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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.
Cervical vertebral canal endoscopy in the horse: intra- and post operative observations. Despite modern medical diagnostic imaging, it is not possible to identify reliably the exact location of spinal cord compression in horses with cervical vertebral stenotic myelopathy (CVSM). Vertebral canal endoscopy has been successfully used in man and a technique for cervical vertebral canal endoscopy (CVCE) has been described in equine cadavers. Objective: To determine the feasibility and safety of CVCE in healthy mature horses. Methods: Six healthy mature horses were anaesthetised. A flexible videoendoscope was subsequently introduced via the atlanto-occipital space into the epidural spac...
Comparison of ketamine and alfaxalone for induction and maintenance of anaesthesia in ponies undergoing castration. To compare alfaxalone with ketamine for total intravenous anaesthesia in ponies undergoing castration. Methods: Prospective, randomised, blinded clinical study. Methods: Forty-two, 12-month-old Welsh Mountain ponies. Methods: Ponies were assigned randomly to receive ketamine or alfaxalone. After administration of romifidine 100 μg kg(-1) and butorphanol 50 μg kg(-1) intravenously (IV), sedation and response to tactile stimulation were scored. If sedation was insufficient, romifidine 30 μg kg(-1) was administered IV. Anaesthesia was induced with ketamine 2.2 mg kg(-1) or alfaxalone 1 mg kg(-...
Effects of isoflurane anesthesia on cerebrovascular autoregulation in horses. To test a hypothesis predicting that isoflurane would interfere with cerebrovascular autoregulation in horses and to evaluate whether increased mean arterial blood pressure (MAP) would increase cerebral blood flow and intracranial pressure (ICP) during isoflurane anesthesia. Methods: 6 healthy adult horses. Methods: Horses were anesthetized with isoflurane at a constant end-tidal concentration sufficient to maintain MAP at 60 mm Hg. The facial, carotid, and dorsal metatarsal arteries were catheterized for blood sample collection and pressure measurements. A sub-arachnoid transducer was used to...
Sensory nerve conduction and nociception in the equine lower forelimb during perineural bupivacaine infusion along the palmar nerves. The purpose of this investigation was to study lateral palmar nerve (LPN) and medial palmar nerve (MPN) morphology and determine nociception and sensory nerve conduction velocity (SNCV) following placement of continuous peripheral nerve block (CPNB) catheters along LPN and MPN with subsequent bupivacaine (BUP) infusion. Myelinated nerve fiber distribution in LPN and MPN was examined after harvesting nerve specimens in 3 anesthetized horses and processing them for morphometric analysis. In 5 sedated horses, CPNB catheters were placed along each PN in both forelimbs. Horses then received in one ...
Treatment of epiglottic entrapment by transnasal axial division in standing sedated horses using a shielded hook bistoury. To report use of a shielded hook bistoury developed for correction of epiglottic fold entrapment in standing sedated horses. Methods: Prospective clinical study. Methods: Standardbreds (n=8), 3-19 years of age. Methods: Epiglottic fold entrapment was corrected during standing sedation using a shielded hook bistoury passed nasally into the pharynx. Owners, trainers, and referring veterinarians were contacted by telephone to establish outcome. Results: Axial division of the entrapping epiglottic fold was successful in all horses. No short- or long-term complications occurred. Axial transection o...
Duration of corneal anaesthesia following multiple doses and two concentrations of tetracaine hydrochloride eyedrops on the normal equine cornea. There is a clinical impression that tetracaine hydrochloride (THCl) eyedrops is a suitable topical anaesthetic in horses. Objective: To determine the duration of corneal anaesthesia following instillation of multiple doses and 2 concentrations of THCl in 10 healthy horses. Methods: The corneal touch threshold (CTT) was determined, in both eyes, before (basal CTT) and after application of one drop of 0.5% THCl, 2 drops at a 1 min interval of 0.5% THCl or one drop of 1% THCl. CTT was measured in mm every 5 min until complete recovery of the basal CTT. Treatments were separated by an interval of ...
Contemporary use of acepromazine in the anaesthetic management of male horses and ponies: a retrospective study and opinion poll. Current use of acepromazine in the anaesthetic management of male horses and ponies and associated risks are largely unknown. Objective: To explore anaesthetic acepromazine use and related adverse effects in the male horse. Methods: Of 8533 anaesthetised horses and ponies medical records of male animals treated perianaesthetically with acepromazine were reviewed. Demographic data, time and dose of acepromazine administration, co-administered drugs, quality of induction and recovery from anaesthesia, arterial blood pressures, and occurrence of penile dysfunction were recorded. Practising ACVA a...
