Comparison of azaperone–detomidine–butorphanol–ketamine and azaperone–tiletamine–zolazepam for anaesthesia in piglets

ObjectiveTo investigate a combination of azaperone, detomidine, butorphanol and ketamine (DBK) in pigs and to compare it with the combination of azaperone, tiletamine and zolazepam (TZ).Study designProspective, randomized, blinded, cross–over study.AnimalsTwelve clinically healthy crossbred pigs aged about 2 months and weighing 16–25 kg.MethodsPigs were pre–medicated with azaperone (4 mg kg^?1). Ten minutes later anaesthesia was induced with intramuscular DBK (detomidine 0.08 mg kg^?1, butorphanol 0.2 mg kg^?1, ketamine 10 mg kg^?1) or TZ (tiletamine and zolazepam 5 mg kg^?1). The pigs were positioned in dorsal recumbency. Heart and respiratory rates, posture, anaesthesia score, PaO₂, PaCO₂, pH and bicarbonate concentration were measured. t–test was used to compare the areas under time–anaesthesia index curve (AUC_anindex) between treatments. Data concerning heart and respiratory rates, PaO₂, PaCO₂ and anaesthesia score were analysed with anova for repeated measurements. Wilcoxon signed rank test was used for the data concerning the duration of sedation and anaesthesia.ResultsThe sedation, analgesia and anaesthesia lasted longer after DBK than TZ. The AUC_anscore were 863 ± 423 and 452 ± 274 for DBK and TZ, respectively (p = 0.002). The duration of surgical anaesthesia lasted a median of 35 minutes (0–105 minutes) after DBK and a median of 15 minutes (0–35 minutes) after TZ (p = 0.05). Four pigs after DBK and six after TZ did not achieve the plane of surgical anaesthesia. The heart rate was lower after DBK than after TZ. Both treatments had similar effects on the other parameters measured.ConclusionsAt the doses used DBK was more effective than TZ for anaesthesia in pigs under field conditions.Clinical relevanceThe combinations can be used for sedation and minor field surgery in pigs. The doses and drugs chosen were insufficient to produce a reliable surgical plane of anaesthesia in these young pigs.     

Comparison of anesthetic effects of tiletamine–zolazepam–medetomidine or ketamine–medetomidine in captive Amur leopard cats (Prionailurus bengalensis euptailurus)

ObjectiveTo evaluate the effects and utility of tiletamine–zolazepam–medetomidine (TZM) and ketamine–medetomidine (KM) for anesthesia of Amur leopard cats (Prionailurus bengalensis euptailurus).Study designProspective, randomized experimental trial.AnimalsA total of six female (3.70 ± 0.49 kg) and six male (5.03 ± 0.44 kg; mean ± standard deviation) Amur leopard cats aged 2–6 years.MethodsEach animal was administered four protocols separated by ≥3 weeks. Each protocol included medetomidine (0.05 mg kg^–1) combined with tiletamine–zolazepam (1 mg kg^–1; protocol MTZ_LO); tiletamine–zolazepam (2 mg kg^–1; protocol MTZ_HI); ketamine (2 mg kg^–1; protocol MK_LO); or ketamine (4 mg kg^–1; MK_HI) administered intramuscularly. At time 0 (onset of lateral recumbency) and 30 minutes, heart rate (HR), respiratory rate (f_R), rectal temperature, noninvasive mean arterial pressure (MAP) and hemoglobin oxygen saturation (SpO₂) were recorded. Times to onset of lateral recumbency, duration of anesthesia and time to standing were recorded.ResultsOverall, animals were anesthetized with all protocols within 10 minutes, anesthesia was maintained ≥57 minutes, and recovery (time from the first head lift to standing) was completed within 5 minutes. During anesthesia with all protocols, HR, f_R, rectal temperature, SpO₂ and MAP were 99–125 beats minute^–1, 33–44 breaths minute^–1, 37.6–39.4 °C, 90–95% and 152–177 mmHg, respectively. No adverse event was observed.Conclusions and clinical relevanceTZM and KM at various dosages resulted in rapid onset of anesthesia, duration of >57 minutes and rapid recovery without administration of an antagonist. Accordingly, all these combinations are useful for anesthetizing Amur leopard cats and for performing simple procedures. However, the low doses of the anesthetic agents are recommended because there was no difference in duration of anesthesia between the dose rates studied.     

