Anesthesia of horses with xylazine and ketamine. 1. Anesthesia of foals

The anaesthesia with Xylazine and Ketamine in 24 foals is described. Special qualities of this form of anaesthesia and dosages for foals of different age are discussed. The combination of Xylazine and Ketamine is well suited for the anaesthesia of foals of all age and risk-groups. The induction takes place quickly and calmly, without signs of cardiorespiratory depression. The maintenance of anaesthesia is possible, without any problem, by repeated injection with Xylazine and Ketamine, as well as by inhalation anaesthesia with volatile anaesthetics. The recovery is short; the animals rise swiftly and safely. For these reasons we prefer, in foals, the anaesthesia with Xylazine and Ketamine to the induction and maintenance of anaesthesia with thiobarbiturates.     

The treatment of insertion desmopathy in the metatarsus of horses

Metacarpal or metatarsal exostoses were diagnosed in 112 horses used for sport purposes between January 1976 to December 1987. Fourteen of these patients were treated surgically by subperiosteal removal of the exostosis. All animals which could be followed up had returned to their original use. The average time of use after discharge from the clinic was 38.4 months. Surgery was successful in completely removing the exostoses in 58.3% of these horses. The indications for anaesthesia and resection of the ulnar nerve are discussed.     

Cortisol and haematological response in sea bream and trout subjected to the anaesthetics clove oil and 2-phenoxyethanol

Clove oil has been tested for anaesthesia induction and recovery time as well as for haematology and stress indicators in the gilthead sea bream and rainbow trout. The former parameters were compared with those generated by 2‐phenoxyethanol. The results showed only slight differences between both anaesthetics in terms of anaesthetic efficiency and physiological effects. In addition, clove oil does not block the cortisol response to stress, as happens with other anaesthetics.     

Combination anesthesia in sheep with ketamine-(fentanyl)-guaifenesin (My 301)-laughing gas-halothane

The concept of combined anaesthesia, the centrally-acting muscle relaxant guaifenesin (My 301) in a 5% solution with ketamine (and/or fentanyl) in addition to the inhalation of nitrous oxide and halothane is based upon the principle of "balanced anaesthesia". Guaifenesin amplifies the effect of several anaesthetics, which complement one another, allowing the dosage to be decreased and thereby reducing the cardiovascular stress. To induce anaesthesia, the combination of a cataleptic anaesthetic (ketamine = Ketanest, Ketolar) and a centrally acting skeletal muscle relaxant (guaifenesin = Myolaxin, My 301) is used. Because of the risk of aspiration the animal should be intubated as soon as possible. Anaesthesia will be prolonged by the carrier gas nitrous oxide (65%, weakly analgesic)/oxygen (65%), low concentrations of halothane (1.0 to 0.6 to 0.4%, weakly hypnotic and analgesic) and by a continuous drip infusion of 5% guaifenesin (relaxing, mild analgesic and sedative). The effect of all the other anaesthetics is increased by guaifenesin. To increase the analgesia and to control the cardiovascular parameters the additional injection of ketamine or fentanyl is recommended. The recovery period is short and the general condition is good both after a lengthy anaesthesia of 9 hours (n = 32) and after anaesthesia of 2 hours. No significant adverse effects on the cardiovascular system were detected.     

The use of lidocaine-sodium bicarbonate as anaesthetic in fish

Lidocaine and lidocaine-sodium bicarbonate mixture were evaluated as anaesthetics for carp (Cyprinus carpio), catfish (Ictalurus punctatus) and tilapia (Tilapia mossambica = Oreochromis mossambicus). Although both induced anaesthesia, the mixture was more effective for induction and recovery, and was able to achieve the required time for the fish to be out of water. The responses varied for the three test species.     