NMDA receptor antagonists and pain: ketamine. N-Methyl-D-aspartate (NMDA) is a synthetic chemical binding molecule (ligand) that selectively binds to the "slow response" glutamate NMDA receptor (NMDAR). NMDARs are important for normal brain function and play a central role in learning, memory, and the development of central nervous system hyperactive states. Diverse chemicals belonging to various drug families have demonstrated NMDAR antagonistic effects. Ketamine has been shown to produce antihyperalgesic effects produced by incision and tissue or nerve damage, and has become popular in equine practice as an anesthetic and more recently ...
Local anesthetics as pain therapy in horses. This article describes the rationale behind the use of systemically administered lidocaine as an analgesic. The analgesic efficacy of intravenously administered lidocaine is well documented by studies in human patients and laboratory animals. The mechanism by which systemically administered lidocaine produces analgesia is uncertain but is thought to include action at sodium, calcium, and potassium channels and the N-methyl-D-aspartate acid receptor. In addition, the anti-inflammatory actions of lidocaine are important in producing analgesia because inflammatory mediators augment neuronal excit...
Spinal anesthetics and analgesics in the horse. In the past 10 years, there have been many recent advances in spinal techniques in horses, both epidural and subarachnoid, to identify drugs or drug combinations that have sensory effects without motor nerve paralysis, thus providing pain control without these horses becoming recumbent. Opioids, alpha-2 agonists, dissociative drugs, and others have been investigated. Many of these drugs, which have serious side effects when injected systemically in horses, have been shown to have useful analgesic effects when injected spinally. Morphine-like opioids have the greatest potential for spinal use a...
Alpha-2 agonists as pain therapy in horses. Alpha-2 agonists, such as xylazine, clonidine, romifidine, detomidine, medetomidine, and dexmedetomidine, are potent analgesic drugs that also induce physiologic and behavioral changes, such as hypertension, bradycardia, atrioventricular block, excessive sedation and ataxia, all of which can potentially limit their systemic use as analgesics in some clinical cases. The use of medetomidine and dexmetomidine has been introduced for equine anesthesia/analgesia, and although not approved in this species, their increased specificity for alpha-2 receptors may offer some potential advantages over the...
Bilateral iatrogenic [corrected] maxillary fractures after dental treatment in two aged horses. This clinical report describes two horses with bilateral maxillary fractures following dental treatment. The fractures occurred during dental treatment by a veterinarian, and both had rostral, transverse, and complete bilateral maxillary fractures with instability and minimal displacement. The fractures were repaired using bilateral intraoral wiring with the patients under general anesthesia. The postoperative period was without complications and the fractures healed as expected. Maxillary fractures during or after routine dental treatment are rare, but can occur, especially in older horses. A...
An XY agonadal Oldenburg warmblood horse exhibiting a male phenotype. In a 1.5-year-old Oldenburg horse, a clitoris-like structure instead of a penis was identified in the prepuce. The external genital organs did not show any abnormalities at visual inspection except that exteriorization of the penis was not possible, not even under general anesthesia. The horse's owner observed a continuous dripping of urine and a tendency to mild colics beginning 2 weeks after birth. Testosterone concentration was 0.01 ng/ml and therefore under the threshold for geldings, and the horse did not respond to the application of gonadotropin-releasing hormone (GnRH). The inner genit...
Efficacy of three tourniquet types for intravenous antimicrobial regional limb perfusion in standing horses. To determine (1) if clinically useful concentrations of amikacin sulfate can be obtained in synovial fluid during regional limb perfusion (RLP) performed above the carpus in standing sedated horses and (2) to determine the efficacy of 3 tourniquet types (narrow rubber [NR], wide rubber [WR], pneumatic [PN]). Methods: Horses (n=9). Methods: Bilateral forelimb RLP with amikacin sulfate (2.5 g) were administered through the cephalic vein in standing sedated horses. Limbs were randomly assigned to the 3 tourniquet types (NR, WR, PN) applied above the carpus. Metacarpophalangeal synovial fluid was ...
Comparative study between atropine and hyoscine-N-butylbromide for reversal of detomidine induced bradycardia in horses. Bradycardia may be implicated as a cause of cardiovascular instability during anaesthesia. Objective: Hyoscine would induce positive chronotropism of shorter duration than atropine, without adversely impairing intestinal motility in detomidine sedated horses. Methods: Ten minutes after detomidine (0.02 mg/kg bwt, i.v.), physiological saline (control), atropine (0.02 mg/kg bwt) or hyoscine (0.2 mg/kg bwt) were randomly administered i.v. to 6 horses, allowing one week intervals between treatments. Investigators blinded to the treatments monitored cardiopulmonary data and intestinal auscultation ...
