Anaesthesia with medetomidine-ketamine-isoflurane with and without midazolam, in eight captive Chimpanzees (Pan troglodytes) premedicated with oral zuclopenthixol

In 8 captive adult chimpanzees of various ages premedicated with oral zuclopenthixol anaesthesia was induced intramuscularly with a combination of medetomidine and ketamine (40 or 50 µg/kg and 5 mg/kg, IM, respectively), with and without midazolam (0.05 mg/kg), and maintained with isoflurane in oxygen. At the end of the procedure, sedation was reversed with atipamezole (0.25 mg/kg, IM) and sarmazenil (0.005 mg/kg, IM) when midazolam had been administered. Oral zuclopenthixol resulted in tranquillization of the whole group and only one animal required a second dart injection to achieve adequately deep anaesthesia. Effective and reliable anaesthesia was achieved in all apes; the depth of hypnosis was stable and sudden arousal did not occur. Physiological parameters remained within normal ranges in the majority of the animals; however, manageable anaesthesia-related complications, namely apnoea after darting, hypotension, hypoventilation, hypoxemia and prolonged recovery, occurred in 6 out of 8 animals. The use of monitoring devices was essential to guarantee adequate management of these complications.

Anaesthesia with medetomidine, midazolam and ketamine in six gorillas after premedication with oral zuclopenthixol dihydrochloride

OBJECTIVE To evaluate the effects of medetomidine, midazolam and ketamine (MMK) in captive gorillas after premedication with oral zuclopenthixol. STUDY DESIGN Case series. ANIMALS Six gorillas, two males and four females, aged 9-52 years and weighing 63-155 kg. METHODS The gorillas were given zuclopenthixol dihydrochloride 0.2 ± 0.05 mg kg(-1) per os twice daily for 3 days for premedication. On the day of anaesthesia the dose of zuclopenthixol was increased to 0.27 mg kg(-1) and given once early in the morning. Anaesthesia was induced with medetomidine 0.04 ± 0.004 mg kg(-1) , midazolam 0.048 ± 0.003 mg kg(-1) and ketamine 4.9 ± 0.4 mg kg(-1) intramuscularly (IM). Upon recumbency, the trachea was intubated and anaesthesia was maintained on 1-2% isoflurane in oxygen. Physiological parameters were monitored every 10 minutes and arterial blood gas analysis was performed once 30-50 minutes after initial darting. At the end of the procedure, 42-115 minutes after initial darting, immobilisation was antagonized with atipamezole 0.21 ± 0.03 mg kg(-1) and sarmazenil 5 ± 0.4 μg kg(-1) IM. RESULTS Recumbency was reached within 10 minutes in five out of six animals. One animal required two additional darts before intubation was feasible. Heart rate ranged from 60 to 85 beats minute(-1) , respiratory rate from 17 to 46 breaths minute(-1) and temperature from 36.9 to 38.3 °C. No spontaneous recoveries were observed and anaesthetic level was stable. Blood gas analyses revealed mild respiratory acidosis, and mean PaO(2) was 24.87 ± 17.16 kPa (187 ± 129 mmHg) with all values being above 13.4 kPa (101 mmHg). Recovery was smooth and gorillas were sitting within 25 minutes. CONCLUSION AND CLINICAL RELEVANCE The drug combination proved to be effective in anaesthetizing captive gorillas of various ages and both sexes, with minimal cardio-respiratory changes.

Electrophoretically mediated microanalysis for characterization of the enantioselective CYP3A4 catalyzed N-demethylation of ketamine