The influence of body mass and thoracic dimensions on arterial oxygenation in anaesthetized horses and ponies

ObjectiveTo examine the relationship between body mass and thoracic dimensions on arterial oxygen tensions (PaO₂) in anaesthetized horses and ponies positioned in dorsal recumbency.Study designProspective clinical study.AnimalsThirty six client-owned horses and ponies, mean [±SD (range)] age 8.1 ± 4.8 (1.5–20) years and mean body mass 467 ± 115 (203–656) kg.MethodsBefore general anaesthesia, food and water were withheld for 12 and 1 hours respectively. Body mass (kg), height at the withers (H), thoracic circumference (C), thoracic depth (length between dorsal spinous process and sternum; D), thoracic width (between point of shoulders; W), and thoracic diagonal length (point of shoulder to last rib; L) were measured. Pre-anaesthetic medication was with intravenous (IV) romifidine (0.1 mg kg⁻¹). Anaesthesia was induced with an IV ketamine (2.2 mg kg⁻¹) and diazepam (0.05 mg kg⁻¹) combination and maintained with halothane in 1:1 oxygen:nitrous oxide (N₂O) mixture. Animals were positioned in dorsal recumbency and allowed to breathe spontaneously. Nitrous oxide was discontinued after 10 minutes, and arterial blood samples obtained and analysed for gas tensions at 15, 30 and 60 minutes after connection to the anaesthetic breathing circuit. Data were analysed using anova and Pearson's correlation co-efficient.ResultsThe height per unit body mass (H kg⁻¹) and thoracic circumference per unit body mass (C kg⁻¹) correlated strongly (r = 0.85, p < 0.001 and r = 0.82, p < 0.001 respectively) with arterial oxygen tensions (PaO₂) at 15 minutes.ConclusionsThere is a strong positive correlation between H kg⁻¹ and C kg⁻¹ and PaO₂ after 15 minutes of anaesthesia in halothane-anaesthetized horses positioned in dorsal recumbency.Clinical relevanceReadily obtained linear measurements (height and thoracic circumference) and body mass may be used to predict the ability of horses to oxygenate during anaesthesia.     

Epidural administration of tiletamine/zolazepam in horses

Objectives To evaluate the analgesic, physiologic, and behavioral effects of the epidural administration of tiletamine/zolazepam in horses. Study design Prospective, double‐blind, randomized experimental study. Animals Five adult, healthy horses aged 10–16 years and weighing (mean ± SD) 400 ± 98 kg. Methods The horses were sedated with 1.0 mg kg^?1 intravenous (IV) xylazine, and an epidural catheter was placed into the first intercoccygeal intervertebral space. After a 48‐hour resting period, epidural tiletamine/zolazepam, 0.5 mg kg^?1 (treatment I) or 1.0 mg kg^?1 (treatment II), diluted up to 5 mL in sterile water, was administered with a 1‐week interval between the treatments. Heart rate, respiratory rate, arterial blood pressure, and sedation were evaluated. In order to evaluate the respiratory effects, blood from the carotid artery was withdrawn at time 0 (baseline), and then after 60 and 240 minutes. Analgesia was evaluated by applying a noxious stimulus with blunt‐tipped forceps on the perineal region, and graded as complete, moderate, or absent. Data were collected before tiletamine/zolazepam administration and at 15‐minute intervals for 120 minutes, and 4 hours after tiletamine/zolazepam administration. Data were analyzed with anova and Bonferroni's test with p < 0.05. Results The results showed no significant difference between treatments in cardiovascular and respiratory measurements. Sedation was observed with both doses, and it was significantly different from baseline at 60, 75, and 90 minutes in treatment II. Moderate analgesia and locomotor ataxia were observed with both the treatments. Conclusions and clinical relevance The results suggest that caudal epidural 0.5 and 1.0 mg kg^?1 tiletamine/zolazepam increases the threshold to pressure stimulation in the perineal region in horses. The use of epidural tiletamine/zolazepam could be indicated for short‐term moderate epidural analgesia. There are no studies examining spinal toxicity of Telazol, and further studies are necessary before recommending clinical use of this technique.     

Determination of the effective dosage of tiletamine–zolazepam–ketamine–xylazine,with or without methadone,in dogs

