Detomidine Injection Research Articles

Sedative effect and physiological changes in horses treated with intramuscular injection of detomidine and morphine

ABSTRACT: This study aimed to elucidate the sedative effect and physiological changes associated with the intramuscular injection of detomidine combined with morphine in horses. Six healthy crossbred horses, aged 2 to 10 years, were included. A crossover experimental design was used to compare the effects of intramuscular injection of 30 µg/kg of detomidine alone (IMD) and intramuscular administration of 30 µg/kg of detomidine and 0.1 mg/kg of morphine (IMDM). The degree of sedation, height of head above ground, were assessed at the time points before and 5, 10, 20, 30, 40, 50, 60, 75, 90, 105, and 120 minutes after drug administration, and heart rate, respiratory rate, systolic blood pressure, rectum temperature and intestinal motility were assessed at the time points before and 10, 20, 30, 40, 50, 60, 75, 90, 105, and 120 minutes after drug administration. The physiological parameters were analyzed using the Kruskal-Wallis test with Dunn’s post-hoc test and analysis of variance with t-test for independent samples and the sedation scores using the Friedman test and Mann Whitney U-test. P-values <0.05 indicated a statistically significant difference. IMDM promoted a higher sedative effect as compared to IMD, but the sedation occurred inconsistently. Additionally, a reduction in intestinal motility was observed with IMDM at 60, 75, 90, and 105 minutes after administration. IMDM promoted more variable sedation and prolonged reduction in the intestinal motility in the horses as compared to IMD.

Endoscopic Finding of Gastric Ulcer in Rural Horse and Relation with Gasterophilus spp

BACKGROUND: Gastric ulcer is one of the most common diseases in racehorses. Colic, weight loss and poor performance are some of the clinical signs. The second and third larval stages of the bot fly Gasterophilus spp live in the stomach of the horse. This parasite is often found in large numbers of horses in all of the countries. OBJECTIVES: The aim of this study was assessment of gastric ulcer in the rural horse and relation with Gasterophilus spp. METHODS: In a cross-sectional study twenty rural horses were randomly selected for endoscopic finding for gastric ulcer. Gender, age, keeping situation, type of feed, history of colic, hair coat condition, deworming plan and presence of GasterophilussSpp. were recorded in a sheet. The horses were kept fasted for 12 hours before endoscopic examination by a VET3M OLYMPUS (Japan). Sedation was done by injection of Detomidine (Detomo Vet ® ceva-Spain) 0.1ml/100kg to look for presence of gastric ulcers with grading and Gasterophilus spp. Statistical analysis of the data was performed with 95% confidence interval and P RESULTS: Out of 20 horses, 13(65%) horses were mares and 7(35%) were males and Mean±2SE of age was 8.9±4. Endoscopic observation showed 9 (45%) of the horses suffered from gastric ulcer. All of the ulcers were in non-glandular part and near the margo plicatus. Overall, 4 (20%) head of the horses had Gasterophilus spp. and all of them were present in the horse with no deworming plan. Based on the results, there was no associ- ation between presence of Gasterophilus with occurrence of Gastric ulcer (P>0.05). Further study with high sample size is proposed. CONCLUSIONS: There was high frequency of gastric ulcer in non-glandular portion of stomach in rural horse and there was not any association between presence of Gasterophilus and gastric ulcer.

Sedative and Respiratory Effects of Intramuscular Detomidine and Butorphanol in Donkeys Sedated for Bronchoalveolar Lavage

The aim of this study was to evaluate the effects of intramuscular (IM) detomidine and butorphanol on sedation, arterial blood gases, and bowel motility in sixteen healthy Amiata donkeys undergoing bronchoalveolar lavage (BAL). Before administration of detomidine and butorphanol, baseline values for heart rate (HR), respiratory frequency (fr), rectal temperature, arterial blood gases, and sedation score (range 0–9) were recorded as Tbase and bowel motility was assessed. Sedation was assessed with a composite sedation scale. After IM injection of detomidine 0.06 mg kg−1 and butorphanol 0.05 mg kg−1, HR, fr, temperature, and sedation score were registered every 5 minutes. Arterial blood was sampled when sedation score was greater than or equal to 6 right before performing the diagnostic procedure (T1) and at a sedation score of 3 or lower, which was considered the end of sedation (T2). Bowel motility was assessed every hour after the end of sedation. Sedation score of 6 or more was reached after 10 minutes in all animals. Mean sedation time was 38.8 ± 5.2 minutes. PaO2, HR, and fr were significantly lower at T1 and T2 compared to Tbase values. Fshunt significantly increased at T2, in comparison to Tbase. Time from injection to return to normal bowel motility was 272 ± 62 minutes. Intramuscular detomidine and butorphanol provided satisfactory sedation for BAL in donkeys, in terms of reliability and duration. Clinicians should be aware of the reduction of PaO2 that can arise.