Execution of an enzymatic reaction performed in a capillary with subsequent electrophoretic analysis of the formed products is referred to as electrophoretically mediated microanalysis (EMMA). An EMMA method was developed to investigate the stereoselectivity of the CYP3A4-mediated N-demethylation of ketamine. Ketamine was incubated in a 50 μm id bare fused-silica capillary together with human CYP3A4 Supersomes using a 100 mM phosphate buffer (pH 7.4) at 37°C. A plug containing racemic ketamine and the NADPH regenerating system including all required cofactors for the enzymatic reaction was injected, followed by a plug of the metabolizing enzyme CYP3A4 (500 nM). These two plugs were bracketed by plugs of incubation buffer to ensure proper conditions for the enzymatic reaction. The rest of the capillary was filled with a pH 2.5 running buffer comprising 50 mM Tris, phosphoric acid, and 2% w/v of highly sulfated γ-cyclodextrin. Mixing of reaction plugs was enhanced via application of -10 kV for 10 s. After an incubation of 8 min at 37°C without power application (zero-potential amplification), the capillary was cooled to 25°C within 3 min followed by application of -10 kV for the separation and detection of the formed enantiomers of norketamine. Norketamine formation rates were fitted to the Michaelis-Menten model and the elucidated values for V(max) and K(m) were found to be comparable to those obtained from the off-line assay of a previous study.

S-ketamine versus racemic ketamine in dogs: their relative potency as induction agents.

OBJECTIVE To determine the potency ratio between S-ketamine and racemic ketamine as inductive agents for achieving tracheal intubation in dogs. STUDY DESIGN Prospective, randomized, 'blinded', clinical trial conducted in two consecutive phases. ANIMALS 112 client-owned dogs (ASA I or II). METHODS All animals were premedicated with intramuscular acepromazine (0.02 mg kg(-1) ) and methadone (0.2 mg kg(-1) ). In phase 1, midazolam (0.2 mg kg(-1) ) with either 3 mg kg(-1) of racemic ketamine (group K) or 1.5 mg kg(-1) of S-ketamine (group S) was administered IV, for induction of anaesthesia and intubation. Up to two additional doses of racemic (1.5 mg kg(-1) ) or S-ketamine (0.75 mg kg(-1) ) were administered if required. In phase 2, midazolam (0.2 mg kg(-1) ) with 1 mg kg(-1) of either racemic ketamine (group K) or S-ketamine (group S) was injected and followed by a continuous infusion (1 mg kg minute(-1) ) of each respective drug. Differences between groups were statistically analyzed via t-test, Fisher exact test and ANOVA for repeated measures. RESULTS Demographics and quality and duration of premedication, induction and intubation were comparable among groups. During phase 1 it was possible to achieve tracheal intubation after a single dose in more dogs in group K (n = 25) than in group S (n = 16) (p = 0.046). A dose of 3 mg kg(-1) S-ketamine allowed tracheal intubation in the same number of dogs as 4.5 mg kg(-1) of racemic ketamine. The estimated potency ratio was 1.5:1. During phase 2, the total dose (mean ± SD) of S-ketamine (4.02 ±1.56 mg kg(-1) ) and racemic ketamine (4.01 ± 1.42) required for tracheal intubation was similar. CONCLUSION AND CLINICAL RELEVANCE Racemic and S-ketamine provide a similar quality of anaesthetic induction and intubation. S-ketamine is not twice as potent as racemic ketamine and, if infused, the potency ratio is 1:1.

International online survey to assess current practice in equine anaesthesia.

REASONS FOR PERFORMING STUDY Multicentre Confidential Enquiries into Perioperative Equine Fatalities (CEPEF) have not been conducted since the initial CEPEF Phases 1-3, 20 years ago. OBJECTIVES To collect data on current practice in equine anaesthesia and to recruit participants for CEPEF-4. STUDY DESIGN Online questionnaire survey. METHODS An online questionnaire was prepared and the link distributed internationally to veterinarians possibly performing equine anaesthesia, using emails, posters, flyers and an editorial. The questionnaire included 52 closed, semiclosed and open questions divided into 8 subgroups: demographic data, anaesthetist, anaesthesia management (preoperative, technical equipment, monitoring, drugs, recovery), areas of improvements and risks and motivation for participation in CEPEF-4. Descriptive statistics and Chi-squared tests for comparison of categorical variables were performed. RESULTS A total of 199 questionnaires were completed by veterinarians from 14 different countries. Of the respondents, 43% worked in private hospitals, 36% in private practices and 21% in university teaching hospitals. In 40 institutions (23%) there was at least one diplomate of the European or American colleges of veterinary anaesthesia and analgesia on staff. Individual respondents reported routinely employ the following anaesthesia monitoring modalities: electrocardiography (80%), invasive arterial blood pressures (70%), pulse oximetry (60%), capnography (55%), arterial blood gases (47%), composition of inspired and expired gases (45%) and body temperature (35%). Drugs administered frequently or routinely as part of a standard protocol were: acepromazine (44%), xylazine (68%), butorphanol (59%), ketamine (96%), diazepam (83%), isoflurane (76%), dobutamine (46%), and, as a nonsteroidal anti-inflammatory drug, phenylbutazone (73%) or flunixin meglumine (66%). Recovery was routinely assisted by 40%. The main factors perceived by the respondents to affect outcome of equine anaesthesia were the preoperative health status of the animal and training of the anaesthetist. CONCLUSIONS Current practice in equine anaesthesia varies widely, and the study has highlighted important topics relevant for designing a future prospective multicentre cohort study (CEPEF-4). The Summary is available in Chinese - see Supporting information.

