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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 a horse with cervical vertebral stenotic myelopathy. A 3-year-old Thoroughbred gelding presented with a history of neurological signs, including incoordination in his hindlimbs, of about 7 months' duration. On initial examination, the horse exhibited ataxia and paresis in all limbs with more severe deficits in the hindlimbs. Cervical radiographs displayed severe osteoarthritis of the articular processes between C5 and C6. On subsequent cervical myelography the dorsal contrast column was reduced by 90% at the level of the intervertebral space between C5 and C6. Cervical vertebral canal endoscopy, including epidural (epiduroscopy) and subarachnoid...
Evaluation of sedation and analgesia in standing horses after administration of xylazine, butorphanol, and subanesthetic doses of ketamine. To evaluate the sedative and analgesic effects of subanesthetic doses of ketamine in horses sedated with xylazine, with or without butorphanol. Methods: Prospective, randomized, controlled study. Methods: 10 adult horses. Methods: Each horse was sedated multiple times by administration of xylazine (treatment X), xylazine and butorphanol (treatment XB), xylazine with 1 of 2 dosages of ketamine (treatment XK1 or XK2), or xylazine and butorphanol with 1 of 2 dosages of ketamine (treatment XBK1 or XBK2). Head height and various behaviors, including responses to noise, insertion of a dental float, ...
Quantitative and qualitative comparison of three scoring systems for assessing recovery quality after general anaesthesia in horses. To assess the reproducibility and repeatability of two commonly used recovery quality scoring systems and compare them with those of a novel system based on a greater number of objective criteria. Methods: The video-recorded recoveries of ten client-owned horses selected from all recovery recordings taken between September 2005 and March 2006 at the Royal (Dick) School of Veterinary Studies. Methods: A digital versatile disc (DVD) was produced using edited video recordings of ten horses recovering from general anaesthesia. Twelve experienced equine anaesthetists (raters) studied the DVD on thr...
Effects of constant rate infusion of lidocaine and ketamine, with or without morphine, on isoflurane MAC in horses. Lidocaine and ketamine are administered to horses as a constant rate infusion (CRI) during inhalation anaesthesia to reduce anaesthetic requirements. Morphine decreases the minimum alveolar concentration (MAC) in some domestic animals; when administered as a CRI in horses, morphine does not promote haemodynamic and ventilatory changes and exerts a positive effect on recovery. Isoflurane-sparing effect of lidocaine, ketamine and morphine coadministration has been evaluated in small animals but not in horses. Objective: To determine the reduction in isoflurane MAC produced by a CRI of lidocaine ...
Effect of 50% and maximal inspired oxygen concentrations on respiratory variables in isoflurane-anesthetized horses. The purpose of this study was to compare the effects of 0.5 fraction of inspired oxygen (FiO₂) and >0.95 FiO₂ on pulmonary gas exchange, shunt fraction and oxygen delivery (DO₂) in dorsally recumbent horses during inhalant anesthesia. The use of 0.5 FiO₂ has the potential to reduce absorption atelectasis (compared to maximal FiO₂) and augment alveolar oxygen (O₂) tensions (compared to ambient air) thereby improving gas exchange and DO₂. Our hypothesis was that 0.5 FiO₂ would reduce ventilation-perfusion mismatching and increase the fraction of pulmonary blood flow that is ox...
The effects of lactated Ringer’s solution (LRS) or LRS and 6% hetastarch on the colloid osmotic pressure, total protein and osmolality in healthy horses under general anesthesia. To investigate changes in colloid osmotic pressure (COP), total protein (TP) and osmolality (OSM) during anesthesia in horses given intravenous lactated Ringer's solution (LRS) or LRS and hetastarch (HES). Methods: Prospective, clinical trial. Methods: Fourteen horses presented for surgery. Mean age 8.3 ± 1.9 years; mean weight 452 ± 25 kg. Methods: Horses were premedicated with xylazine intravenously (IV); anesthesia was induced with ketamine and diazepam IV, and maintained with sevoflurane. Butorphanol was administered IV with pre-medications or immediately after induction. Xylazine was ad...
