Risk assessment in equine anesthesia: a first evaluation of the usability, utility and predictivity of the two-part CHARIOT.

Introduction: An accurate risk score that can predict peri-anesthetic morbidity and mortality in equine patients could improve peri-operative management, outcome and client communication. Materials and methods: Three hunded horses underwent pre-anesthetic risk assessment using the American Society of Anesthesiologists-Physical Status augmented with equine-specific diseases (ASA-PS-Equine), a multifactorial 10-part rubric risk scale (10-RS), and a combination of both, the Combined horse anesthetic risk identification and optimization tool (CHARIOT). Intra-and post-anesthetic complications, the recovery phase and mortality were recorded over a period of 7 days following general anesthesia. To compare the utility and predictive power of the 3 scores, data were analyzed using binominal logistic regression (p ≤ 0.05) and receiver operating characteristic curve analysis. In addition, inter-observer reliability, speed, safety, ease of use and face validity of the ASA-PS-Equine and the 10-RS were analyzed based on five hypothetical patients. Results: All scores showed statistically significant associations with various intra-anesthetic complications and parameters of the recovery phase. The discriminant ability of the scores related to the occurrence of intra-anesthetic (AUC = 0.6093-0.6701) and post-anesthetic (AUC = 0.5373-0.6194) complications was only low. The highest diagnostic accuracy for all scores was observed for overall mortality (AUC = 0.7526-0.7970), with the ASA-PS-Equine differentiating most precisely (AUC = 0.7970; 95% CI 0.7199-0.8741). Inter-observer reliability was fair for the 10-RS (κ = 0.39) and moderate for the ASA-PS-Equine (κ = 0.52). Patient assignment to the CHARIOT was predominantly rated as rather easy and quick or very quick. Limitations and conclusion: The main limitations of the study are the monocentric study design and failure to obtain the full range of points. In conclusion, all 3 scores provide useful information for predicting the mortality risk of equine patients undergoing general anesthesia, whereas intra-and postoperative complications cannot be predicted with these scores.

Cold stimulation is feasible and has limited aversiveness in healthy, pain-free dogs.

OBJECTIVE: The study aimed to evaluate the applicability and repeatability of cold stimulation in dogs. ANIMALS: 10 healthy Beagle dogs were used in a blinded cross-over experiment. METHODS: Measurements were performed in triplicate at 4 skin locations. The probe was manually placed, and temperature decreased (32 to 10 °C) at different cooling rates (0.5, 1, and 5 °C second-1) and latency was measured (11 °C for 60 seconds). Stimulations were discontinued when avoidance reactions were detected. Thermal threshold or time-to-reaction were recorded. Experiments were performed 3 times per animal in weeks 1 (Exp1), 2 (Exp2), and 5 (Exp3). Feasibility of cold stimulation was scored (0-5). Data were analyzed with mixed logistic regression. RESULTS: No significant differences in number of avoidance reactions between cooling-rates were detected. Significantly more reactions (P < .001) were observed during Exp1 compared to Exp2 and Exp3. Thermal thresholds were 13 ± 2.6 °C, 17.7 ± 4 °C and 16.3 ± 4.6 °C for 5, 0.5 and 1 °C second-1, respectively. Latency to the reaction was determinable in 37% of measurements. The mean time-to-reaction was 13 ± 11 seconds. In 85% of measurements, a feasibility score of 0 (best feasibility) was assigned. CLINICAL RELEVANCE: The method is easily applicable and well tolerated, but habituation could not be excluded. Overall, the aversiveness of cold stimulation in healthy dogs is limited and it is not possible to recommend a specific protocol. In future studies, it needs to be determined if the aversiveness of cold stimulation is increased in diseased dogs.

Treatment of Naturally Occurring Tendon Disease with Allogeneic Multipotent Mesenchymal Stromal Cells: A Randomized, Controlled, Triple-Blinded Pilot Study in Horses.

