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.
A systematic review of the prevalence of post-operative complications after general anaesthesia in adult horses (2000-2023). Equine post-operative morbidity represents a significant concern for both veterinary surgeons and horse owners. Objective: To estimate the prevalence of post-operative complications in horses after elective/non-abdominal surgery or colic surgery. Methods: Systematic review. Methods: A database search identified eligible studies which reported the prevalence of equine post-operative complications published as a full paper in English in a peer-reviewed journal between 2000 and 2023. Studies were evaluated using the JBI Critical Appraisal Checklist for Prevalence Studies and GRADE (Grading of Rec...
Influence of acepromazine on the cardiovascular effects of dobutamine in isoflurane-anaesthetised horses premedicated with romifidine. To explore the influence of acepromazine on the cardiovascular effects of dobutamine in isoflurane-anaesthetised horses premedicated with romifidine. Methods: Prospective randomised clinical trial. Methods: A total of 18 horses undergoing elective arthroscopy were enrolled, of which 12 horses requiring dobutamine were included. Methods: Horses were randomised to receive acepromazine 0.02 mg kg (Group A+) intravenously (IV) or none (Group A-), 35 minutes before anaesthesia. Horses received xylazine 0.2 mg kg concurrently to facilitate IV access. Horses were premedicated with romifidine 0.08 mg ...
Total intravenous anesthesia with propofol-ketamine-xylazine with or without remifentanil in thoroughbred horses undergoing castration. We evaluated the clinical efficacy of total intravenous anesthesia (TIVA) with propofol-ketamine-xylazine (PKX) with or without remifentanil for castration in horses. Twenty-four Thoroughbred horses were premedicated with intravenous (IV) xylazine (1.0 mg/kg) and midazolam (0.02 mg/kg) and anesthetized with IV ketamine (1.5 mg/kg) and propofol (1.0 mg/kg). Surgical anesthesia was maintained with constant infusion of propofol (3.0 mg/kg/hr)-ketamine (3.0 mg/kg/hr)-xylazine (1.0 mg/kg/hr) (group PKX: n=8), PKX combined with remifentanil (3.0 µg/kg/hr) (group PKXR3: n=8), or PKX combined with re...
Computed tomography of the equine caudal spine and pelvis: Technique, image quality and anatomical variation in 56 clinical cases (2018-2023). Cross-sectional imaging improves the diagnostic accuracy of complex anatomical regions. Computed tomography (CT) of the pelvis and caudal spine in a large group of live horses and ponies has not been previously reported. Objective: To describe the procedure for acquiring CT images of horses' caudal spine/pelvis under general anaesthesia (GA) and to detail the image quality, artefacts and anatomical variations in this region. Methods: Retrospective case series. Methods: Horses with CT of the caudal spine/pelvis were included. Horses under 6 months and CT examination performed post-mortem were...
Local anaesthetic delivery through indwelling retrobulbar catheters for ocular pain control in horses. Equine corneal disease is common and painful. Current pain mitigation strategies are often suboptimal, especially early in the disease. Objective: To evaluate the effects of local anaesthetic delivery via indwelling retrobulbar catheter on corneal sensitivity, pupil size, pupillary light responses (PLRs), and ocular motility in normal horses. Methods: Randomised, controlled crossover experiment. Methods: One eye was randomly selected from seven horses. A 20-gauge catheter was placed in the retrobulbar space and injected with 10 mL of 0.5% bupivacaine or 0.9% saline. Cochet-Bonnet esthesiomet...
Lameness of horses is effectively ameliorated with a low volume of mepivacaine administered as a palmar digital nerve block. To determine the effect of 1.5 mL 2% mepivacaine, 0.75 mL 2% mepivacaine, and a combination of 0.75 mL 2% mepivacaine with epinephrine (1:200,000 solution) administered over each palmar digital nerve (PDN) to 6 horses with naturally occurring lameness caused by digital pain. Methods: In a crossover study design, 6 horses with forefoot-related lameness were randomly assigned to 1 of 3 groups. Each group received, on different study days, a PDN block using 1.5 mL of 2% mepivacaine, 0.75 mL 2% mepivacaine, or 0.75 mL of a combination of 2% mepivacaine and epinephrine (1:200,000 solution) injected...
