Denervating the pelvic suspensory ligaments of horses causes morphological and histological changes in the ligaments.

OBJECTIVE: To examine changes occurring in normal pelvic suspensory ligaments (SLs) of horses after denervating these ligaments and to investigate the effect chronic inflammation might have on these changes. ANIMALS: 10 horses. PROCEDURES: The SL of 1 randomly selected pelvic limb of each of 5 horses was injected with collagenase to induce desmitis, and 42 days later, the proximal aspect of both pelvic SLs were denervated. The SLs were harvested 120 days after being denervated, and the morphological and histological characteristics of each collagenase-injected, denervated SL were compared with those of the contralateral, non-injected, denervated SL. All denervated SLs were compared with non-denervated pelvic SLs harvested from 5 horses similar in weight and age. RESULTS: The mean width and the cross-sectional area of the musculature of all denervated SLs were significantly less than that of the non-denervated ligaments. The mean thickness of collagenase-injected denervated ligaments, but not that of the non-injected denervated ligaments, was significantly less than that of the non-denervated ligaments. Histological abnormalities typical of neurogenic muscular atrophy were observed in all denervated ligaments. CLINICAL RELEVANCE: Loss of motor neuronal input to the proximal aspect of the SL of the pelvic limb of horses causes neurogenic atrophy of the musculature in that portion of the ligament. Denervating a SL of a pelvic limb may weaken the ligament, increasing its risk of injury. Chronic inflammation of the SL before neurectomy may exacerbate atrophy of the musculature after neurectomy.

Incidence of incompatible crossmatch results in dogs admitted to a veterinary teaching hospital with no history of prior red blood cell transfusion.

OBJECTIVE To determine the incidence of incompatible crossmatch results in dogs without a history of prior RBC transfusion and to evaluate changes in Hct following RBC administration for transfusion-naïve dogs that did and did not have crossmatching performed. DESIGN Retrospective study. ANIMALS 169 client-owned dogs. PROCEDURES Information obtained from the medical records included signalment, pretransfusion Hct or PCV, and crossmatching results where applicable. Dogs that underwent major crossmatching (n = 149) as part of pretransfusion screening were each crossmatched with 3 potential donors. Donor blood was obtained from a commercial source and tested negative for dog erythrocyte antigens (DEAs) 1.1, 1.2, and 7 but positive for DEA 4. Mean change in Hct after transfusion was compared between crossmatch-tested dogs (57/91 that subsequently underwent RBC transfusion) and 20 other dogs that underwent RBC transfusion without prior crossmatching by statistical methods. RESULTS 25 of 149 (17%) dogs evaluated by crossmatching were incompatible with 1 or 2 of the 3 potential donors. All 149 dogs were compatible with ≥ 1 potential donor. Mean ± SD change in Hct after transfusion was significantly higher in dogs that had crossmatching performed (12.5 ± 8.6%) than in dogs that did not undergo crossmatching (9.0 ± 4.3%). CONCLUSIONS AND CLINICAL RELEVANCE Results indicated immunologic incompatibility can exist between first-time transfusion recipients and potential blood donor dogs. The clinical importance of these findings could not be evaluated, but considering the potential for immediate or delayed hemolytic transfusion reactions or shortened RBC life span, the authors suggest veterinarians consider crossmatching all dogs prior to transfusion when possible.

Effect of fentanyl and lidocaine on the end-tidal sevoflurane concentration preventing motor movement in dogs.

OBJECTIVE To determine effects of fentanyl, lidocaine, and a fentanyl-lidocaine combination on the minimum alveolar concentration of sevoflurane preventing motor movement (MACNM) in dogs. ANIMALS 6 adult Beagles. PROCEDURES Dogs were anesthetized with sevoflurane in oxygen 3 times (1-week intervals). Baseline MACNM (MACNM-B) was determined starting 45 minutes after induction of anesthesia. Dogs then received 1 of 3 treatments IV: fentanyl (loading dose, 15 µg/kg; constant rate infusion [CRI], 6 µg/kg/h), lidocaine (loading dose, 2 mg/kg; CRI, 6 mg/kg/h), and the fentanyl-lidocaine combination at the same doses. Determination of treatment MACNM (MACNM-T) was initiated 90 minutes after start of the CRI. Venous blood samples were collected at the time of each treatment MACNM measurement for determination of plasma concentrations of fentanyl and lidocaine. RESULTS Mean ± SEM overall MACNM-B for the 3 treatments was 2.70 ± 0.27 vol%. The MACNM decreased from MACNM-B to MACNM-T by 39%, 21%, and 55% for fentanyl, lidocaine, and the fentanyl-lidocaine combination, respectively. This decrease differed significantly among treatments. Plasma fentanyl concentration was 3.25 and 2.94 ng/mL for fentanyl and the fentanyl-lidocaine combination, respectively. Plasma lidocaine concentration was 2,570 and 2,417 ng/mL for lidocaine and the fentanyl-lidocaine combination, respectively. Plasma fentanyl and lidocaine concentrations did not differ significantly between fentanyl and the fentanyl-lidocaine combination or between lidocaine and the fentanyl-lidocaine combination. CONCLUSIONS AND CLINICAL RELEVANCE CRIs of fentanyl, lidocaine, and the fentanyl-lidocaine combination at the doses used were associated with clinically important and significant decreases in the MACNM of sevoflurane in dogs.

