kg).

Methods: Each dog was anesthetized twice with sevoflurane in oxygen, with at least 10 days separating the anesthetic events. The minimum alveolar concentration (MAC) of sevoflurane was determined using the tail-clamp technique. During the first anesthetic event, the MAC of sevoflurane was determined initially and again after intravenous administration of maropitant (5 mg kg(-1)) and an infusion (150 μg kg(-1) hour(-1)). During the second anesthetic event, an epidural catheter was advanced to the 4th lumbar vertebra and MAC was determined after administration of saline and maropitant (1 mg kg(-1)) epidurally. All MAC determinations were done in duplicate. The MAC values were adjusted to sea level and compared using student's t-test.

Results: The baseline MAC for sevoflurane was 2.08 ± 0.25%. Intravenous maropitant decreased (p < 0.05) MAC by 16% (1.74 ± 0.17%). In contrast, epidural administration of either saline or maropitant did not change (p > 0.05) the MAC (2.17 ± 0.34% and 1.92 ± 0.12%, respectively).

Conclusion And Clinical Relevance: Maropitant decreased the MAC of sevoflurane when administered intravenously to dogs but not after epidural administration.
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http://dx.doi.org/10.1111/j.1467-2995.2011.00670.xDOI Listing
March 2012

Pharmacokinetics and pharmacodynamics of intravenous medetomidine in the horse.

Vet Anaesth Analg 2012 Jan 22;39(1):38-48. Epub 2011 Nov 22.

K.L. Maddy Equine Analytical Chemistry Laboratory, California Animal Health and Food Safety Laboratory, School of Veterinary Medicine, University of California, Davis, CA 95616,, USA.

Objective: To describe the pharmacodynamics and pharmacokinetics following an intravenous (IV) bolus dose of medetomidine in the horse.

Study Design: Prospective experimental trial.

Animals: Eight, mature healthy horses age 11.7 ± 4.6 (mean ± SD) years, weighing 557 ± 54 kg.

Methods: Medetomidine (10 μg kg(-1) ) was administered IV. Blood was sampled at fixed time points from before drug administration to 48 hours post administration. Behavioral, physiological and biochemical data were obtained at predetermined time points from 0 minutes to 24 hours post administration. An algometer was also used to measure threshold responses to noxious stimuli. Medetomidine concentrations were determined by liquid chromatography-Mass Spectrometry and used for calculation of pharmacokinetic parameters using noncompartmental and compartmental analysis.

Results: Pharmacokinetic analysis estimated that medetomidine peaked (8.86 ± 3.87 ng mL(-1) ) at 6.4 ± 2.7 minutes following administration and was last detected at 165 ± 77 minutes post administration. Medetomidine had a clearance of 39.6 ± 14.6 mL kg(-1) minute(-1) and a volume of distribution of 1854 ± 565 mL kg(-1). The elimination half-life was 29.1 ± 12.5 minutes. Glucose concentration reached a maximum of 176 ± 46 mg dL(-1) approximately 1 hour post administration. Decreased heart rate, respiratory rate, borborygmi, packed cell volume, and total protein concentration were observed following administration. Horses lowered their heads from 107 ± 12 to 20 ± 10 cm within 10 minutes of drug administration and gradually returned to normal. Horse mobility decreased after drug administration. An increased mechanical threshold was present from 10 to 45 minutes and horses were less responsive to sound.

Conclusion And Clinical Relevance: Behavioral and physiological effects following intravenous administration positively correlate with pharmacokinetic profiles from plasma medetomidine concentrations. Glucose concentration gradually transiently increased following medetomidine administration. The analgesic effect of the drug appeared to have a very short duration.
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http://dx.doi.org/10.1111/j.1467-2995.2011.00669.xDOI Listing
January 2012
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