Detomidine Infusion Research Articles

Effects of vatinoxan on gastrointestinal motility during and after a long‐lasting detomidine infusion in horses

Effects of vatinoxan on gastrointestinal motility during and after a long‐lasting detomidine infusion in horses

Effect of constant rate infusion of detomidine with and without vatinoxan on blood glucose and insulin concentrations in horses

ObjectiveTo assess the effects of an α2-adrenoceptor agonist (detomidine) constant rate infusion (CRI) with and without an α2-adrenoceptor antagonist (vatinoxan) CRI on blood insulin and glucose concentrations, heart rate, intestinal borborygmi, and sedation during and after infusion in horses. Study designRandomized, blinded, crossover, experimental study. AnimalsA total of nine healthy, adult Finnhorse mares. MethodsHorses were treated with an intravenous (IV) detomidine loading dose (0.01 mg kg–1), followed by CRI (0.015 mg kg–1 hour–1), and the same doses of detomidine combined with an IV vatinoxan loading dose (0.15 mg kg–1), followed by CRI (detomidine and vatinoxan; 0.05 mg kg–1 hour–1) with an 18 day washout period. Infusion time was 60 minutes and horses were monitored for 240 minutes after the infusion. Heart rate, borborygmi score and sedation were assessed, and blood glucose, insulin and triglyceride concentrations were measured. Data were analyzed using repeated measures ancova and Wilcoxon signed-rank tests. Values of p < 0.05 were considered statistically significant. ResultsInsulin concentration decreased during (median nadir 1.7, range 0.0–2.9 μIU mL–1 at 60 minutes, p < 0.0001) and increased after detomidine CRI (median 36.6, range 11.7–78.4 μIU mL–1 at 180 minutes, p = 0.0001) significantly compared with detomidine and vatinoxan CRI. A significant elevation of blood glucose (peak 11.5 ± 1.6 mmol L–1 at 60 minutes, p < 0.0001) was detected during detomidine CRI. Vatinoxan alleviated the insulin changes and abolished the significant increase in blood glucose. Vatinoxan alleviated the decrease in heart rate (p = 0.0001) during detomidine infusion. No significant differences were detected in sedation scores between treatments. Conclusions and clinical relevanceVatinoxan attenuated the negative adverse effects of detomidine CRI and thus is potentially beneficial when used in combination with an α2-adrenoceptor agonist CRI in horses.

Evaluation of lung ventilation distribution using electrical impedance tomography in standing sedated horses with capnoperitoneum

ObjectiveTo determine changes in distribution of lung ventilation with increasing intra-abdominal pressure (IAP) from carbon dioxide (CO2) insufflation in standing sedated horses. Study designProspective experimental study. AnimalsA group of six healthy adult horses. MethodsEach horse was sedated with acepromazine, detomidine and butorphanol and sedation maintained with a detomidine infusion. The horse was restrained in a stocks system and a 32 electrode electrical impedance tomography (EIT) belt was wrapped around the thorax at the fifth–sixth intercostal space. EIT images and arterial blood samples for PaO2 and PaCO2, pH and lactate concentration were obtained during capnoperitoneum at 0 (baseline A), 5, 8 and 12 mmHg as IAP increased and at 8, 5, 0 (baseline B) mmHg as IAP decreased. At each IAP, after a 2 minute stabilization period, EIT images were recorded for ≥ 2 minutes to obtain five consecutive breaths. Statistical analysis was performed using anova for repeated measures with Geisser-Greenhouse correction and a Tukey’s multiple comparison test for parametric data. The relationship between PaO2 and the center of ventilation in the ventral-dorsal (CoV-VD) and right-left (CoV-RL) directions or total impedance change as a surrogate for tidal volume (ΔZVT) were tested using linear regression analysis. Significance was assumed when p ≤ 0.05. ResultsThere were no significant changes in CoV-VD, CoV-RL, PaO2, PaCO2, lactate concentration, pH, heart rate and respiratory rate with targeted IAP. There was a significant decrease in ΔZVT compared with baseline A at 5 mmHg IAP as IAP was increased. Conclusions and clinical relevanceCapnoperitoneum causes a significant decrease in ΔZVT in standing sedated horses with increasing IAP.