The effect of detomidine on clinical signs, serum electrolytes, electrocardiographic indices, and cardiac arrhythmias in Camelus dromedarius

The aim of this study was to document sedation and analgesic effects, electrocardiographic (ECG) parameters, and some physiologic variable and serum concentrations of electrolytes after intravenous (IV) administration of detomidine in camels. Five healthy female dromedary camels (Camelus dromedarius) aged 2 years and average weight of 200 ± 20 kg were used. Data were recorded before and 3, 5, 10, 15, 30, 45, 60, and 90 min after IV administration of detomidine (50 μg kg−1). Sedation and antinociception response were recorded. The ECG was attached as a bipolar base-apex lead, and indices measured and analyzed were P, QRS, and T wave amplitude, duration and configuration, and duration of P-R, Q-T, and R-R intervals. Venous blood was collected for the measurement of sodium (Na+), potassium (K+), chloride (Cl−), calcium (Ca2+), magnesium (Mg2+), and phosphorus (P−) concentrations. Posture and behavioral observed after detomidine administration were depression, swaying, tremors, muscular weakness, nasal discharge, drooling, drooping of head and lower lip, hind limb ataxia, anorexia, frequent urination, staggering, snoring, and nystagmus. Significantly increased in sedation scores and antinociception grades were seen. Heart rate (HR) was significantly decreased. Amplitude of P, QRS, and T waves, and P-R interval durations were not significantly changed from baseline during sedation. Durations of Q-T and R-R intervals were significantly prolonged after detomidine injection (p 0.05). Detomidine produced a rapid and reliable sedation and antinociception, and could be used for a variety of diagnostic and surgical procedures in C. dromedarius without cardiopulmonary disease in the field.

Comparison of midazolam and diazepam as co-induction agents with ketamine for anaesthesia in sedated ponies undergoing field castration

ObjectiveTo compare intravenous (IV) midazolam and diazepam administered with ketamine for induction of anaesthesia in ponies, already sedated with detomidine, undergoing field castration. Study designProspective, randomised, ‘blinded’, clinical study. AnimalsTwenty Welsh pony yearlings. MethodsAfter IV injection of detomidine (20 μg kg−1) and phenylbutazone (4.4 mg kg−1) ponies were allocated to receive either IV midazolam (group M) or diazepam (group D) (both 0.06 mg kg−1) with ketamine (2.2 mg kg−1) for induction of anaesthesia. Using simple descriptive scales, quality of sedation, induction, endotracheal intubation, surgical conditions and recovery were scored by observers blinded to treatment. Time from sedation to induction of anaesthesia, IV injection to lateral recumbency, induction to start of surgery, induction to first head lift and to standing, and total surgical time were measured. Cardiorespiratory function was assessed every 5 minutes. Time, number and total quantity of additional IV ketamine as well as any adverse effects were documented. Data were tested for normality and analysed using two-way anova with Bonferroni post hoc tests, unpaired t-tests and Mann–Whitney U tests as appropriate. Significance was set at p < 0.05. ResultsThere were no significant group differences in any of the measured variables except bodyweight (mean ± SD: group M 163 ± 12 kg; group D 150 ± 7 kg; p = 0.01). One pony in group M required ketamine 15 minutes after induction of anaesthesia. Surgical conditions were good in all cases; time from induction to standing was 50 ± 11 minutes in group M and 48 ± 12 minutes in group D. There were no adverse effects. Recoveries were uneventful with minimal ataxia. Conclusions and clinical relevanceMidazolam and diazepam at 0.06 mg kg−1 can be used interchangeably in combination with ketamine for IV induction of short term anaesthesia in ponies.

