Cardiopulmonary effects of dexmedetomidine and ketamine infusions with either propofol infusion or isoflurane for anesthesia in horses

ObjectiveTo examine the cardiopulmonary effects of two anesthetic protocols for dorsally recumbent horses undergoing carpal arthroscopy.Study designProspective, randomized, crossover study.AnimalsSix horses weighing 488.3 ± 29.1 kg.MethodsHorses were sedated with intravenous (IV) xylazine and pulmonary artery balloon and right atrial catheters inserted. More xylazine was administered prior to anesthetic induction with ketamine and propofol IV. Anesthesia was maintained for 60 minutes (or until surgery was complete) using either propofol IV infusion or isoflurane to effect. All horses were administered dexmedetomidine and ketamine infusions IV, and IV butorphanol. The endotracheal tube was attached to a large animal circle system and the lungs were ventilated with oxygen to maintain end-tidal CO₂ 40 ± 5 mmHg. Measurements of cardiac output, heart rate, pulmonary arterial and right atrial pressures, and body temperature were made under xylazine sedation. These, arterial and venous blood gas analyses were repeated 10, 30 and 60 minutes after induction. Systemic arterial blood pressures, expired and inspired gas concentrations were measured at 10, 20, 30, 40, 50 and 60 minutes after induction. Horses were recovered from anesthesia with IV romifidine. Times to extubation, sternal recumbency and standing were recorded. Data were analyzed using one and two-way anovas for repeated measures and paired t-tests. Significance was taken at p=0.05.ResultsPulmonary arterial and right atrial pressures, and body temperature decreased from pre-induction values in both groups. PaO₂ and arterial pH were lower in propofol-anesthetized horses compared to isoflurane-anesthetized horses. The lowest PaO₂ values (70–80 mmHg) occurred 10 minutes after induction in two propofol-anesthetized horses. Cardiac output decreased in isoflurane-anesthetized horses 10 minutes after induction. End-tidal isoflurane concentration ranged 0.5%–1.3%.Conclusion and clinical relevanceBoth anesthetic protocols were suitable for arthroscopy. Administration of oxygen and ability to ventilate lungs is necessary for propofol-based anesthesia.     

Hemodynamic effects of dexmedetomidine in isoflurane-anesthetized cats

ObjectiveTo characterize the hemodynamic effects of dexmedetomidine in isoflurane-anesthetized cats.Study designProspective experimental study.AnimalsSix healthy adult female cats weighing 4.6 ± 0.8 kg.MethodsDexmedetomidine was administered intravenously using target-controlled infusions to maintain nine plasma concentrations between 0 and 20 ng mL^?1 in isoflurane-anesthetized cats. The isoflurane concentration was adjusted for each dexmedetomidine concentration to maintain the equivalent of 1.25 times the minimum alveolar concentration, based on a previous study. Heart rate, systemic and pulmonary arterial pressures, central venous pressure, pulmonary artery occlusion pressure, body temperature, and cardiac output were measured at each target plasma dexmedetomidine concentration. Additional variables were calculated. Arterial and mixed-venous blood samples were collected for blood gas, pH, and (on arterial blood only) electrolyte, glucose and lactate analysis. Plasma dexmedetomidine concentration was determined for each target. Pharmacodynamic models were fitted to the data.ResultsHeart rate, arterial pH, arterial bicarbonate concentration, mixed-venous PO₂, mixed-venous pH, mixed-venous hemoglobin oxygen saturation, cardiac index, stroke index, and venous admixture decreased following dexmedetomidine administration. Arterial blood pressure, central venous pressure, pulmonary arterial pressure, pulmonary arterial occlusion pressure, packed cell volume, PaO₂, PaCO₂, arterial hemoglobin concentration, mixed-venous PCO₂, mixed-venous hemoglobin concentration, ionized calcium concentration, glucose concentration, rate-pressure product, systemic and pulmonary vascular resistance indices, left ventricular stroke work index, arterial oxygen concentration, and oxygen extraction increased following dexmedetomidine administration. Most variables changed in a dexmedetomidine concentration-dependent manner.Conclusion and clinical relevanceThe use of dexmedetomidine as an anesthetic adjunct is expected to produce greater negative hemodynamic effects than a higher, equipotent concentration of isoflurane alone.     