ObjectiveTo determine the effective dosage of the combination tiletamine–zolazepam–ketamine–xylazine (TKX), with or without methadone, in dogs.Study designProspective, randomized, experimental study.AnimalsA total of 29 dogs.MethodsDogs were randomly administered TKX (group TKX, n = 13) or combined with 0.3 mg kg^–1 of methadone (group TKXM, n = 16) intramuscularly. The TKX solution contained tiletamine (50 mg mL^–1), zolazepam (50 mg mL^–1), ketamine (80 mg mL^–1) and xylazine (20 mg mL^–1). The effective dosages for immobility in 50% and 95% of the population (ED₅₀ and ED₉₅) were estimated using the up-and-down method. Approximately 20 minutes after drug administration, a skin incision was performed and the response was judged as positive or negative if the dogs moved or did not move, respectively. The TKX volume for the subsequent dog in the same group was increased or decreased by 0.005 mL kg^–1 if the response of the previous dog was positive or negative, respectively. Heart and respiratory rates, and sedation/anesthesia scores (range 0–21) were recorded before and 15 minutes after drug administration.ResultsEstimated ED₅₀ and ED₉₅ (95% confidence intervals) were: TKX, 0.025 (0.020–0.029) and 0.026 (0.010–0.042) mL kg^–1; TKXM, 0.022 (0.018–0.025) and 0.033 (0.017–0.049) mL kg^–1. Median (interquartile range) scores for sedation/anesthesia were 17 (16–18) and 17 (15–20), and times until lateral recumbency were 5 (4–6) and 6 (4–10) minutes in TKX and TKXM, respectively (p > 0.05). In both groups heart and respiratory rates decreased, but values remained acceptable for anesthetized dogs.Conclusions and clinical relevanceThe results provide a guide for volumes of TKX and TKXM in dogs requiring restraint for minimally invasive procedures. Inclusion of methadone in the TKX combination did not influence ED₅₀.     

Cardiovascular effects of intravenous vatinoxan (MK-467) in medetomidine–tiletamine–zolazepam anaesthetised red deer (Cervus elaphus)

ObjectiveTo determine the effect of intravenous vatinoxan administration on bradycardia, hypertension and level of anaesthesia induced by medetomidine–tiletamine–zolazepam in red deer (Cervus elaphus).Study design and animalsA total of 10 healthy red deer were included in a randomised, controlled, experimental, crossover study.MethodsDeer were administered a combination of 0.1 mg kg^–1 medetomidine hydrochloride and 2.5 mg kg^–1 tiletamine–zolazepam intramuscularly, followed by 0.1 mg kg^–1 vatinoxan hydrochloride or equivalent volume of saline intravenously (IV) 35 minutes after anaesthetic induction. Heart rate (HR), mean arterial blood pressure (MAP), respiration rate (f_R), end-tidal CO₂ (Pe′CO₂), arterial oxygen saturation (SpO₂), rectal temperature (RT) and level of anaesthesia were assessed before saline/vatinoxan administration (baseline) and at intervals for 25 minutes thereafter. Differences within treatments (change from baseline) and between treatments were analysed with linear mixed effect models (p < 0.05).ResultsMaximal (81 ± 10 beats minute^–1) HR occurred 90 seconds after vatinoxan injection and remained significantly above baseline (42 ± 4 beats minute^–1) for 15 minutes. MAP significantly decreased from baseline (122 ± 10 mmHg) to a minimum MAP of 83 ± 6 mmHg 60 seconds after vatinoxan and remained below baseline until end of anaesthesia. HR remained unchanged from baseline (43 ± 5 beats minute^–1) with the saline treatment, whereas MAP decreased significantly (112 ± 16 mmHg) from baseline after 20 minutes. Pe′CO₂, f_R and SpO₂ showed no significant differences between treatments, whereas RT decreased significantly 25 minutes after vatinoxan. Level of anaesthesia was not significantly influenced by vatinoxan.Conclusions and clinical relevanceVatinoxan reversed hypertension and bradycardia induced by medetomidine without causing hypotension or affecting the level of anaesthesia in red deer. However, the effect on HR subsided 15 minutes after vatinoxan IV administration. Vatinoxan has the potential to reduce anaesthetic side effects in non-domestic ruminants immobilised with medetomidine–tiletamine–zolazepam.     

Pharmacokinetics and pharmacodynamics of l-methadone in isoflurane-anaesthetized and mechanically ventilated ponies