Effects of magnesium sulfate and propofol on the minimum alveolar concentration preventing motor movement in sevoflurane-anesthetized dogs.

OBJECTIVE To evaluate the effect of MgSO4, alone and in combination with propofol, on the minimum alveolar concentration preventing motor movement (MACNM) in sevoflurane-anesthetized dogs. ANIMALS 6 healthy purpose-bred adult male Beagles (least squares mean ± SEM body weight, 12.0 ± 1.1 kg). PROCEDURES Dogs were anesthetized 3 times at weekly intervals. The MACNM was measured 45 minutes after induction of anesthesia (baseline; MACNM-B) and was determined each time by use of a noxious electrical stimulus. Treatments were administered as a loading dose and constant rate infusion (CRI) as follows: treatment 1, MgSO4 loading dose of 45 mg/kg and CRI of 15 mg/kg/h; treatment 2, propofol loading dose of 4 mg/kg and CRI of 9 mg/kg/h; and treatment 3, MgSO4 and propofol combination (same doses used previously for each drug). A mixed-model ANOVA and Tukey-Kramer tests were used to determine effects of each treatment on the percentage decrease from MACNM-B. Data were reported as least squares mean ± SEM values. RESULTS Decrease from MACNM-B was 3.4 ± 3.1%, 48.3 ± 3.1%, and 50.3 ± 3.1%, for treatments 1, 2, and 3, respectively. The decrease for treatments 2 and 3 was significantly different from that for treatment 1; however, no significant difference existed between results for treatments 2 and 3. CONCLUSIONS AND CLINICAL RELEVANCE MgSO4 did not affect MACNM, nor did it potentiate the effects of propofol on MACNM. Administration of MgSO4 in this study appeared to provide no clinical advantage as an anesthetic adjuvant.

The anesthetic interaction of propofol and sevoflurane on the minimum alveolar concentration preventing motor movement (MACNM) in dogs.

The objective of this study was to determine the effects of propofol on the minimum alveolar concentration of sevoflurane needed to prevent motor movement (MAC(NM)) in dogs subjected to a noxious stimulus using randomized crossover design. Six, healthy, adult beagles (9.2 ± 1.3 kg) were used. Dogs were anesthetized with sevoflurane on 3 occasions, at weekly intervals, and baseline MAC(NM) (MAC(NM-B)) was determined on each occasion. Propofol treatments were administered as loading dose (LD) and constant rate infusion (CRI) as follows: Treatment 1 (T1) was 2 mg/kg body weight (BW) and 4.5 mg/kg BW per hour; T2 was 4 mg/kg BW and 9 mg/kg BW per hour; T3 was 8 mg/kg BW and 18 mg/kg BW per hour, respectively. Treatment MAC(NM) (MAC(NM-T)) determination was initiated 60 min after the start of the CRI. Two venous blood samples were collected and combined at each MAC(NM-T) determination for measurement of blood propofol concentration using high-performance liquid chromatography method (HPLC). Data were analyzed using a mixed-model ANOVA and are presented as least square means (LSM) ± standard error of means (SEM). Propofol infusions in the range of 4.5 to 18 mg/kg BW per hour resulted in mean blood concentrations between 1.3 and 4.4 µg/mL, and decreased (P < 0.05) sevoflurane MAC(NM) in a concentration-dependent manner. The percentage decrease in MAC(NM) was 20.5%, 43.0%, and 68.3%, with corresponding blood propofol concentrations of 1.3 ± 0.3 µg/mL, 2.5 ± 0.3 µg/mL, and 4.4 ± 0.3 µg/mL, for T1, T2, and T3, respectively. Venous blood propofol concentrations were strongly correlated (r = 0.855, P < 0.0001) with the decrease in MAC(NM). In dogs, propofol decreased the sevoflurane MAC(NM) in a concentration-dependent manner.

