EVALUATION OF OSCILLOMETRIC BLOOD PRESSURE MEASUREMENT USING A FINGER CUFF IN ANESTHETIZED CHIMPANZEES (PAN TROGLODYTES).

Cardiovascular disease is common among chimpanzees (Pan troglodytes), and serial blood pressure monitoring in conscious animals may improve disease surveillance and guide hypertension treatment strategies. The objective of this study was to compare the accuracy of a noninvasive, oscillometric blood pressure monitor using a finger blood pressure cuff with invasively measured blood pressure in anesthetized chimpanzees. Twelve chimpanzees were anesthetized with tiletamine-zolazepam intramuscularly, intubated, and maintained on inhaled isoflurane to effect. Blood pressure measurements, which included systolic arterial pressure (SAP), mean arterial pressure (MAP), and diastolic arterial pressure (DAP), were collected simultaneously from an oscillometric blood pressure cuff placed on a forelimb digit (FBP) and a direct arterial catheter (IBP) every 5-10 min while anesthetized. One hundred paired samples were collected, and results were compared using Bland-Altman plots and analysis. FBP showed good agreement with IBP for SAP, MAP, and DAP but consistently overestimated values compared with IBP. FBP may be useful for serial blood pressure monitoring in conscious chimpanzees.

Intravenous dexmedetomidine, morphine, or a combination can result in gallbladder wall thickening; with no significant association with plasma histamine concentrations.

The gallbladder is routinely evaluated during ultrasonographic examinations in dogs. However, published studies describing the effects of sedative agents on gallbladder wall thickness are currently lacking. The aims of this prospective, blinded, randomized crossover pilot study were to test hypotheses that IV morphine would result in gallbladder wall thickening, that morphine administration would increase plasma histamine concentrations, and that combining IV morphine with dexmedetomidine would potentiate gallbladder wall thickening. Six healthy Beagle dogs were sedated with intravenous (IV) morphine 0.4 mg/kg (group M), dexmedetomidine 7 µg/kg (group D), or a combination of the two (group MD). Physiologic parameters were measured at baseline and at regular intervals until the last ultrasonographic scan. Ultrasonographic scans were performed at baseline, 90 s, and at 5, 15, 30, 45, 60, 90, and 120 min. Plasma histamine samples were taken at baseline, 90 s, and 5 and 60 min. Cochran's Q-test was used to compare gallbladder wall thickening between groups, while the association between histamine plasma concentration and gallbladder wall thickness was compared with a mixed-effects model. Baseline gallbladder wall thickness was not significantly different between groups. Six of 18 treatments/dogs (33%) developed gallbladder thickening, with no difference between groups. There was no significant difference in baseline plasma histamine concentrations between groups, and no association between plasma histamine concentration and gallbladder wall thickness. Gallbladder wall thickening was observed in at least one dog in each group, therefore caution is recommended for gallbladder wall thickness ultrasonographic interpretation in dogs when these drugs have been administered.

2-PHENOXYETHANOL (2-PE) AND TRICAINE METHANESULFONATE (MS-222) IMMERSION ANESTHESIA OF AMERICAN HORSESHOE CRABS (LIMULUS POLYPHEMUS).

Despite extensive literature examining American horseshoe crab physiology, there are comparatively few publications addressing their medical care. Establishing anesthesia protocols for horseshoe crabs is integral to limiting the potential stress and pain associated with invasive procedures and for advancing euthanasia techniques. The objective of this study was to compare the effects of two immersion anesthetics, tricaine methanesulfonate (MS-222) at 1 g/L (buffered with sodium carbonate) and 2-phenoxyethanol (2-PE) at 2 mL/L, on horseshoe crabs. Twenty horseshoe crabs were assigned to one of two anesthetic treatment groups and individually anesthetized in natural seawater. Water quality, cardiac contractility, and hemolymph gas analytes were measured prior to anesthesia and at 30 min Animals were monitored via heart rate, gilling rate, and sedation score every 5 min until recovered. Transcarapacial ultrasonography was used to obtain heart rate, gilling rate, and percent fractional shortening. Light or surgical anesthesia was produced in 10/10 animals in the 2-PE group and 8/10 animals in the MS-222 group. There was no significant difference in sedation scores, induction time (median 15 min), or recovery time (median 20.5 min). Gilling rate and cardiac contractility decreased during anesthesia, whereas heart rate did not. Hemolymph pH and pO2 were not different among treatment groups or time points. Baseline pCO2 was higher than pCO2 at 30 min for both groups but significantly elevated only in the MS-222 group. This is attributed to increased activity during the handling of awake animals. Invasive blood pressure obtained via cardiac catheterization in two animals was markedly decreased during surgical anesthesia. In conclusion, 2-PE and MS-222 provided effective anesthesia with clinically useful induction and recovery times. 2-PE provided a subjectively more reliable and smoother anesthesia compared to MS-222.