Treatment of equine keratomycosis, part 2: reporting common systemic and ocular complications to enhance decision-making for equine clinicians and owners. The primary aims were to provide descriptive data on systemic and ocular complications associated with the treatment of equine keratomycosis. The secondary aims were to determine if complication rates differ between treatment types or are related to surgical and anesthetic factors. Methods: The study was a retrospective evaluation of 126 cases between 2004 and 2020 with confirmed fungal infection and recorded incidence of complications during hospitalization and surgical intervention if pursued. Additional information recorded included the size of the donor graft if utilized, time under genera...
Technique description and outcome evaluation of Thoroughbred racehorses following soft palate thermocautery performed under standing sedation. Palatal dysfunction (PD), which encompasses palatal instability (PI) and intermittent dorsal displacement of the soft palate, is the most common performance-limiting upper respiratory tract obstruction in young Thoroughbred racehorses. Soft palate thermocautery (SPT) performed under general anaesthesia is a routinely performed procedure for PD in some countries, but the procedure for and outcome of SPT performed under standing sedation has not been published. (1) To describe a technique for SPT performed under standing sedation; and (2) to assess post-operative performance in horses compared t...
Treatment of a urethral stricture by image-guided placement of a custom-made absorbable stent in a standing, sedated horse. A 10-year-old Irish Sport Horse gelding developed complications from a general anesthesia resulting in sling support and recurrent urinary catheterization. The horse subsequently presented signs of dysuria and pollakiuria, was diagnosed with sabulous cystitis, and developed a urethral stricture from the repeated catheterizations, which was confirmed on urethroscopy. Clinical signs persisted despite conservative management with topical corticosteroids and urethral bougienage with balloon dilators. An image-guided approach was used to treat the stricture with a custom-made polydioxanone stent pl...
Oral trazodone results in quantifiable sedation but does not result in a xylazine-sparing effect in healthy adult horses. To evaluate sedation and IV xylazine requirements to achieve 45% of baseline head height above ground measurements following oral (PO) administration of 2 trazodone dosages. Methods: 8 healthy, adult mares of various weights and breeds belonging to a university teaching herd were utilized in a blinded, crossover study design. Horses were randomly assigned to 1 of 3 PO treatments: control (no trazodone), trazodone at 3 mg/kg (low dose [LD]), or trazodone at 6 mg/kg (high dose [HD]). Before treatment, cardiac auscultation, EquiSed sedation score, and head height above ground (HHAG; cm) measureme...
Comparison of a hand-held high-end resolution infrared thermography (FLIR P640) and a smartphone infrared thermographic device (FLIR One) for the assessment of skin surface temperature after anaesthetising the median nerve in Healthy horses. Accuracy of a median nerve block is normally assessed by testing skin sensitivity on the medial and dorsal aspects of fetlock and pastern. The present study evaluated subjective and objective analysis of skin surface temperature obtained with two different infrared (IR) thermography cameras (a high-end [FLIR P640] and a smartphone IR thermography device [FLIR One®]) before and after anaesthesia of the median nerve. Thermographic images were obtained at 0, 30, 60 and 90 minutes after performing a median nerve block with 2% mepivacaine hydrochloride. The subjective analysis of thermographic ima...