L'objectif de la présente étude était de déterminer les effets du propofol sur la concentration alvéolaire minimale de sevoflurane requise pour empêcher les mouvements moteurs (MACNM) chez des chiens soumis à un stimulus délétère en utilisant un modèle expérimental croisé aléatoire. Six chiens Beagle adultes et en santé (9,2 ± 1,3 kg) ont été utilisés. Les chiens étaient anesthésiés avec du sevoflurane à trois occasions, à une semaine d'intervalle, et la valeur de base de MACNM (MACNM-B) déterminée à chaque occasion. Les traitements de propofol furent administrés à une dose d'attaque (LD) et un taux d'infusion constant (CRI) comme suit: Traitement 1 (T1) était de 2 mg/kg de poids corporel (BW) et 4,5 mg/kg BW par heure; T2 était de 4 mg/kg BW et 9 mg/kg BW par heure; T3 était de 8 mg/kg BW et 18 mg/kg BW par heure, respectivement. La détermination de la MACNM du traitement (MACNM-T) fut initiée 60 min après le début du CRI. Deux échantillons de sang veineux furent prélevés et combinés à chaque mesure de MACNM-T pour mesurer la concentration sanguine de propofol par une méthode de chromatographie à haute performance en phase liquide (HPLC). Les données furent analysées par un modèle mixte d'ANOVA et sont présentées sous forme du moindre carré (LSM) ± écart-type (SEM).Les infusions de propofol variant entre 4,5 à 18 mg/kg BW par heure ont résulté en des concentrations sanguines moyennes entre 1,3 et 4,4 µg/mL, et diminuèrent (P < 0,05) la MACNM de sevoflurane d'une manière dépendante de la concentration. Le pourcentage de diminution de MACNM était de 20,5 %, 43,0 % et 68,3 %, avec des concentrations sanguines de propofol correspondantes de 1,3 ± 0,3 µg/mL, 2,5 ± 0,3 µg/mL, et 4,4 ± 0,3 µg/mL, pour T1, T2 et T3, respectivement. Les concentrations veineuses en propofol étaient fortement corrélées (r = 0,855, P < 0,0001) avec la diminution de MACNM. Chez les chiens, le propofol a diminué la MACNM du sevoflurane de manière dépendante de la concentration.(Traduit par Docteur Serge Messier).

The interaction of nitrous oxide and fentanyl on the minimum alveolar concentration of sevoflurane blocking motor movement (MACNM) in dogs.

The study objective was to determine the effects of 70% nitrous oxide (N2O) and fentanyl on the end-tidal concentration of sevoflurane necessary to prevent movement (MACNM) in response to noxious stimulation in dogs. Six healthy, adult, intact male, mixed-breed dogs were used on 3 occasions in a randomized crossover design. After induction of anesthesia with sevoflurane, each of the following treatments was randomly administered: fentanyl loading dose (Ld) of 15 µg/kg and infusion of 6 µg/kg per hour [treatment 1 (T1)], 70% N2O (T2), or fentanyl (Ld of 15 µg/kg and infusion of 6 µg/kg per hour) combined with 70% N2O (T3). Each dog received each of the 3 treatments once during the 3-week period. Determination of MACNM was initiated 90 min after the start of each treatment. The values were compared using the baseline MACNM, which had been determined in a previous study on the same group of dogs. Data were analyzed using a mixed-model analysis of variance (ANOVA) and Tukey-Kramer tests, and expressed as least squares mean ± SEM. The baseline MACNM decreased by 36.6 ± 4.0%, 15.0 ± 4.0%, and 46.0 ± 4.0% for T1, T2, and T3, respectively (P < 0.05), and differed (P < 0.05) among treatments. Mean fentanyl plasma concentrations did not differ (P ≥ 0.05) between T1 (3.70 ± 0.56 ng/mL) and T3 (3.50 ± 0.56 ng/mL). The combination of fentanyl and N2O resulted in a greater sevoflurane MACNM sparing effect than either treatment alone.

L'objectif de la présente étude était de déterminer les effets de l'oxyde nitreux (N2O) à 70 % et du fentanyl sur la concentration de sevoflurane en fin d'expiration nécessaire pour empêcher le mouvement (MACNM) en réponse à une stimulation désagréable chez des chiens. Six chiens mâles intacts adultes en santé de race croisée furent utilisés en 3 occasions dans des études croisées aléatoires. Après induction de l'anesthésie avec du sevoflurane, chacun des traitements suivants fut administré de manière aléatoire : dose d'induction de fentanyl (Ld) de 15 µg/kg et infusion de 6 µg/kg par heure [traitement 1 (T1)], 70 % N2O (T2), ou fentalyl (Ld de 15 µg/kg et infusion de 6 µg/kg par heure) combiné avec 70 % N2O (T3). Chaque chien a reçu chacun des trois traitements une fois durant la période d'essai de 3 semaines. La détermination du MACNM fut débutée 90 min après le début de chaque traitement. Les valeurs furent comparées en utilisant la valeur de base de MACNM, qui avait été déterminée dans une étude antérieure avec le même groupe de chiens. Les données furent analysées en utilisant un modèle mixte d'analyse de variance (ANOVA) et un test de Tukey-Kramer, et présentées comme la moyenne des moindres carrés ± écart-type. La valeur de base de MACNM diminua de 36,6 ± 4,0 %, 15,0 ± 4,0 %, et 46,0 ± 4,0 % respectivement pour T1, T2 et T3 (P < 0,05), et différait (P < 0,05) entre les traitements. Les concentrations plasmatiques moyennes ne différaient pas (P ≥ 0,05) entre T1 (3,70 ± 0,56 ng/mL) et T3 (3,50 ± 0,56 ng/mL). La combinaison de fentanyl et de N2O a produit un plus grand effet réducteur sur le MACNM de sevoflurane que chaque traitement individuel.(Traduit par Docteur Serge Messier).