ObjectiveTo evaluate the pharmacokinetics and selected pharmacodynamic effects of a commercially available l-methadone/fenpipramide combination administered to isoflurane anaesthetized ponies.Study designProspective single-group interventional study.AnimalsA group of six healthy adult research ponies (four mares, two geldings).MethodsPonies were sedated with intravenous (IV) detomidine (0.02 mg kg^–1) and butorphanol (0.01 mg kg^–1) for an unrelated study. Additional IV detomidine (0.004 mg kg^–1) was administered 85 minutes later, followed by induction of anaesthesia using IV diazepam (0.05 mg kg^–1) and ketamine (2.2 mg kg^–1). Anaesthesia was maintained with isoflurane in oxygen. Baseline readings were taken after 15 minutes of stable isoflurane anaesthesia. l-Methadone (0.25 mg kg^–1) with fenpipramide (0.0125 mg kg^–1) was then administered IV. Selected cardiorespiratory variables were recorded every 10 minutes and compared to baseline using the Wilcoxon signed-rank test. Adverse events were recorded. Arterial plasma samples for analysis of plasma concentrations and pharmacokinetics of l-methadone were collected throughout anaesthesia at predetermined time points. Data are shown as mean ± standard deviation or median and interquartile range (p < 0.05).ResultsPlasma concentrations of l-methadone showed a rapid initial distribution phase followed by a slower elimination phase which is best described with a two-compartment model. The terminal half-life was 44.3 ± 18.0 minutes, volume of distribution 0.43 ± 0.12 L kg^–1 and plasma clearance 7.77 ± 1.98 mL minute^–1 kg^–1. Mean arterial blood pressure increased from 85 (±16) at baseline to 100 (±26) 10 minutes after l-methadone/fenpipramide administration (p = 0.031). Heart rate remained constant. In two ponies fasciculations occurred at different time points after l-methadone administration.Conclusions and clinical relevanceAdministration of a l-methadone/fenpipramide combination to isoflurane anaesthetized ponies led to a transient increase in blood pressure without concurrent increases in heart rate. Pharmacokinetics of l-methadone were similar to those reported for conscious horses administered racemic methadone.     

Effects of detomidine or romifidine during maintenance and recovery from isoflurane anaesthesia in horses

ObjectiveTo evaluate the effects of detomidine or romifidine on cardiovascular function, isoflurane requirements and recovery quality in horses undergoing isoflurane anaesthesia.Study designProspective, randomized, blinded, clinical study.AnimalsA total of 63 healthy horses undergoing elective surgery during general anaesthesia.MethodsHorses were randomly allocated to three groups of 21 animals each. In group R, horses were given romifidine intravenously (IV) for premedication (80 μg kg^–1), maintenance (40 μg kg^–1 hour^–1) and before recovery (20 μg kg^–1). In group D2.5, horses were given detomidine IV for premedication (15 μg kg^–1), maintenance (5 μg kg^–1 hour^–1) and before recovery (2.5 μg kg^–1). In group D5, horses were given the same doses of detomidine IV for premedication and maintenance but 5 μg kg^–1 prior to recovery. Premedication was combined with morphine IV (0.1 mg kg^–1) in all groups. Cardiovascular and blood gas variables, expired fraction of isoflurane (Fe′Iso), dobutamine or ketamine requirements, recovery times, recovery events scores (from sternal to standing position) and visual analogue scale (VAS) were compared between groups using either anova followed by Tukey, Kruskal-Wallis followed by Bonferroni or chi-square tests, as appropriate (p < 0.05).ResultsNo significant differences were observed between groups for Fe′Iso, dobutamine or ketamine requirements and recovery times. Cardiovascular and blood gas measurements remained within physiological ranges for all groups. Group D5 horses had significantly worse scores for balance and coordination (p = 0.002), overall impression (p = 0.021) and final score (p = 0.008) than group R horses and significantly worse mean scores for VAS than the other groups (p = 0.002).Conclusions and clinical relevanceDetomidine or romifidine constant rate infusion provided similar conditions for maintenance of anaesthesia. Higher doses of detomidine at the end of anaesthesia might decrease the recovery quality.     

Antagonistic effect of atipamezole, flumazenil and naloxone following anaesthesia with xylazine, tramadol and tiletamine/zolazepam combinations in pigs

ObjectiveTo evaluate the antagonistic effects of atipamezole (ATI), flumazenil (FLU) and naloxone (NAL) alone and in various combinations following administration of tiletamine–zolazepam–xylazine–tramadol.Study designProspective, experimental, randomized cross-over study.AnimalsEight Chinese miniature pigs (three females and five males) mean age 8 (range 7–10) months and bodyweight 57.5 (52.4–62.1) kg.MethodsAll animals were anaesthetized with tiletamine/zolazepam (3.0 mg kg^?1), xylazine (1.2 mg kg^?1) and tramadol (1.6 mg kg^?1) given intramuscularly (IM). Thirty minutes later, one of eight treatments was administered IM: saline control, ATI (0.12 mg kg^?1), FLU (0.1 mg kg^?1), NAL (0.03 mg kg^?1), ATI–FLU, FLU–NAL, ATI–NAL or ATI–FLU–NAL. After injection of antagonists the following times were recorded: to recovery of the palpebral, pedal and tail clamp reflexes, to head movement, sternal recumbency, standing and walking. Posture, sedation, analgesia, jaw relaxation and auditory response were scored at set times until 120 minutes after injection of antagonists. Heart rates, respiratory rates and rectal temperature were measured at those times. Data were analyzed by anova for repeated measures, followed by the Tukey’s test to compare differences between means, or by Kruskal–Wallis test as appropriate.ResultsFLU, NAL alone, or FLU–NAL did not effectively antagonize anaesthesia induced by tiletamine/zolazepam–xylazine–tramadol. ATI, ATI–FLU, ATI–NAL and ATI–FLU–NAL produced an immediate and effective recovery from anaesthesia. The combination of ATI–FLU–NAL was the most effective combination in antagonizing the anaesthetic effect. Adverse effects such as tachycardia, tachypnoea, excitement and muscle tremors were not observed during this study.Conclusion and clinical relevanceATI–FLU–NAL is the most effective combination for antagonizing tiletamine/zolazepam–xylazine–tramadol anaesthesia in pigs. However, ATI alone or in various combinations also provides effective antagonism.     