Evaluation of the isoflurane‐sparing effects of fentanyl,lidocaine, ketamine,dexmedetomidine, or the combination lidocaine‐ketamine‐dexmedetomidine during ovariohysterectomy in dogs

ObjectiveTo evaluate the isoflurane‐sparing effects of an intravenous (IV) constant rate infusion (CRI) of fentanyl, lidocaine, ketamine, dexmedetomidine, or lidocaine‐ketamine‐dexmedetomidine (LKD) in dogs undergoing ovariohysterectomy.Study designRandomized, prospective, blinded, clinical study.AnimalsFifty four dogs.MethodsAnesthesia was induced with propofol and maintained with isoflurane with one of the following IV treatments: butorphanol/saline (butorphanol 0.4 mg kg^?1, saline 0.9% CRI, CONTROL/BUT); fentanyl (5 μg kg^?1, 10 μg kg^?1 hour^?1, FENT); ketamine (1 mg kg^?1, 40 μg kg^?1 minute^?1, KET), lidocaine (2 mg kg^?1, 100 μg kg^?1 minute^?1, LIDO); dexmedetomidine (1 μg kg^?1, 3 μg kg^?1 hour^?1, DEX); or a LKD combination. Positive pressure ventilation maintained eucapnia. An anesthetist unaware of treatment and end‐tidal isoflurane concentration (Fe′Iso) adjusted vaporizer settings to maintain surgical anesthetic depth. Cardiopulmonary variables and Fe′Iso concentrations were monitored. Data were analyzed using anova (p < 0.05).ResultsAt most time points, heart rate (HR) was lower in FENT than in other groups, except for DEX and LKD. Mean arterial blood pressure (MAP) was lower in FENT and CONTROL/BUT than in DEX. Overall mean ± SD Fe′Iso and % reduced isoflurane requirements were 1.01 ± 0.31/41.6% (range, 0.75 ± 0.31/56.6% to 1.12 ± 0.80/35.3%, FENT), 1.37 ± 0.19/20.8% (1.23 ± 0.14/28.9% to 1.51 ± 0.22/12.7%, KET), 1.34 ± 0.19/22.5% (1.24 ± 0.19/28.3% to 1.44 ± 0.21/16.8%, LIDO), 1.30 ± 0.28/24.8% (1.16 ± 0.18/32.9% to 1.43 ± 0.32/17.3%, DEX), 0.95 ± 0.19/54.9% (0.7 ± 0.16/59.5% to 1.12 ± 0.16/35.3%, LKD) and 1.73 ± 0.18/0.0% (1.64 ± 0.21 to 1.82 ± 0.14, CONTROL/BUT) during surgery. FENT and LKD significantly reduced Fe′Iso.Conclusions and clinical relevanceAt the doses administered, FENT and LKD had greater isoflurane‐sparing effect than LIDO, KET or CONTROL/BUT, but not at all times. Low HR during FENT may limit improvement in MAP expected with reduced Fe′Iso.     

Comparison of cardiovascular function and quality of recovery in isoflurane‐anaesthetised horses administered a constant rate infusion of lidocaine or lidocaine and medetomidine during elective surgery

Reasons for performing study: The effects of lidocaine combined with medetomidine or lidocaine alone on cardiovascular function during anaesthesia and their effects on recovery have not been thoroughly investigated in isoflurane‐anaesthetised horses. Objectives: To determine the effects of an intraoperative i.v. constant rate infusion of lidocaine combined with medetomidine (Group 1) or lidocaine (Group 2) alone on cardiovascular function and on the quality of recovery in 12 isoflurane‐anaesthetised horses undergoing arthroscopy. Hypothesis: The combination would depress cardiovascular function but improve the quality of recovery when compared to lidocaine alone in isoflurane‐anaesthetised horses. Methods: Lidocaine (2 mg/kg bwt i.v. bolus followed by 50 µg/kg bwt/min i.v.) or lidocaine (same dose) and medetomidine (5 µg/kg bwt/h i.v.) was started 30 min after induction of anaesthesia. Lidocaine administration was discontinued 30 min before the end of surgery in both groups, whereas medetomidine administration was continued until the end of surgery. Cardiovascular function and quality of recovery were assessed. Results: Horses in Group 1 had longer recoveries, which were of better quality due to better strength and overall attitude during the recovery phase than those in Group 2. Arterial blood pressure was significantly higher in Group 1 than in Group 2 and this effect was associated with medetomidine. No significant differences in cardiac output, arterial blood gases, electrolytes and acid‐base status were detected between the 2 groups. Conclusions and potential relevance: The combination of an intraoperative constant rate infusion of lidocaine and medetomidine did not adversely affect cardiovascular function in isoflurane‐anaesthetised horses and improved the quality of recovery when compared to an intraoperative infusion of lidocaine alone.     

