Analysis of Short-Term Cortisol Stress Response in Channel Catfish by Anesthetization with Metomidate Hydrochloride and Tricaine Methanesulfonate

The ability of the anesthetics metomidate hydrochloride and tricaine methanesulfonate (MS-222) to mitigate the cortisol stress response of Channel Catfish Ictalurus punctatus was evaluated during a 10-min confinement stress. The cortisol concentrations of Channel Catfish anesthetized in metomidate hydrochloride remained consistent throughout the 10-min exposure; however, for fish anesthetized with MS-222 and nonanesthetized fish, cortisol concentrations were approximately 7- and 22-fold higher, respectively, than the baseline concentrations. While both anesthetics reduced cortisol concentrations relative to those of nonanesthetized fish, these results suggest that MS-222 is an appropriate anesthetic to use during the initial 5 min of sedation and that metomidate hydrochloride is appropriate for longer periods of sedation.

Received November 18, 2014; accepted April 9, 2015     

A COMPARISON OF ALFAXALONE AND TRICAINE METHANESULPHONATE (MS-222) IN TWO FISH SPECIES

The purpose of this study was to evaluate the effectiveness of the alfaxalone formulation Alfaxan? as an immersion anesthetic in tropical fish species compared to that of tricaine methanesulfonate (MS-222). 22 black spot barbs (Puntius filamentosis) measuring (mean±SD) 11.4 ±1.4 cm in body length and 22 peacock cichlids (Aulonocara spp.) (measuring 8.4 ± 1.6cm were anesthetized in water baths containing 100 mg/L of MS-222 buffered with 200 mg/L of bicarbonate or 5 mg/L of alfaxalone following a 2-week washout period. Time to maximum effect, recovery periods, self-righting, spontaneous swimming movements, opercular movements, and response to noxious stimuli were recorded. The following results are for the black spot barbs following MS-222 and alfaxalone anesthesia, respectively: mean times (±SD) to surgical anesthesia were 5.5 ± 2.11 and 3.27 ± 1.72 minutes and mean recovery times were 2.95 ± 0.9 and 9.14 ± 3.15 minutes. The peacock cichlid anesthetic protocols for MS-222 (20 of 22 cichlids) and alfaxalone (20 of 21 cichlids) produced the following results, respectively: mean times (±SD) to surgical anesthesia were 14.75 ±5.43 and 11.1 ± 9.84 minutes and mean recovery times were 3.6 ±0.82 and 22.4 ±11.3 minutes. Median recovery time from 5 mg/L alfaxalone was significantly longer (P < 0.001) in both species, by 5 minutes for black spot barbs and by 17 minutes for peacock cichlids. Variation in induction and recovery times between species was observed, with black spot barbs having significantly (P < 0.0001) faster induction times when treated with both drugs, and a faster recovery time from 5 mg/L alfaxalone.     

Cardiopulmonary effects and induction and recovery characteristics of isoflurane and sevoflurane in foals

OBJECTIVE: To compare induction and recovery characteristics and cardiopulmonary effects of isoflurane and sevoflurane in foals. DESIGN: Prospective crossover study. ANIMALS: 6 healthy foals. PROCEDURE: Foals were anesthetized twice (once at 1 month of age and again at 3 months of age). Anesthesia was induced by administration of the agent in oxygen through a nasotracheal tube. During maintenance of anesthesia, foals were positioned in dorsal recumbency; intermittent positive-pressure ventilation was performed. Characteristics of induction and recovery were recorded. Cardiopulmonary variables were recorded 10 minutes after anesthetic induction and 15, 30, 45, and 60 minutes later. RESULTS: All 6 foals were successfully anesthetized with isoflurane and sevoflurane. There were no significant differences between the 2 drugs in regard to characteristics of induction or recovery, and induction and recovery were generally smooth and unremarkable. There were no significant differences between drugs in regard to measured cardiopulmonary variables; however, both drugs caused initial hypotension that resolved over time. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that isoflurane and sevoflurane can both be used for general anesthesia of 1- to 3-month-old foals. Significant differences between the 2 agents were not detected for any of the variables measured, suggesting that quality of anesthesia with these 2 agents was comparable.     