Development of a method for analysis of ketamine and norketamine enantiomers in equine brain and cerebrospinal fluid by capillary electrophoresis

Ketamine and norketamine are being transported across the blood brain barrier and are also entering from blood into cerebrospinal fluid (CSF). Enantioselective distributions of these compounds in brain and CSF have never been determined. The enantioselective CE based assay previously developed for equine plasma was adapted to the analysis of these compounds in equine brain via use of an acidic pre-extraction of interferences prior to liquid/liquid extraction at alkaline pH. CSF can be treated as plasma. With 100 mg of brain tissue and 0.5 mL of CSF or plasma, assay conditions for up to 30 nmol/g and 6 μM, respectively, of each enantiomer with LOQs of 0.5 nmol/g and 0.1 μM, respectively, were established and the assays were applied to equine samples. CSF and plasma samples analyzed stemmed from anesthetized patient horses and brain, CSF and plasma were obtained from anesthetized horses that were euthanized with an overdose of pentobarbital. Data obtained indicate that ketamine and norketamine enantiomers are penetrating into brain and CSF with those of ketamine being more favorably transported than norketamine, whereas metabolites of norketamine are hindered. More work is required to properly investigate possible stereoselectivities of the ketamine metabolism and transport of metabolites from blood into brain tissue and CSF.

Clinical and pharmacokinetic evaluation of S-ketamine for intravenous general anaesthesia in horses undergoing field castration.

BACKGROUND Intravenous anaesthetic drugs are the primary means for producing general anaesthesia in equine practice. The ideal drug for intravenous anaesthesia has high reliability and pharmacokinetic properties indicating short elimination and lack of accumulation when administered for prolonged periods. Induction of general anaesthesia with racemic ketamine preceded by profound sedation has already an established place in the equine field anaesthesia. Due to potential advantages over racemic ketamine, S-ketamine has been employed in horses to induce general anaesthesia, but its optimal dose remains under investigation. The objective of this study was to evaluate whether 2.5 mg/kg S-ketamine could be used as a single intravenous bolus to provide short-term surgical anaesthesia in colts undergoing surgical castration, and to report its pharmacokinetic profile. RESULTS After premedication with romifidine and L-methadone, the combination of S-ketamine and diazepam allowed reaching surgical anaesthesia in the 28 colts. Induction of anaesthesia as well as recovery were good to excellent in the majority (n = 22 and 24, respectively) of the colts. Seven horses required additional administration of S-ketamine to prolong the duration of surgical anaesthesia. Redosing did not compromise recovery quality. Plasma concentration of S-ketamine decreased rapidly after administration, following a two-compartmental model, leading to the hypothesis of a consistent unchanged elimination of the parent compound into the urine beside its conversion to S-norketamine. The observed plasma concentrations of S-ketamine at the time of first movement were various and did not support the definition of a clear cut-off value to predict the termination of the drug effect. CONCLUSIONS The administration of 2.5 mg/kg IV S-ketamine after adequate premedication provided good quality of induction and recovery and a duration of action similar to what has been reported for racemic ketamine at the dose of 2.2 mg/kg. Until further investigations will be provided, close monitoring to adapt drug delivery is mandatory, particularly once the first 10 minutes after injection are elapsed. Taking into account rapid elimination of S-ketamine, significant inter-individual variability and rapid loss of effect over a narrow range of concentrations a sudden return of consciousness has to be foreseen.