Clinical efficacy of dexmedetomidine combined with lidocaine for femoral and sciatic nerve blocks in dogs undergoing stifle surgery

ObjectiveTo evaluate the effects of dexmedetomidine administered perineurally or intramuscularly (IM) on sensory, motor function and postoperative analgesia produced by lidocaine for sciatic and femoral nerve blocks in dogs undergoing unilateral tibial tuberosity advancement surgery.Study designProspective, blinded, clinical study.AnimalsA group of 30 dogs.MethodsDogs were anaesthetized with acepromazine, propofol and isoflurane in oxygen/air. Electrolocation-guided femoral and sciatic nerve blocks were performed: group L, 0.15 mL kg^–1 2% lidocaine (n = 10); group LD_loc, lidocaine and 0.15 μg kg^–1 dexmedetomidine perineurally (n = 10); group LD_sys, lidocaine and 0.3 μg kg^–1 dexmedetomidine IM (n = 10). After anaesthesia, sensory blockade was evaluated by response to forceps pinch on skin innervated by the saphenous/femoral, common fibular and tibial nerves. Motor blockade was evaluated by observing the ability to walk and proprioception. Analgesia was monitored with Short Form of Glasgow Composite Pain Scale for up to 4 hours after extubation. Methadone IM was administered as rescue analgesia. Data were analysed by linear mixed effect models and Kaplan-Meier test (p < 0.05).ResultsMedian duration of the sensory blockade for all nerves was longer (p < 0.001) for group LD_loc than for groups L and LD_sys and was longer (p = 0.0011) for group LD_sys than for group L. Proprioception returned later (p < 0.001) for group LD_loc [285 (221–328) minutes] compared with group L [160 (134–179) minutes] or LD_sys [195 (162–257) minutes]. Return of the ability to walk was similar among all groups. Dogs in group LD_loc required postoperative rescue analgesia later (p = 0.001) than dogs in groups LD_sys and L.Conclusions and clinical relevanceDexmedetomidine administered perineurally with lidocaine prolonged sensory blockade and analgesia during the immediate postoperative period. Systemic dexmedetomidine also prolonged the sensory blockade of perineural lidocaine.     

Evaluation of the isoflurane-sparing effects of lidocaine infusion during umbilical surgery in calves

ObjectiveTo evaluate the isoflurane-sparing effects of lidocaine administered by constant rate infusion (CRI) during umbilical surgery in calves.Study designRandomized ‘blinded’ prospective clinical study.AnimalsThirty calves (mean 4.7 ± SD 2.5 weeks old) undergoing umbilical surgery.MethodsAfter premedication with xylazine (0.1 mg kg^?1, IM), anaesthesia was induced with ketamine (4 mg kg^?1, IV) and maintained with isoflurane in O₂ administered through a circle breathing system. The calves were assigned randomly to receive a bolus of 2 mg kg^?1 lidocaine IV after induction of anaesthesia, followed by CRI of 50 μg kg^?1 minute^?1 (group L, n = 15) or a bolus and CRI of 0.9% sodium chloride (NaCl, group S, n = 15). End-tidal isoflurane was adjusted to achieve adequate depth of anaesthesia. Heart rate, direct arterial blood pressure and body temperature were measured intraoperatively. Groups were compared by t- tests, anova or Mann–Whitney rank sum test as appropriate.ResultsThe end-tidal concentration of isoflurane (median, IQR) was significantly lower in group L [1.0% (0.94–1.1)] compared to group S [1.2% (1.1–1.5)], indicating a 16.7% reduction in anaesthetic requirement during lidocaine CRI. Cardiopulmonary parameters and recovery times did not differ significantly between groups.Conclusion and clinical relevanceLidocaine CRI may be used as a supplement to inhalation anaesthesia during umbilical surgery in calves in countries where such a protocol would be within the legal requirements for veterinary use in food animals. This study did not show any measurable benefit to the calves other than a reduction in isoflurane requirement.     

