Plasma concentrations at two dexmedetomidine constant rate infusions in isoflurane anaesthetized horses: a clinical study.

OBJECTIVE: To determine dexmedetomidine plasma concentrations at two infusion rates in isoflurane anaesthetized horses and compare cardiovascular effects and anaesthetic recovery between treatments. STUDY DESIGN: Prospective, randomized, masked clinical study. ANIMALS: Healthy, adult, client-owned, non-food producing horses presented for castration. METHODS: Premedication consisted of acepromazine, romifidine and morphine, and anaesthesia was induced with ketamine and midazolam. The horses were randomized to receive dexmedetomidine 0.5 µg kg-1 hour-1 (treatment DL, n = 7) or 1.75 µg kg-1 hour-1 (treatment DH, n = 7) for 90 minutes of isoflurane anaesthesia at an end-tidal concentration of 1.2%. Venous plasma concentrations were determined with liquid chromatography-electrospray-ionization-tandem mass spectrometry. Jugular venous and arterial blood was sampled for blood gas analysis at the start and end of the infusion. Changes in cardiovascular variables from the start to the end of the infusion, and recovery parameters were statistically compared between treatments. RESULTS: Fourteen male horses, 2-6 years old, 325-536 kg were included. Mean ± standard deviation dexmedetomidine plasma concentrations at 30, 60 and 90 minutes with treatment DL were 0.22 ± 0.05, 0.29 ± 0.07 and 0.33 ± 0.08 ng mL-1, and with treatment DH were 0.65 ± 0.11, 0.89 ± 0.10 and 1.01 ± 0.10 ng mL-1. The 95% confidence interval for change minute-1 in dexmedetomidine plasma concentrations between 75 and 90 minutes was 0-1% for both treatments. With treatment DH, the heart rate decreased significantly more from the beginning to the end of the infusion compared to DL (p = 0.043). No other significant differences were found between treatments in cardiovascular or recovery parameters. CONCLUSIONS AND CLINICAL RELEVANCE: Infusion of dexmedetomidine in isoflurane anaesthetized horses resulted in plasma concentrations with low variation at both infusion rates, approaching stable levels after 75 minutes of infusion. No differences of clinical importance were found when comparing cardiovascular variables and quality of recovery between treatments.

Rocuronium infusion: A higher rate is needed in diabetic than nondiabetic dogs.

OBJECTIVE: To determine the infusion rates that maintain the train-of-four (TOF) ratio within 20-70% in dogs and compare the infusion rates between diabetic and nondiabetic dogs. STUDY DESIGN: Prospective clinical study. ANIMALS: In total, 47 dogs scheduled for phacoemulsification were included with a median (80% central range) bodyweight of 10.6 (5.7-35.5) kg and age of 7 (1-11) years. Diabetes mellitus was previously diagnosed in nine dogs. METHODS: After premedication using acepromazine and methadone, anaesthesia was induced by intravenous (IV) propofol and maintained by isoflurane and fentanyl or remifentanil. The TOF ratio was monitored by stimulating the peroneal nerve and the response quantified by accelerometry. Rocuronium 0.5 mg kg-1 was administered IV, and further infused to maintain the TOF ratio between 20% and 70%. The infusion rates of rocuronium were compared by the Mann-Whitney test between diabetic and nondiabetic dogs, and the influence of age, sex, bodyweight, body temperature, end-tidal carbon dioxide, end-tidal isoflurane concentration, mean arterial blood pressure, pulse rate and time from induction and time from rocuronium bolus to stable rocuronium infusion rate were investigated in a stepwise, forward regression model. RESULTS: A stable infusion rate was found in 42 dogs. A higher median (80% central range) infusion rate was found in diabetic [0.43 (0.35-0.50) mg kg-1 hour-1] compared with nondiabetic dogs [0.30 (0.20-0.50) mg kg-1 hour-1] (p = 0.013). None of the other variables investigated were found to significantly influence the infusion rate. CONCLUSIONS AND CLINICAL RELEVANCE: There is a quite large individual variation in the infusion rates of rocuronium needed to maintain a stable neuromuscular block in a varied population of dogs. Of the variables investigated, diabetes mellitus was the only one found to significantly influence the infusion rate of rocuronium.

Temporary hindlimb paresis following dystocia due to foetal macrosomia in a Celebes crested macaque (Macaca nigra).

A multiparous Celebes crested macaque presented with dystocia due to foetal macrosomia, causing foetal mortality and hindlimb paresis. After emergency caesarean section, recovery of motor function took 1 month before hindlimbs were weight bearing and 2 months before re-integration with the troop.

Development of a Multimodal Apparatus to Generate Biomechanically Reproducible Spinal Cord Injuries in Large Animals.

Rodents are widespread animal models in spinal cord injury (SCI) research. They have contributed to obtaining important information. However, some treatments only tested in rodents did not prove efficient in clinical trials. This is probably a result of significant differences in the physiology, anatomy, and complexity between humans and rodents. To bridge this gap in a better way, a few research groups use pig models for SCI. Here we report the development of an apparatus to perform biomechanically reproducible SCI in large animals, including pigs. We present the iterative process of engineering, starting with a weight-drop system to ultimately produce a spring-load impactor. This device allows a graded combination of a contusion and a compression injury. We further engineered a device to entrap the spinal cord and prevent it from escaping at the moment of the impact. In addition, it provides identical resistance around the cord, thereby, optimizing the inter-animal reproducibility. We also present other tools to straighten the vertebral column and to ease the surgery. Sensors mounted on the impactor provide information to assess the inter-animal reproducibility of the impacts. Further evaluation of the injury strength using neurophysiological recordings, MRI scans, and histology shows consistency between impacts. We conclude that this apparatus provides biomechanically reproducible spinal cord injuries in pigs.