Effect of different inspired fractions of oxygen on F-shunt and arterial partial pressure of oxygen in isoflurane-anaesthetized and mechanically ventilated Shetland ponies

ObjectiveTo determine the effect of fraction of inspired oxygen (FiO2) on intrapulmonary shunt fraction as measured by F-shunt in ponies during isoflurane anaesthesia. Study designProspective, randomized clinical study. AnimalsA group of 23 adult Shetland ponies undergoing a total of 32 anaesthetic procedures. MethodsPonies were premedicated intravenously (IV) with detomidine (0.01 mg kg–1) and either morphine (0.1 mg kg–1) or butorphanol (0.02 mg kg–1). Anaesthesia was induced with ketamine (2.2 mg kg–1) and midazolam (0.07 mg kg–1) administered IV. Ponies were randomly allocated to maintenance of anaesthesia with isoflurane in oxygen (group TH; FiO2 = 0.95) or a mixture of oxygen and medical air (group TL; FiO2 = 0.65); all ponies were given a constant rate of infusion of detomidine. Animals were mechanically ventilated to maintain PaCO2 between 40 and 50 mmHg. Arterial blood gas analysis was performed every 30 minutes. The F-shunt equation was calculated for each time point T0, T30, T60 and T90. Data were analysed using linear mixed model analysis and presented as mean ± standard deviation (p < 0.05). ResultsPaO2 was greater in group TH than in group TL (TH: 406 ± 90, 438 ± 83, 441 ± 69 and 464 ± 53 mmHg versus TL: 202 ± 90, 186 ± 84, 172 ± 85 and 191 ± 98 mmHg at T0, T30, T60 and T90, respectively; p < 0.0001). In TH, F-shunt was < TL. Significant differences were found at T60 (TH: 13.2% ± 4.3 versus TL: 19.4% ± 8.3; p = 0.016) and T90 (TH: 11.7% ± 3.5 versus TL: 18.6% ± 9.5; p = 0.036). Conclusions and clinical relevanceOur findings do not support a beneficial effect of using a reduced FiO2 to improve oxygenation in anaesthetized and mechanically ventilated Shetland ponies.

Development and validation of the facial scale (FaceSed) to evaluate sedation in horses.

Although facial characteristics are used to estimate horse sedation, there are no studies measuring their reliability and validity. This randomised controlled, prospective, horizontal study aimed to validate a facial sedation scale for horses (FaceSed). Seven horses received detomidine infusion i.v. in low or high doses/rates alone (DL 2.5 μg/kg+6.25 μg/kg/h; DH 5 μg/kg+12.5 μg/kg/h) or combined with methadone (DLM and DHM, 0.2 mg/kg+0.05 mg/kg/h) for 120 min, or acepromazine boli i.v. in low (ACPL 0.02 mg/kg) or high doses (ACPH 0.09 mg/kg). Horses' faces were photographed at i) baseline, ii) peak, iii) intermediate, and iv) end of sedation. After randomisation of moments and treatments, photos were sent to four evaluators to assess the FaceSed items (ear position, orbital opening, relaxation of the lower and upper lip) twice, within a one-month interval. The intraclass correlation coefficient of intra- and interobserver reliability of FaceSed scores were good to very good (0.74-0.94) and moderate to very good (0.57-0.87), respectively. Criterion validity based on Spearman correlation between the FaceSed versus the numerical rating scale and head height above the ground were 0.92 and -0.75, respectively. All items and the FaceSed total score showed responsiveness (construct validity). According to the principal component analysis all FaceSed items had load factors >0.50 at the first dimension. The high internal consistency (Cronbach´s α = 0.83) indicated good intercorrelation among items. Item-total Spearman correlation was adequate (rho 0.3-0.73), indicating homogeneity of the scale. All items showed sensitivity (0.82-0.97) to detect sedation, however only orbital opening (0.79) and upper lip relaxation (0.82) were specific to detect absence of sedation. The limitations were that the facial expression was performed using photos, which do not represent the facial movement and the horses were docile, which may have reduced specificity. The FaceSed is a valid and reliable tool to assess tranquilisation and sedation in horses.