Use of an inverse dynamics method to describe the motion of the canine pelvic limb in three dimensions.

OBJECTIVE: To use an inverse dynamics method to describe the motion of the canine pelvic limb in 3 dimensions. ANIMALS: 6 healthy adult dogs. PROCEDURES: For each dog, 16 anatomic and tracking markers were used to define the center of rotation for the pelvic limb joints and a kinematic model was created to describe the motion of the pelvic limb. Kinetic, kinematic, and morphometric data were combined so that an inverse dynamics method could be used to define angular displacement, joint moment, and power of the hip, stifle, and tibiotarsal (hock) joints in the sagittal, frontal, and transverse planes. RESULTS: Movement and energy patterns were described for the hip, stifle, and hock joints in the sagittal, frontal, and transverse planes. CONCLUSIONS AND CLINICAL RELEVANCE: Knowledge of the 3-D movement of the pelvic limb can be used to better understand its motion, moment, and energy patterns in healthy dogs and provide a referent with which gaits of dogs with pelvic limb injuries before and after surgical repair or rehabilitation can be compared and characterized. This information can then be used to guide decisions regarding treatment options for dogs with pelvic limb injuries.

Use of an inverse dynamics method to compare the three-dimensional motion of the pelvic limb among clinically normal dogs and dogs with cranial cruciate ligament-deficient stifle joints following tibial plateau leveling osteotomy or lateral fabellar-tibial suture stabilization.

OBJECTIVE: To compare the 3-D motion of the pelvic limb among clinically normal dogs and dogs with cranial cruciate ligament (CCL)-deficient stifle joints following tibial plateau leveling osteotomy (TPLO) or lateral fabellar-tibial suture (LFS) stabilization by use of an inverse dynamics method. ANIMALS: 6 clinically normal dogs and 19 dogs with CCL-deficient stifle joints that had undergone TPLO (n = 13) or LFS (6) stabilization at a mean of 4 and 8 years, respectively, prior to evaluation. PROCEDURES: For all dogs, an inverse dynamics method was used to describe the motion of the pelvic limbs in the sagittal, frontal, and transverse planes. Motion and energy patterns for the hip, stifle, and tibiotarsal (hock) joints in all 3 planes were compared among the 3 groups. RESULTS: Compared with corresponding variables for clinically normal dogs, the hip joint was more extended at the beginning of the stance phase in the sagittal plane for dogs that had a TPLO performed and the maximum power across the stifle joint in the frontal plane was greater for dogs that had an LFS procedure performed. Otherwise, variables in all planes were similar among the 3 groups. CONCLUSIONS AND CLINICAL RELEVANCE: Gait characteristics of the pelvic limb did not differ between dogs that underwent TPLO and dogs that underwent an LFS procedure for CCL repair and were similar to those of clinically normal dogs. Both TPLO and LFS successfully provided long-term stabilization of CCL-deficient stifle joints of dogs with minimal alterations in gait.

Detection of papillomavirus in equine periocular and penile squamous cell carcinoma.

Squamous cell carcinoma (SCC) is the most common tumor arising in the periocular and penile areas of horses. Both ultraviolet radiation and papillomaviruses have been implicated in the pathogenesis of SCC in various species, including the horse. This retrospective study used polymerase chain reaction (PCR) to detect papillomavirus DNA in archival biopsy samples from equine periocular and penile SCC from 3 different geographic areas (northeast, southeast, and central United States). Forty-two periocular SCCs were tested; none contained papillomavirus DNA. Twenty-two penile SCCs were tested, and papillomavirus DNA was identified in 10 (43%) cases. Sequencing of the PCR products revealed homology with Equus caballus papillomavirus 2 (EcPV-2). No geographic distribution in the detection of papillomavirus was identified. Penile SCCs were significantly more likely to be papillomavirus positive than the periocular SCCs (P < 0.001). The role of papillomavirus in the development of penile SCC requires further investigation. The differing pathogeneses of periocular and penile SCC suggest that the tumors may respond differently to treatment.