Caudal epidural anti‐nociception using lidocaine,bupivacaine or their combination in cows undergoing reproductive procedures

ObjectiveTo evaluate the anti-nociceptive effects of lidocaine, lidocaine-bupivacaine combination or bupivacaine following caudal epidural administration in cows undergoing reproductive procedures.Study designBlinded, randomized experimental study.AnimalsThirty seven healthy Holstein cows (mean weight ± SD, 633 ± 41 kg).MethodsAnimals were allocated randomly to receive one of four treatments: group LID, 0.2 mg kg^?1 lidocaine 2%; group LID-BUP, lidocaine-bupivacaine mixture in a 1:1 volume ratio (0.1 mg kg^?1 and 0.025 mg kg^?1, respectively); group BUP-LD, 0.05 mg kg^?1 bupivacaine 0.5%; and group BUP-HD, 0.06 mg kg^?1 bupivacaine 0.5%. The onset and duration of perineal anti-nociception were determined using superficial and deep pin pricks and the number of cows with complete perineal anti-nociception was recorded. Parameters were compared using anova followed by Duncan's test where relevant.ResultsMean ± SD time to onset of anti-nociception following epidural administration of BUP-LD was significantly longer than for LID-BUP (p < 0.05). The duration (in minutes) of perineal anti-nociception was significantly longer following epidural administration of BUP-HD (247 ± 31) versus LID-BUP (181 ± 33) and LID (127 ± 25) minutes respectively. The % of cows with complete anti-nociception was increased in the group treated with BUP-HD compared to BUP-LD. Severe ataxia or recumbency did not occur in any groups.Conclusions and clinical relevanceEpidurally administered bupivacaine, at a dose of 0.06 mg kg^?1, may provide satisfactory caudal epidural anti-nociception for longer-duration obstetric and surgical procedures.     

Effects of dopamine,norepinephrine or phenylephrine on the prevention of hypotension in isoflurane-anesthetized cats administered vatinoxan or vatinoxan and dexmedetomidine

ObjectiveTo determine the dose of phenylephrine, norepinephrine and dopamine necessary to maintain mean arterial pressure (MAP) within 70–80 mmHg during administration of isoflurane, isoflurane and vatinoxan and isoflurane, vatinoxan and dexmedetomidine at three plasma concentrations.Study designRandomized crossover experimental study.AnimalsA group of five adult healthy neutered male cats.MethodsInstrumentation occurred during anesthesia with isoflurane in oxygen. Isoflurane end-tidal concentration was set to 1.25 × minimum alveolar concentration (MAC). Phenylephrine, norepinephrine or dopamine was administered to maintain MAP 70–80 mmHg. A target-controlled infusion system was used to administer vatinoxan at a target plasma concentration of 1 μg mL^–1 and three dexmedetomidine concentrations (5, 10 and 20 ng mL^–1). Isoflurane concentration was altered to maintain an equivalent 1.25 MAC. Heart rate, arterial blood pressure, central venous pressure, pulmonary artery pressure, pulmonary artery occlusion pressure, body temperature, arterial and mixed venous blood gas, cardiac output and drug concentrations were measured at baseline (isoflurane alone), during vatinoxan administration, and during administration of vatinoxan and dexmedetomidine at the three target concentrations.ResultsMAP < 70 mmHg was observed with vatinoxan alone and in the dopamine treatment with dexmedetomidine concentrations ≤ 10 ng mL^–1. Norepinephrine and phenylephrine maintained MAP 70–80 mmHg during vatinoxan and dexmedetomidine ≤ 10 ng mL^–1. As the target dexmedetomidine concentration increased, the dose of norepinephrine and phenylephrine needed to maintain MAP 70–80 mmHg decreased; no treatment was necessary to maintain MAP > 70 mmHg at the 20 ng mL^–1 target dexmedetomidine concentration in most cats.Conclusions and clinical relevanceNorepinephrine and phenylephrine, but not dopamine, are effective to prevent hypotension in isoflurane-anesthetized cats administered dexmedetomidine and vatinoxan.     

Comparison of two intravenous anesthetic infusion regimens for alfaxalone in cats

Objective

To compare the performance of an alfaxalone constant rate intravenous (IV) infusion versus a 3-step IV infusion, both following a loading dose, for the maintenance of a target plasma alfaxalone concentration of 7.6 mg L^–1 (effective plasma alfaxalone concentration for immobility in 99% of the population) in cats.