The principle of "balanced anesthesia" in high risk canine patients

The concept of balanced anaesthesia aims at an anaesthetic method for high risk patients by combination of different anaesthetic drugs. The anaesthetics and muscle-relaxants have to work in a way as to potentiate their effects and to reduce the side effects as well as the applied dosage. With this sensible regime the circulation and the metabolic energy should be less burdened. For the introduction of balanced anaesthesia, a combination of benzodiazepines (relaxing and sedative), morphine (analgetic and sedative) and quickly metabolizing hypnotics of the imidazol group (hypnotic and relaxing) is used. A fentanyl-drip-infusion continues and deepens the analgesia. After endotracheal intubation with the help of the carrier-gas nitrous oxide (weakly analgetic) and oxygen (2:1) a low concentration of volatile inhalation anaesthetics (weakly hypnotic) is added. Under artificial respiration low doses of competitive antidepolarizing neuromuscular blockers help to potentiate and reduce drug amounts of other anaesthetics especially of that for inhalation. At the end of balanced anaesthesia an antagonization of benzodiazepines, morphines and competitive neuromuscular blockers is recommended for emergency situations only because of possibly occurring changes of cardiovascular parameters.     

Plasma gastrin levels in horses with colic]

The plasma gastrin levels in fasted horses (21.1 +/- 15.6 pg/ml), in horses with spasmodic colic (7.3 +/- 5.4 pg/ml) and in horses with impaction of the left ventral large colon and/or pelvic flexure (11.4 +/- 3.1 pg/ml) were not significantly different. The plasma gastrin concentrations of horses with strangulation obstruction of the small intestine, large colon displacement or adynamic ileus, and which had no gastric reflux, were 12.9 +/- 8.7 pg/ml and did not differ from fasted gastrin levels. Horses which had 5-10 litres of stomach content reflux had a higher mean gastrin level (32.2 +/- 22.6 pg/ml) (range 8.7-83.0) than the fasted horses. The mean plasma gastrin level (69.0 +/- 32.2 pg/ml) (range 27.0-122.0 pg/ml) in horses which had gastric reflux and 11-20 litres of stomach content outflow through the nasogastric tube were significantly higher (P less than 0.0004) than in fasted horses or in horses with spasmodic colic, impaction of the left ventral large colon or in horses from which no gastric reflux could be obtained.     

Anaesthesia of farmed fish: implications for welfare

During their life cycle as farmed animals, there are several situations in which fish are subjected to handling and confinement. Netting, weighing, sorting, vaccination, transport and, at the end, slaughter are frequent events under farming conditions. As research subjects, fish may also undergo surgical procedures that range from tagging, sampling and small incisions to invasive procedures. In these situations, treatment with anaesthetic agents may be necessary in order to ensure the welfare of the fish. The main objective of this paper is to review our knowledge of the effects of anaesthetic agents in farmed fish and their possible implications for welfare. As wide variations in response to anaesthesia have been observed both between and within species, special attention has been paid to the importance of secondary factors such as body weight, water temperature and acute stress. In this review, we have limited ourselves to the anaesthetic agents such as benzocaine, metacaine (MS-222), metomidate hydrochloride, isoeugenol, 2-phenoxyethanol and quinaldine. Anaesthetic protocols of fish usually refer to one single agent, whereas protocols of human and veterinary medicine cover combinations of several drugs, each contributing to the effects needed in the anaesthesia. As stress prior to anaesthesia may result in abnormal reactions, pre-anaesthetic sedation is regularly used in order to reduce or avoid stress and is an integral part of the veterinary protocols of higher vertebrates. Furthermore, the anaesthetic agents that are used in order to obtain general anaesthesia are combined with analgesic agents that target nociception. The increased use of such combinations in fish is therefore included as a special section. Anaesthetic agents are widely used to avoid stress during various farming procedures. While several studies report that anaesthetics are effective in reducing the stress associated with confinement and handling, there are indications that anaesthesia may in itself induce a stress response, measured by elevated levels of cortisol. MS-222 has been reported to elicit high cortisol release rates immediately following exposure, while benzocaine causes a bimodal response. Metomidate has an inhibitory effect on cortisol in fish and seems to induce the lowest release of cortisol of the agents reported in the literature. Compared to what is observed following severe stressors such as handling and confinement, the amount of cortisol released in response to anaesthesia appears to be low but may represent an extra load under otherwise stressful circumstances. Furthermore, anaesthetics may cause secondary adverse reactions such as acidosis and osmotic stress due to respiratory arrest and insufficient exchange of gas and ions between the blood and the water. All in all, anaesthetics may reduce stress and thereby improve welfare but can also have unwanted side effects that reduce the welfare of the fish and should therefore always be used with caution. Finally, on the basis of the data reported in the literature and our own experience, we recommend that anaesthetic protocols should always be tested on a few fish under prevailing conditions in order to ensure an adequate depth of anaesthesia. This recommendation applies whether a single agent or a combination of agents is used, although it appears that protocols comprising combinations of agents provide wider safety margins. The analgesic effects of currently used agents, in spite of their proven local effects, are currently being debated as the agents are administrated to fish via inhalation rather than locally at the target site. We therefore recommend that all protocols of procedures requiring general anaesthesia should be complemented by administration of agents with analgesic effect at the site of tissue trauma.     