Limited usefulness of the observation of eye bulb rotation and neuro-ophthalmic responses for assessing the depth of equine anesthesia: an observational study comparing three protocols

The observation of the neuro-ophthalmic responses is an established basic tool for monitoring the depth of anesthesia in horses. However, their usefulness during balanced anesthesia in the clinic is questionable. The aim of this study was to compare the usefulness of neuro-ophthalmic responses during 3 commonly used anesthetic protocols. An observational study was performed on 22 horses, 5 maintained only with isoflurane (ISO group), 12 maintained with isoflurane and a constant rate infusion of ketamine (ISO+KET group), and 5 maintained with isoflurane and a constant rate infusion of detomidine (ISO+DET group). The occurrence of all five responses was noted: spontaneous palpebral and provoked palpebral response, corneal response, nystagmus and eye bulb rotation. The most consistent with the literature and most useful for anesthetic depth assessment was the observation of spontaneous palpebral reflex in all of the groups (p = 0.788) and the most significant differences were visible for the observation of the provoked palpebral reflex (p = 0.015) for all groups. The reflexes in the group ISO+DET were less consistent with the literature than in other groups, making them least useful. The group ISO seemed to have the reflexes’ observations most consistent with the literature expectations. The corneal reflex was always present and nystagmus always absent which confirmed the observations from literature. The above results suggest that neuro-ophthalmic responses, especially eye bulb rotation and provoked palpebral reflexes, should not be the only indicators in assessing the depth of anesthesia during maintenance with ketamine or detomidine with concurrent isoflurane.

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.

Effects of lidocaine associated with detomidine on sedation of horses undergoing dental procedures

Due to the growing increase in the dental routine in equine medicine, along with the need for patient sedation to perform this procedure, this study aimed to assess sedation by detomidine alone and/or associated with lidocaine under continuous infusion. Twenty-two horses from the dental routine of the veterinary hospital of the institution of origin were used. A jugular catheter was implanted on the day of study and animals were allocated into two distinct groups (n=11): GD, which received detomidine (20 µg kg?1), followed by continuous infusion (20 µg kg?1 h?1); and GDL, animals which received detomidine (10 µg kg?1) and lidocaine (1.3 mg kg?1), followed by continuous infusion of detomidine (10 µg kg?1 h?1) and lidocaine (25 µg kg?1 min?1). The assessed moments were as follows: M0, before catheter placement; M1, 5 minutes after bolus and beginning of infusion; M2, placement of mouth speculum; and M3, wear with an electric rasp. The assessed parameters were heart rate (HR), respiratory rate (f), systolic blood pressure (SBP), and intestinal motility. In addition to the clinical parameters, sedation was assessed by measuring head height in relation to the ground before (M0) and after treatment administration (M1) and during the dental procedure using a scale adapted for dental procedures. Statistical analysis was performed using the Shapiro-Wilk normality test by applying one-way RM ANOVA, followed by the Dunnett test for comparison in relation to M0, t-test, and Mann-Whitney test between groups (p ? 0.05). HR decreased by 20% at M2 and M3 compared to M0 only in GD, while SBP increased 35% at the same moments compared to M0 in GD and 27, 42, and 27% at M1, M2, and M3 compared to M0 in GDL, respectively. Intestinal motility decreased by 75% at all moments compared to M0 in both groups. Head height decreased by 67% in GD and 60% in GDL, with no difference between groups. Sedation scores provided by the scale did not differ between groups, with values of 1 [0–3] in GD and 3 [0–4] in GDL at M2 and 1 [0–3] in GD and 1 [1.5–3] in GDL at M3. Thus, sedation by the association between detomidine and lidocaine allowed reducing detomidine dose in half but offering similar results for dental procedures.