INHALANT ANESTHETIC RECOVERY FOLLOWING INTRAMUSCULAR EPINEPHRINE IN THE LOGGERHEAD SEA TURTLE ( CARETTA CARETTA).

Prolonged anesthetic recovery time is a common complication of chelonian inhalant anesthesia and may be exacerbated by right-to-left intracardiac shunting of blood. Epinephrine may decrease intracardiac shunting, which may shorten anesthetic recovery time. The study objective was to assess inhalant anesthetic recovery time following intramuscular epinephrine compared with saline in the loggerhead sea turtle ( Caretta caretta). With the use of a prospective, randomized, blinded, crossover design with a 1-wk washout period, six turtles were anesthetized with intravenous (IV) alfaxalone 3 mg/kg, orotracheally intubated, manually ventilated with 3.5% isoflurane inhalant in 100% oxygen for 90 min, and administered either intramuscular (IM) epinephrine 0.1 mg/kg or IM saline 0.1 ml/kg. Isoflurane administration was immediately discontinued and turtles were manually ventilated with room air until extubation. Physiologic variables, sedation scores, end-tidal carbon dioxide (ETCO2) and isoflurane (ETISO) concentrations, time to first movement, and time to extubation were recorded and two-time-point venous blood gas analyses performed. Data were compared with the use of paired t-tests and repeated-measures analyses of variance (ANOVA) ( P < 0.05). No morbidity, mortality, or adverse events occurred. ETCO2 and ETISO did not significantly change over time during the isoflurane delivery period ( P = 0.990). Mean time to first movement was significantly faster following epinephrine (69.24 ± 12.28 min) compared with saline (87.71 ± 27.05 min, P = 0.047). Although differences were not statistically significant ( P = 0.133), time to extubation was at least 30 min faster (31-123 min) in 4/6 turtles following epinephrine compared with saline. Intramuscular epinephrine significantly reduces time to first movement during isoflurane anesthetic recovery in loggerhead sea turtles.

Veterinary Medical Students' Motivations for Exercise.

The Centers for Disease Control (CDC) declares exercise to be one of the most important activities one can do to improve health. The benefits of exercise are well documented and include both physiologic and psychological health. Given the current landscape of wellness issues in veterinary medical education, it is necessary that students engage in exercise activities to manage stress and increase overall health. Therefore, to develop targeted interventions with the greatest likelihood for success, it is first necessary to understand what motivates veterinary medical students to exercise given their unique situational and environmental factors. This study is the first to explore this issue systematically in veterinary medical education, thus it is the authors' hope that the findings from this research will help identify exercise-related wellness interventions that could be implemented in veterinary medical schools.

Recovery of horses from general anesthesia after induction with propofol and ketamine versus midazolam and ketamine.

OBJECTIVE To evaluate quality of recovery from general anesthesia in horses after induction with propofol and ketamine versus midazolam and ketamine. DESIGN Prospective randomized crossover study. ANIMALS 6 healthy adult horses. PROCEDURES Horses were premedicated with xylazine (1.0 mg/kg [0.45 mg/lb], IV), and general anesthesia was induced with midazolam (0.1 mg/kg [0.045 mg/lb], IV) or propofol (0.5 mg/kg [0.23 mg/lb], IV), followed by ketamine (3.0 mg/kg [1.36 mg/lb], IV). Horses were endotracheally intubated, and anesthesia was maintained with isoflurane. After 60 minutes, horses were given romifidine (0.02 mg/kg [0.009 mg/lb], IV) and allowed to recover unassisted. Times to first movement, sternal recumbency, and standing and the number of attempts to stand were recorded. Plasma concentrations of propofol or midazolam were measured following induction and immediately before recovery. Recovery quality was scored by 3 graders with a recovery rubric and a visual analog scale. RESULTS Number of attempts to stand was significantly lower when horses received propofol (median, 2; range, 1 to 3) than when they received midazolam (median, 7.5; range, 3 to 16). For both the recovery rubric and visual analog scale, recovery quality was significantly better when horses received propofol than when they received midazolam. Plasma drug concentration at recovery, as a percentage of the concentration at induction, was significantly lower when horses received propofol than when they received midazolam. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that for horses undergoing short (ie, 60 minutes) periods of general anesthesia, recovery quality may be better following induction with propofol and ketamine, compared with midazolam and ketamine.