Goniometry: is it a reliable tool to monitor passive joint range of motion in horses? Simple objective assessment tools are essential to monitor the clinical efficacy of therapeutic interventions used in equine orthopaedics and rehabilitation. In human medicine, goniometry is a validated tool to quantify restrictions in joint range of motion (ROM); however, the technique is not validated in horses. Objective: To validate 2 different goniometry techniques for the measurement of passive flexion of the fetlock, carpus and hock by examining; 1) the intra- and inter-tester reliability; 2) the differences between 2 goniometry techniques and 3) differences between standing and anaesth...
Occupational exposure to isoflurane during anaesthesia induction with standard and scavenging double masks in dogs, pigs and ponies. Induction of anaesthesia using a face mask may cause workplace pollution with anaesthetics. The aim of this study was to compare the effect of the use of a standard versus a scavenging double face mask on isoflurane pollution during induction of anaesthesia in experimental animals: six dogs, 12 pigs and five ponies. Pigs were anaesthetized only once using either mask type randomly (n = 6). Dogs and ponies were anaesthetized twice, using different mask types for each occasion in a random order with at least 14 days between experiments. The masks were attached to a Bain breathing system (dogs an...
Clinical Evaluation of Xylazine-Butorphanol-Guaifenesin-Ketamine as Short-Term TIVA in Equines. Xylazine (1.1 mg/kg), butorphanol (0.02 mg/kg), guaifenesin 5% (20 mg/kg), and ketamine (2.2 mg/kg) combinations were able to induce short-term surgical anaesthesia for 23.33 ± 2.57 min in Spiti ponies with excellent to good muscle relaxation and analgesia. Urination and neighing was a constant feature during recovery period. Biphasic P wave, biphasic T wave, and depressed PR segment were common electrocardiographic findings. Biochemical attributes were within physiological limits except a significant increase in ALT values during anaesthesia. The values returned to normal during re...
Preliminary investigation of somatosensory evoked potentials in equine headshaking. The aim of this study was to develop a technique for recording electrical activity of the equine cerebral cortex following application of a noxious electrical stimulus to the maxillary branch of the trigeminal nerve in order to investigate trigeminal nerve neurophysiology in control and headshaking horses. Triphasic somatosensory evoked potentials (SEPs) were recorded using subcutaneous needle electrodes in four control and four headshaking horses under general anaesthesia. Dural electroencephalography electrodes were used to record SEPs in one further control and one further headshaking horse...
Internal fixation of a fractured axis in an adult horse. To report internal fixation of a fractured axis with a dynamic compression plate (DCP). Methods: Case report. Methods: A 7-year-old Warmblood gelding. Methods: Surgery was performed under anesthesia in sternal recumbency. After fracture reduction the complete transverse fracture in the cranial third of the axis was stabilized with a 7-hole 4.5 mm DCP. Optimal positioning of the plate and the length of the screws were facilitated by fluoroscopy. Recovery from anesthesia was supervised in a pool. Results: The horse had an excellent outcome and returned to its previous activity level. Conclusions...
Pulmonary gas exchange and plasma lactate in horses with gastrointestinal disease undergoing emergency exploratory laparotomy: a comparison with an elective surgery horse population. To characterize pulmonary gas exchange and arterial lactate in horses with gastrointestinal disease undergoing anesthesia, compared with elective surgical horses, and to correlate these variables with postoperative complications and mortality. Methods: Prospective clinical study. Methods: Horses undergoing emergency laparotomy for acute intestinal disease (n = 50) and healthy horses undergoing elective surgery in dorsal recumbency (n = 20). Methods: Arterial blood gas analysis was performed at predetermined intervals on horses undergoing a standardized anesthetic protocol. Alveolar-arterial ox...