Clinical applicability of detomidine and methadone constant rate infusions for surgery in standing horses

ObjectiveTo determine the required rate of a detomidine infusion (loading dose 5 μg kg−1; initial rate 12.5 μg kg−1 hour−1) added to a constant infusion of methadone (0.2 mg kg−1; 0.05 mg kg−1 hour−1) for sedation in standing horses and ponies undergoing elective surgeries with appropriate local anaesthetic techniques. Study designProspective, clinical study. AnimalsAdult, healthy, client-owned, non-food-producing horses or ponies sedated for elective standing surgeries longer than 45 minutes. MethodsAt baseline (in the stables before administration of sedative agents), at 10 minutes after sedation and every 5 minutes thereafter, ataxia, sedation and surgical condition were evaluated; each scored 0–3. These scores were used to adjust the detomidine administration rate using the Ghent Sedation Algorithm. A 10 cm visual analogue scale (VAS) was used by the main surgeon at the end of the procedure to evaluate the surgical conditions. Heart rate, systolic arterial pressure and respiratory frequency were also recorded at each time point. For statistical analysis, anova for normal, Kruskal–Wallis H-test for non-normal variables, and Mann–Whitney U test for VAS were used. ResultsFrom the 42 horses/ponies included in this study, 28 underwent dental procedures and 14 other types of procedures. Overall, dental procedures required higher mean detomidine rates compared with other types of surgeries (16.9 ± 4.5 versus 9.0 ± 1.9 μg kg−1 hour−1) (p < 0.001). Dental procedures were assigned similar VAS scores, median (range), of 7.8 (5.8–10) with other procedures, 8.7 (2.8–10). Cardiovascular changes were not clinically significant. No signs or behavioural changes of abdominal pain were observed postoperatively. Conclusions and clinical relevanceSatisfactory surgical conditions were achieved using a combination of detomidine and methadone infusions with locoregional anaesthesia, with no adverse effects. Dental procedures required higher detomidine dose rates compared with other surgeries.

Laparoscopic evaluation of the small intestine in the standing horse: Technique and effects.

To evaluate the feasibility and clinical outcomes after laparoscopic evaluation of the small intestines via laparoscopy. Prospective pilot study. Healthy adult horses (n = 5). Horses were restrained in standing stocks and received an infusion of detomidine. One port was placed in the left last intercostal space and 3 ports were placed in the right paralumbar fossa. The small intestine was run with atraumatic laparoscopic grasping forceps, from the duodenocolic plica to the ileocecal plica. Postoperative pain was scored every 4 hours for the first 48 hours. Horses were monitored via physical examinations for 2 weeks. Second look laparoscopy was repeated at 2 weeks, to run the small intestine and assess iatrogenic changes. An exploratory celiotomy was performed in 2 horses, 2 months later and long-term follow-up was recorded in 3 horses. Laparoscopic evaluation of the entire small intestine was successfully completed twice in every horse. This evaluation lasted 39 ± 21.2 minutes (mean ± SD), while total surgery time was 73 ± 34.1 minutes. Postoperative physical examinations remained normal in all horses, and pain scores were scored as mild. The only abnormalities at second look laparoscopy consisted of multifocal petechiae and ecchymoses in all horses, resolved by 2 months in the 2 horses explored via celiotomy. Three horses with long-term follow-up were healthy 8 months after the study. Running the small intestine laparoscopically is a feasible procedure in standing normal horses, and does not cause significant discomfort nor complications.

Cardiopulmonary effects of pleural insufflation with CO2 during two-lung ventilation in dorsally recumbent anesthetized horses