Bupivacaine and liposomal bupivacaine do not produce prolonged perineural anesthesia in a lameness model and are detectable beyond clinical effect in conditioned Thoroughbreds. To determine (1) the dose of liposomal bupivacaine (LB) to eliminate grade 2 of 5 lameness, the (2) duration of analgesia of LB versus bupivacaine hydrochloride (BH), and (3) LB pharmacokinetics versus BH. Methods: A reversible lameness model was validated in conditioned Thoroughbred horses (n = 12), aged 3 to 10 years. A dose-response trial compared subjective and objective lameness following abaxial sesamoid block with 25 mg BH/nerve or 30, 60, or 133 mg LB/nerve (n = 3/group). The LB dose that eliminated lameness and reduced lameness for the longest was used for blinded, randomized, crossov...
Peri-anaesthetic complications in 1798 equids undergoing high-field elective orthopaedic MRI at a tertiary referral hospital. Antimicrobial prophylaxis for elective orthopaedic magnetic resonance imaging (MRI) in equids is a topic of debate among practitioners and can have negative detrimental effects on patients if used unnecessarily. Objective: To describe the complications with elective orthopaedic MRI of horses, mules, and donkeys under general anaesthesia without the use of peri-anaesthetic antimicrobial prophylaxis at a single large tertiary referral centre. We hypothesised that horses, mules, and donkeys undergoing general anaesthesia for elective orthopaedic MRI, without antimicrobial prophylaxis, will not be...
Current practices in equine minimally invasive soft tissue surgery. Equine minimally invasive surgical techniques are frequently utilized in the treatment of a variety of conditions. Standing sedated endoscopic surgery is commonly selected in horses, requiring specialized facilities, anesthetic protocols, and surgeon and assistant expertise. This review examines current methods and potential strategies in equine soft tissue surgery, in which there is an emphasis on laparoscopic urogenital and gastrointestinal diagnostic and therapeutic procedures. Thoracoscopy is less frequently reported in horses and may be underutilized. Optimizing procedures and outcomes in...
Effects of general anesthesia on airway immune cell function in an equine in vivo model. Complications from general anesthesia, including pneumonia and decreased wound healing, are influenced by changes in immune cell function secondary to sedatives and anesthetics. It was hypothesized that immune cell function would be depressed in the early postanesthetic period. The objective was to investigate airway immune cell function before and after a general anesthetic episode in an equine in vivo model using ex vivo cell stimulations with lipopolysaccharide (LPS) for assessment of immune function. Methods: Prospective experimental study. Methods: Six healthy, adult, institution-owned ...
Feasibility of transthoracic echocardiographic guidance for multicatheter electrophysiological mapping studies in horses. Improved characterization of arrhythmias is based on minimally invasive catheterizations. However, these catheterizations have been poorly explored in horses because apart from 3-dimensional (3D) mapping systems, continuous guidance of the catheter's position with adequate detail is difficult using current imaging modalities. Objective: Position multiple electrophysiology catheters simultaneously at predetermined strategical positions in the heart using transthoracic echocardiographic guidance. Methods: Eight adult healthy horses. Methods: Observational study. Two electrophysiological studies ...
Effects of intra-articular anesthesia of the tarsometatarsal joint on skin sensation of the distal limb in horses. To determine with mechanical nociceptive threshold (MNT) testing whether distal limb skin sensation is affected by intra-articular anesthesia of the tarsometatarsal joint (TMTJ). Unassigned: This was a prospective cohort study. Ten client-owned horses that had intra-articular TMTJ anesthesia were included in the study. The MNT was measured at 6 sites on the distal limb at 3 time points: before anesthesia (T0) and at 10 min (T10) and 30 min (T30) post-injection. Linear mixed-model analyses were done, with the significance level set at P < 0.05. Unassigned: There was an increase in MNT (P = 0.00...
Inhalational anaesthetic agent consumption within a multidisciplinary veterinary teaching hospital: an environmental audit. Inhalational anaesthetic agents are routinely used in veterinary anaesthesia practices, yet their consumption contributes significantly to greenhouse gas emissions and environmental impact. We conducted a 55-day observational study at a veterinary teaching hospital in Switzerland, monitoring isoflurane and sevoflurane consumption across small, equine and farm animal clinics and analysed the resulting environmental impact. Results revealed that in total, 9.36 L of isoflurane and 1.27 L of sevoflurane were used to anaesthetise 409 animals across 1,489 h. Consumption rates varied among species...