Atrial Fibrillation Associated with Anesthesia in a Standardbred Gelding

A Standardbred gelding was anesthetized on three occasions over a 3 year period. Anesthesia was induced with xylazine and thiamylal on the first occasion, with xylazine, guaifenesin, and thiamylal on the second, and with acepromazine, guaifenesin, and ketamine on the third. Anesthesia was maintained with halothane during each episode. The horse had atrial fibrillation (AF) after induction of anesthesia on the first two occasions. Because arterial blood pressure remained within normal limits during AF and anesthesia, conversion to normal sinus rhythm with quinidine was not attempted. Reversion to normal sinus rhythm occurred within 12 hours of recovery after each of the first two anesthetic episodes. The gelding remained in normal sinus rhythm throughout the third anesthetic period and recovered uneventfully. Potential causes for AF in anesthetized horses are discussed.     

Comparison of four drug combinations for total intravenous anesthesia of horses undergoing surgical removal of an abdominal testis

OBJECTIVE: To evaluate anesthetic effects of 4 drug combinations used for total intravenous anesthesia of horses undergoing surgical removal of an abdominal testis. DESIGN: Clinical trial. ANIMALS: 32 healthy cryptorchid horses. PROCEDURE: Horses were sedated with xylazine and butorphanol and were randomly assigned to 1 of 4 groups: induction of anesthesia with ketamine and diazepam and maintenance with bolus administration of ketamine and xylazine (KD/KX); induction and maintenance of anesthesia with bolus administration of tiletamine-zolazepam, ketamine, and detomidine (TKD); induction and maintenance of anesthesia with continuous infusion of xylazine, guaifenesin, and ketamine; and induction and maintenance of anesthesia with continuous infusion of guaifenesin and thiopental. Horses that moved 3 consecutive times in response to surgical stimulation or for which surgery time was > 60 minutes were administered an inhalant anesthetic, and data from these horses were excluded from analysis. RESULTS: Quality of induction was not significantly different among groups. Muscle relaxation and analgesia scores were lowest for horses given KD/KX, but significant differences among groups were not detected. Horses anesthetized with TKD had a significantly greater number of attempts to stand, compared with the other groups, and mean quality of recovery from anesthesia for horses in the TKD group was significantly worse than for the other groups. Anesthesia, surgery, and recovery times were not significantly different among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that all 4 drug combinations can be used to induce short-term anesthesia for abdominal cryptorchidectomy in horses. However, horses receiving TKD had a poorer recovery from anesthesia, often requiring assistance to stand.     

Clinical examination of fish in private collections.

The rapid advancement of fish medicine over the past 10 years has led to a drastically improved ability to manage the individual pet fish successfully. Principle physiologic differences between fish and higher vertebrates include the lack of ability to regulate body temperature (this has a profound effect on the immune system), the use of gills for respiration, and the importance of osmoregulation in the aquatic environment. Components of the clinical history for a fish patient should include information on the environment, tank mates, recent medical history, and specific information on the affected individual. Fish can be manually restrained or safely anesthetized with methane tricaine sulfonate, depending on their size, condition, and circumstances. Diagnostic techniques useful for fish patients include gill, skin, and fin biopsy; hematology; cytology; radiology; and ultrasound. Preventive medicine programs should include water quality, nutritional management, sanitation, and quarantine.     