Clinical evaluation of ketamine and lidocaine intravenous infusions to reduce isoflurane requirements in horses under general anaesthesia

OBJECTIVE To compare isoflurane alone or in combination with systemic ketamine and lidocaine for general anaesthesia in horses. STUDY DESIGN Prospective, randomized, blinded clinical trial. ANIMALS Forty horses (ASA I-III) undergoing elective surgery. METHODS Horses were assigned to receive isoflurane anaesthesia alone (ISO) or with ketamine and lidocaine (LKI). After receiving romifidine, diazepam, and ketamine, the isoflurane end-tidal concentration was set at 1.3% and subsequently adjusted by the anaesthetist (unaware of treatments) to maintain a light plane of surgical anaesthesia. Animals in the LKI group received lidocaine (1.5 mg kg(-1) over 10 minutes, followed by 40 microg kg(-1) minute(-1)) and ketamine (60 microg kg(-1) minute(-1)), both reduced to 65% of the initial dose after 50 minutes, and stopped 15 minutes before the end of anaesthesia. Standard clinical cardiovascular and respiratory parameters were monitored. Recovery quality was scored from one (very good) to five (very poor). Differences between ISO and LKI groups were analysed with a two-sample t-test for parametric data or a Fischer's exact test for proportions (p < 0.05 for significance). Results are mean +/- SD. RESULTS Heart rate was lower (p = 0.001) for LKI (29 +/- 4) than for ISO (34 +/- 6). End-tidal concentrations of isoflurane (ISO: 1.57% +/- 0.22; LKI: 0.97% +/- 0.33), the number of horses requiring thiopental (ISO: 10; LKI: 2) or dobutamine (ISO:8; LKI:3), and dobutamine infusion rates (ISO:0.26 +/- 0.09; LKI:0.18 +/- 0.06 microg kg(-1) minute(-1)) were significantly lower in LKI compared to the ISO group (p < 0.001). No other significant differences were found, including recovery scores. CONCLUSIONS AND CLINICAL RELEVANCE These results support the use of lidocaine and ketamine to improve anaesthetic and cardiovascular stability during isoflurane anaesthesia lasting up to 2 hours in mechanically ventilated horses, with comparable quality of recovery.

Effects of medetomidine and its active enantiomer dexmedetomidine on N-demethylation of ketamine in canines determined in vitro using enantioselective capillary electrophoresis.

Cytochrome P450 (CYP) enzymes catalyze the metabolism of both, the analgesic and anesthetic drug ketamine and the α2 -adrenergic receptor-agonist medetomidine that is used for sedation and analgesia. As racemic medetomidine or its active enantiomer dexmedetomidine are often coadministered with racemic or S-ketamine in animals and dexmedetomidine together with S- or racemic ketamine in humans, drug-drug interactions are likely to occur and have to be characterized. Enantioselective CE with highly sulfated γ-cyclodextrin as chiral selector was employed for analyzing in vitro (i) the kinetics of the N-demethylation of ketamine mediated by canine CYP3A12 and (ii) interactions occurring with racemic medetomidine and dexmedetomidine during coincubation with ketamine and canine liver microsomes (CLM), canine CYP3A12, human liver microsomes (HLM), and human CYP3A4. For CYP3A12 without an inhibitor, Michaelis-Menten kinetics was determined for the single enantiomers of ketamine and substrate inhibition kinetics for racemic ketamine. Racemic medetomidine and dexmedetomidine showed an inhibition of the N-demethylation reaction in the studied canine enzyme systems. Racemic medetomidine is the stronger inhibitor for CLM, whereas there is no difference for CYP3A12. For CLM and CYP3A12, the inhibition of dexmedetomidine is stronger for the R- compared to the S-enantiomer of ketamine, a stereoselectivity that is not observed for CYP3A4. Induction is observed at a low dexmedetomidine concentration with CYP3A4 but not with CYP3A12, CLM, and HLM. Based on these results, S-ketamine combined with dexmedetomidine should be the best option for canines. The enantioselective CE assay with highly sulfated γ-cyclodextrin as chiral selector is an effective tool for determining kinetic and inhibition parameters of metabolic pathways.

