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Topic:Anesthesia
Anesthesia in horses involves the administration of drugs to induce a temporary loss of sensation or consciousness, facilitating surgical procedures and other medical interventions. This complex process requires a deep understanding of equine physiology and pharmacology to ensure the safety and well-being of the animal. Anesthesia in horses can be challenging due to their size, temperament, and unique anatomical and physiological characteristics. Common anesthetic agents used in equine practice include inhalants like isoflurane and sevoflurane, as well as injectable drugs such as ketamine and xylazine. The management of anesthesia in horses also involves careful monitoring of vital signs and the use of supportive measures to prevent complications such as hypotension, hypoventilation, and post-anesthetic myopathy. This page compiles peer-reviewed research studies and scholarly articles that explore the techniques, advancements, and clinical outcomes associated with anesthesia in equine medicine.
Comparison of the effects of an intravenous lidocaine infusion combined with 1% isoflurane versus 2% isoflurane alone on selected cardiovascular variables and recovery characteristics during equine general anaesthesia. To compare the effects of a lidocaine constant rate infusion (CRI) combined with 1% isoflurane versus those of 2% isoflurane alone on cardiovascular variables in anaesthetized horses, and to estimate the sample size required to detect a difference in recovery quality. Methods: Prospective, randomized, blinded, crossover study. Methods: Twelve healthy experimental horses. Methods: Horses were anaesthetized twice using an intravenous (IV) administration of acepromazine, romifidine, diazepam and ketamine. Horses were placed in dorsal recumbency and ventilated mechanically. During the first 10 min...
Pharmacokinetics and pharmacodynamics of intravenous romifidine and propranolol administered alone or in combination for equine sedation. Propranolol has been suggested for anxiolysis in horses, but its sedation efficacy and side effects, both when administered alone and in combination with α-adrenoceptor agonists, remain undetermined. This study aimed to document the pharmacokinetics and pharmacodynamics of propranolol, romifidine and their combination. Methods: Randomized, crossover study. Methods: Six adult horses weighing 561 ± 48 kg. Methods: Propranolol (1 mg kg; treatment P), romifidine (0.1 mg kg; treatment R) or their combination (treatment PR) were administered intravenously with a minimum of 1 week between treatment...
Effects of intravenous terbutaline on heart rate, arterial pressure and blood gases in anesthetized horses breathing air. To investigate the effects of intravenous (IV) administration of terbutaline on PaO, PaCO, pH, heart rate (HR) and arterial pressures in healthy, laterally recumbent horses breathing ambient air under total intravenous anesthesia (TIVA). Methods: Prospective experimental study. Methods: Eight healthy adult horses were enrolled. Six horses, four mares and two geldings weighing 433-624 kg, completed the study. Methods: Horses were sedated with xylazine (1.0 mg kg) IV for placement of arterial and venous catheters. Anesthesia was induced with midazolam (0.1 mg kg) and ketamine (2.2 mg kg) IV and ...
Regional distribution of ventilation in horses in dorsal recumbency during spontaneous and mechanical ventilation assessed by electrical impedance tomography: a case series. To evaluate the regional distribution of ventilation in horses during spontaneous breathing and controlled mechanical ventilation (CMV) using electrical impedance tomography (EIT). Methods: Prospective, experimental case series. Methods: Four anaesthetized experimental horses. Methods: Horses were anaesthetized with isoflurane in an oxygen-air mixture and medetomidine continuous rate infusion, placed in dorsal recumbency with an EIT belt around the thorax, and allowed to breathe spontaneously until PaCO reached 13.3 kPa (100 mmHg), when volume CMV was started. For each horse, the EIT signal wa...