Treatment of a coxofemoral luxation in a pony using a prosthetic capsule technique. To report open reduction and joint stabilization using a prosthetic capsule technique for treatment of a craniodorsal coxofemoral luxation in a lightweight pony. Methods: Clinical report. Methods: Pony stallion (8 years old, 113 kg). Methods: A craniodorsal approach to the coxofemoral joint was performed under general anesthesia. After open reduction, a prosthetic capsule technique was used. Four 3.5 mm self-tapping cortical anchor screws were implanted: 2 screws were inserted above the cranial aspect of the dorsal acetabular rim, and 2 screws were inserted into the femoral neck. Subsequently,...
Evaluation of four techniques for injecting the trochanteric bursa of horses. To describe the anatomic features of the equine trochanteric bursa and to evaluate 4 techniques for bursa centesis. Methods: Prospective, randomized design. Methods: Equine cadavers (n=2) and 20 live horses. Methods: The trochanteric bursae of 2 equine cadavers were injected with latex to identify the boundaries of the bursae. Four techniques for centesis of the trochanteric bursa were evaluated by attempting to inject dye into both trochanteric bursae of 20 live horses. Techniques included injection of the bursa with the limb-bearing weight and injection with the limb nonweight bearing and su...
Neuromuscular blockade with rocuronium bromide for ophthalmic surgery in horses. The production of a central eye to ease surgical access for intraocular surgery is generally dependent on the depth of anesthesia. The aim of this study was to evaluate the eyeball position under muscle relaxation with rocuronium during general anesthesia. Methods: Twenty horses, body weight 480 ± 62 kg; age 12.6 ± 6.2 years (mean ± SD) were anesthetised for various ophthalmic surgeries. Horses were premedicated with acepromazine, xylazine, and butorphanol intravenously and anesthesia induced with ketamine and diazepam. Anesthesia was maintained with isoflurane in 100% oxyge...
Continuous peripheral neural blockade to alleviate signs of experimentally induced severe forelimb pain in horses. To investigate the efficacy and safety of a low-volume, single-catheter, continuous peripheral neural blockade (CPNB) technique to locally deliver bupivacaine to alleviate signs of severe forelimb pain resulting from experimentally induced tendonitis in horses. Methods: Randomized controlled experimental trial. Methods: 14 horses and 5 forelimbs from equine cadavers. Methods: Horses underwent collagenase-induced superficial digital flexor tendonitis in the midmetacarpal region of 1 forelimb. To deliver analgesia, a closed-tip catheter was placed from lateral to medial, approximately 12 cm dist...
A clinical study on the effect in horses during medetomidine-isoflurane anaesthesia, of butorphanol constant rate infusion on isoflurane requirements, on cardiopulmonary function and on recovery characteristics. To test if the addition of butorphanol by constant rate infusion (CRI) to medetomidine-isoflurane anaesthesia reduced isoflurane requirements, and influenced cardiopulmonary function and/or recovery characteristics. Methods: Prospective blinded randomised clinical trial. Methods: 61 horses undergoing elective surgery. Methods: Horses were sedated with intravenous (i.v.) medetomidine (7 μg kg(-1)); anaesthesia was induced with i.v. ketamine (2.2 mg kg(-1)) and diazepam (0.02 mg kg(-1)) and maintained with isoflurane and a CRI of medetomidine (3.5 μg kg(-1) hour(-1)). Group MB (n = 31) receive...
Intermittent positive pressure ventilation with constant positive end-expiratory pressure and alveolar recruitment manoeuvre during inhalation anaesthesia in horses undergoing surgery for colic, and its influence on the early recovery period. To compare, ventilation using intermittent positive pressure ventilation (IPPV) with constant positive end-expiratory pressure (PEEP) and alveolar recruitment manoeuvres (RM) to classical IPPV without PEEP on gas exchange during anaesthesia and early recovery. Methods: Prospective randomized study. Methods: Twenty-four warm-blood horses, weight mean 548 ± SD 49 kg undergoing surgery for colic. Methods: Premedication, induction and maintenance (isoflurane in oxygen) were identical in all horses. Group C (n = 12) was ventilated using conventional IPPV, inspiratory pressure (PIP) 35-45 cmH2O; gr...