ObjectiveTo record the cardiopulmonary effects of pleural CO2 positive pressure insufflation in anesthetized horses. Study designProspective study. AnimalsSeven horses (mean ± standard deviation, 530.9 ± 68.1 kg) undergoing terminal surgery. MethodsHorses were sedated with xylazine. Anesthesia was induced with ketamine–propofol and maintained with isoflurane, positive pressure ventilation, detomidine infusion, and butorphanol with the horses in dorsal recumbency. Baseline measurements were cardiac output, heart rate, pulmonary and systemic arterial and right atrial blood pressures, body temperature, expired and inspired gas concentrations, and arterial and mixed venous blood gases, electrolytes, glucose, and lactate concentrations. An 18 gauge 6.6 cm needle was inserted into the right pleural cavity midway between the sternum and dorsal midline in the sixth or seventh intercostal space for pleural pressure (PP) measurement. A 14 gauge 18 cm needle placed 5 cm below the previous needle allowed CO2 insufflation into the pleural cavity. All measurements were repeated after: needle insertion, at 2, 5, and 8 mmHg PPs, and after pleural gas removal (GR). Data were compared with baseline using one-way analysis of variance with repeated measures. p < 0.05 was considered significant. ResultsActual PPs were within 1.1 mmHg of the targeted PP. Pulmonary systolic and mean arterial pressures, alveolar dead space to tidal volume ratio, and isoflurane requirements increased at 8 mmHg PP and GR. Cardiac index decreased at 5 mmHg PP. Stroke index decreased at 2 mmHg PP to GR. PaO2 decreased at 5 mmHg PP to GR. PaCO2 increased at 8 mmHg PP and GR. Oxygen delivery decreased at 5 and 8 mmHg PP. Intrapulmonary shunt fraction and lactate concentration increased with GR. Conclusions and clinical relevance:Severe adverse cardiopulmonary effects arise from CO2 positive pressure insufflation into the right hemithorax in dorsally recumbent isoflurane-anesthetized horses. PP should be ≤2 mmHg.

Visual evoked potentials in the horse.

BackgroundElectrical potentials generated in the central nervous system in response to brief visual stimuli, flash visual evoked potentials (FVEPs), can be recorded non-invasively over the occipital cortex. FVEPs are used clinically in human medicine and also experimentally in a number of animal species, but the method has not yet been evaluated in the horse. The method would potentially allow the ophthalmologist and equine clinician to evaluate visual impairment caused by disorders affecting post-retinal visual pathways. The aim was to establish a method for recording of FVEPs in horses in a clinical setting and to evaluate the waveform morphology in the normal horse.MethodsTen horses were sedated with a continuous detomidine infusion. Responses were recorded from electrodes placed on the scalp. Several positions were evaluated to determine suitable electrode placement. Flash electroretinograms (FERGs) were recorded simultaneously. To evaluate potential contamination of the FVEP from retinal potentials, a retrobulbar nerve block was performed in two horses and transection of the optic nerve was performed in one horse as a terminal procedure.ResultsA series of positive (P) and negative (N) peaks in response to light stimuli was recorded in all horses. Reproducible wavelets with mean times-to-peaks of 26 (N1), 55 (P2), 141 (N2) and 216 ms (P4) were seen in all horses in all recordings. Reproducible results were obtained when the active electrode was placed in the midline rostral to the nuchal crest. Recording at lateral positions gave more variable results, possibly due to ear muscle artifacts. Averaging ≥100 responses reduced the impact of noise and artifacts. FVEPs were reproducible in the same horse during the same recording session and between sessions, but were more variable between horses. Retrobulbar nerve block caused a transient loss of the VEP whereas transection of the optic nerve caused an irreversible loss.ConclusionsWe describe the waveform of the equine FVEP and our results show that it is possible to record FVEPs in sedated horses in a clinical setting. The potentials recorded were shown to be of post-retinal origin. Further studies are needed to provide normative data and assess potential clinical use.

Effects of a constant rate infusion of detomidine on cardiovascular function, isoflurane requirements and recovery quality in horses