Effects of repeated handling, with or without anaesthesia, on feed intake and growth in juvenile rainbow trout, Oncorhynchus mykiss (Walbaum)

The effects of weekly anaesthetization with clove oil and tricaine methanesulphonate (MS‐222) on feed intake and growth were examined in juvenile rainbow trout, Oncorhynchus mykiss (Walbaum), held individually. Repeated handling without anaesthetics significantly reduced feed intake and weight gain compared with an unhandled control group during an 8‐week experiment. When anaesthetics were used during handling the feed consumption and weight gain were significantly (MS‐222) or not significantly (clove oil) higher than in fish handled without anaesthesia. When compared with the unhandled control group, neither of these two anaesthetics had significant effects on feed intake but, in contrast to MS‐222, repeated anaesthesia with clove oil had a significant negative effect on growth. However, the effects of MS‐222 and clove oil on the growth were not significantly different from each other. Feed conversion ratio (feed/gain) of MS‐222‐anaesthetized fish was significantly higher compared with unhandled control and handled control fish but was not significantly different from fish anaesthetized with clove oil. These results suggest that both MS‐222 and clove oil alleviate handling stress in juvenile rainbow trout, and that these two anaesthetics are rather similar with respect to their effects during repeated exposures.     

Detection of dexamethasone in horses

Due to their marked antiinflammatory effect, synthetic corticosteroids are used to mask illness, especially lameness in horses. The detection of these drugs in equine body fluids requires accurate methods, particularly where misuse of corticosteroids is suspected. Gas chromatography/mass spectrometry (GC/MS) is well established as a reliable technique for the identification of drugs in biological fluids. Using GC/MS, we determined dexamethasone levels in horse urine and serum after intravenous application of a therapeutic dose. Dexamethasone was detectable, in serum for up to six hours, and in urine for up to 32 hours, after its administration. These findings indicate that serum measurements are unreliable for the detection of corticosteroid abuse, and demonstrate urine to be a more suitable body fluid for investigation. Nevertheless, it should be emphasized that, regardless of the technique employed, the clinical effects of dexamethasone last longer than 32 hours; thus, failure to detect dexamethasone does not disprove corticosteroid abuse.     

Anesthesia in swine

Pigs are not only anaesthetized in case of operations but often also if diagnostic and therapeutic procedures are necessary. Choice of the anaesthetic and way of application depend on the size of the patient and the indication. The only important local anaesthesia in pigs is epidural anaesthesia. It is indicated in all longer lasting painful procedures in caudal regions. The technique of this anaesthesia is described. From the possible methods of general anaesthesias, in practice injection anaesthesia has been generally accepted for several reasons. Together with barbiturate anaesthesia neurolept-analgesia with Azaperone--Metomidate has become more and more important, because with this form of anaesthesia the technically easy intra-abdominal application is possible in pigs under 15 kg of body weight.     

Effects of anaesthesia with MS-222, clove oil and CO2 on feed intake and plasma cortisol in steelhead trout (Oncorhynchus mykiss)

We examined the effects tricaine methanesulfonate (MS-222), clove oil and CO₂ on feed intake and cortisol response in steelhead trout, Oncorhynchus mykiss. Even though a body of literature exists about the effects of different anaesthetics on fish, no comparative information seems to be available about their effects on feed intake after anaesthesia, which would be important to know especially in aquaculture research. We anaesthetised juvenile steelhead trout with these three anaesthetics, and then sampled them 4, 24 and 48 h later. Fish in all groups ate relatively well already 4 h after anaesthesia. However, feed intake in fish treated with clove oil or MS-222 was lower than in the controls. There were no differences in feed intake among anaesthetised groups. Plasma cortisol concentrations were elevated 48 h after anaesthetisation, but the treatment means were equal throughout the experiment. Our results support previous findings that clove oil is a reasonable alternative to MS-222.     