The treatment of tendinopathies with multipotent mesenchymal stromal cells (MSCs) is a promising option in equine and human medicine. However, conclusive clinical evidence is lacking. The purpose of this study was to gain insight into clinical treatment efficacy and to identify suitable outcome measures for larger clinical studies. Fifteen horses with early naturally occurring tendon disease were assigned to intralesional treatment with allogeneic adipose-derived MSCs suspended in serum or with serum alone through block randomization (dosage adapted to lesion size). Clinicians and horse owners remained blinded to the treatment during 12 months (seven horses per group) and 18 months (seven MSC-group and five control-group horses) of follow-up including clinical examinations and diagnostic imaging. Clinical inflammation, lameness, and ultrasonography scores improved more over time in the MSC group. The lameness score difference significantly improved in the MSC group compared with the control group after 6 months. In the MSC group, five out of the seven horses were free of re-injuries and back to training until 12 and 18 months. In the control group, three out of the seven horses were free of re-injuries until 12 months. These results suggest that MSCs are effective for the treatment of early-phase tendon disease and provide a basis for a larger controlled study.

Surgical removal of an atypical histiocytic cell proliferation in a bearded dragon (Pogona vitticeps).

A 4-year-old female bearded dragon (Pogona vitticeps) was referred to the Clinic for Small Mammals, Reptiles and Birds of the University of Veterinary Medicine, Hannover, Germany for diagnostics and treatment of a growing mass in the right cervical region. The owner reported that the mass had grown over the past 4 weeks with only little alteration in the lizard´s behavior when the animal started rubbing its neck against the cage equipment. Physical examination as well as ultrasonographic and computed tomographic diagnostics revealed a highly vascularized mass, which allowed for the hypothesis of an aneurysm or a neoplasia. Complete surgical resection of the mass could be performed uneventfully. The bearded dragon recovered well from anesthesia and the surgical procedure. The microbiological sample of the excised mass revealed Group F-67 Salmonella. Histopathological examination of the excised mass revealed a histiocytic cell proliferation with centrally located blood filled cavities, hemorrhages and granulation tissue resembling features of a pseudoaneurysm. This report describes the diagnosis of an atypical growing mass in a bearded dragon and its successful removal.

Comparison of desflurane and propofol at equipotent doses in combination with a constant rate infusion of dexmedetomidine on global and peripheral perfusion and oxygenation in horses.

OBJECTIVE To determine global and peripheral perfusion and oxygenation during anesthesia with equipotent doses of desflurane and propofol combined with a constant rate infusion of dexmedetomidine in horses. ANIMALS 6 warmblood horses. PROCEDURES Horses were premedicated with dexmedetomidine (3.5 µg•kg-1, IV). Anesthesia was induced with propofol or ketamine and maintained with desflurane or propofol (complete crossover design) combined with a constant rate infusion of dexmedetomidine (7 µg•kg-1 •h-1). Microperfusion and oxygenation of the rectal, oral, and esophageal mucosa were measured before and after sedation and during anesthesia at the minimal alveolar concentration and minimal infusion rate. Heart rate, mean arterial blood pressure, respiratory rate, cardiac output, and blood gas pressures were recorded during anesthesia. RESULTS Mean ± SD minimal alveolar concentration and minimal infusion rate were 2.6 ± 0.9% and 0.04 ± 0.01 mg•kg-1 •min-1, respectively. Peripheral microperfusion and oxygenation decreased significantly after dexmedetomidine administration for both treatments. Oxygenation returned to baseline values, whereas tissue microperfusion remained low during anesthesia. There were no differences in peripheral tissue microperfusion and oxygenation between treatments. Cardiac index was significantly higher and systemic vascular resistance was significantly lower for desflurane treatment than for propofol treatment. For the propofol treatment, Pao2 was significantly higher and there was less dead space and venous admixture than for the desflurane treatment. CONCLUSIONS AND CLINICAL RELEVANCE Dexmedetomidine decreased blood flow and oxygen saturation in peripheral tissues. Peripheral tissues were well oxygenated during anesthesia with desflurane and propofol combined with dexmedetomidine, whereas blood flow was reduced.

Effect of dexmedetomidine and xylazine followed by MK-467 on gastrointestinal microperfusion in anaesthetized horses.