Characteristics of residency training associated with first-time pass rate on the American College of Veterinary Ophthalmologists certifying examination.

OBJECTIVE: The aim of this study was to examine the association of various aspects of veterinary ophthalmology residency training with the first-time pass rate (FTPR) of the American College of Veterinary Ophthalmologists (ACVO) examination, as well as the individual written, image recognition, animal examination, and surgical sections of the examination. PROCEDURES: Program type, resident evaluations, cumulative surgery and case logs, and scores from ACVO examinations from 2007 to 2010 were evaluated. RESULTS: Data were available for 71 candidates. The overall FTPR was 35% (n = 25). For the different sections of the examination, FTPRs were as follows: written (68%), image recognition (76%), intraocular surgery (80%), extraocular surgery (65%), and animal examination (75%). The overall FTPR among candidates from academic residency (AR) programs was 43% (20 of 47), while the FTPR of residents in private practice (PPR) programs was 21% (5 of 24; P = 0.07). The AR candidates were more likely to pass the written portion than PPR residents (P = 0.02), and AR candidates had significantly more time off clinics (median 25%) vs PPR residents (median 18%; P = 0.007). The AR residents also had a higher reported percentage of direct supervision than PPR residents (95% vs 76%, respectively). Although PPR residents did significantly more surgeries and examined significantly more dogs and cats, those from ARs examined significantly more equine, bovine, avian, camelid, and reptile species. CONCLUSIONS: Overall, AR residents had a higher FTPR and were more likely to pass the written portion of the examination. Total case and surgery numbers were not associated with FTPR.

The effect of nitrous oxide on the minimum alveolar concentration (MAC) and MAC derivatives of isoflurane in dogs.

This study investigated the effects of 70% nitrous oxide (N2O) on the minimum alveolar concentration (MAC) of isoflurane (ISO) that prevents purposeful movement, the MAC of ISO at which there is no motor movement (MACNM), and the MAC of ISO at which autonomic responses are blocked (MACBAR) in dogs. Six adult, healthy, mixed-breed, intact male dogs were anesthetized with ISO delivered via mask. Baseline MAC, MACNM, and MACBAR of ISO were determined for each dog using a supra-maximal electrical stimulus (50 V, 50 Hz, 10 ms). Nitrous oxide (70%) was then administered and MAC and its derivatives (N2O-MAC, N2O-MACNM, and N2O-MACBAR) were determined using the same methodology. The values for baseline MAC, MACNM, and MACBAR were 1.39 ± 0.14, 1.59 ± 0.10, and 1.72 ± 0.16, respectively. The addition of 70% N2O decreased MAC, MACNM, and MACBAR by 32%, 15%, and 25%, respectively.

Cette étude avait comme objectif d'évaluer chez des chiens les effets de 70 % d'oxyde nitreux (N2O) sur la concentration alvéolaire minimum (MAC) d'isoflurane (ISO) qui empêche les mouvements volontaires, la MAC d'ISO à laquelle il n'y a pas de mouvement moteur (MACNM), et la MAC d'ISO à laquelle les réponses autonomes sont bloquées (MACBAR).Six chiens mâles intacts adultes de race mélangée ont été anesthésiés avec de l'ISO administré via un masque. Les valeurs de base de MAC, MACNM et de MACBAR d'ISO ont été déterminées pour chaque chien à l'aide d'un stimulus électrique supra-maximal (50 V, 50 Hz, 10 ms). De l'oxyde nitreux (70 %) fut ensuite administré et la MAC et ses dérivées (N2O-MAC, N2O-MACNM et N2O-MACBAR) déterminées à l'aide de la même méthodologie. Les valeurs des données de base de MAC, MACNM et MACBAR étaient respectivement 1,39 ± 0,14, 1,59 ± 0,10 et 1,72 ± 0,16. L'ajout de 70 % de N2O a entrainé des diminutions de MAC, MACNM et MACBAR de 32 %, 15 % et 25 %, respectivement.(Traduit par Docteur Serge Messier).

Effects of butorphanol versus dexmedetomidine sedation on intradermal allergen and histamine responses in dogs with atopic dermatitis.