English

Datura innoxia indigenous shrub in South Asia region belongs to the family Solanaceae which contains medicinal important alkaloids (hyoscine, atropine, hycosamine, etc). Thirty adult rabbits of mixed breed, male and female were pretreated with 0.1 mg/500 mg of crude extract (1% of dimethyl sulfoxide (DMSO) solution) and injected 5 min later with 0.01 mg/500 mg of detomidine (group A, n=15) or Saline (group B, n=15). Mean arterial pressure, measurements and electrocardiography were performed for 65 min. After injecting crude extract of D. innoxia, the heart rate was increased by 45 and 46.34% in groups A and B, respectively. Heart rate remained increased after the injection of detomidine returning to base line values after 15 min. No increase in the mean arterial pressure (MAP) was noted in group B rabbits. Crude extract shortened PR and QT interval in both groups but after detomidine, PR and QT interval were enlarged significantly at the end of the experiment. The second degree atrioventricular was blocked in two rabbits after 40 min only in group B. It was concluded that alkaloid present in D. innoxia prevented detomidine induced Bradycardia and might be useful during combination against the Bradycardia induced by alpha-2 agonist in the rabbits. Key words: Datura innoxia, crude extract, rabbits, detomidine.

Evaluation of the sedative, analgesic, clinicophysiological and haematological effects of intravenous detomidine, detomidine‐butorphanol, romifidine and romifidine‐butorphanol in standing donkeys

SummaryThe aim of this investigation was to determine and evaluate the sedative, analgesic, clinicophysiological and haematological effects of intravenous (i.v.) injection of detomidine, detomidine‐butorphanol, romifidine and romifidine‐butorphanol. Six standing donkeys were used. Each donkey received 4 i.v. treatments and the order of treatment was randomised with a one‐week interval between each treatment. We found that i.v. injection of a combination of detomidine‐butorphanol or romifidine‐butorphanol produced potent neuroleptanalgesic effects thus providing better, safe and effective sedation with complete analgesia in standing donkeys compared with injection of detomidine or romifidine alone. The changes and reduction in pulse rate were within acceptable limits. The changes in clinicophysiological, haematological and biochemical values were mild and transient in these clinically healthy donkeys.

α2-Adrenoceptor-mediated Inhibitory and Excitatory Effects of Detomidine on Rat Gastric Acid Secretion

The effects of the selective alpha 2-adrenoceptor agonist detomidine on gastric acid secretion from pylorus-ligated and stomach-perfused rats have been investigated. In pylorus-ligated rats i.p. injection of detomidine markedly inhibited acid secretion, this effect being prevented by yohimbine or idazoxan. Under the same conditions, idazoxan significantly increased secretion in a dose-independent fashion. In non-vagotomized and vagotomized stomach-perfused rats i.p. detomidine stimulated acid secretion: this excitatory effect was antagonized by idazoxan. The present results suggest that both inhibitory and excitatory gastric secretory effects of detomidine are mediated by alpha 2-adrenoceptors on cholinergic and adrenergic nerves, respectively. The stimulant activity of idazoxan on gastric secretion from pylorus-ligated rats may be interpreted in terms of increased excitatory vagal tone following the blockade of inhibitory alpha 2-adrenoceptors.

Analgesic And Cardio-Pulmonary Effects Induced By Lumbosacral Epidural Injection Of Detomidine In Goats

The present study was carried out in order to evaluate analgesia, heart and respiration rates and rectal temperature values after lumbosacral epidural injection of three doses (20, 40 and 80 Kg/kg) of detomidine in Small East African goats. Twelve clinically healthy, adult, goats of both sexes whose weight ranged from 13 to 22 (mean ± SD; 16.5 ± 2.6) kg were used. Six out of the twelve goats were randomly assigned separately to each treatment group and at least one-week interval was left between subsequent injections. Heart and respiration rates and rectal temperature values were determined at time 0 (pre-injection) and at 5, 10, 15, 20, and 30 minutes, thereafter at 15 minutes intervals up to 180 minutes after injection. Analgesia was determined after cardio-pulmonary measurements in unrestrained animal before administration of analgesics and thereafter at 5, 10, 15, 30 60, 120 and 180 minutes. All three doses induced adequate analgesia of the flank and perineum within 5 minutes, and persisted for the entire 180 minutes of the observation period. No significant differences were found between the analgesic effects of the three tested doses of detomidine. All doses induced significant drop of the mean respiration rate (RR) within 5 to 10 minutes. The RR depression effect persisted for the entire 180 minutes of the observation period. Significant drop of the mean heart rate (HR) was observed only for the two lower doses of 20 and 40 Kg/kg and persisted for 120 and 90 minutes respectively. All three doses induced a considerable rise in rectal temperature (RT) values that was followed by a gradual fall to normal. It was concluded that a two to four fold increase in the dose of detomidine administered through the lumbosacral epidural space does not increase the level and duration of the flank and perineal analgesia in Small East African goats. Tanzania Veterinary Journal Vol. 24 (2) 2007: pp. 102-111