OBJECTIVE: To compare the effects of MK-467 during isoflurane anaesthesia combined with xylazine or dexmedetomidine on global and gastrointestinal perfusion parameters. STUDY DESIGN: Prospective, randomized experimental trial. ANIMALS: A total of 15 warmblood horses. METHODS: Horses were divided into two groups for administration of either dexmedetomidine (D) or xylazine (X) for premedication (D: 3.5 µg kg-1; X: 0.5 mg kg-1) and as constant rate infusion during isoflurane anaesthesia (D: 7 µg kg-1 hour-1; X: 1 mg kg-1 hour-1). During anaesthesia, heart rate, mean arterial blood pressure (MAP), systemic vascular resistance index (SVRI) and cardiac index (CI) were measured. Microperfusion of the colon, jejunum and stomach was measured using laser Doppler flowmetry. After 2 hours of stabilization, MK-467 (250 µg kg-1) was administered, and measurements were continued for another 90 minutes. For statistical analysis, the permutation test and Wilcoxon rank-sum test were used (p < 0.05). RESULTS: There were no differences in baseline measurements between groups. The MK-467 bolus resulted in a significant decrease in MAP (D: -58%; X: -48%) and SVRI (D: -68%; X: -65%) lasting longer in group D (90 minutes) compared to group X (60 minutes). While CI increased (D: +31%; X: +35%), microperfusion was reduced in the colon (D: -44%; X: -34%), jejunum (D: -26%; X: -33%) and stomach (D: -37%; X: -35%). CONCLUSIONS AND CLINICAL RELEVANCE: Alpha-2-agonist induced vasoconstriction was reversed by the MK-467 dose used, resulting in hypotension and rise in CI. Gastrointestinal microperfusion decreased, probably as a result of insufficient perfusion pressure. An infusion rate for MK-467 as well as an ideal agonist/antagonist ratio should be determined.

The relationship between intestinal and oral mucosa microcirculation in anaesthetized horses.

OBJECTIVE: To compare alteration in intestinal blood flow in anaesthetized horses with changes in oral mucosa blood flow. STUDY DESIGN: Prospective, randomized clinical study. ANIMALS: Eight warmblood horses. METHODS: After induction with guaifenesin and ketamine, anaesthesia was maintained with isoflurane at 1.5 vol% in oxygen. The tissue blood flow was measured using laser Doppler flowmetry at the jejunum, colon, rectal mucosa, oesophageal mucosa and the oral mucosa. After three baseline measurements, blood flow was first increased by dobutamine infusion and thereafter decreased by increasing isoflurane concentration and all measurements repeated twice. anova was used for comparing the measured parameters to baseline and correlation between the different measurement localizations was examined using Pearson correlation (p < 0.05). RESULTS: Microperfusion at all measurement sites increased significantly during dobutamine infusion and decreased significantly during high isoflurane concentration. There was a significant correlation between flow at the oral mucosa and flow at the jejunum (r2 = 0.77, p = 0.002), colon (r2 = 0.76, p < 0.001), rectal mucosa (r2 = 0.88, p < 0.001) and oesophageal mucosa (r2 = 0.83, p <0.001). CONCLUSIONS AND CLINICAL RELEVANCE: Oral mucosa blood flow can be used in isoflurane anaesthetized horses to reflect changes of intestinal microcirculation.

Effects of controlled hypoxemia or hypovolemia on global and intestinal oxygenation and perfusion in isoflurane anesthetized horses receiving an alpha-2-agonist infusion.

BACKGROUND: Aim of this prospective experimental study was to assess effects of systemic hypoxemia and hypovolemia on global and gastrointestinal oxygenation and perfusion in anesthetized horses. Therefore, we anesthetized twelve systemically healthy warmblood horses using either xylazine or dexmedetomidine for premedication and midazolam and ketamine for induction. Anesthesia was maintained using isoflurane in oxygen with either xylazine or dexmedetomidine and horses were ventilated to normocapnia. During part A arterial oxygen saturation (SaO2) was reduced by reducing inspiratory oxygen fraction in steps of 5%. In part B hypovolemia was induced by controlled arterial exsanguination via roller pump (rate: 38 ml/kg/h). Mean arterial blood pressure (MAP), heart rate, pulmonary artery pressure, arterial and central venous blood gases and cardiac output were measured, cardiac index (CI) was calculated. Intestinal microperfusion and oxygenation were measured using laser Doppler flowmetry and white-light spectrophotometry. Surface probes were placed via median laparotomy on the stomach, jejunum and colon. RESULTS: Part A: Reduction in arterial oxygenation resulted in a sigmoid decrease in central venous oxygen partial pressure. At SaO2 < 80% no further decrease in central venous oxygen partial pressure occurred. Intestinal oxygenation remained unchanged until SaO2 of 80% and then decreased. Heart rate and pulmonary artery pressure increased significantly during hypoxemia. Part B: Progressive reduction in circulating blood volume resulted in a linear decrease in MAP and CI. Intestinal perfusion was preserved until blood loss resulted in MAP and CI lower 51 ± 5 mmHg and 40 ± 3 mL/kg/min, respectively, and then decreased rapidly. CONCLUSIONS: Under isoflurane, intestinal tissue oxygenation remained at baseline when arterial oxygenation exceeded 80% and intestinal perfusion remained at baseline when MAP exceeded 51 mmHg and CI exceeded 40 mL/kg/min in this group of horses. TRIAL REGISTRY NUMBER: 33.14-42,502-04-14/1547.