Assessment of the sedative effects of buprenorphine administered with 20 microg/kg detomidine in horses. The aim of this randomised, observer-blinded, crossover study was to compare the effects of four treatments, administered intravenously to six horses: saline and saline; 10 µg/kg detomidine and 7.5 µg/kg buprenorphine; 20 µg/kg detomidine and 7.5 µg/kg buprenorphine; and 20 µg/kg detomidine and 10 µg/kg buprenorphine. Sedation was subjectively assessed and recorded on a visual analogue scale. Peak sedation and duration of sedation were investigated using a univariate general linear model with post-hoc Tukey tests (P<0.05). Increasing the dose of detomidine from 10 to 20 µg/kg increas...
Repulsion of maxillary and mandibular cheek teeth in standing horses. To report the technique and results of cheek teeth repulsion in standing, sedated horses. Methods: Case series. Methods: Horses (n = 12), ponies (6). Methods: Medical records (2006-2009) of horses that had cheek tooth repulsion while standing were reviewed. Inclusion criteria included: maxillary or mandibular cheek tooth disease diagnosed by clinical and radiographic examination where attempted oral extraction failed necessitating repulsion. Horses were sedated and a local nerve block performed. Intraoperative radiographs facilitated instrument positioning and ensured repulsion of all dental r...
Comparison of the cardiovascular effects of equipotent anesthetic doses of sevoflurane alone and sevoflurane plus an intravenous infusion of lidocaine in horses. To compare cardiovascular effects of sevoflurane alone and sevoflurane plus an IV infusion of lidocaine in horses. Animals-8 adult horses. Methods: Each horse was anesthetized twice via IV administration of xylazine, diazepam, and ketamine. During 1 anesthetic episode, anesthesia was maintained by administration of sevoflurane in oxygen at 1.0 and 1.5 times the minimum alveolar concentration (MAC). During the other episode, anesthesia was maintained at the same MAC multiples via a reduced concentration of sevoflurane plus an IV infusion of lidocaine. Heart rate, arterial blood pressures, blood...
Effects of intravenous administration of lidocaine on the minimum alveolar concentration of sevoflurane in horses. To determine effects of a continuous rate infusion of lidocaine on the minimum alveolar concentration (MAC) of sevoflurane in horses. Methods: 8 healthy adult horses. Methods: Horses were anesthetized via IV administration of xylazine, ketamine, and diazepam; anesthesia was maintained with sevoflurane in oxygen. Approximately 1 hour after induction, sevoflurane MAC determination was initiated via standard techniques. Following sevoflurane MAC determination, lidocaine was administered as a bolus (1.3 mg/kg, IV, over 15 minutes), followed by constant rate infusion at 50 μg/kg/min. Determination...
Assessment of the sedative effects of buprenorphine administered with 10 μg/kg detomidine in horses. The aim of this randomised, observer-blinded, crossover study was to compare the effects of six treatments, administered intravenously to six horses: saline and saline (S/S); detomidine and saline (D/S); detomidine and 5 µg/kg buprenorphine (D/B5); detomidine and 7.5 µg/kg buprenorphine (D/B7.5); detomidine and 10 µg/kg buprenorphine (D/B10); and detomidine and 25 µg/kg butorphanol (D/BUT). The detomidine dose was 10 µg/kg for all treatments in which it was included. Sedation was subjectively assessed and recorded on a visual analogue scale. Peak sedation, duration of sedation and the are...
Reaction to intraarterial ionic iodinated contrast medium administration in anesthetized horses. The purpose of this report was to evaluate the frequency and type of reactions to intraarterial iodinated contrast medium injection in horses. Ninety-seven received an intraarterial injection of ionic, iodinated contrast medium for computed tomographic assessment of the distal limb. Nine (9.0%) horses developed a reaction attributable to the contrast medium administration. Of those, 4/97 (4.0%) developed a skin response (three with urticaria, one with facial edema) within 20 min. Five (5.0%) developed elevation of heart rate and/or blood pressure immediately upon administration of the contrast...