Pharmacokinetics and pharmacodynamic effects in koi carp (Cyprinus carpio) following immersion in propofol.

OBJECTIVE: To test the hypothesis that plasma propofol concentration (PPC) is associated with anesthetic effect in koi carp administered propofol by immersion. STUDY DESIGN: Prospective study. ANIMALS: Twenty mature koi carp (mean ± standard deviation, 409.4 ± 83.7 g). METHODS: Fish were immersed in propofol (5 mg L-1). Physiological variables and induction and recovery times were recorded. In phase I, blood was sampled for PPC immediately following induction and at recovery. In phase II, following induction, fish were maintained with propofol (4 mg L-1) via a recirculating system for 20 minutes. Following established induction, blood was sampled at 1, 10 and 20 minutes. In phase III (n = 19), fish were anesthetized as in phase II with blood sampled nine times in a sparse sampling strategy. Simultaneously, a pharmacodynamics rubric was used to evaluate anesthetic depth. PPC was determined using high performance liquid chromatography with fluorescence detection. Following evaluation of normality, data were analyzed using paired t test or Spearman correlation test (significance was set at p < 0.05). RESULTS: In phase I, mean PPCs at induction (20.12 µg mL-1) and recovery (11.62 µg mL-1) were different (p < 0.001). In phase II, only mean PPCs at induction (17.92 µg mL-1) and 10 minutes (21.50 µg mL-1) were different (p = 0.013). In phase III, a correlation between PPCs and the pharmacodynamic rubric scores was found (p < 0.001, r = -0.93). There was no correlation between PPCs and recovery time (p = 0.057, r = 0.433). A two-compartment open model was chosen for the pharmacokinetic model. Absorption rate constant, elimination rate constant and intercompartmental rate constant were 0.48, 0.006 and 0.02 minute-1, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Measurable PPCs were achieved in koi carp anesthetized with propofol by immersion. Anesthetic depth of fish was negatively correlated with PPCs, but recovery time was not.

Veterinary Medical Students' Motivations for Exercise.

The Centers for Disease Control (CDC) declares exercise to be one of the most important activities one can do to improve health. The benefits of exercise are well documented and include both physiologic and psychological health. Given the current landscape of wellness issues in veterinary medical education, it is necessary that students engage in exercise activities to manage stress and increase overall health. Therefore, to develop targeted interventions with the greatest likelihood for success, it is first necessary to understand what motivates veterinary medical students to exercise given their unique situational and environmental factors. This study is the first to explore this issue systematically in veterinary medical education, thus it is the authors' hope that the findings from this research will help identify exercise-related wellness interventions that could be implemented in veterinary medical schools.

Sulfatide Preserves Insulin Crystals Not by Being Integrated in the Lattice but by Stabilizing Their Surface.

BACKGROUND: Sulfatide is known to chaperone insulin crystallization within the pancreatic beta cell, but it is not known if this results from sulfatide being integrated inside the crystal structure or by binding the surface of the crystal. With this study, we aimed to characterize the molecular mechanisms underlying the integral role for sulfatide in stabilizing insulin crystals prior to exocytosis. METHODS: We cocrystallized human insulin in the presence of sulfatide and solved the structure by molecular replacement. RESULTS: The crystal structure of insulin crystallized in the presence of sulfatide does not reveal ordered occupancy representing sulfatide in the crystal lattice, suggesting that sulfatide does not permeate the crystal lattice but exerts its stabilizing effect by alternative interactions such as on the external surface of insulin crystals. CONCLUSIONS: Sulfatide is known to stabilize insulin crystals, and we demonstrate here that in beta cells sulfatide is likely coating insulin crystals. However, there is no evidence for sulfatide to be built into the crystal lattice.

Pyruvate sensitizes pancreatic tumors to hypoxia-activated prodrug TH-302.