Emergency Standing Laparoscopic Treatment of Uncontrolled Post-Castration Hemorrhage in Two Geldings. Persistent hemorrhage of testicular vessels is a potentially life-threatening complication of equine castration. Frequently, general anesthesia is required to retrieve and ligate the bleeding vasculature when standing wound packing and retrieval of the spermatic cord are unsuccessful. We propose standing laparoscopic ligation of the testicular arteries via the paralumbar fossa as a rapid, effective means of halting hemorrhage while avoiding castration site trauma as well as the cardiovascular and recovery risks of general anesthesia. Methods: Two geldings, 6 and 9 months old, presented for eme...
Intracardiac ultrasound-guided transseptal puncture in horses: Outcome, follow-up, and perioperative anticoagulant treatment. Cardiac catheterizations in horses are mainly performed in the right heart, as access to the left heart traditionally requires an arterial approach. Transseptal puncture (TSP) has been adapted for horses but data on follow-up and closure of the iatrogenic atrial septal defect (iASD) are lacking. Objective: To perform TSP and assess postoperative complications and iASD closure over a minimum of 4 weeks. Methods: Eleven healthy adult horses. Methods: Transseptal puncture was performed under general anesthesia. Serum cardiac troponin I concentrations were measured before and after puncture. Wee...
An Explorative Anatomical Study on Inter-Individual Variation of the Tibial Nerve and Landmarks for Perineural Anesthesia in Horses. Perineural anesthesia of the tibial nerve can be performed ultrasound-guided or blindly, with the latter still being commonly used in equine practice due to practical constraints, despite its lower accuracy and hence, common failure to achieve desensitization. This may be associated with anatomical variations or inadequate landmarks for injection. To examine the course of the tibial nerve, document potential anatomical variations, and determine optimal landmarks for perineural injection, dissection was conducted along the medial aspect of the tibia in 10 paired cadaver hindlimbs. No anatomical...
Hoof wall masses removal in 30 standing sedated horses: Surgical technique, postoperative complications and long-term outcome. To describe the surgical technique for removal of hoof wall masses in horses under standing sedation (SS) and local anesthesia (LA), and to report complications and long-term outcome following surgery. Methods: Observational retrospective study. Methods: Client-owned horses (n = 30). Methods: Horses undergoing keratoma removal under SS and LA in a single equine hospital between August 2016 and July 2023 were included in the study. Signalment, affected foot, history of lameness and/or foot abscesses, degree of lameness on admission, imaging findings (radiography and magnetic resonance imagi...
[Brainstem auditory evoked responses in horses with hearing loss and during general anesthesia]. The brainstem auditory evoked response (BAER) is a diagnostic approach to examine the hearing system of horses objectively. The aim of this BAER examination was the diagnosis of conductive or sensorineural hearing loss or deafness in horses with external otitis, head trauma, headshaking, tinnitus or skittish horses with eye disease. Brainstem dysfunction is induced by intracranial hypotension. BAER was used in horses with colic surgery which had a low arterial blood pressure during general anesthesia. The endoscopic finding of the guttural pouch was the ipsilateral mild to severe hypertrophy o...
Use of wound infusion catheters for delivery of local anesthetic following standing partial ostectomy of thoracolumbar vertebral spinous processes in horses is not associated with increased surgical site infections. Wound infusion catheters (WICs) have been used in humans and some veterinary species for post-operative local anesthetic administration following a variety of surgical procedures, aiming to reduce post-operative analgesia requirements and improve patient comfort. Benefit in reduction in pain, post-operative analgesia requirements and length of hospital stay are well documented in humans, but use of WICs may not have been widely adopted in veterinary species due to the concern of increased complications, such as dehiscence or surgical site infection (SSI), creating a barrier to their use. This ...