ObjectiveTo examine the influence of a detomidine constant rate infusion (CRI) on cardiovascular function, isoflurane requirements and recovery quality in horses undergoing elective surgery. Study designProspective, randomized, blinded, clinical trial. AnimalsTwenty adult healthy horses. MethodsAfter sedation (detomidine, 10 μg kg−1 intravenously [IV]) and induction of anaesthesia (midazolam 0.06 mg kg−1, ketamine 2.2 mg kg−1 IV), anaesthesia was maintained with isoflurane in oxygen/air (inspiratory oxygen fraction 55%). When indicated, the lungs were mechanically ventilated. Dobutamine was administered when MAP < 70 mmHg. The horses were randomly allocated to one of two groups and throughout anaesthesia, received either a detomidine (5 μg kg−1 hour−1) (D) or saline (S) CRI, with the anaesthetist unaware of the treatment. Monitoring included end-tidal isoflurane concentration, arterial pH, PaCO2, PaO2, dobutamine administration rate, heart rate (HR), arterial pressure, cardiac index (CI), systemic vascular resistance (SVR), stroke index and oxygen delivery index ( D˙O2I). For recovery from anaesthesia, all horses received 2.5 μg kg−1 detomidine IV. Recovery quality and duration were recorded in each horse. For statistical analysis, anova, Pearson chi-square and Wilcoxon rank sum tests were used as relevant. ResultsHeart rate (p = 0.0176) and D˙O2I (p = 0.0084) were lower and SVR higher (p = 0.0126) in group D, compared to group S. Heart rate (p = 0.0011) and pH (p = 0.0187) increased over time. Significant differences in isoflurane requirements were not detected. Recovery quality and duration were comparable between treatments. Conclusions and clinical relevanceA detomidine CRI produced cardiovascular effects typical for a2-agonists, without affecting isoflurane requirements, recovery duration or recovery quality.

Comparison of Intraoperative Behavioral and Hormonal Responses to Noxious Stimuli between Mares Sedated with Caudal Epidural Detomidine Hydrochloride or a Continuous Intravenous Infusion of Detomidine Hydrochloride for Standing Laparoscopic Ovariectomy

To compare the presence or absence of pain, pain-related behavioral responses, and hormonal responses to noxious stimuli during standing laparoscopic ovariectomy in mares sedated with continuous intravenous (IV) detomidine infusion and caudal epidural detomidine. A double blind prospective study. Mares (n=12) Mares were divided into 2 treatment groups; 6 were sedated using continuous IV detomidine infusion and 6 were sedated with caudal epidural detomidine. All mares received IV xylazine (0.33 mg/kg) and butorphanol tartrate (5 mg) premedication before detomidine administration. Venous blood samples were taken to assess serum cortisol levels in each mare at 4 time points: a baseline cortisol measurement after the mares' arrival to the clinic, 10 minutes before surgery, at the removal of the 2nd ovary, and 10 minutes postsurgery. Two surgeons performed bilateral ovariectomy and at 8 time points involving surgical manipulations, noted the presence or absence of pain (yes/no) and scored the patient's response on a 10 cm visual analogue scale (VAS) for pain assessment with 0 indicating no pain responses and 10 cm indicating pain so severe that the mare required additional sedation or analgesia to complete the procedure. Each mare was also assigned a VAS score by each surgeon for the overall satisfaction of analgesia during the entire procedure. Serum cortisol levels between the 2 detomidine administration groups differed significantly at the baseline (precortisol) measurement but not at the 3 remaining time points. Seven of the procedures within the surgeries did not differ significantly in VAS scores between the 2 groups. The initial grasp of the left ovary (the 1st ovary) in the continuous infusion group had a significantly higher (P=.05) median VAS score compared with the caudal epidural group. Mares sedated with a continuous IV infusion of detomidine have similar hormonal and behavioral responses to painful stimuli during standing laparoscopic ovariectomy as mares sedated with caudal epidural detomidine. Sedation using a continuous IV infusion of detomidine can be used for laparoscopic ovariectomy in mares.

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

To evaluate pulmonary and cardiovascular effects of a recruitment maneuver (RM) combined with positive end-expiratory pressure (PEEP) during total intravenous anesthesia in ponies. 6 healthy adult Shetland ponies. 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. 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. 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.

Cardiovascular effects of insufflation of the abdomen with carbon dioxide in standing horses sedated with detomidine