BACKGROUND: Sedation is commonly used during intradermal testing (IDT). Morphine and its derivatives have long been avoided because of their histamine-releasing effects. HYPOTHESIS/OBJECTIVES: Butorphanol, an opioid agonist/antagonist, will not adversely affect IDT in dogs. ANIMALS: Ten client-owned dogs diagnosed with atopic dermatitis. METHODS: Dogs were randomized to be sedated with butorphanol (0.4 mg/kg) or dexmedetomidine (5 µg/kg). Routine IDT along with intradermal injections of various dilutions of histamine were performed on the lateral thorax, followed 7 days later by the alternative sedative and IDT on the opposite side. The injection sites were subjectively scored and objectively measured by one investigator, blinded to the sedatives, and compared between groups. RESULTS: When the mean wheal diameters from the objective measurements of all antigens, including saline and histamine dilutions, were compared, butorphanol was associated with significantly smaller reactions than dexmedetomidine (P = 0.0001). There was a high level of agreement between sedatives when positive reactions subjectively scored as ≥3+ were compared (κ = 0.91). When mean wheal diameters of histamine at concentrations of 1:100,000, 1:400,000, 1:1,600,000 and 1:6,400,000 were compared, there were no significant differences between sedative types. Moreover, the percentage agreement when comparing subjective interpretation of all histamine dilutions between sedations was high (κ = 0.90). However, there was only 69% agreement beyond chance when objective and subjective interpretations of all antigens were compared between sedative groups. CONCLUSIONS: Although butorphanol resulted in significantly smaller wheal size in comparison to dexmedetomidine, it did not affect the overall subjective interpretation of the results of IDT.

The effect of fentanyl on the end-tidal sevoflurane concentration needed to prevent motor movement in dogs.

OBJECTIVE: The objectives of this study were to determine the effects of fentanyl on the end-tidal concentration of sevoflurane needed to prevent motor movement (MACNM ) in response to noxious stimulation, and to evaluate if acute tolerance develops. STUDY DESIGN: Randomized cross-over experimental study. ANIMALS: Six healthy, adult (2-3 years old), intact male, mixed-breed dogs weighing 16.2 ± 1.1 kg. METHODS: Six dogs were randomly assigned to receive one of three separate treatments over a 3 week period. After baseline sevoflurane MACNM (MACNM-B) determination, fentanyl treatments (T) were administered as a loading dose (Ld) and constant rate infusion (CRI) as follows: T1-Ld of 7.5 µg kg(-1) and CRI at 3 µg kg(-1) hour(-1); T2-Ld of 15 µg kg(-1) and CRI at 6.0 µg kg (-1) hour(-1); T3-Ld of 30 µg kg(-1) and CRI at 12 µg kg(-1) hour(-1). The MACNM was defined as the minimum end-tidal sevoflurane concentration preventing motor movement. The first post-treatment MACNM (MACNM-I) determination was initiated 90 minutes after the start of the CRI, and a second MACNM (MACNM - II) determination was initiated 3 hours after MACNM-I was established. RESULTS: The overall least square mean MACNM-B for all groups was 2.66%. All treatments decreased (p < 0.05) MACNM, and the decrease from baseline was 22%, 35% and 41% for T1, T2 and T3, respectively. Percentage change in T1 differed (p < 0.05) from T2 and T3; however, T2 did not differ from T3. MACNM-I was not significantly different from MACNM-II within treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl doses in the range of 3-12 µg kg(-1) hour(-1) significantly decreased the sevoflurane MACNM. Clinically significant tolerance to fentanyl did not occur under the study conditions.

Effect of nitrous oxide on the minimum alveolar concentration for sevoflurane and the minimum alveolar concentration derivatives that prevent motor movement and autonomic responses in dogs.

OBJECTIVE: To investigate the effects of the concurrent administration of 70% N(2)O on the minimum alveolar concentration (MAC) for sevoflurane in dogs, the MAC derivative that blocks motor movement (MAC(NM)), and the MAC derivative that blocks autonomic responses (MAC(BAR)). ANIMALS: 7 adult sexually intact male mixed-breed dogs. PROCEDURES: For each dog, anesthesia was induced with sevoflurane delivered via a face mask. Initially, the baseline MAC, MAC(NM), and MAC(BAR) for sevoflurane were determined by use of a noxious stimulus (50 V, 50 Hz, and 10 milliseconds) applied subcutaneously over a midulnar region. Nitrous oxide (70%) was added to the breathing circuit, and MAC, MAC(NM), and MAC(BAR) were determined again. Percentage changes from the respective baseline concentrations for MAC, MAC(NM)' and MAC(BAR) were calculated after the administration of N(2)O. RESULTS: Baseline median values for the MAC, MAC(NM), and MAC(BAR) for sevoflurane were 1.75%, 2.00%, and 2.50%, respectively. Addition of 70% N(2)O significantly decreased MAC, MAC(NM), and MAC(BAR) by 24.4%, 25.0%, and 35.2%, respectively, and these values did not differ significantly from each other. CONCLUSIONS AND CLINICAL RELEVANCE: Supplementation with 70% N(2)O caused a clinically important and significant decrease in the MAC, MAC(NM)' and MAC(BAR) for sevoflurane in dogs.

Treatment outcome of dogs with meticillin-resistant and meticillin-susceptible Staphylococcus pseudintermedius pyoderma.