Xylazine infusion in isoflurane-anesthetized and ventilated healthy horses: Effects on cardiovascular parameters and intestinal perfusion.

To investigate the effects of a xylazine infusion during isoflurane anesthesia on global perfusion parameters and gastrointestinal oxygenation and microperfusion, 8 adult warmblood horses were sedated with xylazine and anesthesia induced with midazolam and ketamine. Horses were mechanically ventilated during anesthesia. After 3 h of stable isoflurane anesthesia (FEIso 1.3 Vol %), a xylazine infusion with 1 mg/kg body weight (BW) per hour was started for 1 h and then stopped. Before, during, and after xylazine infusion, heart rate (HR), arterial blood pressure (MAP), cardiac output (CO), central venous pressure (CVP), and pulmonary artery pressure (PAP) were measured and systemic vascular resistance (SVR) was calculated. Arterial blood gases were taken and oxygen delivery (DO2) and alveolar dead space (VDalv) were calculated. Further intestinal oxygen and microperfusion were measured using white light spectroscopy and laser Doppler flowmetry. Surface probes were placed via median laparotomy on the stomach, the jejunum, and the colon. Wilcoxon rank-sum test was used to compare values over time (P < 0.05). During xylazine infusion, MAP, CVP, PAP, SVR, and VDalv increased significantly, whereas CO, DO2, and intestinal microperfusion decreased. Intestinal oxygenation remained unchanged. All parameters returned to pre-xylazine values within 1 h after stopping xylazine infusion. A xylazine infusion during constant isoflurane anesthesia in horses impairs global and intestinal perfusion without changing tissue oxygenation in normoxic healthy horses. Further studies are necessary, however, to evaluate whether a possible reduction of isoflurane concentration by xylazine infusion will ameliorate these negative effects.

Afin d'étudier les effets d'une infusion de xylazine durant une anesthésie à l'isoflurane sur les paramètres globaux de perfusion ainsi que d'oxygénation et micro-perfusion gastro-intestinale, huit chevaux Warmblood adultes ont reçu une sédation avec de la xylazine et l'anesthésie induite avec du midazolam et de la kétamine. Les chevaux ont été ventilés mécaniquement durant l'anesthésie. Après 3 h d'anesthésie stable à l'isoflurane (FEIso 1,3 Vol %) une infusion de xylazine à 1 mg/kg de poids corporel par heure a été débutée pour 1 h puis arrêtée. Avant, durant et après l'infusion de xylazine, le rythme cardiaque (RC), la pression artérielle (PA), le débit cardiaque (DC), la pression veineuse centrale (PVC), et la pression artérielle pulmonaire (PAP) ont été mesurés et la résistance vasculaire systémique (RVS) fut calculée. Les gaz sanguins artériels ont été pris et l'apport en oxygène (AO) et l'espace mort alvéolaire (EMA) calculés. On mesura également l'oxygène intestinal et la micro-perfusion en utilisant la spectroscopie à la lumière blanche et la débitmétrie Doppler au laser. Des sondes de surface ont été placées via laparotomie médiane sur l'estomac, le jéjunum, et le côlon. Le test de somme de rangs de Wilcoxon a été utilisé pour comparer les valeurs dans le temps (P < 0,05).Pendant l'infusion de xylazine, la PA, la PVC, la PAP, la RVS et l'EMA ont augmenté significativement, alors que le DC, l'AO et la micro-perfusion intestinale ont diminué. L'oxygénation intestinale est demeurée inchangée. Tous les paramètres sont retournés aux valeurs pré-xylazine en dedans d'une heure après l'arrêt de l'infusion de xylaxine.Chez les chevaux, une infusion de xylazine pendant une anesthésie constante à l'isoflurane affecte la perfusion totale et intestinale sans changer l'oxygénation des tissus chez des chevaux normoxiques en santé. Des études supplémentaires sont nécessaires toutefois pour évaluer si une réduction possible de la concentration d'isoflurane par infusion de xylazine améliorerait ces effets négatifs.(Traduit par Docteur Serge Messier).