Medetomidine continuous rate intravenous infusion in horses in which surgical anaesthesia is maintained with isoflurane and intravenous infusions of lidocaine and ketamine

ObjectiveTo evaluate medetomidine as a continuous rate infusion (CRI) in horses in which anaesthesia is maintained with isoflurane and CRIs of ketamine and lidocaine.Study designProspective, randomized, blinded clinical trial.AnimalsForty horses undergoing elective surgery.MethodsAfter sedation and induction, anaesthesia was maintained with isoflurane. Mechanical ventilation was employed. All horses received lidocaine (1.5 mg kg^?1 initially, then 2 mg kg^?1 hour^?1) and ketamine (2 mg kg^?1 hour^?1), both CRIs reducing to 1.5 mg kg^?1 hour^?1 after 50 minutes. Horses in group MILK received a medetomidine CRI of 3.6 μg kg^?1 hour^?1, reducing after 50 minutes to 2.75 μg kg^?1 hour^?1, and horses in group ILK an equal volume of saline. Mean arterial pressure (MAP) was maintained above 70 mmHg using dobutamine. End-tidal concentration of isoflurane (FE′ISO) was adjusted as necessary to maintain surgical anaesthesia. Group ILK received medetomidine (3 μg kg^?1) at the end of the procedure. Recovery was evaluated. Differences between groups were analysed using Mann-Whitney, Chi-Square and anova tests as relevant. Significance was taken as p < 0.05.ResultsFE′ISO required to maintain surgical anaesthesia in group MILK decreased with time, becoming significantly less than that in group ILK by 45 minutes. After 60 minutes, median (IQR) FE′ISO in MILK was 0.65 (0.4–1.0) %, and in ILK was 1 (0.62–1.2) %. Physiological parameters did not differ between groups, but group MILK required less dobutamine to support MAP. Total recovery times were similar and recovery quality good in both groups.Conclusion and clinical relevanceA CRI of medetomidine given to horses which were also receiving CRIs of lidocaine and ketamine reduced the concentration of isoflurane necessary to maintain satisfactory anaesthesia for surgery, and reduced the dobutamine required to maintain MAP. No further sedation was required to provide a calm recovery.     

Clinical comparison of two regimens of lidocaine infusion in horses undergoing laparotomy for colic

ObjectiveTo compare, in horses undergoing laparotomy for colic, the effects of administering or not administering a loading intravenous (IV) bolus of lidocaine prior to its constant rate infusion (CRI). Effects investigated during isoflurane anaesthesia were end-tidal isoflurane concentration (Fe’ISO), cardiovascular function, anaesthetic stability and the quality of recovery.Study designProspective, randomized clinical study.AnimalsThirty-six client-owned horses.MethodsHorses were assigned randomly to receive lidocaine as a CRI (50 μg kg⁻¹ minute⁻¹) either preceded (LB) or not preceded (L) by a loading dose (1.5 mg kg⁻¹ IV over 15 minutes). Lidocaine infusion (LInf) was started (T0) within 20 minutes after induction of general anaesthesia and discontinued approximately 30 minutes before the end of surgery. Anaesthetic depth, Fe’ISO, intra-operative physiological parameters and quality of recovery were assessed or measured. Data were analysed using one-way anova, t-test, Fisher test, Wilcoxon and Kruskal–Wallis tests as appropriate (p < 0.05).ResultsMean ± SD Fe’ISO was 1.21 ± 0.08% in group LB and 1.23 ± 0.06% in group L. Heart rate was significantly higher in group L than in group LB at times T5-T15, T25, T35 and T95. No difference was found between groups in other measured physiological values, nor in any measure taken to improve these parameters. Recovery phase was comparable and satisfactory in all but one full term pregnant horse in group L which fractured a femur during recovery.ConclusionPreloading with a lidocaine bolus prior to a CRI of lidocaine did not influence isoflurane requirements, cardiopulmonary effects (other than a reduction in heart rate at some time points) or recovery compared to no preloading bolus.Clinical relevanceA loading dose of lidocaine prior to CRI does not confer any advantage in horses undergoing laparotomy for colic.     