LC-MS/MS screening method for designer amphetamines, tryptamines, and piperazines in serum

Since the late 1990s and early 2000s, derivatives of well-known designer drugs as well as new psychoactive compounds have been sold on the illicit drug market and have led to intoxications and fatalities. The LC-MS/MS screening method presented covers 31 new designer drugs as well as cathinone, methcathinone, phencyclidine, and ketamine which were included to complete the screening spectrum. All but the last two are modified molecular structures of amphetamine, tryptamine, or piperazine. Among the amphetamine derivatives are cathinone, methcathinone, 3,4-DMA, 2,5-DMA, DOB, DOET, DOM, ethylamphetamine, MDDMA, 4-MTA, PMA, PMMA, 3,4,5-TMA, TMA-6 and members of the 2C group: 2C-B, 2C-D, 2C-H, 2C-I, 2C-P, 2C-T-2, 2C-T-4, and 2C-T-7. AMT, DPT, DiPT, MiPT, DMT, and 5MeO-DMT are contained in the tryptamine group, BZP, MDBP, TFMPP, mCPP, and MeOPP in the piperazine group. Using an Applied Biosystems LC-MS/MS API 365 TurboIonSpray it is possible to identify all 35 substances. After addition of internal standards and mixed-mode solid-phase extraction the analytes are separated using a Synergi Polar RP column and gradient elution with 1 mM ammonium formate and methanol/0.1% formic acid as mobile phases A and B. Data acquisition is performed in MRM mode with positive electro spray ionization. The assay is selective for all tested substances. Limits of detection were determined by analyzing S/N-ratios and are between 1.0 and 5.0 ng/mL. Matrix effects lie between 65% and 118%, extraction efficiencies range from 72% to 90%.

Castration of lambs: a welfare comparison of different castration techniques in lambs over 10 weeks of age

Seventy male lambs over 10 weeks of age were castrated using Burdizzo, rubber rings, or surgery to assess the acute and long-term effects of castration. All castrations were performed under local anaesthesia. The surgically castrated lambs were additionally sedated with xylazine and the sedation reversed with tolazoline. The frequency of abnormal postures and immediate behavioural responses indicated that surgically castrated lambs were most distressed; the lambs castrated using Burdizzo and rubber rings were not dissimilar to those of the control group. Between 1.5 and 9h after castration, signs of pain and distress were at a lower level in lambs anaesthetised with bupivacaine compared with those treated with lidocaine. Due to the markedly faster wound healing, Burdizzo castration seemed to be preferable (fewer signs of long-term pain) when compared to the rubber ring technique. It was concluded that local anaesthesia with bupivacaine, followed by the Burdizzo method is the preferable technique for the castration of lambs older than 10 weeks of age.

Continuous extradural analgesia in a cow with complex regional pain syndrome

A chronic pain syndrome, similar to the complex regional pain syndrome (CRPS) described in human beings, was diagnosed in a cow with persisting severe pelvic limb lameness. Diagnosis was based on the disproportionate relationship between the severity and duration of pain and the lesion, the failure of conventional analgesic and surgical therapy and the presence of characteristic clinical features. Multimodal therapy, i.e. a mixture of methadone, ketamine and bupivacaine was administered continuously for 17 days via an extradural catheter to counteract nociceptive hypersensitization. Doses were adjusted daily after assessing the effect, using a composite pain score. Physiotherapy was also performed. The diagnosis of CRPS in cattle is unusual. In this case, treatment was successful and the cow was discharged mildly lame and in improving physical condition. Long-term extradural analgesia proved to be safe and effective in the treatment of this syndrome, which was nonresponsive to conventional therapy.