To determine the cardiovascular effects of 60 minutes of abdominal insufflation with CO2 to an intra-abdominal pressure of 15 mm Hg in standing horses receiving a constant rate infusion of detomidine. 5 horses. Horses were randomly allocated into treatment or control groups. A washout period of a minimum of 7 days separated the 2 experimental periods of the crossover study. Catheters were placed into the right atrium, pulmonary artery, jugular vein, and right transverse facial artery after lidocaine infiltration. All horses were sedated with detomidine (8.54 microg/kg/h, i.v.). Horses in the treatment group received abdominal insufflation with CO2 via a laparoscopic cannula to a final and constant intra-abdominal pressure of 15 mm Hg for 60 minutes. Systemic arterial pressure, right atrial pressure, heart rate, cardiac output, core body temperature, and the pH and gas tensions of arterial and mixed venous blood were obtained. Cardiac index and systemic vascular resistance were calculated. Data were collected in 3 stages: preinsufflation (-10 and -5 minutes), insufflation (0, 15, 30, 45, and 60 minutes), and postinsufflation (70 and 80 minutes). The quality of sedation and level of analgesia were determined. The PaO2 of horses in the treatment group was significantly higher after 60 minutes of pneumoperitoneum than in the control group. Core body temperature decreased significantly from baseline in both groups. A 60-minute period of abdominal insufflation to an intra-abdominal pressure of 15 mm Hg did not induce significant cardiovascular abnormalities in healthy horses.

Hormonal, metabolic and physiological effects of laparoscopic surgery using a detomidine-buprenorphine combination in standing horses

ObjectiveTo assess the hormonal, metabolic and physiological effects of laparascopic surgery performed under a sedative analgesic combination of detomidine and buprenorphine in standing horses. Study designProspective study. AnimalsEight healthy adult Dutch Warmblood horses and five healthy adult ponies undergoing laparoscopy were studied. Five healthy adult horses not undergoing laparoscopy were used as a control group. MethodsThe sedative effect of an initial detomidine and buprenorphine injection was maintained using a continuous infusion of detomidine alone. The heart and respiratory rate, arterial blood pH and arterial oxygen and carbon dioxide tensions were monitored, while blood samples were taken for the measurement of glucose, lactate, cortisol, insulin and nonesterified fatty acids (NEFA). The same variables were monitored in a control group of horses which were sedated, but which did not undergo surgery. At the end of the sedation period the effects of detomidine were antagonized using atipamezole. ResultsThe protocol provided suitable conditions for standing laparoscopy in horses. Laparoscopy induced obvious metabolic and endocrine responses which, with the exception of NEFA values, were not significantly different from changes found in the control group. While atipamezole did not produce detectable adverse effects, it is possible that anatagonism may not be essential. ConclusionsThe technique described reliably produces adequate sedation and analgesia for laparoscopic procedures. The level of sedation/analgesia was controlled by decreasing or increasing the infusion rate. Antagonism of the effects of detomidine may not be necessary in all cases.

Retrospective analysis of detomidine infusion for standing chemical restraint in 51 horses

ObjectiveTo assess the effectiveness of a detomidine infusion technique to provide standing chemical restraint in the horse. DesignRetrospective study. AnimalsFifty–one adult horses aged 9.5 ± 6.9 years (range 1–23 years) and weighing 575 ± 290.3 kg. MethodsRecords of horses presented to our clinic over a 3–year period in which a detomidine infusion was used to provide standing chemical restraint were reviewed. Information relating to the types of procedure performed, duration of infusion, drug dosages and adjunct drugs administered was retrieved. ResultsDetomidine was administered as an initial bolus loading dose (mean ± SD) of 7.5 ± 1.87 μg kg−1. The initial infusion rate was 0.6 μg kg−1 minute−1, and this was halved every 15 minutes. The duration of the infusion ranged from 20 to 135 minutes. Twenty horses received additional detomidine or butorphanol during the procedure. All horses undergoing surgery received local anesthesia or epidural analgesia in addition to the detomidine infusion. A wide variety of procedures were performed in these horses. ConclusionsDetomidine administered by infusion provides prolonged periods of chemical restraint in standing horses. Supplemental sedatives or analgesics may be needed in horses undergoing surgery. Clinical relevanceAn effective method that provides prolonged periods of chemical restraint in standing horses is described. The infusion alone did not provide sufficient analgesia for surgery and a significant proportion of animals required supplemental sedatives and analgesics.