Recovery Quality After Romifidine Versus Detomidine Infusion During Isoflurane Anesthesia in Horses

To examine the influence of detomidine or romifidine on recovery quality from isoflurane anesthesia, 78 anesthetic records were reviewed, from horses that had received romifidine (group R) during premedication [80–120 μg kg⁻¹ IV], anesthetic maintenance (40 μg kg⁻¹ hour⁻¹ IV), and recovery (20 μg kg⁻¹ IV) or detomidine (group D), at doses of 10–20 μg kg⁻¹ IV, 5 μg kg⁻¹ hour⁻¹ IV, and 2.5 μg kg⁻¹ IV, respectively. Duration of the different recovery phases, the number of attempts to sternal and standing, scores for transition to standing (TrSta), balance and coordination once standing (BC), and final recovery score (FS) were compared between groups using a Mann–Whitney U-test, independent t-test, or chi-squared test, as appropriate (alpha 0.05). Parametric data are represented as the mean ± standard deviation, and nonparametric data as the median (interquartile range). Compared with group D (25 horses), horses in group R (53 horses) needed significantly fewer attempts to achieve sternal recumbency [R 1 (1–1) vs. D 1 (1–2)], remained significantly longer in sternal recumbency [R 10 (3–14,5) vs. D 5 (1–9,5) minutes], needed significantly less attempts to stand [R 1 (1–1) vs. D 2 (1–4)], and a significantly shorter time to stand after making their first attempt [R 0 (0–0) vs. D 3 (0–6) minutes], with significantly better scores for TrSta, BC, and FS in group R. The results suggest that, at the doses used, romifidine provides a better recovery quality.     

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

ObjectiveTo compare isoflurane alone or in combination with systemic ketamine and lidocaine for general anaesthesia in horses.Study designProspective, randomized, blinded clinical trial.AnimalsForty horses (ASA I-III) undergoing elective surgery.MethodsHorses 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 μg kg⁻¹ minute⁻¹) and ketamine (60 μg 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.ResultsHeart 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 μg 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 relevanceThese 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.     

Behavioural and cardiovascular effects of medetomidine constant rate infusion compared with detomidine for standing sedation in horses

ObjectiveTo compare the efficacy of a medetomidine constant rate infusion (CRI) with a detomidine CRI for standing sedation in horses undergoing high dose rate brachytherapy.Study designRandomized, controlled, crossover, blinded clinical trial.AnimalsA total of 50 horses with owner consent, excluding stallions.MethodsEach horse was sedated with intravenous acepromazine (0.02 mg kg^–1), followed by an α₂-adrenoceptor agonist 30 minutes later and then by butorphanol (0.1 mg kg^–1) 5 minutes later. A CRI of the same α₂-adrenoceptor agonist was started 10 minutes after butorphanol administration and maintained for the treatment duration. Treatments were given 1 week apart. Each horse was sedated with detomidine (bolus dose, 10 μg kg^–1; CRI, 6 μg kg^–1 hour^–1) or medetomidine (bolus dose, 5 μg kg^–1; CRI, 3.5 μg kg^–1 hour^–1). If sedation was inadequate, a quarter of the initial bolus of the α₂-adrenoceptor agonist was administered. Heart rate (HR) was measured via electrocardiography, and sedation and behaviour evaluated using a previously published scale. Between treatments, behaviour scores were compared using a Wilcoxon signed-rank test, frequencies of arrhythmias with chi-square tests, and HR with two-tailed paired t tests. A p value <0.05 indicated statistical significance.ResultsTotal treatment time for medetomidine was longer than that for detomidine (p = 0.04), and ear movements during medetomidine sedation were more numerous than those during detomidine sedation (p = 0.03), suggesting there may be a subtle difference in the depth of sedation. No significant differences in HR were found between treatments (p ≥ 0.09). Several horses had arrhythmias, with no difference in their frequency between the two infusions.Conclusions and clinical relevanceMedetomidine at this dose rate may produce less sedation than detomidine. Further studies are required to evaluate any clinical advantages to either drug, or whether a different CRI may be more appropriate.     