Vertical dimensions of suspended horses. The dimensions of anaesthetised hobbled horses during suspension and transfer onto the operating table are unknown. These data are required for the cost-effective construction of equine surgical facilities. Objective: To measure the distance from the toe to dependent back margin (Bsusp) and poll (Psusp) of anaesthetised suspended horses and correlate them with readily obtained measures from standing animals. Methods: Digital photographs of suspended horses were taken in the anaesthesia induction box at a fixed position that allowed trigonometric determination of Bsusp and Psusp. These values w...
Clinical application of Patlak plot CT-GFR in animals with upper urinary tract disease. Glomerular filtration rate (GFR), an important parameter of renal function, is difficult to assess clinically. Serum creatinine and blood urea nitrogen measurements lack sensitivity, whereas radionuclide determination of GFR is not always available and requires postinjection patient isolation. GFR can be determined using computed tomography (CT), most commonly via Patlak plot analysis. Four adult cats, two adult dogs, and a foal underwent abdominal CT under general anesthesia for various diseases of the upper urinary tract. CT-GFR was measured with a single-slice dynamic acquisition and Patlak...
Right dorsal colon resection and bypass for treatment of right dorsal colitis in a horse. To describe a novel surgical technique for management of right dorsal colitis in the horse. Methods: Clinical report. Methods: 14-year-old Warmblood gelding. Methods: The horse was referred for treatment of a stromal abscess and signs of right dorsal colitis. Plasma chemistry revealed marked hypoproteinemia. Abdominal ultrasonographic examination showed a thickened right dorsal colon (RDC). Medical treatment was unsuccessful. With the horse in left lateral recumbency under general anesthesia, an approach to the right side of the abdomen through a 16th rib resection was made. The thoracic cavit...
The effect of isotonic multiple electrolyte infusions during anesthesia on blood gas and enzymatic values in horses. General equine anesthesia is accompanied by the risk of complications and even death. The majority of general anesthetics used in veterinary practice lead to arterial hypotension, decreased capillary perfusion and ventilatory depression leading to pathological changes referred to as postanesthetic myopathy. In this study an attempt was made to analyze changes in the perioperative and postoperative acid-base equilibrium and blood enzymatic activity in horses, subject to the intensity of the applied fluid therapy. The horses were divided into two groups: I--administered Ringer's solution during ...
The use of sedatives, analgesic and anaesthetic drugs in the horse: an electronic survey of members of the American Association of Equine Practitioners (AAEP). To determine the sedative, analgesic and anaesthetic drugs and techniques that are used by equine veterinarians. HYPOTHESIS OR OBJECTIVES: To provide equine veterinarians with information concerning veterinary use of anaesthetic techniques, a reflection of the collective experiences of the profession. Methods: A survey was conducted of those members of the American Association of Equine Practitioners (AAEP) with an electronic mail address on file with the organisation using proprietary, web-based software. The survey was comprised of 30 questions divided into 8 sections: nonsteroidal anti-infl...
A cadaver study comparing two approaches to perform a maxillary nerve block in the horse. Anaesthesia of the maxillary nerve of the horse has been described using several approaches, but sparse data exist to evaluate the accuracy of these methods. Objective: This study compared 2 previously described approaches to the maxillary nerve to assess their relative accuracies. Methods: Thirty severed heads from horse cadavers were arranged to approximate the position of a live horse. Methylene blue (0.25 or 0.1 ml) was injected using a 19 gauge 90 mm spinal needle by one of 2 approaches, the method used being randomly allocated in each instance. Method ANG: angulated needle insertion on t...
Romifidine as a constant rate infusion in isoflurane anaesthetized horses: a clinical study. To evaluate the effects of a constant rate infusion (CRI) of romifidine on the requirement of isoflurane, cardiovascular performance and recovery in anaesthetized horses undergoing arthroscopic surgery. Methods: Randomized blinded prospective clinical trial. Methods: Thirty horses scheduled for routine arthroscopy. Methods: After premedication (acepromazine 0.02 mg kg(-1), romifidine 80 microg kg(-1), methadone 0.1 mg kg(-1)) and induction (midazolam 0.06 mg kg(-1) ketamine 2.2 mg kg(-1)), anaesthesia was maintained with isoflurane in oxygen. Horses were assigned randomly to receive a CRI of s...
Evaluation of cardiovascular, respiratory and biochemical effects, and anesthetic induction and recovery behavior in horses anesthetized with a 5% micellar microemulsion propofol formulation. To characterize cardiovascular, respiratory and biochemical effects and recovery behavior associated with a 3-hour continuous infusion of a micellar microemulsion propofol formulation in horses. Methods: Prospective experimental trial. Methods: Six healthy adult horses, 9 +/- 2 years old and weighing 557 +/- 14 kg. Methods: All horses received xylazine (1 mg kg(-1), IV) 5 minutes prior to anesthetic induction. Each horse was anesthetized on two occasions with a 5% micellar microemulsion propofol formulation (2 mg kg(-1), IV); first as a single bolus (phase I) and then as a 3-hour continuous in...