BACKGROUND: Hypoxic niches in solid tumors harbor therapy-resistant cells. Hypoxia-activated prodrugs (HAPs) have been designed to overcome this resistance and, to date, have begun to show clinical efficacy. However, clinical HAPs activity could be improved. In this study, we sought to identify non-pharmacological methods to acutely exacerbate tumor hypoxia to increase TH-302 activity in pancreatic ductal adenocarcinoma (PDAC) tumor models. RESULTS: Three human PDAC cell lines with varying sensitivity to TH-302 (Hs766t > MiaPaCa-2 > SU.86.86) were used to establish PDAC xenograft models. PDAC cells were metabolically profiled in vitro and in vivo using the Seahorse XF system and hyperpolarized (13)C pyruvate MRI, respectively, in addition to quantitative immunohistochemistry. The effect of exogenous pyruvate on tumor oxygenation was determined using electroparamagnetic resonance (EPR) oxygen imaging. Hs766t and MiaPaCa-2 cells exhibited a glycolytic phenotype in comparison to TH-302 resistant line SU.86.86. Supporting this observation is a higher lactate/pyruvate ratio in Hs766t and MiaPaCa xenografts as observed during hyperpolarized pyruvate MRI studies in vivo. Coincidentally, response to exogenous pyruvate both in vitro (Seahorse oxygen consumption) and in vivo (EPR oxygen imaging) was greatest in Hs766t and MiaPaCa models, possibly due to a higher mitochondrial reserve capacity. Changes in oxygen consumption and in vivo hypoxic status to pyruvate were limited in the SU.86.86 model. Combination therapy of pyruvate plus TH-302 in vivo significantly decreased tumor growth and increased survival in the MiaPaCa model and improved survival in Hs766t tumors. CONCLUSIONS: Using metabolic profiling, functional imaging, and computational modeling, we show improved TH-302 activity by transiently increasing tumor hypoxia metabolically with exogenous pyruvate. Additionally, this work identified a set of biomarkers that may be used clinically to predict which tumors will be most responsive to pyruvate + TH-302 combination therapy. The results of this study support the concept that acute increases in tumor hypoxia can be beneficial for improving the clinical efficacy of HAPs and can positively impact the future treatment of PDAC and other cancers.

Evaluation of the "steal" phenomenon on the efficacy of hypoxia activated prodrug TH-302 in pancreatic cancer.

Pancreatic ductal adenocarcinomas are desmoplastic and hypoxic, both of which are associated with poor prognosis. Hypoxia-activated prodrugs (HAPs) are specifically activated in hypoxic environments to release cytotoxic or cytostatic effectors. TH-302 is a HAP that is currently being evaluated in a Phase III clinical trial in pancreatic cancer. Using animal models, we show that tumor hypoxia can be exacerbated using a vasodilator, hydralazine, improving TH-302 efficacy. Hydralazine reduces tumor blood flow through the "steal" phenomenon, in which atonal immature tumor vasculature fails to dilate in coordination with normal vasculature. We show that MIA PaCa-2 tumors exhibit a "steal" effect in response to hydralazine, resulting in decreased tumor blood flow and subsequent tumor pH reduction. The effect is not observed in SU.86.86 tumors with mature tumor vasculature, as measured by CD31 and smooth muscle actin (SMA) immunohistochemistry staining. Combination therapy of hydralazine and TH-302 resulted in a reduction in MIA PaCa-2 tumor volume growth after 18 days of treatment. These studies support a combination mechanism of action for TH-302 with a vasodilator that transiently increases tumor hypoxia.

Physiologic and biochemical assessments of koi (Cyprinus carpio) following immersion in propofol.