Anesthetic effects of ketamine–medetomidine–hydromorphone in dogs during high-quality,high-volume surgical sterilization program under field conditions

ObjectiveTo describe the anesthetic and adverse effects of an injectable anesthetic protocol in dogs as part of a high-volume sterilization program under field conditions in Belize.Study designProspective, observational, field study.AnimalsA total of 23 female and eight male dogs (14.2 ± 7.7 kg; age ≥ 8 weeks).MethodsUsing a volume per kg-based dose chart, dogs were administered ketamine (4.5 mg kg⁻¹), medetomidine (0.04 mg kg⁻¹) and hydromorphone (0.09 mg kg⁻¹) intramuscularly. After induction of anesthesia, an endotracheal tube was inserted and dogs were allowed spontaneous breathing in room air. Monitoring included peripheral oxygen saturation (SpO₂), mean arterial pressure (MAP), heart rate (HR), respiratory rate, rectal temperature and end-tidal carbon dioxide (Pe′CO₂). Meloxicam (0.2 mg kg⁻¹) was administered subcutaneously after surgery. Data were analyzed with linear models and chi-square tests (p < 0.05).ResultsOnset of lateral recumbency (3.4 ± 2 minutes) was rapid. Desaturation (SpO₂ < 90%) was observed at least once in 64.5% of dogs and was more frequent in large dogs (p = 0.019). Hypercapnia (Pe′CO₂ ≥ 50 mmHg; 6.7 kPa) was observed in 48.4% of dogs. MAP was 111 ± 19 mmHg, mean ± standard deviation. Hypertension (MAP ≥ 120 mmHg), bradycardia (HR ≤ 60 beats minute⁻¹) and tachycardia (HR ≥ 140 beats minute⁻¹) were observed in 45.2%, 16.1% and 3.3% of dogs, respectively. Hypotension and hypothermia were not observed. Sex was not significantly associated with any complication. Return of swallowing reflex and time to standing were 71 ± 23 and 152 ± 50 minutes after injection, respectively. Return of swallowing was significantly longer in large dogs.Conclusions and clinical relevanceAt the doses used, ketamine–medetomidine–hydromorphone was effective in dogs for high-volume sterilization. In this field setting, adverse effects included hypoventilation, hypoxemia and prolonged recovery.     

Sedative effects and pharmacokinetics of detomidine when administered intravenously and intravaginally as a gel in alpacas

ObjectivesTo evaluate the sedative effects and pharmacokinetics of detomidine gel administered intravaginally to alpacas in comparison with intravenously (IV) administered detomidine.Study designRandomized, crossover, blinded experiment.AnimalsA group of six healthy adult female Huacaya alpacas (70.3 ± 7.9 kg).MethodsAlpacas were studied on two occasions separated by ≥5 days. Treatments were IV detomidine hydrochloride (70 μg kg⁻¹; treatment DET–IV) or detomidine gel (200 μg kg⁻¹; treatment DET–VAG) administered intravaginally. Sedation and heart rate (HR) were evaluated at intervals for 240 minutes. Venous blood was collected at intervals for 360 minutes after treatment for analysis of detomidine, carboxydetomidine and hydroxydetomidine using liquid chromatography–tandem mass spectrometry. Measured variables were compared between treatments and over time using mixed model analysis. Data are presented as the mean ± standard error of the mean, and a p value of <0.05 was considered significant.ResultsOnset of sedation was faster in treatment DET–IV (1.6 ± 0.2 minutes) than in treatment DET–VAG (13.0 ± 2.5 minutes). Time to maximum sedation was shorter in treatment DET–IV (8.3 ± 1.3 minutes) than in treatment DET–VAG (25 ± 4 minutes). Duration of sedation was not different between treatments. There was a significant linear relationship between sedation score and plasma detomidine concentration. HR was less than baseline for 60 and 125 minutes for treatments DET–IV and DET–VAG, respectively. The maximal decrease in HR occurred at 15 minutes for both treatments. The mean maximum plasma concentration of detomidine, time to maximum concentration and bioavailability for treatment DET–VAG were 39.6 ng mL⁻¹, 19.9 minutes and 20%, respectively.Conclusions and clinical relevanceDetomidine administration at the doses studied resulted in moderate sedation when administered IV or intravaginally to alpacas.     

