Selected clinical, biochemical, and electrolyte alterations in anesthetized captive tigers (Panthera tigris) and lions (Panthera leo).

A prospective study to assess changes in selected plasma biochemistry and electrolyte values, plasma insulin and aldosterone concentrations, and electrocardiography (ECG) was performed on eight female captive tigers (Panthera tigris) and three lions (Panthera leo) undergoing general anesthesia for elective laparoscopic ovariectomy. Each animal was sedated with medetomidine (18-25 microg/kg) and midazolam (0.06-0.1 mg/kg) intramuscularly, and anesthesia was induced with ketamine (1.9-3.5 mg/kg) intramuscularly and maintained with isoflurane. Venous blood samples were collected and analyzed for plasma biochemistry parameters and insulin and aldosterone concentrations. An ECG was recorded at the time of each blood sample collection. Mean plasma potassium, glucose, phosphorus, and aldosterone concentrations increased during anesthesia (P < or = 0.05). One tiger developed hyperkalemia (6.5 mmol/L) 2.5 hr after anesthetic induction. Plasma insulin concentrations were initially below the low end of the domestic cat reference interval (72-583 pmol/L), but mean insulin concentration increased (P < or = 0.05) over time compared with the baseline values. Three tigers and two lions had ECG changes that were representative of myocardial hypoxemia. Based on these results, continuous monitoring of clinical and biochemical alterations during general anesthesia in large nondomestic felids is warranted, and consideration should be given to reversal of medetomidine in these animals should significant changes in electrolytes or ECG occur.

Local anesthetics as pain therapy in horses.

This article describes the rationale behind the use of systemically administered lidocaine as an analgesic. The analgesic efficacy of intravenously administered lidocaine is well documented by studies in human patients and laboratory animals. The mechanism by which systemically administered lidocaine produces analgesia is uncertain but is thought to include action at sodium, calcium, and potassium channels and the N-methyl-D-aspartate acid receptor. In addition, the anti-inflammatory actions of lidocaine are important in producing analgesia because inflammatory mediators augment neuronal excitability. The available studies of systemically administered lidocaine in horses provide evidence for the analgesic and anesthetic effects of intravenous lidocaine in this species.

The effect of chondrocyte cryopreservation on cartilage engineering.

Chondrocytes were collected from the stifle joints of four pigs to study the effect of cryopreservation on the chondrogenic potential of chondrocytes. Half of the cells were cryopreserved for 3months. Polyglycolic acid scaffolds were cultured with fresh or cryopreserved chondrocytes for 4weeks. Cell morphology and the quality of engineered tissue were evaluated by scanning electron microscopy, histopathology and biochemical methods. More cells attached to scaffolds at 48h when fresh chondrocytes were seeded. At 4weeks, the numbers of cells, DNA and collagen II were greater in constructs engineered by fresh cells. However, the collagen II/DNA ratio did not differ between the two groups. More matrix was identified on a scanning electron microscope and by histopathology in the fresh group. Cartilage engineered with cryopreserved chondrocytes may contain less matrix and fewer cells. These findings most likely resulted from a lack of cell attachment on the matrix secondary to cryopreservation. Future studies are needed to further evaluate the mechanism by which cryopreservation may affect chondrocyte attachment.

Effect of ketamine on the minimum infusion rate of propofol needed to prevent motor movement in dogs.

OBJECTIVE: To determine the minimum infusion rate (MIR) of propofol required to prevent movement in response to a noxious stimulus in dogs anesthetized with propofol alone or propofol in combination with a constant rate infusion (CRI) of ketamine. ANIMALS: 6 male Beagles. PROCEDURES: Dogs were anesthetized on 3 occasions, at weekly intervals, with propofol alone (loading dose, 6 mg/kg; initial CRI, 0.45 mg/kg/min), propofol (loading dose, 5 mg/kg; initial CRI, 0.35 mg/kg/min) and a low dose of ketamine (loading dose, 2 mg/kg; CRI, 0.025 mg/kg/min), or propofol (loading dose, 4 mg/kg; initial CRI, 0.3 mg/kg/min) and a high dose of ketamine (loading dose, 3 mg/kg; CRI, 0.05 mg/kg/min). After 60 minutes, the propofol MIR required to prevent movement in response to a noxious electrical stimulus was determined in duplicate. RESULTS: Least squares mean ± SEM propofol MIRs required to prevent movement in response to the noxious stimulus were 0.76 ± 0.1 mg/kg/min, 0.60 ± 0.1 mg/kg/min, and 0.41 ± 0.1 mg/kg/min when dogs were anesthetized with propofol alone, propofol and low-dose ketamine, and propofol and high-dose ketamine, respectively. There were significant decreases in the propofol MIR required to prevent movement in response to the noxious stimulus when dogs were anesthetized with propofol and low-dose ketamine (27 ± 10%) or with propofol and high-dose ketamine (30 ± 10%). CONCLUSIONS AND CLINICAL RELEVANCE: Ketamine, at the doses studied, significantly decreased the propofol MIR required to prevent movement in response to a noxious stimulus in dogs.

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).