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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.
The minimum infusion rate (MIR) of propofol for total intravenous anesthesia after premedication with xylazine in horses. To investigate an adequate infusion rate of propofol for total intravenous anesthesia (TIVA) in horses, the minimum infusion rate (MIR) comparable to the minimum alveolar anesthetic concentration (MAC) of inhalation anesthetic was determined under constant ventilation condition by intermittent positive pressure ventilation (IPPV). In addition, arterial propofol concentration was measured to determine the concentration corresponding to the MIR (concentration preventing reaction to stimulus in 50% of population, Cp(50)). Further, 95% effective dose (ED(95)) was estimated as infusion rate for acq...
Transient complete atrioventricular block following transvenous electrical cardioversion of atrial fibrillation in a horse. Transvenous electrical cardioversion was attempted in a horse with drug refractory atrial fibrillation. A temporary pacing catheter and two defibrillation catheters were inserted transvenously into the right ventricular apex, the right atrium and the pulmonary artery, respectively. Under general anaesthesia 100, 200, 300 and 360 J monophasic shocks were delivered between both defibrillation catheters but sinus rhythm could not be restored. Immediately after the 200, 300 and 360 J shock, transient third-degree atrioventricular block occurred for a period of, respectively, 15, 40 and 55 s. These...
The effects of halothane and isoflurane on cardiovascular function in laterally recumbent horses. Experimental studies in adult horses have shown that general anaesthesia maintained with isoflurane is associated with less depression of cardiovascular function compared with halothane anaesthesia. Adverse effects of intermittent positive-pressure ventilation (IPPV) have also been demonstrated. Nevertheless, the haemodynamic effects of these agents and the effects of differing modes of ventilation have not been assessed during clinical anaesthesia in horses undergoing surgery. Methods: The haemodynamic effects of isoflurane or halothane anaesthesia during spontaneous or IPPV were studied non-...
L-Bupivacaine 0.5% vs. racemic 0.5% bupivacaine for caudal epidural analgesia in horses. Bupivacaine is available as a racemic mixture of its enantiomers, d-bupivacaine and l-bupivacaine (LB). The aim of this randomized, double-blind study was to investigate the clinical efficacy and safety of S(-)-bupivacaine compared with standard racemic bupivacaine (RB) in horses under caudal epidural analgesia. Two treatments were administered to each horse, with a 2-week interval between subsequent treatments. Treatment 1 consisted of 0.5% LB at a dose of 0.06 mg/kg of body weight, and treatment 2 consisted of 0.5% RB at a dose of 0.06 mg/kg of body weight. Epidural injections were given in ...
Comparison of topical lidocaine/prilocaine anesthetic cream and local infiltration of 2% lidocaine for episioplasty in mares. Local anesthesia and tissue inflammation associated with lidocaine infiltration and lidocaine/prilocaine topical anesthetic cream for episioplasty in mares were compared. Twenty-two mares were randomly assigned to lidocaine or lidocaine/prilocaine topical anesthetic cream treatment groups. Perineum and vulva were cleaned, 8-12 g (approximately 1 g/cm per side of vulva) of topical anesthetic cream was applied, and the area was covered by plastic wrap 30 min prior to beginning procedure. Alternately, lidocaine was injected (1 mL) every centimeter just prior to the procedure. Episioplasty was con...
Influence of general anesthesia on pharmacokinetics of intravenous lidocaine infusion in horses. To compare the disposition of lidocaine administered IV in awake and anesthetized horses. Methods: 16 horses. Methods: After instrumentation and collection of baseline data, lidocaine (loading infusion, 1.3 mg/kg administered during 15 minutes (87 microg/kg/min); constant rate infusion, 50 microg/kg/min) was administered IV to awake or anesthetized horses for a total of 105 minutes. Blood samples were collected at fixed times during the loading and maintenance infusion periods and after the infusion period for analysis of serum lidocaine concentrations by use of liquid chromatography with mass...
Post-anaesthetic myelomalacia in a horse. This article describes a rare neurological complication of anaesthesia in a 2 year-old Clydesdale colt undergoing castration. Anaesthesia was induced with glyceryl guaiacol ether and ketamine and maintained with halothane. Following an uneventful anaesthetic of 40 minutes, the horse recovered from anaesthesia in a padded recovery stall. After approximately 70 minutes in the recovery stall, the horse attempted to stand and adopted a dog sitting position. One hundred and fifty minutes later, the horse became distressed and was sedated with xylazine. Clinical examination of the horse did not reve...