Comparison of intraoperative pain responses following intratesticular or mesorchial injection of lidocaine in standing horses undergoing laparoscopic cryptorchidectomy

To compare pain responses in stallions undergoing standing laparoscopic cryptorchidectomy following intratesticular or mesorchial infiltration of lidocaine. Clinical trial. 20 stallions with 1 or 2 undescended testes. Standing horses were administered a nonsteroidal anti-inflammatory drug and a caudal epidural injection of detomidine hydrochloride and underwent laparoscopic cryptorchidectomy. The undescended testis (1/horse) was grasped to determine the preoperative pain response (present vs absent) and assess severity of pain (by use of a visual analog scale [VAS]). The undescended testis or its mesorchium was injected with 2% lidocaine (10 mL); saline (0.9% NaCl) solution (10 mL) was injected in the untreated structure. Presence and severity of pain was determined by 2 individuals as the testis was grasped following infiltration and at the times of ligature placement and transection of the spermatic cord. Serum cortisol concentration was analyzed preoperatively, after ligation, and after transection. Presence or absence of signs of pain, severity of pain, and serum cortisol concentrations were compared within and between treatment groups. Detection of signs of pain and VAS pain scores did not differ between observers at any time point. Perceived pain responses associated with ligature placement differed significantly from preoperative responses. Pain responses and serum cortisol concentrations after intratesticular and mesorchial infiltration of lidocaine did not differ. Results suggested that intratesticular or mesorchial infiltration of lidocaine combined with administration of a nonsteroidal anti-inflammatory drug and caudal epidural injection of detomidine provides adequate analgesia in standing stallions undergoing laparoscopic cryptorchidectomy.

Effects of detomidine HCl on the biochemical and cytological properties of synovial fluid after administration into the radiocarpal joint in horses

Detomidine may induce analgesia when administered at peripheral sites, e.g., at joint cavities or around nerves. The purpose of this study was to document the effects of detomidine HCl on biochemical and cytological properties of synovial fluid in horses. Five horses underwent clinical examination for lameness and flexion test to document limb health prior to acceptance to the study. Synovial fluids were taken from both radiocarpal joints, and 20 μg/kg detomidine HCl diluted in 3 ml saline and 3.2 ml saline was injected randomly to joints at day 0. Synovial fluid collection from the joints was performed at days 1, 2, and 7 after injection. Twenty-five-meter straight-line trot was used to assess lameness at days 1, 2, and 7 post detomidine injection. Total white blood cells (WBC), cytological examination, total protein, specific gravity, alkaline phosphates (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine phosphokinase (CK), glucose, and quality of mucin clot were measured. No detectable lameness was observed throughout the study. Mucin clot quality test revealed no significant differences between various sampling times (P>0.05). Cytological examination of synovial fluid of horses showed no significant differences between various sampling times for total WBC and also various types of leukocytes (P>0.05). The amount of total protein, specific gravity, ALP, CK, glutamic–pyruvic transaminase (GPT), and glucose revealed no significant differences between various sampling times between test and control groups (P>0.05). The only significant difference was seen at day 7 for AST between test and control groups (P<0.05).

EFFECTS OF XYLAZINE, MEDETOMIDINE, DETOMIDINE, AND DIAZEPAM ON SEDATION, HEART AND RESPIRATORY RATES, AND CLOACAL TEMPERATURE IN ROCK PARTRIDGES (ALECTORIS GRAECA)