Antithrombin III determination in horses. Reference values and acquired antithrombin III deficiency

Antithrombin III (AT III) determinations were done in healthy and sick horses using the chromogenic substrate Chromozym TH. Reference values for adult horses at 25 degrees C were 18-25 IU AT III per ml plasma and 84-118% AT III activity of normal horse plasma, respectively. Precision and accuracy were good (intra assay coefficient of variation less than 2%, accuracy 10%). Surgical operations on healthy horses led to a biphasic decrease in AT III activity touching the lower border of the reference values on the second postoperative day. Other reasons for acquired AT III deficiencies included disseminated intravascular coagulation (DIC), liver disease and glomerulonephritis. Using follow-up studies, differences in the dynamics of acquired AT III deficiency and coagulation promoting factors were demonstrated. 12 of 35 horses with decreased AT III values suffered from phlebothrombosis of the jugular veins. It was presumed that acquired AT III deficiencies promote development and progression of phlebothrombosis/thrombophlebitis in horses.     

Chemical composition of the essential oil of Aloysia triphylla under seasonal influence and its anaesthetic activity in fish

Plants are sources of secondary metabolites, and some are rich in essential oils (EOs), which possess a bioactive pharmacological importance as sedatives and anaesthetics that have been experimentally demonstrated in fish. In search of products with lower residual effects and optimization of the production based on the local flora, the properties of the EO of Aloysia triphylla (EOAT) have been investigated. The samples of two years were analysed for the percentage variability of the chemical composition and the totality of the major components according to the season. Limonene, citral isomers (α and β), caryophyllene, caryophyllene oxide and spathulenol were the main constituents of the EOAT throughout these two years. In the second year, caryophyllene predominates over its oxide in all seasons; however, in the first year, it occurs only in autumn and winter. Seasonal pools of EOs were made for the biennium obtaining four samples, and silver catfish (Rhamdia quelen) juveniles were subjected to a concentration range of 20–800 μl/L EOAT in order to assess induction and recovery times of anaesthesia. The relationships between percentages of individual components in EOAT and time to induce deep anaesthesia indicate that its activity may be attributed to the association of several of its components.     

Stomach ulcers in the horse--clinical and gastroscopic findings in 12 horses (1989-1990)

Twelve horses with clinical symptoms of a gastric disorder were studied by gastroscopy. Symptoms of gastric disorders were periprandial colic, bruxism, ructus and reflux. Preliminary to gastroscopy the horses were fasted for 24 h. Access to water was not restricted. The gastroscopy could be conducted easily using a fiberscope 2.5 m in length and 11 mm in outer diameter. While ulcers were present in the squamous fundus of all horses only one horse showed ulceration of the glandular fundus. Solitary ulcers near the margo plicatus were found in horses with mild clinical symptoms. In contrast, diffuse gastroesophageal ulceration was accompanied by severe clinical symptoms. Four horses were affected by an acute gastroesophageal ulceration with gastric reflux and subsequent aspiration pneumonia. Two of those horses suffered from acute gastric ulceration 3-4 days following laparatomy. All horses were treated with cimetidine (5 mg/kg bwt/q.i.d.) until clinical symptoms ceased.     

Trichomonad infections of the oral cavity in horses in southern Germany]

Trichomonads of the oral cavity were found in 9 of 60 investigated horses. Apart from dental tartar, the oral cavity showed no clinical signs in all positive horses. The clinical investigation of these horses additionally revealed colic in 4 and coughing in 4 horses as well as lumbago in 1 animal. By means of scanning electron microscopy the trichomonads were shown to be round or piriform with an average length of 7.6 microns and greatest width of 6.3 microns. They had 4 anterior flagella with an average length of 8.3 microns, an undulating membrane measuring 8.7 microns with no trailing flagellum as well as an axostyle extending on average 7.8 microns beyond the body, and therefore have to be placed into the genus Trichomonas.     