Reversal of profound rocuronium block monitored in three muscle groups with sugammadex in ponies. This clinical study evaluated the speed of reversal of profound rocuronium block in ponies using sugammadex and investigated the differences in onset and recovery from block in three different muscle groups. Methods: Anaesthesia was induced and maintained with isoflurane in oxygen 100% in eight ponies. Neuromuscular monitoring was performed at each site using acceleromyography: in the extensor muscles of the pelvic limb (peroneal nerve) and thoracic limb (radial nerve), and in the orbicularis oris muscle (OOM; facial nerve). Rocuronium 0.6 mg kg(-1) i.v. was administered, followed 5 min later ...
A comparison of four systems for scoring recovery quality after general anaesthesia in horses. The recovery quality scoring systems (RQSSs) in current use have not been critically reviewed for reliability. Objective: To examine reliability (reproducibility) of 4 RQSSs when applied to a ranked series. Methods: A DVD incorporating the recordings of 9 horses recovering from general anaesthesia was evaluated by final year students over 5 days. On Day 1, each evaluator ranked recoveries from 1-9 (1 = best). Over the following 4 days, each evaluator scored the same recoveries using 4 different RQSSs (3 of them in common usage and previously published) applied in random order. The scores from ...
Cardiopulmonary effects of two constant rate infusions of dexmedetomidine in isoflurane anaesthetized ponies. To evaluate the cardiopulmonary effects of two different constant rate infusions (CRI) of dexmedetomidine (1 and 1.75 microg kg(-1 )hour(-1)) in experimental ponies. Methods: Six healthy ponies (mean 306 +/- SD 71 kg, 7.0 +/- 1.6 years). Methods: Prospective, randomized, experimental study. Methods: After premedication with intravenous (IV) dexmedetomidine (3.5 microg kg(-1)), anaesthesia was induced (T0) with ketamine (2.2 mg kg(-1) IV) and midazolam (0.06 mg kg(-1) IV) and maintained with isoflurane (Fe'ISO 1.50%) in 55% oxygen for 150 minutes. Normocapnia was maintained using artificial ven...
Surgical extraction of an intraocular infection of Parelaphostrongylus tenuis in a horse. A 4-year-old Hanoverian gelding was evaluated because of a mobile worm-like structure in the right eye. Results: Ophthalmologic examination of the right eye revealed a white, thin, coiled, mobile parasite, which was presumed to be a nematode, located in the ventral portion of the anterior chamber of the eye; there also were vitreal strands located temporally and inferiorly near the margin of the pupil. Results of ophthalmologic examination of the left eye were unremarkable. Results: The horse was treated with a neomycin-polymyxin B-dexamethasone ophthalmic solution applied topically (1 drop, q...
Clinical application and reliability of a post abdominal surgery pain assessment scale (PASPAS) in horses. The aim of this study was to refine a multi-dimensional scale based on physiological and behavioural parameters, known as the post abdominal surgery pain assessment scale (PASPAS), to quantify pain after laparotomy in horses. After a short introduction, eight observers used the scale to assess eight horses at multiple time points after laparotomy. In addition, a single observer was used to test the correlation of each parameter with the total pain index in 34 patients, and the effect of general anaesthesia on PASPAS was investigated in a control group of eight horses. Inter-observer variabilit...
Use of a pinless external fixator for unilateral mandibular fracture repair in nine equids. To report use of a pinless external fixator (PEF) for unilateral mandibular fractures in 9 equids. Methods: Case series. Methods: Equids (n=9) with unilateral mandibular fractures. Methods: All fractures were stabilized with the AO/ASIF PEF using a minimum of 4 clamps, under general anesthesia. Fracture configuration, complications, outcome, and owner satisfaction were evaluated. Results: All fractures were stabilized; 2 equids were euthanatized; 1 because of an inability to stand after surgery and 1 because of owner decision after PEF dislodgement. Seven repairs healed with good outcome and o...
A study of the correlation between objective and subjective indices of recovery quality after inhalation anaesthesia in equids. To examine the association between objective and subjective descriptors used for assessing recovery quality in horses after anaesthesia. Methods: Prospective clinical study. Methods: Two hundred and seventy-six equids (110 mares, 85 entire males and 81 geldings), ASA 1-5, weighing 50-850 kg and aged 1 month - 25 years. Methods: Recoveries after general anaesthesia were assisted with head and tail ropes by two anaesthetists. One scored dichotomous objective descriptors (DOD) of recovery. Two dichotomous objective scales (DOS) were then generated from those descriptors. The same individual also ...