Effects of desflurane and mode of ventilation on cardiovascular and respiratory functions and clinicopathologic variables in horses. To quantitate the effects of desflurane and mode of ventilation on cardiovascular and respiratory functions and identify changes in selected clinicopathologic variables and serum fluoride values associated with desflurane anesthesia in horses. Methods: 6 healthy adult horses. Methods: Horses were anesthetized on 2 occasions: first, to determine the minimum alveolar concentration (MAC) of desflurane in O2 and second, to characterize cardiopulmonary and clinicopathologic responses to 1X, 1.5X, and 1.75X desflurane MAC during both controlled and spontaneous ventilation. Results: Mean +/- SEM MAC ...
Effects of sevoflurane dose and mode of ventilation on cardiopulmonary function and blood biochemical variables in horses. To quantitate effects of dose of sevoflurane and mode of ventilation on cardiovascular and respiratory function in horses and identify changes in serum biochemical values associated with sevoflurane anesthesia. Methods: 6 healthy adult horses. Methods: Horses were anesthetized twice: first, to determine the minimum alveolar concentration (MAC) of sevoflurane and second, to characterize cardiopulmonary and serum biochemical responses of horses to 1.0, 1.5, and 1.75 MAC multiples of sevoflurane during controlled and spontaneous ventilation. Results-Mean (+/- SEM) MAC of sevoflurane was 2.84 +/- ...
The effects of spontaneous and mechanical ventilation on central cardiovascular function and peripheral perfusion during isoflurane anaesthesia in horses. To compare the effects of spontaneous breathing and mechanical ventilation on haemodynamic variables, including muscle and skin perfusion measured with laser Doppler flowmetery, in horses anaesthetized with isoflurane. Methods: Prospective controlled study. Methods: Ten warm-blood trotter horses (five males, five females). Mean mass was 492 kg (range 420-584 kg) and mean age was 5 years (range 4-8 years). Methods: After pre-anaesthetic medication with detomidine (10 microg kg(-1)) anaesthesia was induced with intravenous (IV) guaifenesin and thiopental (4-5 mg kg(-1) IV) and maintained using i...
Electroencephalographic and cardiovascular variables as nociceptive indicators in isoflurane-anaesthetized horses. To evaluate Fourier-transformed electroencephalographic (EEG) variables, mean arterial blood pressure (MAP) and pulse rate as nociceptive indicators in isoflurane-anaesthetized horses. Methods: Five standardbred and three Norwegian cold-blooded trotter stallions undergoing castration, aged 2-4 years, mass 378-538 kg. Methods: All horses received intravenous (IV) detomidine (10 microg kg(-1) IV) and butorphanol (0.01 mg kg(-1) IV). Additional detomidine (4 microg kg(-1) IV) was administered in the induction area. Anaesthesia was induced with ketamine (2.5 mg kg(-1) IV) and diazepam (40 microg k...
In vivo interaction of pulmonary intravascular macrophages with activated platelets in microvessels of equine lung after multiple exposures to halothane, isoflurane, and thiamylal: a comparative ultrastructural and cytochemical study. The pulmonary intravascular macrophages (PIMs) of equines contain a unique electron-dense surface coat that is predominantly composed of lipoproteins. A single exposure of inhalatory halothane causes mobilization of the surface coat into the endocytotic system of the PIMs, followed by expansion of the Golgi apparatus and its enrichment with acid phosphatase. Simultaneously, the cells of the lymphocytic series show hyperplasia in the form of mitotic changes inside the microvascular compartment of the lung. Halothane is known to cause acute and chronic hepatotoxicity because of its biotransforma...
Anesthetic and cardiovascular effects of balanced anesthesia using constant rate infusion of midazolam-ketamine-medetomidine with inhalation of oxygen-sevoflurane (MKM-OS anesthesia) in horses. The anesthetic sparring and cardiovascular effects produced by midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.05 mg/ml (0.025 ml/kg/hr) drug infusion during sevoflurane in oxygen (MKM-OS) anesthesia was determined in healthy horses. The anesthetic sparring effects of MKM-OS were assessed in 6 healthy thoroughbred horses in which the right carotid artery was surgically relocated to a subcutaneous position. All horses were intubated and ventilated with oxygen using intermittent positive pressure ventilation (IPPV). The end-tidal concentration of sevoflurane (ET(SEV)) required to maintain s...