OBJECTIVE: To determine efficacy of propofol as an immersion agent to induce general anesthesia in koi (Cyprinus carpio). DESIGN: Prospective, crossover study. ANIMALS: 10 adult koi (mean ± SD weight, 325 ± 81 g). PROCEDURES: Koi were exposed to each of 4 concentrations of propofol (1, 2.5, 5, and 10 mg/L) with a 1-week washout period between trials. In a subsequent trial, koi were anesthetized with propofol (5 mg/L) and anesthesia was maintained with propofol (3 mg/L) for 20 minutes. Response to a noxious stimulus was assessed by means of needle insertion into an epaxial muscle. RESULTS: At a propofol concentration of 1 mg/L, koi were sedated but never anesthetized. At propofol concentrations of 2.5, 5, and 10 mg/L, mean ± SD anesthetic induction times were 13.4 ± 3.3, 3.8 ± 1.1, and 2.3 ± 0.9 minutes, respectively; mean recovery times were 12.9 ± 8.3, 11.0 ± 6.3, and 18.1 ± 13.0 minutes; mean heart rates were 57 ± 25, 30 ± 14, and 22 ± 14 beats/min; mean opercular rates were 58 ± 18, 68 ± 15, and 48 ± 22 beats/min; and 1 of 10, 2 of 10, and 0 of 10 fish responded to needle insertion. All fish recovered satisfactorily. Following 20 minutes of anesthesia, 2 fish had recovery times > 4 hours and 1 fish died. CONCLUSIONS AND CLINICAL RELEVANCE: Immersion in propofol at concentrations ≥ 2.5 mg/L induced general anesthesia in koi. Maintenance of anesthesia with propofol for 20 minutes was associated with prolonged recovery times in 2 of 9 and death in 1 of 9 koi.

Mechanisms of buffer therapy resistance.

Many studies have shown that the acidity of solid tumors contributes to local invasion and metastasis. Oral pH buffers can specifically neutralize the acidic pH of tumors and reduce the incidence of local invasion and metastatic formation in multiple murine models. However, this effect is not universal as we have previously observed that metastasis is not inhibited by buffers in some tumor models, regardless of buffer used. B16-F10 (murine melanoma), LL/2 (murine lung) and HCT116 (human colon) tumors are resistant to treatment with lysine buffer therapy, whereas metastasis is potently inhibited by lysine buffers in MDA-MB-231 (human breast) and PC3M (human prostate) tumors. In the current work, we confirmed that sensitive cells utilized a pH-dependent mechanism for successful metastasis supported by a highly glycolytic phenotype that acidifies the local tumor microenvironment resulting in morphological changes. In contrast, buffer-resistant cell lines exhibited a pH-independent metastatic mechanism involving constitutive secretion of matrix degrading proteases without elevated glycolysis. These results have identified two distinct mechanisms of experimental metastasis, one of which is pH-dependent (buffer therapy sensitive cells) and one which is pH-independent (buffer therapy resistant cells). Further characterization of these models has potential for therapeutic benefit.

The efficacy of alfaxalone for immersion anesthesia in koi carp (Cyprinus carpio).

OBJECTIVE: To characterize the physiologic and behavioral effects of a single induction dose and two maintenance doses of alfaxalone delivered by water immersion in the anesthesia of koi (Cyprinus carpio). STUDY DESIGN: Prospective, within-subject complete crossover design. ANIMALS: Six adult koi (Cyprinus carpio) with a median body weight of 344.5 g (range 292.0-405.0 g). METHODS: Koi were immersed in water containing 10 mg L(-1) alfaxalone until immobile and then maintained with alfaxalone at either 1 or 2.5 mg L(-1) via a recirculating water system. Times for anesthetic induction and recovery periods were recorded. Physiologic and blood gas parameters were evaluated before, during and after the anesthetic trial. Response to noxious stimuli was also assessed. RESULTS: Median anesthesia induction time for all fish was 5.4 minutes. Median recovery time was 11.8 and 26.4 minutes in the 1.0 and 2.5 mg L(-1) doses, respectively, which were significantly different (p = 0.04). Cessation of opercular movement occurred in 0/6 and 4/6 fish exposed to 1.0 and 2.5 mg L(-1) dose respectively. No difference was observed in median heart rate over the duration of the anesthetic events. Response to noxious stimulation was 4/6 and 0/6 in the 1.0 and 2.5 mg L(-1) doses respectively. Oxygenation and ventilation did not change during the experiment, but there was a significant decrease in blood pH along with an increase in blood lactate concentration. CONCLUSION AND CLINICAL RELEVANCE: Administration of alfaxalone, via water immersion, as an induction and maintenance anesthesia agent provided rapid and reliable anesthesia of koi with no mortality. The maintenance dose of 2.5 mg L(-1) was sufficient to prevent response to noxious stimuli but was associated with a clinically relevant depression in opercular rate.

Alfaxalone as an intramuscular injectable anesthetic in koi carp (Cyprinus carpio).