Effect of nose twitching on the pupillary dilation in awake and anesthetized horses. Pupillometry is used in humans to monitor pain, nociception and analgesia. This single-center, non-randomized, non-blinded intervention trial, evaluated the effect of nose twitching on the pupil size in awake, sedated, and anesthetized horses. Pupil height (H) and length (L) were measured before (Be) and after (Af) nose twitching in fourteen non-painful adult awake horses (T0). The percentage of variation (PSV) was calculated (PSVTn = [(TnAf-TnBe)/TnBe]*100). Measurements were repeated (Tn) after acepromazine (0.04 mg kg IV) (T1), romifidine (0.04 mg kg IV) (T2), morphine (0.1 mg...
Retrospective study of the changes in dynamic compliance and ventilation/perfusion mismatch following salbutamol inhalation in hypoxaemic mechanically ventilated anaesthetized horses. To study the changes in dynamic compliance (C), ventilation/perfusion (V˙/ Q˙) mismatch and haemodynamic variables in hypoxaemic anaesthetized horses whose PaO increased following salbutamol inhalation. Methods: Retrospective, clinical, cohort study. Methods: A group of 73 client-owned horses treated with salbutamol when PaO <100 mmHg (13.3 kPa) during anaesthesia. Methods: Horses were divided into two groups: responders (R), where PaO after salbutamol ≥1.2 PaO before treatment (i.e. ≥20% increase), and non-responders (NR), where PaO after salbutamol <1.2 PaO before treatment. Demographi...
Clinical and echocardiographic evaluations of sedative and cardiovascular effects of combination of xylazine-acepromazine versus xylazine-pregabalin in horses. The aim of this study was to compare the sedative and cardiovascular effects of the combination of xylazine-acepromazine versus xylazine-pregabalin - in horses. Four healthy crossbred horses were included in the study and assigned to two treatments. In treatment I (T1), the animals received xylazine hydrochloride (1.00 mg kg) in combination with acepromazine maleate (0.05 mg kg) intravenously. In treatment II (T2), the animals received intragastric administration of pregabalin (4.00 mg kg) followed by xylazine hydrochloride (1.00 mg kg) intravenously after 60 min. Head height above ground (HHA...
A Review of Equine Anesthetic Induction: Are all equine anesthetic inductions “crash” inductions? Horses are the most challenging of the common companion animals to anesthetize. Induction of anesthesia in the horse is complicated by the fact that it is accompanied by a transition from a standing position to recumbency. The purpose of this article is to review the literature on induction of anesthesia with a focus on the behavioral and physiologic/pharmacodynamic responses and the actions and interactions of the drugs administered to induce anesthesia in the healthy adult horse with the goal of increasing consistency and predictability.
Fasting horses perioperatively decreases manure production and increases time to manure output postoperatively: a controlled randomized trial. To compare 3 perioperative feeding regimens and their effect on anesthetic complications, manure output, and colic proportion in healthy horses. Methods: 45 horses presenting for elective orthopedic procedures were randomly assigned to 1 of 3 groups: not fasted (NF; continuous access to hay perioperatively), fasted muzzled (FM; 10-hour preoperative fast with slow refeeding postoperatively and muzzle placement), or fasted not muzzled (FNM; same as FM without muzzle placement). Anesthetic protocol was standardized. Outcomes compared between groups included anesthesia time, arterial oxygenation, ...
A novel approach to ear pain in the horse: A case report. During electrochemotherapy (ECT), a chemotherapeutic drug is injected into the tumor and then an electroporation is provided. In horses, ear manipulation may be very painful, and combining a loco-regional technique with sedation might be a good option to avoid anesthesia-related risks. A two-injection-point block of the internal and external pinna and acoustic meatus was described in horse cadavers, and it permitted complete stain of all three branches of the great auricular nerve (GAN), internal auricular nerve branch (IAB), lateral auricular branch (LAB), and caudal auricular nerve (CAN), su...