In this study, heart and respiratory rates, cloacal temperature, and quality of sedation were evaluated before (0 min) and after (10, 20, and 30 min) i.m. administration of xylazine (10 mg/kg; n = 7), medetomidine (75 li; n = 6), detcmidine (0.3 mg/kg; n = 6), or diazepam (6 mg/kg; n = 7) in rock partridges (Alectoris graeca). All partridges recovered from sedation without any disturbance. Xylazine and diazepam administration did not induce significant changes in heart rate, which did decrease significantly after medetomidine and detomidine administration (P < 0.001). Mean respiratory rate was decreased dramatically at 20 and 30 min after xylazine (P < 0.001) and medetomidine (P < 0.005) administration, and at all stages of sedation after detomidine injection (P < 0.001), whereas there was not any significant change after diazepam injection. In all groups, cloacal temperature measured at 10, 20, and 30 min tended to decrease compared with baseline values. Sedative effects of the drugs started within 2.1+/-0.2 min for detomidine, 2.6 +/- 0.4 min for diazepam, 3.1 -+/-.4 min for xylazine, and 4.8+/-0.8 min for medetomidine application. There was an extreme variability in time to recovery for each drug: 205 +/-22.2 min for xylazine, 95 -12.2 min for medetomidine, 260+/-17.6 min for detomidine, and 149 + 8.3 min for diazepam. In conclusion, xylazine, medetomidine, detomidine, and diazepam produced sedation, which could permit some clinical procedures such as handling and radiographic examination of partridges to occur. Of the four drugs, xylazine produced stronger and more efficient sedation compared to the others, which could permit only minor procedures to be performed. However, depending on the drug used, monitoring of heart and respiratory rates and cloacal temperature might be required.

The relationship of muscle perfusion and metabolism with cardiovascular variables before and after detomidine injection during propofol–ketamine anaesthesia in horses

ObjectivesTo study in horses (1) the relationship between cardiovascular variables and muscle perfusion during propofol–ketamine anaesthesia, (2) the physiological effects of a single intravenous (IV) detomidine injection, (3) the metabolic response of muscle to anaesthesia, and (4) the effects of propofol–ketamine infusion on respiratory function. Study designProspective experimental study. AnimalsSeven standardbred trotters, 5–12 years old, 416–581 kg. MethodsAnaesthesia was induced with intravenous (IV) guaifenesin and propofol (2 mg kg−1) and maintained with a continuous IV infusion of propofol (0.15 mg kg−1 minute−1) and ketamine (0.05 mg kg−1 minute−1) with horses positioned in left lateral recumbency. After 1 hour, detomidine (0.01 mg kg−1) was administered IV and 40–50 minutes later anaesthesia was discontinued. Cardiovascular and respiratory variables (heart rate, cardiac output, systemic and pulmonary artery blood pressures, respiratory rate, tidal volume, and inspiratory and expiratory O2 and CO2) and muscle temperature were measured at pre-determined times. Peripheral perfusion was measured continuously in the gluteal muscles and skin using laser Doppler flowmetry (LDF). Muscle biopsy samples from the left and right gluteal muscles were analysed for glycogen, creatine phosphate, creatine, adenine nucleotides, inosine monophosphate and lactate. Arterial blood was analysed for PO2, PCO2, pH, oxygen saturation and HCO3. Mixed venous blood was analysed for PO2, PCO2, pH, oxygen saturation, HCO3, cortisol, lactate, uric acid, hypoxanthine, xanthine, creatine kinase, creatinine, aspartate aminotransferase, electrolytes, total protein, haemoglobin, haematocrit and white blood cell count. ResultsCirculatory function was preserved during propofol–ketamine anaesthesia. Detomidine caused profound hypertension and bradycardia and decreased cardiac output and muscle perfusion. Ten minutes after detomidine injection muscle perfusion had recovered to pre-injection levels, although heart rate and cardiac output had not. No difference in indices of muscle metabolism was found between dependent and independent muscles. Anaerobic muscle metabolism, indicated by decreased muscle and creatine phosphate levels was evident after anaesthesia. ConclusionMuscle perfusion was closely related to cardiac output but not arterial blood pressure. Total intravenous anaesthesia with propofol–ketamine deserves further study despite its respiratory depression effects, as the combination preserves cardiovascular function. Decreases in high-energy phosphate stores during recovery show that muscle is vulnerable after anaesthesia. Continued research is required to clarify the course of muscle metabolic events during recovery.