Evaluation of a combination of xylazine, ketamine, and halothane for anesthesia in llamas

Anesthesia induced by use of a combination of xylazine, ketamine, and halothane, under conditions of spontaneous and mechanically controlled ventilation, was evaluated in 5 llamas positioned in dorsal recumbency. Using chronically implanted catheters, systemic arterial blood pressure, pulmonary arterial pressure, right atrial pressure, heart rate and rhythm, cardiac output, blood pH and gas tensions, body temperature, and respiratory rate were measured before anesthesia induction (baseline), throughout the anesthetic period, and for 1 hour into the recovery period. During anesthesia, llamas undergoing spontaneous ventilation developed hypercapnia and respiratory acidosis. Cardiovascular function was decreased during both types of ventilation. The combination of xylazine, ketamine, and halothane in various doses and 2 ventilation procedures (spontaneous and controlled) provided a reliable method for general anesthesia in llamas, but marked cardiovascular depression developed during anesthesia maintenance with halothane. Spontaneous ventilation resulted in potentially clinically important respiratory acidosis.     

氨氟醚吸入麻醉妊娠犬及其胎儿动脉血药浓度和血气分析

选用 10只妊娠犬 ,实施母体及胎儿股动脉血管插管后 ,测定了氨氟醚麻醉期间母犬及胎儿的动脉血药浓度和血液 p H、PO2 (动脉氧分压 )、PCO2 (动脉 CO2 分压 )、T- CO2 (血浆 CO2 总量 )、HCO- 3 (实际碳酸氢盐 )、SB(标准碳酸氢盐 )、BEb(全血碱超 )、Sat.O2 (血氧饱和度 )。结果 :氨氟醚可透过胎盘进入胎儿血液 ,胎儿血药浓度低于母犬 ,但两者上升和消除变化趋势接近 ;麻醉期间 ,母犬及胎儿血液 p H、BEb下降 (P<0 .0 1或 P<0 .0 5 ) ,PO2 、PCO2 、Sat.O2 升高(P<0 .0 1或 P<0 .0 5 ) ,HCO- 3 、T- CO2 表现升高趋势 (P>0 .0 5 ) ,SB表现下降趋势 (P>0 .0 5 )。结果表明 ,氨氟醚吸入麻醉期间 ,母犬及其胎儿呈现轻度呼吸性酸中毒和代谢性酸中毒并存 ,并随氨氟醚血药浓度的降低而逐渐恢复     

Evaluation of a point-of-care blood analyzer and determination of reference ranges for blood parameters in rockfish

OBJECTIVE: To compare values of blood parameters in rockfish obtained by use of a point-of-care portable blood analyzer with values determined by a veterinary diagnostic laboratory, calculate reference ranges for various blood parameters in black rockfish, and compare values of blood parameters in clinically normal fish with those of fish with clinical abnormalities. DESIGN: Prospective study. ANIMALS: 41 captive adult black rockfish (Sebastes melanops) and 4 captive adult blue rockfish (Sebastes mystinus). PROCEDURE: Rockfish were anesthetized with tricaine methanesulfonate for collection of blood samples. Heparinized blood samples were immediately analyzed with a point-of-care analyzer. Blood sodium, potassium, chloride, urea nitrogen, and glucose concentrations; Hct; pH; partial pressure of carbon dioxide; total carbon dioxide concentration; bicarbonate concentration; base excess; and hemoglobin concentration were determined. A microhematocrit technique was used to determine PCV, and a refractometer was used to estimate total plasma protein concentration. Paired heparinized blood samples were transported to a veterinary diagnostic laboratory for analyses. RESULTS: Data obtained with the point-of-care analyzer were reproducible; however, values for most blood parameters were significantly different from those obtained by the veterinary diagnostic laboratory. Fish with poor body condition had several blood parameter values that were lower than corresponding values in clinically normal fish. CONCLUSIONS AND CLINICAL RELEVANCE: Point-of-care blood analyses may prove useful in rockfish. Point-of-care data for a large number of clinically normal fish must be obtained for reference ranges to be calculated, and further assessments of clinically abnormal fish are necessary to determine the relevance of the data.     