Destructive lesions of the proximal sesamoid bones as a complication of dorsal metatarsal artery catheterization in three horses. To describe focal destructive lesions of the proximal sesamoid bones (PSBs) as a complication of dorsal metatarsal artery catheterization performed for direct blood pressure monitoring during equine general anesthesia. Methods: Retrospective study. Methods: Three client-owned horses. Methods: A dorsal metatarsal artery was catheterized in each of 3 horses for direct blood pressure monitoring during anesthesia. Radiography, ultrasonography, synoviocentesis, and arthroscopy were used to diagnose postoperative lameness that occurred in the limb used for blood pressure monitoring. Results: Horses ...
Extensive nasal septum resection in horses using a 3-wire method. To describe a surgical technique for, and report outcome after, extensive nasal septum resection in horses with congenital or acquired septal diseases. Methods: Retrospective study. Methods: Horses (5) with nasal septal deformity. Methods: Under general anesthesia, obstetrical wires were preplaced around the ventral, caudal, and dorsal aspects of the nasal septum by combinations of manual guidance (ventral and caudal wires) and use of a trephine hole on the dorsal mid-line (dorsal and caudal wires). The rostral part of the septum was incised with a scalpel and the ventral, dorsal, and caudal s...
Effects of Carolina rinse solution, dimethyl sulfoxide, and the 21-aminosteroid, U-74389G, on microvascular permeability and morphology of the equine jejunum after low-flow ischemia and reperfusion. To evaluate effects of Carolina rinse solution, dimethyl sulfoxide (DMSO), and 21-aminosteroid, U-74389G, on microvascular permeability and morphology of the equine jejunum after low-flow ischemia and reperfusion. Methods: 20 healthy adult horses. Methods: Under anesthesia, full-thickness biopsy specimens of a distal portion of the jejunum were obtained for baseline measurements. In addition to a control segment, 2 jejunal segments were identified as sham-operated or experimental segments. Experimental segments underwent 60 minutes of low-flow ischemia and 3.5 hours of reperfusion. Treatments ...
Standing oral extraction of cheek teeth in 100 horses (1998–2003). Extraction of cheek teeth (CT) by the conventional repulsion technique requires general anaesthesia and carries a high rate of post operative complications. Consequently, an alternative method of extraction, i.e. orally in standing horses, was evaluated. Objective: The need for and risks of general anaesthesia could be avoided and post extraction sequelae reduced by performing extractions orally in standing horses. Methods: One hundred mainly younger horses (median age 8, range 2-18 years) with firmly attached CT that required extraction because of apical infections, displacements, diastemata,...
Effect of systemic lidocaine on visceral and somatic nociception in conscious horses. Commonly used analgesics (nonsteroidal anti-inflammatory agents, opioids and alpha2-agonists) have unwanted side effects. An effective alternative with minimal adverse effects would benefit clinical equine pain management. Objective: To compare the effect of lidocaine or saline on duodenal and rectal distension threshold pressure and somatic thermal threshold in conscious mature horses. Objective: Systemically administered lidocaine would increase somatic and visceral nociceptive thresholds. Methods: Lidocaine (2 mg/kg bwt bolus followed by 50 microg/kg bwt/min for 2 h) or saline was administe...
Modified frontonasal sinus flap surgery in standing horses: surgical findings and outcomes of 60 cases. Previous studies of sinus surgery on standing horses have been based on techniques which utilise powered hand bone saws and preserve the bone flap, which was thought to be essential for a good cosmetic result. This report describes a simplified technique applied to the standing horse where the sinus flap construction used a large skull trephine and where the bone flap is necessarily discarded. Objective: To assess whether the modified standing frontonasal flap (SFF) surgery offers an effective method to investigate and/or treat sinunasal disorders in the horse. Methods: The case records of 60 ...
Isoflurane measurement error using short wavelength infrared techniques in horses: influence of fresh gas flow and pre-anaesthetic food deprivation. To quantify the isoflurane measurement error arising from the use of short wavelength infrared (IR) anaesthetic gas analysis during low flow anaesthesia in horses. Methods: Prospective clinical study. Methods: Sixty-four client-owned horses referred for elective or emergency surgery (age 1-16 years, body mass 400-650 kg). Methods: Horses were divided into four groups based on duration of pre-anaesthetic food deprivation period (FDP) and fresh gas flow during anaesthesia: a high flow group with normal FDP (n = 16) and three groups with low flow and normal (n = 29), long (n = 5) or no (n = 14) F...
Effects of acepromazine on pulmonary gas exchange and circulation during sedation and dissociative anaesthesia in horses. To study pulmonary gas exchange and cardiovascular responses to sedation achieved with romifidine and butorphanol (RB) alone, or combined with acepromazine, and during subsequent tiletamine-zolazepam anaesthesia in horses. Methods: Six (four males and two females) healthy Standardbred trotters aged 3-12 years; mass 423-520 kg. Methods: Randomized, cross-over, experimental study. Methods: Horses were anaesthetized on two occasions (with a minimum interval of 1 week) with intravenous (IV) tiletamine-zolazepam (Z; 1.4 mg kg(-1)) after pre-anaesthetic medication with IV romifidine (R; 0.1 mg kg(-1...