Immunomodulation during and after castration under inhalation anaesthetic without genotoxic effects on equine lymphocytes. Genotoxic DNA damage due to inhalation anaesthesia has been demonstrated in human lymphocytes. In order to evaluate anaesthesia-associated changes in cell-mediated immunity on the basis of a potential DNA damage as a health risk in horses, single cell gel electrophoresis and lymphocyte proliferation assay were performed on equine lymphocytes which were obtained before, during and after regular castration under inhalation anaesthetic. No significant lymphocytic DNA damage due to isoflurane anaesthesia was observed, whereas lymphocyte proliferative reactivity and lymphocyte counts decreased sign...
Ultrasonographic findings in horses with foot pain but without radiographically detectable osseous abnormalities. Foot pain is an important cause of lameness in horses. When horses with foot pain have no detectable radiographic abnormalities, soft-tissue assessment remains a diagnostic challenge without magnetic resonance (MR) imaging. Ultrasonography can provide an alternative to MR imaging when that modality is not available but the extent of changes that might be seen has not been characterized. We reviewed the ultrasonographic findings in 39 horses with lameness responding positively to anesthesia of the palmar digital nerves and without radiographically detectable osseous abnormalities. Thirty of the...
Successful treatment of hyperkalaemic periodic paralysis in a horse during isoflurane anaesthesia. A 3-year-old, 400 kg, gelding Quarter Horse was presented for investigation of epistaxis. Methods: The horse was bright, alert and responsive with rectal temperature, heart rate and respiration rate within normal limits. Results: During a second general anaesthetic for surgical treatment of guttural pouch mycosis by balloon-tipped catheter occlusion of the right major palatine artery and ligation of the right external carotid artery, signs consistent with hyperkalaemic periodic paralysis (HYPP) were exhibited. These included concurrent hyperkalaemia, hypercapnoea, sinus tachycardia, and muscle...
Comparison of water manometry to 2 commercial electronic pressure monitors for central venous pressure measurement in horses. Central venous pressure (CVP) customarily has been measured in veterinary patients with water manometry. However, many institutions are now using stallside electronic monitors in both anesthesia and intensive care units for many aspects of patient monitoring. Objective: Electronic stall side monitoring devices will agree with water manometry for measurement of CVP in horses. Methods: Ten healthy adult horses from the university research herd. Methods: Central venous catheters were placed routinely, and measurements were obtained in triplicate with each of the 3 methods every 12 hours for 3 day...
Influence of modified open lung concept ventilation on the cardiovascular and pulmonary function of horses during total intravenous anaesthesia. The influence of a modified open lung concept (mOLC) on pulmonary and cardiovascular function during total intravenous anaesthesia (TIVA) in horses was evaluated. Forty-two warmblood horses (American Society of Anesthesiologists class 1 to 2), scheduled for elective surgery (mean [sd] weight 526 [65] kg, age 6.4 [5.4] years) were randomly divided into three groups: ventilation with mOLC, intermittent positive-pressure ventilation (IPPV), and spontaneous breathing. Premedication (0.8 mg/kg xylazine), induction (2.2 mg/kg ketamine and 0.05 mg/kg diazepam) and maintenance of anaesthesia with TIVA...
Effects of ophthalmic disease on concentrations of plasma fibrinogen and serum amyloid A in the horse. There is little scientific information available about the ability of ocular disease to cause a systemic inflammatory response. Horses are frequently affected with ocular disease and ensuring their systemic health prior to performing vision saving surgery under anaesthesia is essential for the successful treatment of ophthalmic disease. Objective: Ocular disease will cause elevations in the concentration of the acute phase proteins fibrinogen and serum amyloid A in peripheral blood. Methods: Whole blood and serum samples were obtained from 38 mature horses with ulcerative keratitis or uveitis ...