速眠新和异氟烷对蟒蛇的全麻效果研究

本试验通过使用速眠新和异氟烷两种常用全身麻醉剂对缅甸蟒的麻醉效果进行了研究。对15条蟒蛇肌肉注射和腹腔注射(0.1、0.2、0.4 mL/kg)速眠新麻醉剂和对6条蟒蛇使用异氟烷吸入性麻醉后,进行麻醉效果的评估。试验结果表明,常规动物2~4倍的速眠新Ⅱ注射剂对蟒蛇的麻醉效果不明显;4%的异氟烷吸入性麻醉剂可用于蟒蛇的诱导麻醉,2.5%的异氟烷可用于蟒蛇的维持麻醉,其麻醉效果显著,具有诱导麻醉迅速、维持麻醉稳定、肌松作用好、安全性高、可控性强、苏醒快、副作用小等优点。结果显示,异氟烷吸入性麻醉剂可运用于蟒蛇的临床麻醉保定中。     

Endoscopic sex determination and gonadal manipulation in Gulf of Mexico sturgeon (Acipenser oxyrinchus desotoi).

Seventeen Gulf of Mexico sturgeons (Acipenser oxyrinchus desotoi) underwent endoscopic sex determination, gonadal biopsy, and various reproductive surgeries as part of a conservation development plan. The fish were anesthetized with tricaine methanesulfonate (MS-222) buffered with sodium bicarbonate and maintained on a recirculating water anesthesia circuit. A 6-mm Ternamian EndoTip Cannula, placed through the ventral midline, midway between pectoral and pelvic fins, permitted the introduction of a 5-mm telescope. Swim bladder aspiration and CO2 insufflation of the coelomic cavity provided excellent observation. Second and third cannulae were placed under direct visual control, lateral and cranial or caudal to the telescope cannula. Sex determination was successfully performed in all fish; however, five of 17 sturgeons (29%) required endoscopic gonadal biopsy to confirm sex. Bilateral ovariectomy or orchidectomy was successfully performed in three males and four females. Unilateral ovariectomy and bilateral ligation of the müllerian ducts using an extracorporeal suturing technique was accomplished in an additional three females. No apparent morbidity was associated with the anesthesia or endoscopic surgery in any fish. The ability to safely perform minimally invasive reproductive surgery in fish may have important management and conservation benefits.     

Cardiovascular effects of halothane anesthesia after diazepam and ketamine administration in beavers (Castor canadensis) during spontaneous or controlled ventilation

Fourteen adult beavers (Castor canadensis) weighing 16.5 +/- 4.14 kg (mean +/- SD) were anesthetized for surgical implantation of radio telemetry devices. Beavers were anesthetized with diazepam (0.1 mg/kg) and ketamine (25 mg/kg) administered IM, which provided smooth anesthetic induction and facilitated tracheal intubation. Anesthesia was maintained with halothane in oxygen via a semiclosed circle anesthetic circuit. Values for heart rate, respiratory rate, esophageal temperature, direct arterial blood pressure, end-tidal halothane concentration, and end-tidal CO2 tension were recorded every 15 minutes during the surgical procedure. Arterial blood samples were collected every 30 minutes to determine pH, PaO2, and PaCO2. Values for plasma bicarbonate, total CO2, and base excess were calculated. Ventilation was spontaneous in 7 beavers and controlled to maintain normocapnia (PaCO2 approx 40 mm of Hg) in 7 others. Vaporizer settings were adjusted to maintain a light surgical plane of anesthesia. Throughout the surgical procedure, all beavers had mean arterial pressure less than 60 mm of Hg and esophageal temperature less than 35 C. Mean values for arterial pH, end-tidal CO2, PaO2, and PaCO2 were significantly (P less than 0.05) different in spontaneously ventilating beavers, compared with those in which ventilation was controlled. Respiratory acidosis during halothane anesthesia was observed in spontaneously ventilating beavers, but not in beavers maintained with controlled ventilation. All beavers recovered unremarkably from anesthesia.     