Fish are commonly anesthetized with MS-222 (tricaine methanesulfonate), a sodium-channel-blocker used as an immersion anesthetic, but its mechanism of action as a general anesthetic is uncertain. Alfaxalone is a neurosteroid that acts at the GABA(A) receptors. Alfaxalone has been evaluated and was deemed successful as an immersion agent in koi carp. Alfaxalone is an effective intramuscular anesthetic in multiple species. A reliable intramuscular anesthetic in fish would be useful in multiple settings. The purpose of this study was to investigate alfaxalone as an intramuscular injectable anesthetic agent in koi carp (Cyprinus carpio). Eight koi carp were utilized in a crossover design. In each trial, six fish received 1 mg/kg, 5 mg/kg, or 10mg/kg of alfaxalone intramuscularly. They were assessed every 15 min for opercular rate and sedation score. The sedation score was based on a visual scale from 0 to 5, 0 indicating no response and 5 indicating absent righting reflex and anesthesia. Anesthetized koi were placed on a fish anesthesia delivery system (FADS). Time to anesthesia/recovery was recorded and heart rate was recorded every 15 min. Anesthesia was achieved in 0/6, 1/6, and 5/6 fish at 1, 5, and 10 mg/kg, respectively. Duration of anesthesia for one fish at 5 mg/kg was 2 hr. At 10 mg/kg, median anesthesia duration was 6.5 (3-10) hr. At 10 mg/kg, prolonged apnea (2-3 hr) was observed in 3/6 fish, 2/3 died under anesthesia, and 1/3 recovered 10 hr post-injection. Median peak sedation scores were 1.5, 2.5, and 5, at 1, 5, and 10 mg/kg, respectively. A dosage of 10 mg/kg alfaxalone resulted in 33% mortality. The duration of anesthesia and opercular rate were unpredictable. Due to variation in response despite consistent conditions, as well as risk of mortality, intramuscular alfaxalone cannot be recommended for anesthesia in koi carp.

Acid-mediated tumor proteolysis: contribution of cysteine cathepsins.

One of the noncellular microenvironmental factors that contribute to malignancy of solid tumors is acidic peritumoral pH. We have previously demonstrated that extracellular acidosis leads to localization of the cysteine pro-tease cathepsin B on the tumor cell membrane and its secretion. The objective of the present study was to determine if an acidic extracellular pH such as that observed in vivo (i.e., pHe 6.8) affects the activity of proteases, e.g., cathepsin B, that contribute to degradation of collagen IV by tumor cells when grown in biologically relevant three-dimensional (3D) cultures. For these studies, we used 1) 3D reconstituted basement membrane overlay cultures of human carcinomas, 2) live cell imaging assays to assess proteolysis, and 3) in vivo imaging of active tumor proteases. At pHe 6.8, there were increases in pericellular active cysteine cathepsins and in degradation of dye-quenched collagen IV, which was partially blocked by a cathepsin B inhibitor. Imaging probes for active cysteine cathepsins localized to tumors in vivo. The amount of bound probe decreased in tumors in bicarbonate-treated mice, a treatment previously shown to increase peritumoral pHe and reduce local invasion of the tumors. Our results are consistent with the acid-mediated invasion hypothesis and with a role for cathepsin B in promoting degradation of a basement membrane protein substrate, i.e., type IV collagen, in an acidic peritumoral environment.

Efficacy of alfaxalone for intravascular anesthesia and euthanasia in blue crabs (Callinectes sapidus).

The objective of this study was to characterize the behavioral effects and changes in heart rate of four doses of alfaxalone delivered by intravascular injection to blue crabs (Callinectes sapidus). Thirty (male, n = 27; female, n = 3) blue crabs were randomly assigned to one of four treatment groups of alfaxalone: eight animals were assigned to each of the 5-, 10-, and 15-mg/kg treatment groups, and the remaining six animals were assigned to the 100-mg/kg group. Times for anesthetic induction and recovery periods were recorded. Righting reflex, defensive posturing, and heart rate were evaluated before, during, and after the anesthetic trial. Anesthesia was induced in all 14 animals consolidated into the high-dosage group (15 mg/kg [n = 8] and 100 mg/kg [n = 6]), which was significantly greater than 8 of 16 animals in the low-dosage group (5 mg/kg [n = 2] and 10 mg/kg [n = 6]). Median anesthesia induction time for all crabs was 0.4 min, with no significant difference in induction time between groups observed. Median recovery time was 9.4 min (n = 2), 6.1 min (n = 5), 11.3 min (n = 8), and 66.1 min (n = 5) for the 5-, 10-, 15-, and 100-mg/kg groups, respectively. Recovery times were significantly longer for crabs exposed to an induction dose of 100 mg/kg compared with the 10- and 15-mg/kg induction doses. A significant decrease in the median heart rate was observed between the baseline value and that observed at both induction and 5 min postinjection in the 100-mg/kg dose trial. Two mortalities were observed during the anesthesia trials (n = 1, 10 mg/kg; n = 1, 100 mg/kg), both associated with the autotomization of limbs. In summary, the intravascular administration of alfaxalone at 15 mg/kg provided rapid and reliable sedation, whereas alfaxalone administered at 100 mg/kg produced rapid and long lasting anesthesia.