Comparative analgesic and sedative effects of tramadol,tramadol‐lidocaine and lidocaine for caudal epidural analgesia in donkeys (Equus asinus)

ObjectiveTo compare anti-nociceptive and sedative effects of tramadol, a combination of tramadol-lidocaine, and lidocaine alone for perineal analgesia in donkeys.Study designExperimental ‘blinded’ randomized cross-over study.AnimalsSix healthy adult donkeys.MethodsTreatments were tramadol (TR) (1.0 mg kg⁻¹), tramadol-lidocaine (TRLD) (0.5 and 0.2 mg kg⁻¹ respectively) and lidocaine (LD) (0.4 mg kg⁻¹) given into the epidural space. The volume of all treatments was 0.02 mL kg⁻¹. Nociception was tested at the perineal region by pin prick, followed, if no reaction, by pressure from a haemostat clamp. Times to onset, degree and duration of anti-nociception of the perineal region were recorded. Response was tested immediately after drug administration and at: 2, 5, 10, 15, 30, 45, and 60 minutes post-administration and then at 30 minute intervals thereafter until a response re-occurred. Physiologic data and degree of sedation and ataxia were recorded pre-administration and at intervals for 240 minutes post-administration. Results were analyzed using anova, Kruskal–Wallis tests, and Wilks’ Lambda test as relevant. Significance was taken as p < 0.05.ResultsTimes (minutes, mean ± SD) to onset and duration of anti-nociception, respectively were; TR 13 ± 1.6 and 220 ± 4.6; TRLD 6 ± 0.8 and 180 ± 8.5; LD 4 ± 1.4 and 75 ± 4. Onset and duration times were significantly longer with TR than the other two treatments. TR never produced complete anti-nociception, whereas the TRLD and LD induced complete anti-nociceptive effects. Duration was significantly longer with TRLD than with LD alone. Epidural injections of TR and TRLD induced mild sedation.Conclusions and clinical relevanceEpidural combination of TRLD produced an anti-nociceptive effect in the perineum, which was rapid in onset and had a longer duration of action than LD alone. An epidural single dose of TRLD combination would appear to provide an acceptable analgesic effect in the perineal region of donkeys.     

Cardiovascular effects of dexmedetomidine,with or without MK-467, following intravenous administration in cats

Objective

To characterize the cardiovascular effects of dexmedetomidine, with or without MK-467, following intravenous (IV) administration in cats.

Cardiopulmonary effects of an infusion of remifentanil or morphine in horses anesthetized with isoflurane and dexmedetomidine

ObjectiveTo examine the cardiopulmonary effects of infusions of remifentanil or morphine, and their influence on recovery of horses anesthetized with isoflurane and dexmedetomidine.Study designRandomized crossover study with 7-day rest periods.AnimalsSix adult horses (507 ± 61 kg).MethodsAfter the horses were sedated with xylazine, anaesthesia was induced with ketamine and diazepam, and maintained with isoflurane. After approximately 60 minutes, a dexmedetomidine infusion was started (0.25 μg kg^?1 then 1.0 μg^?1 kg^?1 hour^?1) in combination with either saline (group S), morphine (0.15 mg kg^?1 then 0.1 mg kg^?1 hour^?1; group M), or remifentanil (6.0 μg kg^?1 hour^?1; group R) for 60 minutes. Mean arterial pressure, heart rate, end-tidal carbon dioxide tension, and end-tidal isoflurane concentration were recorded every 5 minutes. Core body temperature, cardiac output, right ventricular and arterial blood-gas values were measured every 15 minutes. Cardiac index, systemic vascular resistance (SVR), intrapulmonary shunt fraction, alveolar dead space, oxygen delivery and extraction ratio were calculated. Recoveries were videotaped and scored by two observers blinded to the treatment. Data were analyzed using repeated measures anova followed by Dunnett’s or Bonferroni’s significant difference test. Recovery scores were analyzed using a Kruskal–Wallis test.ResultsNo significant differences were found among groups. Compared to baseline, heart rate decreased and SVR increased significantly in all groups, and cardiac index significantly decreased in groups S and M. Hemoglobin concentration, oxygen content and oxygen delivery significantly decreased in all groups. The oxygen extraction ratio significantly increased in groups M and R. Lactate concentration significantly increased in group S. Recovery scores were similar among groups.Conclusions and clinical relevanceDexmedetomidine alone or in combination with remifentanil or morphine infusions was infused for 60 minutes without adverse effects in the 6 healthy isoflurane-anesthetized horses in this study.