Infusion of guaifenesin,ketamine, and medetomidine in combination with inhalation of sevoflurane versus inhalation of sevoflurane alone for anesthesia of horses

OBJECTIVE: To evaluate effects of infusion of guaifenesin, ketamine, and medetomidine in combination with inhalation of sevoflurane versus inhalation of sevoflurane alone for anesthesia of horses. DESIGN: Randomized clinical trial. ANIMALS: 40 horses. PROCEDURE: Horses were premedicated with xylazine and anesthetized with diazepam and ketamine. Anesthesia was maintained by infusion of guaifenesin, ketamine, and medetomidine and inhalation of sevoflurane (20 horses) or by inhalation of sevoflurane (20 horses). A surgical plane of anesthesia was maintained by controlling the inhaled concentration of sevoflurane. Sodium pentothal was administered as necessary to prevent movement in response to surgical stimulation. Hypotension was treated with dobutamine; hypoxemia and hypercarbia were treated with intermittent positive-pressure ventilation. The quality of anesthetic induction, maintenance, and recovery and the quality of the transition to inhalation anesthesia were scored. RESULTS: The delivered concentration of sevoflurane (ie, the vaporizer dial setting) was significantly lower and the quality of transition to inhalation anesthesia and of anesthetic maintenance were significantly better in horses that received the guaifenesin-ketamine-medetomidine infusion than in horses that did not. Five horses, all of which received sevoflurane alone, required administration of pentothal. Recovery time and quality of recovery were not significantly different between groups, but horses that received the guaifenesin-ketamine-medetomidine infusion required fewer attempts to stand. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that in horses, the combination of a guaifenesin-ketamine-medetomidine infusion and inhalation of sevoflurane resulted in better transition and maintenance phases while improving cardiovascular function and reducing the number of attempts needed to stand after the completion of anesthesia, compared with inhalation of sevoflurane.     

Evaluation of the induction and recovery characteristics of anesthesia with desflurane in cats

OBJECTIVE: To qualitatively and quantitatively evaluate the characteristics of desflurane with regard to the induction of and recovery from anesthesia in cats. ANIMALS: 6 cats. PROCEDURE: Anesthesia was induced and maintained with desflurane in oxygen. Individual minimum alveolar concentration (MAC) values were determined; anesthesia was maintained at 1.25 x MAC for a total anesthesia time (including MAC determination) of 5 hours. Cats were allowed to recover from anesthesia. Induction and recovery periods were video recorded and later scored by use of a grading scale from 0 to 100 (100 being the best outcome). Timing of events was recorded. RESULTS: The MAC of desflurane was 10.27 +/- 1.06%, and mean dose was 5.6 +/- 0.2 MAC-hours. Times to loss of coordination, recumbency, and endotracheal intubation were 1.3 +/- 0.4, 2.3 +/- 0.3, and 6.4 +/- 1.1 minutes, respectively. Median score for quality of anesthetic induction was 93 (range, 91 to 94). Times to first movement, extubation, standing, and ability to jump and land with coordination were 2.8 +/- 1.0, 3.8 +/- 0.5, 14.3 +/- 3.9, and 26.4 +/- 5.1 minutes, respectively. Alveolar washout of desflurane was rapid. Median score for quality of anesthetic recovery was 94 (range, 86 to 96). CONCLUSIONS AND CLINICAL RELEVANCE: Desflurane was associated with rapid induction of and recovery from anesthesia in cats; assessors rated the overall quality of induction and recovery as excellent. Results appear to support the use of desflurane for induction and maintenance of anesthesia in healthy cats.     