Controlled mechanical ventilation with constant positive end-expiratory pressure and alveolar recruitment manoeuvres during anaesthesia in laterally or dorsally recumbent horses. To compare the effects of controlled mechanical ventilation (CMV) and constant positive end-expiratory pressure (PEEP) and interposed recruitment manoeuvres (RMs) with those of CMV without PEEP on gas exchange during general anaesthesia and the early recovery period. Methods: Prospective, randomized clinical trial. Methods: A total of 48 Warmblood horses undergoing elective surgery in lateral (Lat) (n = 24) or dorsal (Dors) (n = 24) recumbency. Methods: Premedication (romifidine), induction (diazepam and ketamine) and maintenance (isoflurane in oxygen) were identical in all horses. Groups La...
A novel ultrasonographic assisted technique for desmotomy of the palmar/plantar annular ligament in horses. To describe an ultrasound assisted technique for desmotomy of the palmar/plantar annular ligament (PAL), determine its efficacy and intraoperative complications. Methods: Cadaveric and in vivo study. Methods: Cadaveric limbs (n = 12), adult horses (n = 4), and clinical cases (n = 2). Methods: Ultrasound assisted desmotomy of the palmar/plantar annular ligament (UAD-PAL) was performed in cadaveric limbs and in standing horses with the operated limb placed in a distal limb splint. The procedure was performed under general anesthesia and was followed by tenoscopic examination in 2 cli...
Investigation of perioperative and anesthetic variables affecting short-term survival of horses with small intestinal strangulating lesions. To determine if preoperative and intraoperative physiologic variables, and surgical factors correlate with survival to anesthetic recovery or hospital discharge, repeat celiotomy, and postoperative nasogastric intubation (NGT) in horses undergoing exploratory celiotomy for small intestinal (SI) strangulating lesions. Methods: Retrospective case series. Methods: Horses that had surgical correction of SI strangulating lesions (n = 258). Methods: Medical records (January 2000-December 2014) of horses that had surgical correction of SI strangulating lesions were reviewed. Data collection inclu...
Duodenojejunal mesenteric rents: Survival and complications after surgical correction in 38 broodmares (2006-2014). To describe short-term and long-term survival of horses with duodenojejunal mesenteric rents, and to examine the association of selected preoperative, intraoperative, and postoperative factors with survival or colic after discharge, in horses with duodenojejunal mesenteric rents. Methods: Retrospective case series. Methods: Horses undergoing surgery for correction of small intestinal lesions secondary to duodenojejunal mesenteric rents (n = 38). Methods: Medical records (2006-2014) of horses admitted to a referral hospital in Kentucky were reviewed. Data for preoperative and intraoperative...
Assessment of distribution of ventilation and regional lung compliance by electrical impedance tomography in anaesthetized horses undergoing alveolar recruitment manoeuvres. To examine changes in the distribution of ventilation and regional lung compliances in anaesthetized horses during the alveolar recruitment manoeuvre (ARM). Methods: Experimental study in which a series of treatments were administered in a fixed order on one occasion. Methods: Five adult Warmblood horses. Methods: Animals were anaesthetized (xylazine, midazolam-ketamine, isoflurane), placed in dorsal recumbency and ventilated with 100% oxygen using peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) of 20 cmHO and 0 cmHO, respectively. Thoracic electrical impedance tomo...
Caudal epidural anesthesia in mares after bicarbonate addition to a lidocaine-epinephrine combination. To investigate the nociceptive and clinical effects of buffering a lidocaine-epinephrine solution with sodium bicarbonate in caudal epidural block in mares. Methods: Prospective randomized controlled trial. Methods: Six mixed-breed mares weighing 350-440Â kg. Methods: Each animal was administered two caudal epidural injections, 72 hours apart, using different solutions prepared immediately before injection. The control solution was 7Â mL 2% lidocaine hydrochloride with epinephrine hemitartrate (1:200,000) added to 3Â mL sterile water for injection (pH 2.9). The alkalinized solution was 7Â mL o...