Effects of an alveolar recruitment maneuver on cardiovascular and respiratory parameters during total intravenous anesthesia in ponies

OBJECTIVE: To evaluate pulmonary and cardiovascular effects of a recruitment maneuver (RM) combined with positive end-expiratory pressure (PEEP) during total intravenous anesthesia in ponies. ANIMALS: 6 healthy adult Shetland ponies. PROCEDURE: After premedication with detomidine (10 microg/kg, IV), anesthesia was induced with climazolam (0.06 mg/kg, IV) and ketamine (2.2 mg/kg, IV) and maintained with a constant rate infusion of detomidine (0.024 mg/kg/h), climazolam (0.036 mg/kg/h), and ketamine (2.4 mg/kg/h). The RM was preceded by an incremental PEEP titration and followed by a decremental PEEP titration, both at a constant airway pressure difference (deltaP) of 20 cm H2O. The RM consisted of a stepwise increase in deltaP by 25, 30, and 35 cm H2O obtained by increasing peak inspiratory pressure (PIP) to 45, 50, and 55 cm H2O, while maintaining PEEP at 20 cm H2O. Hemodynamic and pulmonary variables were analyzed at every step of the PEEP titration-RM. RESULTS: During the PEEP titration-RM, there was a significant increase in PaO 2 (+12%), dynamic compliance (+ 62%), and heart rate (+17%) and a decrease in shunt (-19%) and mean arterial blood pressure (-21%) was recorded. Cardiac output remained stable. CONCLUSIONS AND CLINICAL RELEVANCE: Although baseline oxygenation was high, Pa(O2) and dynamic compliance further increased during the RM. Despite the use of high PIP and PEEP and a high tidal volume, limited cardiovascular compromise was detected. A PEEP titration-RM may be used to improve oxygenation in anesthetized ponies. During stable hemodynamic conditions, PEEP titration-RM can be performed with acceptable adverse cardiovascular effects.

Insulin-like growth factor type-1 receptor down-regulation associated with dwarfism in Holstein calves

Perturbations in endocrine functions can impact normal growth. Endocrine traits were studied in three dwarf calves exhibiting retarded but proportionate growth and four phenotypically normal half-siblings, sired by the same bull, and four unrelated control calves. Plasma 3,5,3'-triiodothyronine and thyroxine concentrations in dwarfs and half-siblings were in the physiological range and responded normally to injected thyroid-releasing hormone. Plasma glucagon concentrations were different (dwarfs, controls>half-siblings; P<0.05). Plasma growth hormone (GH), insulin-like growth factor-1 (IGF-1) and insulin concentrations in the three groups during an 8-h period were similar, but integrated GH concentrations (areas under concentration curves) were different (dwarfs>controls, P<0.02; half-siblings>controls, P=0.08). Responses of GH to xylazine and to a GH-releasing-factor analogue were similar in dwarfs and half-siblings. Relative gene expression of IGF-1, IGF-2, GH receptor (GHR), insulin receptor, IGF-1 type-1 and -2 receptors (IGF-1R, IGF-2R), and IGF binding proteins were measured in liver and anconeus muscle. GHR mRNA levels were different in liver (dwarfs

CE provides evidence of the stereoselective hydroxylation of norketamine in equines

CE with multiple isomer sulfated-CD as selector was used for the simultaneous analysis of the stereoisomers of ketamine, norketamine, 5,6-dehydronorketamine and hydroxylated metabolites of norketamine in liquid/liquid extracts of (i) in vitro incubations with ketamine or norketamine and equine liver microsomes and (ii) plasma and urine of ponies receiving a target-controlled infusion of ketamine under isoflurane anesthesia. Hydroxynorketamine metabolites with the hydroxy group at the cyclohexanone ring could be shown to be formed stereoselectively both in vitro and in vivo. Due to the lack of standard compounds, urinary extracts were fractionated by HPLC followed by characterization of the collected fractions with CE and LC-MS(n) with 0.7 mmu mass discrimination. Comparison of LC-MS(n) data obtained with the fractions, an in vitro microsomal sample, and both pony urine and hydrolyzed pony urine led to the identification of four hydroxylated norketamine metabolites with hydroxylation at the cyclohexanone ring, two with hydroxylation at the aromatic ring and four hydroxylated metabolites of ketamine. Due to the lower detection sensitivity, only the four hydroxynorketamine metabolites with hydroxylation at the cyclohexanone ring were observed by CE. The data suggest that demethylation of ketamine followed by hydroxylation of norketamine at the cyclohexanone ring is the major metabolic pathway in equine species and that the ketamine metabolism is highly stereoselective.