Pharmacokinetics and anesthetic activity of eugenol in male Sprague-Dawley rats

Eugenol, the principle chemical constituent of clove oil, has recently been evaluated for its anesthetic and analgesic properties in fish and amphibians. The objective of this study was to determine the pharmacokinetic (PK) and anesthetic activity of eugenol in rats. Male Sprague–Dawley rats received single i.v. doses of eugenol (0, 5, 10, 20, 40 and 60 mg/kg) and anesthetic level was evaluated with the withdrawal reflex. For the 20 mg/kg dose level, blood and urinary samples were collected over 1 h for the PK assessment. Plasma and blood concentrations of eugenol, as well as metabolite identification in urine, were determined using a novel dansyl chloride derivatization method with liquid chromatography mass spectrometry (LC/MS/MS). PK parameters were calculated using noncompartmental methods. Eugenol-induced loss of consciousness in a dose-dependent manner, with mean (±SEM) recovery in reflex time of 167 ± 42 sec observed at the highest dose level. Mean systemic clearance ( Cl ) in plasma and blood were 157 and 204 mL/min/kg, respectively. Glucuronide and sulfate conjugates were identified in urine. Overall, eugenol produced a reversible, dose-dependent anesthesia in male Sprague–Dawley rats.     

Surgical removal of a seminoma from a black sea bass

An adult black sea bass was examined because of abdominal distention and decreased appetite. A large abdominal swelling was evident and was firm on palpation. Differential diagnoses included neoplasia, abscess or granuloma, hematoma, or swim bladder abnormality. Diagnostic tests included survey radiography, positive-contrast radiography, and computed tomography. The sea bass was anesthetized with tricaine methanesulfonate. A ventral midline abdominal incision was made, and adhesions to the mass were gently dissected. The fish recovered without complications. Radiography was repeated 8 weeks after surgery, and there was no evidence of mass regrowth. To the authors' knowledge, this is the first report of a barium enema being performed in a fish. Although surgical procedures are performed more commonly on fish for research, a few reports of clinical surgical cases have been described. Our experience supports the conclusions of other reports that certain surgical procedures can be performed safely in fish.     

The influence of butorphanol dose on characteristics of xylazine-butorphanol-propofol anesthesia in horses at altitude

OBJECTIVE: To characterize behavioral and physiological responses to short-term, unsupplemented intravenous (IV) anesthesia in healthy horses at high altitude (2240 m), and to test the hypothesis that the dose of butorphanol modifies the response of the horse to propofol anesthesia following xylazine pre-medication. STUDY DESIGN: Randomized prospective butorphanol dose cross-over experimental design. Animals Eight healthy horses, 13 +/- 6 (mean +/- SD) years of age, and weighing 523 +/- 26 kg. METHODS: Each horse was anesthetized three times with at least 3 weeks between each anesthesia. After collecting pre-drug data, xylazine (0.5 mg kg(-1)) was given IV. Five minutes later butorphanol was given IV according to a randomized order of three doses: 0.025, 0.05 and 0.075 mg kg(-1). Five minutes later, anesthesia was induced with propofol, 2 mg kg(-1) IV. Data on heart rate (HR) and respiratory rate (f(r)), mean arterial blood pressure, P(a)O(2), P(a)CO(2) and pH(a) were collected before, during and for 60 minutes following anesthesia, and quality of induction and recovery was scored. RESULTS: The pre-drug values for the three butorphanol groups did not differ. The combined pre-drug values from the 24 studies were HR, 33 +/- 7 beats minute(-1); f(r), 11 +/- 3 breaths minute(-1); P(a)O(2), 67 +/- 7 mmHg; P(a)CO(2), 36 +/- 4 mmHg; and pH(a), 7.42 +/- 0.04. Five minutes after anesthetic induction P(a)O(2) decreased and P(a)CO(2) increased 14.5 +/- 7.7 and 5.1 +/- 4.9 mmHg, respectively, but returned to pre-drug levels within 15 minutes of anesthetic recovery. There were no significant butorphanol dose-related differences in physiological results, anesthetic induction and recovery quality scores or recovery time. CONCLUSIONS AND CLINICAL RELEVANCE: Dose of butorphanol did not markedly influence study results. Notably, low P(a)O(2) values related to geographic location of study and general anesthesia indicates a narrow margin of error for hypoxemia-related complications in anesthetized horses breathing unsupplemented air at high altitude.     