The effect of anesthetic drug choice on accuracy of high-definition oscillometry in laterally recumbent horses. To determine the accuracy of high-definition oscillometry (HDO) for arterial pressure measurement during injectable or inhalation anesthesia in horses. Methods: Prospective, clinical study. Methods: Twenty-four horses anesthetized for procedures requiring lateral recumbency. Methods: Horses were premedicated with xylazine, and anesthesia induced with diazepam-ketamine. Anesthesia was maintained with xylazine-ketamine-guaifenesin combination [TripleDrip (TD; n = 12) or isoflurane (ISO; n = 12)]. HDO was used to obtain systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures, and he...
Comparison between the effects of postanesthetic xylazine and dexmedetomidine on characteristics of recovery from sevoflurane anesthesia in horses. To compare postanesthetic xylazine and dexmedetomidine on recovery characteristics from sevoflurane anesthesia in horses. Methods: Randomized, crossover study. Methods: Six geldings, mean±standard deviation (SD) (range), 17±4 (11-24) years and 527±80 (420-660) kg. Methods: Horses were anesthetized with sevoflurane for 60 minutes under standardized conditions for a regional limb perfusion study. In recovery, horses were administered either xylazine (200 μg kg) or dexmedetomidine (0.875 μg kg) intravenously. Recoveries were unassisted and were video-recorded for later evaluation of rec...
Review of hypoxaemia in anaesthetized horses: predisposing factors, consequences and management. To discuss how hypoxaemia might be harmful and why horses are particularly predisposed to developing it, to review the strategies that are used to manage hypoxaemia in anaesthetized horses, and to describe how successful these strategies are and the adverse effects associated with them. Methods: Google Scholar and PubMed, using the search terms horse, pony, exercise, anaesthesia, hypoxaemia, oxygen, mortality, morbidity and ventilation perfusion mismatch. Conclusions: Although there is no evidence that hypoxaemia is associated with increased morbidity and mortality in anaesthetized horses, mos...
Comparison of arterial blood pressure measurements obtained invasively or oscillometrically using a Datex S/5 Compact monitor in anaesthetised adult horses. To assess agreement between noninvasive blood pressure (NIBP) oscillometrically-derived values from a multiparameter monitor (Datex Ohmeda S/5 Compact) with those obtained by invasive blood pressure (IBP) measurement in anaesthetised horses undergoing elective surgery. Methods: Prospective clinical study. Methods: A total of 40 healthy adult horses. Methods: Horses were anaesthetised with various anaesthetic protocols (based on clinical requirements). Depending on positioning, cannulation of the facial or lateral metatarsal artery was performed for IBP measurement. The cannula was connected vi...
Measurement of intraocular pressure in healthy anesthetized horses during hoisting. To measure intraocular pressure (IOP) in horses during hoisting after induction of anesthesia. Methods: Prospective nonrandomized clinical study. Methods: Eighteen healthy adult horses aged [mean±standard deviation (SD)] 10±4.2 years and weighing 491±110 kg anesthetized for elective procedures. Methods: IOP was measured in the superior eye of each horse based on planned recumbency after induction of anesthesia. Measurements were taken directly after premedication with xylazine or detomidine with butorphanol, after induction with diazepam-ketamine, after intubation, when suspended by the ho...
A novel approach for regional anaesthesia of the auricular region in horses: an anatomic and imaging study. To investigate the anatomy of the ear innervation in horses and develop a new approach for the block of the internal and external pinna and acoustic meatus. Methods: Prospective, descriptive, cadaveric study. Methods: A total of 25 heads and necks from horse cadavers. Methods: Phase I: anatomical dissection and dye deposition on 19 heads. With the head positioned in lateral recumbency, 10 mL methylene blue (1:1 sterile water) for the internal auricular and 2 mL for the great auricular nerve block were injected in 21 ears (seven left, 10 right and two bilaterally). The anatomy of all the ears (...
Cardiopulmonary effects of pleural insufflation with CO2 during two-lung ventilation in dorsally recumbent anesthetized horses. To record the cardiopulmonary effects of pleural CO2 positive pressure insufflation in anesthetized horses. Methods: Prospective study. Methods: Seven horses (mean ± standard deviation, 530.9 ± 68.1 kg) undergoing terminal surgery. Methods: Horses 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,...