Intravenous anaesthesia using detomidine, ketamine and guaiphenesin for laparotomy in pregnant pony mares

Objective To characterize intravenous anaesthesia with detomidine, ketamine and guaiphenesin in pregnant ponies.Animals Twelve pony mares, at 260–320 days gestation undergoing abdominal surgery to implant fetal and maternal vascular catheters.Materials and methods Pre-anaesthetic medication with intravenous (IV) acepromazine (30 µg kg−1), butorphanol (20 µg kg−1) and detomidine (10 µg kg−1) preceded induction of anaesthesia with detomidine (10 µg kg−1) and ketamine (2 mg kg−1) IV Maternal arterial blood pressure was measured directly throughout anaesthesia and arterial blood samples were taken at 20-minute intervals for measurement of blood gases and plasma concentrations of cortisol, glucose and lactate. Anaesthesia was maintained with an IV infusion of detomidine (0.04 mg mL−1), ketamine (4 mg mL−1) and guaiphenesin (100 mg mL−1) (DKG) for 140 minutes. Oxygen was supplied by intermittent positive pressure ventilation (IPPV) adjusted to maintain PaCO2 between 5.0 and 6.0 kPa (38 and 45 mm Hg), while PaO2 was kept close to 20.0 kPa (150 mm Hg) by adding nitrous oxide. Simultaneous fetal and maternal blood samples were withdrawn at 90 minutes. Recovery quality was assessed.Results DKG was infused at 0.67 ± 0.17 mL kg−1 hour−1 for 1 hour then reduced, reaching 0.28 ± 0.14 mL kg−1 hour−1 at 140 minutes. Arterial blood gas values and pH remained within intended limits. During anaesthesia there was no change in heart rate, but arterial blood pressure decreased by 10%. Plasma glucose and lactate increased (10-fold and 2-fold, respectively) and cortisol decreased by 50% during anaesthesia. Fetal umbilical venous pH, PO2 and PCO2 were 7.34 ± 0.06, 5.8 ± 0.9 kPa (44 ± 7 mm Hg) and 6.7 ± 0.8 kPa (50 ± 6 mm Hg); and fetal arterial pH, PO2 and PCO2 were 7.29 ± 0.06, 4.0 ± 0.7 kPa (30 ± 5 mm Hg) and 7.8 ± 1.7 kPa (59 ± 13 mm Hg), respectively. Surgical conditions were good but four ponies required a single additional dose of ketamine. Ponies took 60 ± 28 minutes to stand and recovery was good.Conclusions and clinical relevance Anaesthesia produced with DKG was smooth while cardiovascular function in mare and fetus was well preserved. This indicates that DKG infusion is suitable for maintenance of anaesthesia in pregnant equidae.

Equine thoracoscopy: normal anatomy and surgical technique

Six normal, healthy horses age 3-10 years underwent left and right thoracoscopic examination using a rigid telescope. A minimum of 30 days was allowed between procedures. Horses were restrained in stocks and sedated with a continuous detomidine infusion. After surgical preparation of the hemithorax elected for surgery, and administration of local or regional anaesthesia of the surgery sites, thoracoscopy was completed during two 15 min pneumothorax periods. During the procedures, the thoracic structures were viewed using a 57 cm, 10 mm diameter, 30 degrees rigid telescope connected to a digital camcorder to allow computer capture of digital images. The telescope was inserted into the thoracic cavity via 3 different intercostal spaces. The 8th, 10th and 12th intercostal spaces were randomly selected and used among horses. The exploration of each hemithorax started from the dorsal-caudal quadrant continued toward the cranial thorax and was completed by observing the diaphragmatic and caudal pulmonary region. Collapsed lung, aorta, oesophagus and diaphragm were viewed readily in either hemithorax. On exploration of the right hemithorax, the azygos vein, thoracic duct and pulmonary veins were also identified. Horses tolerated thoracoscopy well. Signs of discomfort, such as increased respiratory rate, coughing and decreased level of sedation, were associated with lung collapse in one horse, with pneumothorax on 2 occasions, and when the thorax was approached through the 8th intercostal space. Surgery performed via the 8th intercostal space was hindered by the rigidity of the 8th and 9th ribs, and by the presence of a greater musculature, which did not allow easy cranial and caudal movements of the telescope.