Anesthesia induced by administration of xylazine hydrochloride alone or in combination with ketamine hydrochloride and reversal by administration of yohimbine hydrochloride in captive Axis deer (Axis axis)

OBJECTIVE: To determine the anesthetic dose and cardiopulmonary effects of xylazine hydrochloride when used alone or in combination with ketamine hydrochloride and evaluate the efficacy of yohimbine hydrochloride to reverse anesthetic effects in captive Axis deer. ANIMALS: 35 adult (10 males and 25 females) Axis deer (Axis axis). PROCEDURES: All deer were anesthetized by IM administration of xylazine (3.5 mg/kg; experiment 1), a combination of ketamine and xylazine (1.25 and 1.5 mg/kg, respectively; experiment 2), or another combination of ketamine and xylazine (2.5 and 0.5 mg/kg, respectively; experiment 3). In addition, female deer were also anesthetized by IM administration of a third combination of ketamine and xylazine (1.5 and 1 mg/kg, respectively; experiment 4). Ten to 40 minutes after induction, anesthesia was reversed by IV administration of yohimbine (5, 8, or 10 mg). RESULTS: In male deer, experiment 3 yielded the most rapid induction of anesthesia. In females, experiment 4 yielded the best induction of anesthesia without adverse effects. All doses of yohimbine reversed anesthesia. Duration of anesthesia before administration of yohimbine had no effect on recovery time. CONCLUSIONS AND CLINICAL RELEVANCE: A combination of ketamine and xylazine can be used to induce anesthesia in Axis deer. Furthermore, anesthetic effects can be reversed by administration of yohimbine.     

S‐(+)‐Linalool from Lippia alba: sedative and anesthetic for silver catfish (Rhamdia quelen)

ObjectiveThe present study describes the isolation of linalool from the essential oil of Lippia alba (Mill.) N. E. Brown, and its anesthetic effect in silver catfish (Rhamdia quelen) in comparison with essential oil. The potentiation of depressant effects of linalool with a benzodiazepine (BDZ) and the involvement of GABAergic system in its antagonism by flumazenil were also evaluated.Study designProspective experimental study.AnimalsJuvenile silver catfish unknown sex weighing mean 9.24 ± 2.83 g (n = 6 for each experimental group per experiment).MethodsColumn chromatography was used for the isolation of S-(+)-linalool. Fish (n = 6 for each concentration) were transferred to aquaria with linalool (30, 60, and 180 μL L^?1) or EO of L. alba (50, 100, and 300 μL L^?1) to determine the induction time for anesthesia. After induction, the animals were transferred to anesthetic-free aquaria to assess their recovery time. To observe the potentiation, fish were exposed to linalool (30, 60, and 180 μL L^?1) in the presence or absence of BDZ (diazepam 150 μm). In another experiment, fish exposed to linalool (30 and 180 μL L^?1) or BDZ were transferred to an anesthetic-free aquaria containing flumazenil (5 μm) or water to assess recovery time.ResultsLinalool had a similar sedation profile to the essential oil at a proportional concentration in silver catfish. However, the anesthesia profile was different. Potentiation of linalool effect occurred only when tested at low concentration. Fish exposed to BDZ showed faster anesthesia recovery in water with flumazenil, but the same did not occur with linalool.Conclusions and clinical relevanceThe use of linalool as a sedative and anesthetic for silver catfish was effective at 30 and 180 μL L^?1, respectively. The mechanism of action seems not to involve the benzodiazepine site of the GABAergic system.     

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

ObjectiveTo 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 designProspective, within-subject complete crossover design.AnimalsSix adult koi (Cyprinus carpio) with a median body weight of 344.5 g (range 292.0–405.0 g).MethodsKoi 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.ResultsMedian 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 relevanceAdministration 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.