Evaluation of the effect of hyoscine-N-butyl bromide on the cardiovascular actions of detomidine in the horse

Twenty one adult horses, males and females, were pretreated with 0.14 mg/kg of hyoscine-N-butylbromide intravenously and injected 5 minutes later with 0.02 mg/kg, iv of detomidine (group A, n = 9) or saline (group B, n = 12). Mean arterial pressure measurements and electrocardiography were performed during 65 minutes. After hyoscine injection the heart rate was increased by 43% and 65% in A and B groups, respectively. Heart rate remained increased after injection of detomidine, returning to baseline values after 15 minutes. No increase in the mean arterial pressure (MAP) was noticed after hyoscine but the MAP was increased by 62% after detomidine, returning to basal measurements until the end of observation time. No additional increase was noted in the group B horses. Hyoscine shortened PR and QT intervals in both groups, but after detomidine, PR and QT intervals enlarged significantly at the end of the experiment. The second degree atrioventricular block occurred in 3 horses after 40 minutes only in group B. It was concluded that hyoscine prevented detomidine induced bradycardia and may be an useful drug combination against the bradycardia induced by this alpha-2 agonist, in horses.

Development and characterization of an equine behaviour chamber and the effects of amitraz and detomidine on spontaneous locomotor activity.

This report describes the development of a behaviour chamber and the validation of the chamber of measure locomotor activity of a horse. Locomotor activity was detected by four Mini-beam sensors and recorded on a data logger every 5 min for 22 h. Horses were more active during daytime than in the evening, which was at least partially related to human activity in their surroundings. To validate the ability of the chambers to detect changes in activity, fentanyl citrate and xylazine HCl, agents well-characterized as a stimulant and a depressant, respectively, were administered to five horses. Fentanyl citrate (0.016 mg/kg) significantly increased locomotor activity which persisted for 30 min. Xylazine HCl (1 mg/kg) significantly reduced locomotor activity for 90 min. Amitraz produced a dose-dependent decrease in locomotor activity, lasting 75 min for the 0.05 mg/kg dose, 120 min for the 0.10 mg/kg dose, and 180 min for the 0.15 mg/kg dose. In a separate experiment, yohimbine administration immediately reversed the sedative effect of amitraz. This suggests there is a similarity in the mode of action of amitraz, xylazine and detomidine, as yohimbine acts primarily by blocking central alpha 2 -adrenoceptors that are stimulated by agents like xylazine. There was also a significant decrease in locomotor activity following injection of detomidine (0.02, 0.04 and 0.08 mg/kg) for 1.5, 3.5 and 5.0 h, respectively. The locomotor chamber is a useful, sensitive and highly reproducible tool for measuring spontaneous locomotor activity in the horse, which allows investigators to determine an agent's average time of onset, duration and intensity of effect on movement.

Effects of detomidine in young water buffalo

SUMMARY Following preliminary studies with detomidine hydrochloride in 10 young buffaloes (Bubalus bubalis), the effects of an intramuscular injection of 40 /ixg.kg −1 were studied in 6 healthy buffaloes of VA to 2 years of age, weighing between 85 and 140 kg. Arterial blood pressure, central venous pressure, heart rate, electrocardiogram, electroencephalogram, respiratory rate, arterial pH, arterial and venous blood gases and rectal temperature were monitored before, and for an hour after, intramuscular injection of detomidine. Marked ataxia and sternal recumbency occurred within 10 minutes of injection, and an apparent complete recovery occurred in about 90 minutes. The electroencephalograms never demonstrated the high-voltage-low-frequency wave forms normally associated with sedation, but the animals appeared well sedated. After injection there was marked decrease in heart rate which then tended to increase but it remained significantly (P Rectal temperature, arterial pH, arterial carbon dioxide tension, standard bicarbonate and cranial vena caval oxygen tension did not show any significant variation. Respiratory rate and arterial oxygen tension decreased significantly.

Propofol compared with propofoVguaiphenesin after detornidine premedication for equine surgery