BACKGROUND: The prevalence of meticillin- and multidrug-resistant Staphylococcus pseudintermedius (MRSP) in canine pyoderma has been increasing in recent years; thus, treatment of these cases has become challenging. HYPOTHESIS/OBJECTIVES: To compare treatment outcome (clinical resolution and treatment duration), adverse effects of medication, and concurrent diseases and medications in dogs with meticillin-susceptible S. pseudintermedius (MSSP) and MRSP pyoderma. ANIMALS/METHODS: Medical records were reviewed retrospectively, and 123 MSSP and 93 MRSP clinical cases between January 2008 and April 2010 were included. RESULTS: In MSSP infections, cefalexin and cefpodoxime were the most commonly prescribed antimicrobials, accounting for 43.2 and 34.4% of cases, respectively. In MRSP infections, chloramphenicol and doxycycline were most commonly prescribed, accounting for 52.6 and 14.4% of cases, respectively. Adverse effects were reported in seven MSSP and 31 MRSP cases. The most commonly reported adverse effects were gastrointestinal, prompting antibiotic discontinuation in three MSSP and 20 MRSP cases. Chloramphenicol was associated with the highest incidence of adverse reactions (27 of 51 cases). Of 164 cases with follow up, 43 of 88 MSSP infections and 29 of 76 MRSP infections achieved complete clinical resolution at the first recheck examination. Three MSSP and seven MRSP cases failed to improve or resolve at subsequent visits assessed at 3-4 week intervals. CONCLUSIONS AND CLINICAL IMPORTANCE: Results from this study showed that the majority of pyodermas resolved regardless of meticillin susceptibility. Although some cases of MRSP pyoderma took longer to treat, this is likely to be because of chronicity and not the organism. In addition, adverse effects were frequently associated with chloramphenicol administration.

Effects of hyperbaric oxygen treatment on horses with experimentally induced endotoxemia.

OBJECTIVE: To determine the effectiveness of preinduction hyperbaric oxygen treatment (HBOT) in ameliorating signs of experimentally induced endotoxemia in horses. ANIMALS: 18 healthy adult horses. PROCEDURES: Horses were randomly assigned to 1 of 3 equal-sized treatment groups to receive normobaric ambient air and lipopolysaccharide (LPS), HBOT and LPS, or HBOT and physiologic saline (0.9% NaCl) solution. Horses were physically examined, and blood was obtained for a CBC and to determine concentration or activity of plasma tissue necrosis factor-α, blood lactate, and blood glucose before the horses were treated with HBOT and then intermittently for 6 hours after administration of LPS or physiologic saline solution. RESULTS: All LPS-treated horses developed signs and biochemical and hematologic changes consistent with endotoxemia. Treatment with HBOT significantly ameliorated the effect of LPS on clinical endotoxemia score but did not significantly improve other abnormalities associated with endotoxemia. CONCLUSIONS AND CLINICAL RELEVANCE: The protective effect of HBOT was minimal, and results did not support its use as a treatment for horses prior to development of endotoxemia.

Risk factors associated with failure of heartworm prophylaxis among members of a national hunting dog club.

OBJECTIVE: To identify practices associated with failure of heartworm prophylaxis among dog and kennel owners and dog trainers. DESIGN: Online survey and mail-in questionnaire. Sample-708 members of a national hunting dog club. PROCEDURES: Heartworm prevention practices used by respondents that reported failure of prophylaxis were compared with practices used by respondents that reported success. RESULTS: Univariate analyses indicated failure of heartworm prophylaxis was inversely related to the number of dogs under a respondent's care. Year-round prophylactic practice was not significantly associated with reduced odds of failure, and efforts to control exposure to mosquitoes were similar among the comparison groups. Respondents reporting prophylaxis failure were more likely to test for heartworm infection ≥ 1 time/y, compared with those reporting success. In a multivariable analysis, residence south of the Virginia-North Carolina state line (ie, the 37th geographic parallel), testing for heartworm infection < once a year when the test was administered prior to April 1, and keeping dogs outdoors for longer periods at dusk, at dawn, or after dark were associated with increased odds of prophylaxis failure. CONCLUSIONS AND CLINICAL RELEVANCE: Veterinarians should stress the importance of annual heartworm testing 6 to 7 months after the last possible date of exposure to heartworm, regardless of whether a dog receives prophylactic treatment year-round. Reducing the number of hours dogs spend outdoors at dusk, at dawn, or after dark may reduce the odds of heartworm disease even when dogs are given preventive treatment.

The effect of midazolam on the end-tidal concentration of isoflurane necessary to prevent movement in dogs.