Sub-Tenon’s injection in equine cadaver eyes: MRI visualization of anesthetic fluid distribution and comparison of two different volumes. To compare the localization and distribution of two different anesthetic fluid volumes around equine cadaver eyes to determine an appropriate volume for a single sub-Tenon's injection in horses. Methods: A single sub-Tenon's injection of 2% lidocaine was performed in 10 equine cadaver heads (20 eyes) using two different volumes (7 mL on one side and 10 mL on the opposite side). The posterior circular distribution of the anesthetic was quantified in sagittal, dorsal, and transverse MRI (T2W-TSE) sequences and evaluated independently by three board-certified radiologists. The distribution of the...
Validation of the bispectral index as an indicator of anesthetic depth in Thoroughbred horses anesthetized with sevoflurane. To evaluate the bispectral index (BIS) as an indicator of anesthetic depth in Thoroughbred horses, BIS values were measured at multiple stages of sevoflurane anesthesia in five horses anesthetized with guaifenesin and thiopental following premedication with xylazine. There was no significant difference between the BIS values recorded at end-tidal sevoflurane concentrations of 2.8% (median 60 ranging from 47 to 68) and 3.5% (median 71 ranging from 49 to 82) in anesthetized horses. These BIS values during anesthesia were significantly lower (P<0.01) than those in awake horses (median 98 ranging ...
Incidence of post-anesthetic colic in non-fasted adult equine patients. The purpose of this study was to determine the incidence of post-anesthetic colic in non-fasted adult horses undergoing isoflurane inhalant anesthesia for an elective, non-abdominal procedure at a single referral center. Medical records were searched from May 1, 2012 to May 31, 2014. Inclusion criteria included non-fasted patients ≥ 2 years of age that were anesthetized for an elective, non-abdominal procedure. The incidence of post-anesthetic colic for this study population was 2.5%. None of the risk factors examined (season, age, gender, breed, surgeon, procedure, recumbency, butorphanol a...
Effects of dobutamine hydrochloride on cardiovascular function in horses anesthetized with isoflurane with or without acepromazine maleate premedication. OBJECTIVE To determine the effects of acepromazine maleate premedication on cardiovascular function before and after infusion of dobutamine hydrochloride for 30 minutes in isoflurane-anesthetized horses. ANIMALS 6 healthy adult horses. PROCEDURES Each horse was anesthetized once following premedication with acepromazine (0.02 mg/kg, IV) administered 30 minutes prior to anesthetic induction (ACP+ treatment) and once without premedication (ACP- treatment). Anesthesia was induced with IV administration of xylazine hydrochloride (0.8 mg/kg), ketamine hydrochloride (2.2 mg/kg), and diazepam (0.08 m...
Modified technique for common carotid artery transposition in standing horses. To describe a modified technique for permanent translocation of the common carotid artery (CCA) to a subcutaneous position in standing horses. Methods: Experimental study. Methods: Healthy adult Standardbred and Warmblood horses (n = 8). Methods: Surgery was performed with the horses standing under sedation and with local anesthesia. A combination of previously described techniques was used modifying the approach and closure of the incision. The right CCA was approached through a linear skin incision dorsal and parallel to the jugular vein and through the brachiocephalicus and omohyoideus ...
Evaluation of xylazine and ketamine for maintenance of anesthesia in horses. Eight horses [5.6 ± 3.6 years, 489 ± 48.6 kg (mean ± SD)] were anesthetized four times under laboratory conditions to characterize physiologic and behavioral (reported elsewhere) responses associated with a 1-hours period of total intravenous anesthesia (TIA). Each horse was premedicated with xylazine (X, 0.75 mg kg−1) and anesthesia induced 5 minutes later with 5% guaifenesin (75 mg kg−1) and ketamine (K, 2 mg kg−1), all given IV After anesthetic induction, horses were intubated and received one of six treatments [X 35, K 90, O2; X 35, K 120, O2; X 35, K 120, air; X 35, K150, O2; X 7...