Behavioral responses following eight anesthetic induction protocols in horses

Objective To compare behavioral characteristics of induction and recovery in horses anesthetized with eight anesthetic drug protocols. Study design Randomized prospective experimental study. Animals Eight horses, 5.5 ± 2.4 years (mean ± SD) of age, and weighing 505 ± 31 kg. Methods After xylazine pre‐medication, each of eight horses was anesthetized on four occasions using one of eight different anesthetic induction protocols which incorporated various combinations of ketamine (KET), propofol (PRO), and thiopental (THIO): THIO 8 mg kg^?1; THIO 6 mg kg^?1 + PRO 0.5 mg kg^?1; THIO 4 mg kg^?1 + PRO 1 mg kg^?1; THIO 2 mg kg^?1 + PRO 1.5 mg kg^?1; KET 2 mg kg^?1; KET 1.5 mg kg^?1 + PRO 0.5 mg kg^?1; KET 1 mg kg^?1 + PRO 1 mg kg^?1; KET 0.5 mg kg^?1 + PRO 1.5 mg kg^?1. Quality of induction and recovery were scored from 1 (poor) to 5 (excellent), and time taken to achieve lateral recumbency, first movement, sternal recumbency, and standing were evaluated. Results Time taken to achieve lateral recumbency after drug administration differed significantly (p < 0.0001) among the various combinations, being shortest in horses receiving THIO‐8 (mean ± SD, 0.5 ± 0.3 minutes) and longest in horses receiving KET‐2 (1.4 ± 0.2 minutes). The best scores for induction quality were associated with KET‐1.5 + PRO‐0.5, and the worst scores for induction quality were associated with KET‐2, although the difference was not significant. Time to first movement varied significantly among drug protocols (p = 0.0133), being shortest in horses receiving KET‐2 (12.7 ± 3.6 minutes) and longest in horses receiving THIO‐8 (29.9 ± 1.5 minutes). Horses receiving THIO‐8 made the greatest number of attempts to attain sternal posture (6.5 ± 4.7) and to stand (1.6 ± 0.8). Horses in the THIO‐8 treatment also received the poorest recovery scores (3.3 ± 1.0 and 3.0 ± 0.7 for sternal and standing postures, respectively). The best recovery scores were associated with combinations comprised mainly of propofol. Conclusions Combining propofol with either ketamine or thiopental modifies behaviors associated with use of the individual drugs. Clinical relevance Quality of early anesthesia recovery in horses may be improved by some combinations of propofol with either thiopental or ketamine.     

A comparison of sedative effects of xylazine alone or combined with levomethadone or ketamine in calves prior to disbudding

ObjectiveTo compare the sedative effects of intramuscular xylazine alone or combined with levomethadone or ketamine in calves before cautery disbudding.Study designRandomized, blinded, clinical trial.AnimalsA total of 28 dairy calves, aged 21 ± 5 days and weighing 61.0 ± 9.3 kg (mean ± standard deviation).MethodsCalves were randomly allocated to three groups: xylazine (0.1 mg kg^–1) and levomethadone (0.05 mg kg^–1; group XL), xylazine (0.1 mg kg^–1) and ketamine (1 mg kg^–1; group XK) and xylazine alone (0.2 mg kg^–1; group X). Local anaesthesia (procaine hydrochloride) and meloxicam were administered subcutaneously 15 minutes after sedation and 15 minutes before disbudding. The calves’ responses to the administration of local anaesthesia and disbudding were recorded. Sedation was assessed at baseline and at intervals up to 240 minutes postsedation. Times of recumbency, first head lift and first standing were recorded. Drug plasma concentrations were measured.ResultsData were obtained from 27 animals. All protocols resulted in sedation sufficient to administer local anaesthesia and to perform disbudding. Sedation scores significantly correlated with drug plasma concentrations (p ≤ 0.002). Times to recumbency did not differ among protocols (2.8 ± 0.3, 3.1 ± 1.1 and 2.1 ± 0.8 minutes for groups XL, XK and X, respectively), whereas interval from drug(s) administration until first head lift was significantly shorter in group XK than X (47.3 ± 14.1, 34.4 ± 5.3 and 62.6 ± 31.9 minutes for groups XL, XK and X, respectively). The area under the time-sedation curve was significantly greater in group X than XK or XL (754 ± 215, 665 ± 118 and 1005 ± 258 minutes for groups XL, XK and X, respectively).Conclusions and clinical relevanceLevomethadone or ketamine with a low dose of xylazine produced short but sufficient sedation for local anaesthesia and disbudding with minimum resistance.     