Evaluation of the effects of tricaine methanesulfonate on retinal structure and function in koi carp (Cyprinus carpio).

OBJECTIVE: To determine whether repeated exposure to clinically relevant concentrations of tricaine methanesulfonate (MS-222) would alter retinal function or induce histologically detectable retinal lesions in koi carp (Cyprinus carpio). DESIGN: Prospective, controlled, experimental study. ANIMALS: 18 healthy koi carp. PROCEDURES: 2 fish were euthanized at the start of the study, and eyes were submitted for histologic evaluation as untreated controls. Anesthesia was induced in the remaining fish with 200 mg of MS-222/L and maintained with concentrations of 125 to 150 mg/L for a total exposure time of 20 minutes daily on 1 to 13 consecutive days. On days 1, 7, and 13, electroretinography of both eyes was performed in all fish remaining in the study, and 2 fish were euthanized immediately after each procedure for histologic evaluation of the eyes. Median b-wave amplitudes were compared among study days for right eyes and for left eyes via 1-way repeated-measures ANOVA with a Bonferroni correction for multiple comparisons. RESULTS: Median b-wave amplitudes on days 1, 7, and 13 were 17.7, 20.9, and 17.6 µV, respectively, for right eyes and 15.1, 16.9, and 14.3 µV, respectively, for left eyes. No significant differences in b-wave amplitudes were detected among study days. No histopathologic abnormalities were identified in the retinas of any fish treated with MS-222 or in control fish. CONCLUSIONS AND CLINICAL RELEVANCE: Short-term exposure of koi carp to clinically relevant concentrations of MS-222 daily for up to 13 days was not associated with changes in retinal structure or function as measured in this study.

Alfaxalone anesthesia in bullfrogs (Lithobates catesbeiana) by injection or immersion.

This project evaluated alfaxalone, a neurosteroid, as an anesthetic in bullfrogs. Eight adult bullfrogs (Lithobates catesbeiana), averaging 593 g (411-780 g) each, were used in a crossover design. Frogs were administered alfaxalone i.m. at 10, 12, 15, or 17.5 mg/kg with a 1-wk washout. Following injection, time to recumbency, first limb movement following induction, and recovery were recorded. Respiratory rate was recorded following injection and then every 15 min following induction. Heart rate was assessed via Doppler every 15 min following induction. At 20 and 40 min, a 25-ga needle was inserted in a thigh muscle to assess response to noxious stimuli. Frogs were also immersed in 2 g/L of alfaxalone for up to 30 min and similarly assessed. At dosages of 10, 12, 15, and 17.5 mg/kg, the median time to recumbency was 15.4, 12.6, 12.3, and 6.6 min, respectively. At dosages of 10, 12, 15, and 17.5 mg/kg, median time to first limb movement was 68.5, 77.5, 89.0, and 115 min, respectively. At dosages of 10, 12, 15, and 17.5 mg/kg, median time to recovery was 90, 68.5, 124.5, 115 min, respectively. Following induction, at 10, 12, 15, and 17.5 mg/kg, median heart rate was 42, 40, 40, and 42, respectively; and median respiratory rate was 44, 36, 29, and 35, respectively. Following administration of 10, 12, 15, and 17.5 mg/ kg, 8/8, 6/8, 7/8, and 8/8 frogs, respectively, responded to needle insertion. None of the frogs dosed by immersion became anesthetized. Intramuscular alfaxalone produced immobilization in frogs but did not provide sufficient anesthesia to prevent response to noxious stimuli. Alfaxalone immersion at 2 g/L for 30 min did not produce immobilization or anesthesia.