Anaesthesia using propofol alone and in combination with guaiphenesin, after detomidine premedication, was evaluated for performance of minor surgical procedures (castration and tenotomy) in horses. Twelve male horses were premedicated with 0.015 mg/kg of detomidine intravenously (iv) and divided into two groups of six. One group of horses received 2 mg/kg of propofol iv and the other group received 0.5 mg/kg of propofol mixed with 100 mg/kg of a 7.5% solution of guaiphenesin in saline iv. Induction of anaesthesia was fast and smooth in both groups. All horses were easily intubated immediately afterwards but intubation was easier in the horses which received propofol and guaiphenesin. Heart rate fell by 20% in both groups after detomidine injection, stabilising between 45 and 53 beats/minute during anaesthesia with no difference between the groups. Respiratory depression developed after detomidine injection and was slightly intensified after induction of anaesthesia. Respiratory rate was significantly lower in the propofol group (14 ± 3 breaths/minute) than with propofol/guaiphenesin (19 ± 4 breaths/minute) at five minutes after induction. Anaesthesia induced respiratory acidosis in both groups and hypoxaemia also occurred, but once the horses stood up the arterial blood oxygen partial pressure returned to basal values. Surgical time ranged between 8 and 16 minutes and with the exception of one horse in the propofol/guaiphenesin group the horses did not show signs of pain or discomfort during surgery. Recovery to standing was fast and took 26 ± 2 minutes in the propofol and 29 ± 5 minutes in the propofol/guaiphenesin group. Most horses stood up at the first attempt with minimal ataxia. These two anaesthetic techniques appear to be useful for minor surgical procedures performed within 16 minutes of induction of anaesthesia.

The influence of detomidine and epinephrine on heart rate, arterial blood pressure, and cardiac arrhythmia in horses.

Detomidine (10 micrograms/kg and 20 micrograms/kg) was administered to seven horses with and without epinephrine infusion (0.1 microgram/kg/min) from 5 minutes before to 5 minutes after detomidine injection. One or more single supraventricular premature heartbeats were observed in three horses after detomidine administration. Epinephrine infusion did not modify the incidence of cardiac arrhythmias in detomidine-treated horses at the doses tested. Relatively high momentary peak systolic pressures were registered in some horses after detomidine administration during epinephrine infusion. The highest systolic arterial blood pressure was 290 mm Hg, but this value was not higher than that reported in horses during maximum physical exercise. Epinephrine infusion did not alter blood gases, arterial pH, or base excess.

Modulation of gastric acid secretion by peripheral presynaptic α2‐adrenoceptors at both sympathetic and parasympathetic pathways

1. The effects of the alpha 2-adrenoceptor agonist detomidine, and the antagonists idazoxan and CH-38083 were examined on gastric acid secretion from non-vagotomized and vagotomized stomach lumen-perfused rats. The effects of detomidine on acid secretion from isolated guinea-pig gastric fundus were also evaluated. 2. In both non-vagotomized and vagotomized rats i.p. administration of detomidine significantly increased acid secretion, whereas i.c.v. detomidine was without effect. The stimulant action of i.p. detomidine was antagonized by both i.p. idazoxan and CH-38083 as well as by pretreatment with reserpine. 3. In vagotomized and reserpinized rats whose acid secretion was increased by electrical stimulation of the left vagus nerve, i.p. injection of detomidine caused inhibitory effects on acid secretion which were fully antagonized by both i.p. idazoxan and CH-38083. 4. Both idazoxan and CH-38083 caused a significant increase in acid secretion induced by vagal stimulation. At higher doses the two antagonists displayed a potentiating effect on vagally induced acid secretion only when they were associated to i.v. infusion of prazosin and propranolol. 5. Detomidine was without effect on acid secretion from isolated guinea-pig gastric fundus, whereas histamine or bethanechol caused a marked and dose-dependent stimulant action. 6. Overall, these results provide evidence that peripheral presynaptic alpha 2-adrenoceptors modulate both adrenergic inhibitory and cholinergic excitatory influences on rat gastric acid secretion.

The influence of atipamezole on the cardiovascular effects of detomidine in horses

The reversal of the cardiovascular effects of the α2-adrenoceptor agonist detomidine by the α2-antagonist atipamezole was studied. Nine horses were given detomidine 20 μg/kg iv. On a separate occasion they were given atipamezole 100 μg/kg iv 15 mins after the detomidine injection. Blood gas tensions were measured and clinical signs of sedation were also observed. Bradycardia and the frequency of heart blocks induced by detomidine were reduced after atipamezole and blood pressure decreased. These reversal effects of atipamezole were of short duration (a few minutes) at the dose level tested. Two of the nine horses exhibited premature depolarisations after administration of detomidine, but not after atipamezole injection. PaO2 decreased and PaCO2 increased slightly after detomidine injection, but the arterial pH was within reference values or slightly elevated. Administration of atipamezole did not alter these values. Base excess rose after detomidine, and it decreased more quickly towards the baseline level, when the horses were given detomidine alone. No clinical adverse effects were seen from the administration of atipamezole. Atipamezole may be beneficial, if detomidine-induced bradycardia needs to be reversed in horses.