Efficacy of tricaine methanesulphonate and clove oil as anaesthetics for juvenile cobia Rachycentron canadum

Six experiments were designed to determine the optimal anaesthetic dosage of tricaine methanesulphonate (TMS) and clove oil that could be used safely on juvenile cobia Rachycentron canadum of two sizes [G1=4.9±0.8 g; G2=13.9±3.1 g]. We documented the stage of anaesthesia and the acute toxicity as 96 h LC₅₀ (lethal concentration 50% population) at various exposure times of the two anaesthetics. At 10 min induction time, the TMS 96 h LC₅₀ was 93.9 mg L⁻¹ in G1 and 97.0 mg L⁻¹ in G2. Compared with clove oil, the 96 h LC₅₀ was 60.0 mg L⁻¹ in G1 and 69.8 mg L⁻¹ in G2. The difference between the two groups (G1, G2) did not influence anaesthesia safety ( P >0.05). Rachycentron canadum achieved stage 3 anaesthesia more rapidly at a lower clove oil concentration level (40 mg L⁻¹, 10 min) than TMS (60 mg L⁻¹, 10 min), but the recovery period of clove oil, was significantly longer. Clove oil was the most effective in reducing the short-term stress induced by routine biometry (20 mg L⁻¹, 10 min) and also by transporting (1 mg L⁻¹, 8 h). Whereas, for long-term exposure, 40 mg L⁻¹ TMS was found to be safe.     

Alpinia galanga oil—A new natural source of fish anaesthetic

This study explores the anaesthetic activity of Alpinia galanga oil (AGO) in fish. Cyprinus carpio (koi carp) was used as a fish model. It was found that the induction time to stage 3 anaesthesia and the recovery time of the fish after exposure to AGO were exponentially and polynomially correlated to AGO concentrations. The viability of normal blood cells of koi carp anaesthetized with 500 mg/L AGO was found to be higher than 90% for normal red blood cells and white blood cells and 89% for peripheral blood nuclear cells indicating nontoxicity of AGO to the fish. A concentration of 300 mg/L of AGO was the most suitable for anaesthetizing koi carp due to the safety and effectiveness aspects as being ideally fitted to anaesthetic criteria. This concentration gave the induction time of 205.55 ± 5.07 s and the recovery time of 202.50 ± 9.30 s. Determination of stress biomarker such as blood cortisol and glucose as well as gene expression showed that the blood cortisol level of the fish anaesthetized with AGO was similar to normal levels. Moreover, blood glucose level was significantly less increased than those anaesthetized with tricaine methanesulfonate. Gene expressions of the fish cortisol receptor, cytochrome oxidase subunit1, heat shock protein 70 and Na⁺/K⁺‐ATPaseα₃ were significantly reduced after exposure to AGO indicating the advantages of AGO on fish stress reduction. Thus, AGO is a promising natural source for an alternative fish anaesthetics.     

Anesthesia in birds

Anaesthesia in birds is ordered by law and is also necessary for various operations and manipulations. Anaesthesia by injection of Ketamin, which in special cases may be combined with Diazepam, has been found useful. Anaesthesia by inhalation with Halothan, Methoxyfluran or Isofluran is the most careful method. Local anaesthesia has few indications.     

Comparative efficacy of MS-222 and benzocaine as anaesthetics under simulated transport conditions of a tropical ornamental fish Puntius filamentosus (Valenciennes)

There is a growing commercial interest in the fish, Puntius filamentosus , in the ornamental fish trade in India and elsewhere. The trade is, however, hampered by severe mortalities during transport of the fish owing to insufficient data available on the use of anaesthetics. To resolve this problem, we evaluated the efficacy of two anaesthetics, MS-222 and benzocaine, in sedating P. filamentosus in simulated transportation experiments and used stress response parameters such as cortisol and blood glucose levels to perform assessments. We observed that MS-222 at 40 mg L⁻¹ and benzocaine at 20 mg L⁻¹ were sufficient to induce sedation for 48 h. Above these concentrations, both the anaesthetics adversely affected the fish and resulted in mortalities. Both anaesthetics significantly lowered the blood cortisol and glucose levels compared with the unsedated controls. Importantly, the anaesthetics treatment significantly lowered the post-transport mortality in the fish. The results of the study show that MS-222 and benzocaine could be used as sedatives to alleviate transport-related stress in P. filamentosus to improve their post-transport survival and hence reduce economic loss.