Muscle metabolic changes associated with long-term inhalation anaesthesia in the horse analysed by muscle biopsy and microdialysis techniques. During anaesthesia in the horse, muscle blood flow has been found to be reduced, possibly leading to hypoxia or ischaemia in the muscle. The aim of this study was to use the muscle biopsy and microdialysis techniques to determine whether long-term inhalation anaesthesia in laterally recumbent horses induces metabolic changes in gluteal muscle indicative of anaerobic metabolism. Muscle biopsies and plasma samples were taken from seven horses at the start and end of halothane anaesthesia. In six isoflurane-anaesthetised horses, given three pharmacological provocations (dobutamine, detomidine, ac...
Suspected venous air embolism in a horse. A horse which had had a caecal impaction for 10 days was treated by means of an ileocolostomy [corrected] but failed to respond satisfactorily. Before a second laparotomy was performed it was observed to have dislodged the extension set from a jugular catheter and air was heard being sucked into the vein. It became very agitated but was anaesthetised again and the impaction was removed through an incision in the apex of the colon [corrected] After recovering from the anaesthesia it developed severe signs of pruritus which subsided only after 12 hours. These signs were considered most likely to...
Communications of normal nasal and paranasal cavities in computed tomography of horses. Heads from 15 male and female horses of various breeds and ages were examined with computed tomography under general anesthesia in dorsal recumbency. The main interest was the evaluation of the entire paranasal sinus system. Special attention was paid to the location, size, and shape of the conchomaxillary, nasomaxillary, frontomaxillary, and sphenopalatinal openings. The frontomaxillary opening was the largest aperture and was found to be age-dependent in size mostly. Orientation and shape of the openings were sagittal or horizontal; the narrowest of them was the slit-like nasomaxillary apert...
Current practice relating to equine castration in the UK. This study aimed to characterise current practice relating to equine castration in the UK. A questionnaire was posted to all 655 veterinary practices specified to provide veterinary care for horses, or classified as specialist equine practices. Respondents were asked to cite the number of equine castrations performed annually by the practice, describe techniques used for castration, outline anaesthetic/sedative/analgesic drug protocols used and provide details of post-operative medication. There was a 43% response rate to the questionnaire. Considerable variation in techniques and analgesia pr...
Comparison of morphine and butorphanol as pre-anaesthetic agents in combination with romifidine for field castration in ponies. The aim of this study was to compare two different alpha2 agonist-opioid combinations in ponies undergoing field castration. Methods: Prospective double-blind randomized clinical trial. Methods: Fifty-four ponies undergoing field castration. Methods: The ponies were randomly allocated to receive one of three different pre-anaesthetic medications [intravenous (IV) romifidine 100 microg kg(-1) and butorphanol 50 micro kg(-1); romifidine 100 microg kg(-1) and morphine 0.1 mg kg(-1) IV, or romifidine 100 microg kg(-1) and saline IV] before induction of anaesthesia with ketamine 2.2 mg kg(-1) IV. F...
The effects of two endotracheal tube cuff inflation pressures on liquid aspiration and tracheal wall damage in horses. To investigate the effect of endotracheal tube cuff inflation pressure on the occurrence of liquid aspiration and tracheal wall damage. Methods: Prospective, randomized experimental study. Methods: Ten healthy horses, weighing 535 +/- 55 kg. Methods: Horses were anesthetized, orotracheally intubated, placed in dorsal recumbency, and maintained on isoflurane in oxygen with controlled ventilation for 175 +/- 15 minutes. The horses were randomly assigned to an endotracheal cuff pressure of 80-100 or 120 cm H2O. The cuff pressure was continuously monitored and maintained at a constant pressure. Me...
Effects of peri-operative morphine administration during halothane anaesthesia in horses. To study the effects of morphine on haemodynamic variables, blood gas values and the requirement for additional anaesthetic drugs in horses undergoing surgery. Methods: Prospective randomized study. Methods: Thirty-eight client-owned horses, ASA(American Society of Anesthesiologists) category I or II, undergoing elective surgical procedures, were studied. Horses were divided between two groups, and were paired according to operation, anaesthetist, body position during surgery, mass and breed. Group M+ received morphine by intravenous (IV) injection (0.15 mg kg(-1)) before induction of anaesthe...