Physiologic and blood gas effects of xylazine–ketamine versus xylazine–tiletamine–zolazepam immobilization of white-tailed deer before and after oxygen supplementation: a preliminary study

ObjectiveTo compare oxygenation and ventilation in white-tailed deer (Odocoileus virginianus) anesthetized with two treatments with and without oxygen supplementation.Study designRandomized, blinded, crossover study.AnimalsA total of eight healthy adult white-tailed deer weighing 49–62 kg.MethodsEach deer was anesthetized twice intramuscularly: 1) treatment XK, xylazine (2 mg kg^–1) and ketamine (6 mg kg^–1) and 2) treatment XTZ, xylazine (2 mg kg^–1) and tiletamine–zolazepam (4 mg kg^–1). With the deer in sternal position, arterial and venous blood was collected before and at 30 minutes during administration of oxygen at 1 L minute^–1 through a face mask. PaO₂ and heart rate (HR) were compared using two-way repeated measures anova. pH, PaCO₂ and lactate concentration were analyzed using mixed-effects linear models, p < 0.05.ResultsWhen breathing air, PaO₂ was < 80 mmHg (10.7 kPa) in six and seven deer with XK and XTZ, respectively, and of these, PaO₂ was < 60 mmHg (8.0 kPa) in three and five deer, respectively. With oxygen supplementation, PaO₂ increased to 128 ± 4 and 140 ± 5 mmHg (17.1 ± 0.5 and 18.7 ± 0.7 kPa), mean ± standard error, with XK and XTZ, respectively (p < 0.001). PaO₂ was not significantly different between treatments at either time point. HR decreased during oxygen supplementation in both treatments (p < 0.001). Lactate was significantly lower (p = 0.047) with XTZ than with XK (2.2 ± 0.6 versus 3.5 ± 0.6 mmol L^–1) and decreased (p < 0.001) with oxygen supplementation (4.1 ± 0.6 versus 1.6 ± 0.6 mmol L^–1). PaCO₂ increased in XTZ during oxygen breathing.Conclusions and clinical relevanceTreatments XK and XTZ resulted in hypoxemia, which responded to oxygen supplementation. Both treatments are suitable for immobilization of white-tailed deer under the study circumstances.     

Plasma histamine concentrations in horses administered sodium penicillin,guaifenesin–xylazine–ketamine and isoflurane with morphine or butorphanol

ObjectiveVarious drugs administered to horses undergoing surgical procedures can release histamine. Histamine concentrations were evaluated in horses prepared for surgery and administered butorphanol or morphine intraoperative infusions.Study designProspective studies with one randomized.AnimalsA total of 44 client-owned horses.MethodsIn one study, anesthesia was induced with xylazine followed by ketamine–diazepam. Anesthesia was maintained with guaifenesin–xylazine–ketamine (GXK) during surgical preparation. For surgery, isoflurane was administered with intravenous (IV) morphine (group M: 0.15 mg kg^–1 and 0.1 mg kg^–1 hour^–1; 15 horses) or butorphanol (group B: 0.05 mg kg^–1 and 0.01 mg kg^–1 hour^–1; 15 horses). Histamine and morphine concentrations were measured using enzyme-linked immunoassay before opioid injection (time 0), and after 1, 2, 5, 30, 60 and 90 minutes. In a subsequent study, plasma histamine concentrations were measured in 14 horses before drug administration (baseline), 15 minutes after IV sodium penicillin and 15 minutes after starting GXK IV infusion. Statistical comparison was performed using anova for repeated measures. Pearson correlation compared morphine and histamine concentrations. Data are presented as mean ± standard deviation. Significance was assumed when p ≤ 0.05.ResultsWith histamine, differences occurred between baseline (3.2 ± 2.4 ng mL^–1) and GXK (5.2 ± 7.1 ng mL^–1) and between baseline and time 0 in group B (11.9 ± 13.4 ng mL^–1) and group M (11.1 ± 12.4 ng mL^–1). No differences occurred between baseline and after penicillin or between groups M and B. Morphine concentrations were higher at 1 minute following injection (8.1 ± 5.1 ng mL^–1) than at 30 minutes (4.9 ± 3.1 ng mL^–1) and 60 minutes (4.0 ± 2.5 ng mL^–1). Histamine correlated with morphine at 2, 30 and 60 minutes.Conclusions and clinical relevanceGXK increased histamine concentration, but concentrations were similar with morphine and butorphanol.