OBJECTIVE: To determine the possible additive effect of midazolam, a GABA(A) agonist, on the end-tidal concentration of isoflurane that prevents movement (MAC(NM) ) in response to noxious stimulation. STUDY DESIGN: Randomized cross-over experimental study. ANIMALS: Six healthy, adult intact male, mixed-breed dogs. METHODS: After baseline isoflurane MAC(NM) (MAC(NM-B) ) determination, midazolam was administered as a low (LDS), medium (MDS) or high (HDS) dose series of midazolam. Each series consisted of two dose levels, low and high. The LDS was a loading dose (Ld) of 0.2 mg kg(-1) and constant rate infusion (CRI) (2.5 µg kg(-1) minute(-1)) (LDL), followed by an Ld (0.4 mg kg(-1)) and CRI (5 µg kg(-1) minute(-1)) (LDH). The MDS was an Ld (0.8 mg kg(-1)) and CRI (10 µg kg(-1) minute(-1)) (MDL) followed by an Ld (1.6 mg kg(-1)) and CRI (20 µg kg(-1) minute(-1)) (MDH). The HDS was an Ld (3.2 mg kg(-1)) and CRI (40 µg kg(-1) minute(-1)) (HDL) followed by an Ld (6.4 mg kg(-1)) and CRI (80 µg kg(-1) minute(-1)) (HDH). MAC(NM) was re-determined after each dose in each series (MAC(NM-T)). RESULTS: The median MAC(NM-B) was 1.42. MAC(NM-B) did not differ among groups (p > 0.05). Percentage reduction in MAC(NM) was significantly less in the LDS (11 ± 5%) compared with MDS (30 ± 5%) and HDS (32 ± 5%). There was a weak correlation between the plasma midazolam concentration and percentage MAC(NM) reduction (r = 0.36). CONCLUSION AND CLINICAL RELEVANCE: Midazolam doses in the range of 10-80 µg kg(-1) minute(-1) significantly reduced the isoflurane MAC(NM) . However, doses greater than 10 µg kg(-1) minute(-1) did not further decrease MAC(NM) indicating a ceiling effect.

Survey of heartworm prevention practices among members of a national hunting dog club.

Surveillance data indicate that failures have been reported for virtually all heartworm prevention product categories. Resistance of third and fourth stage larvae of Dirofilaria immitis to macrocyclic lactones, lack of compliance, other unknown factors, or a combination of these reasons may be the cause of failure. A survey of members of a national hunting dog club was conducted to identify practices used to prevent canine heartworm infections. Questionnaires were completed by 708 dog owners. Year-round administration of heartworm preventive medication was reported by 208 (88%) respondents residing north of the 37th parallel. Dosing was based on the estimated weight of the dog by 54 (7%) respondents, 389 (55%) did not record the date prophylaxis was administered, and 89 (13%) observed the dogs spit out pills. Heartworm testing at least once per year was done by 556 (79%) respondents and test dates were spread throughout the year. Only 448 (64%) respondents tested newly acquired dogs for heartworm. These findings suggest that veterinarians should place a greater emphasis on the frequency and timing of heartworm diagnostic tests, the importance of weighing dogs, duration of administration, recording the date monthly heartworm prophylaxis is given, and observing dogs to ensure that oral medication is retained.

Ocular lesions in canine mucopolysaccharidosis I and response to enzyme replacement therapy.

PURPOSE: Mucopolysaccharidosis I (MPS I) is an inherited metabolic disorder resulting from deficiency of α-L-iduronidase and lysosomal accumulation of glycosaminoglycans (GAG) in multiple tissues. Accumulation of GAG in corneal stromal cells causes corneal opacity and reduced vision. The purpose of this study was to determine the extent of ocular GAG accumulation and investigate the effectiveness of intravenous enzyme replacement therapy (ERT) on corneal GAG accumulation in dogs. METHODS: Ocular tissues were obtained from 58 dogs with mucopolysaccharidosis I and four unaffected controls. Affected dogs received either low-dose ERT, high-dose ERT, or no treatment; some low-dose dogs also received intrathecal treatments. Histologic severity of corneal stromal GAG accumulation was scored. RESULTS: Accumulation of GAG was found in corneal stromal cells and scleral fibroblasts but not in corneal epithelium, endothelium, ciliary epithelium, choroid, retina, retinal pigment epithelium, or optic nerve. Corneal GAG accumulation increased in severity with increasing age. Although low-dose ERT did not significantly reduce corneal stromal GAG accumulation in comparison with untreated animals, high-dose ERT did result in significantly less GAG accumulation compared with the untreated dogs (adjusted P = 0.0143) or the low-dose ERT group (adjusted P = 0.0031). Intrathecal treatments did not significantly affect GAG accumulation. Dogs that began ERT shortly after birth also had significantly less (P < 0.0001) GAG accumulation in the corneal stroma than dogs with a later onset of treatment. CONCLUSIONS: These data suggest that high-dose, intravenous ERT is effective at preventing and/or clearing corneal stromal GAG accumulation, particularly if initiated early after birth.