Ketamine is a dissociative anesthetic commonly used in veterinary medicine for horses. It acts on the central nervous system, primarily influencing the N-methyl-D-aspartate (NMDA) receptors, leading to a trance-like state characterized by analgesia, sedation, and amnesia. In equine practice, ketamine is frequently used for induction and maintenance of anesthesia during surgical procedures, as well as for pain management. It is often administered in combination with other drugs to enhance its effectiveness and minimize side effects. This page compiles peer-reviewed research studies and scholarly articles that explore the pharmacokinetics, pharmacodynamics, and clinical applications of ketamine in equine medicine.
Blanton A, Glass KG, Bayer J, Baetge C, Watanabe R, Sampson SN, Lépiz M, Moreno K, Ida KK.Pregabalin reduces excitatory neurotransmitter release and is used for anxiolysis in humans, cats, and horses. The effects of pregabalin on equine recovery following isoflurane anaesthesia are unknown. Objective: To determine if pre-anaesthetic oral pregabalin influences recovery time and/or quality from isoflurane anaesthesia in horses undergoing elective magnetic resonance imaging (MRI) of the appendicular skeleton. Methods: Retrospective cohort study. Methods: Anaesthetic and recovery data from 52 healthy horses in which pregabalin (PG) was administered and 76 control horses (CG) undergoing...
Bardhi A, Barbarossa A, Joubert A, Gehring R, Lambertini C, Romagnoli N.Dried blood spot (DBS) sampling has emerged as a promising microsampling technique in biomedical and clinical research, offering advantages such as reduced invasiveness, minimal blood volume requirements, and enhanced analyte stability. Although well established in human medicine for neonatal screening and diagnostic applications, its potential in veterinary pharmacology remains underexplored. This study investigated the feasibility of using DBS samples to quantify anesthetic agents-ketamine and medetomidine in cats and lidocaine in horses-during routine surgical procedures at a veterinary tea...
Midon M, Clark-Price SC, Lin HC, Lascola KM, Boone L.To determine if serum iron concentrations decrease acutely during and after general anesthesia in healthy horses. Methods: Prospective experimental study. Methods: A convenience sample of 24 healthy adult horses (eight females, 16 geldings), weighing 545 ± 33 kg (mean ± standard deviation). Methods: Horses were anesthetized for 120 minutes with isoflurane, after premedication with intravenous (IV) xylazine (0.8 mg kg-1) and induction with IV midazolam (0.1 mg kg-1) and ketamine (2.2 mg kg-1). Blood samples for serum iron analysis were obtained just before premedication (baseline), after 60 m...
Bustamante R, Segura IÁ, Santiago I.Locoregional techniques promote multimodal analgesia and may reduce general anaesthetic requirements. However, there is limited evidence in foals. The rectus sheath block (RSB) is an interfascial plane block previously described in other species such as dogs, cats, pigs, and calves, and recently in foals, which targets desensitization of ventral abdominal midline. This block may provide an efficacious analgesic alternative for ventral celiotomies and umbilical surgeries. This case series reports the use of a bilateral RSB with 0.25-0.3 mL kg-1 bupivacaine (maximum dose of 2 mg kg-1) per hemiab...
Sauter PK, Steblaj B, Kästner SBR, Söbbeler FJ, Reiners JK, Kutter APN, Bautitsta AJG, Neudeck S.Microcirculation is the essential link between macrocirculation and cellular metabolism. Objective: To test our hypotheses that microcirculation variables will show a heterogeneous flow pattern during experimental endotoxaemia, and that fluid therapy and noradrenaline (NA) infusion will normalise altered microcirculation variables. Methods: In vivo experiments. Methods: Six healthy adult horses were anaesthetised with dexmedetomidine, ketamine, and diazepam and were mechanically ventilated under isoflurane anaesthesia. Endotoxaemia was induced with 30 ng kg Escherichia coli lipopolysacchar...
Henderson ARP, Valverde A, Koenig J, Sears W.The objective of this prospective study was to investigate whether repeated consecutive general anesthesia in horses undergoing 2 different anesthetic protocols could lead to improved recovery scores. Six healthy female Standardbred horses (453 ± 57 kg; 6.5 ± 4.2 y old) underwent 4 anesthetic protocols over 12 to 13 wk. Procedures 1 and 4 were arthroscopic surgeries [induction: xylazine, diazepam, and ketamine; and maintenance: Fe'Isoflurane (1.1%), lidocaine (2 mg/kg body weight [BW], 50 to 100 μg/min per kg BW), dexmedetomidine (2.5 μg/h per kg BW)]. Procedures 2 and 3 were preparation f...
Hordle T, Ranninger E, Bettschart-Wolfensberger R.A 24 year old warmblood mare (case 1) and a 12 year old Holsteiner gelding (case 2) were anaesthetized for bursoscopy and phacoemulsification, respectively. Both were premedicated with intramuscular acepromazine (30 μg kg-1). The horses were sedated with intravenous (IV) medetomidine (7-9 μg kg-1 to effect), before anaesthetic induction with ketamine-diazepam. Anaesthesia was maintained with isoflurane in a mixture of oxygen and medical air, alongside a medetomidine constant rate infusion at 3.5 μg kg-1 hour-1. In recovery, 3 and 5 μg kg-1 of medetomidine were administered IV to cases 1 an...
Lambertini C, Boanini E, Casalini I, Spaccini F, Rinnovati R, Romagnoli N.The aim of this retrospective clinical study was to compare the combinations of ketamine/diazepam (KD group) and tiletamine/zolazepam (TZ group) for the induction of general anaesthesia in horses undergoing elective surgery. The data from the clinical and the anaesthetic records of 138 horses from 2021 to 2023 were evaluated, and the horses were divided in two groups: KD ( = 60) and TZ ( = 72). The horses were premedicated with romifidine and methadone IV; anaesthesia was induced with ketamine/diazepam for the KD group and tiletamine/zolazepam for the TZ group and was maintained with isofluran...
Wong AM, Schier MF, Hosgood G, Drynan E, Raisis AL.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 ...
Otsuka T, Araki M, Mita H, Kambayashi Y, Yoshihara E, Ohta M.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...
Ruíz-López P, Cuypers C, Schauvliege S.This retrospective study investigated the effect of a xylazine infusion on heart rate; mean arterial pressure; blood gases; anesthetic and dobutamine requirements; recovery quality and duration; percentage of death/survival; and days to die/discharge in horses after colic surgery under partial intravenous anesthesia with isoflurane and lidocaine infusion. Anesthetic records of equine colic surgery were reviewed from similar periods in 2020-2021 and 2021-2022. In both groups, after sedation with xylazine 0.7 mg/kg intravenously (IV) and induction with ketamine 2.2 mg/kg and midazolam 0.06 mg/kg...
Parra Martínez C, Rico Pérez B, Kaartinen J.To evaluate the agreement between noninvasive arterial blood pressure (NIBP) measured from the tongue and thoracic limb with invasive blood pressure (IBP), and to compare NIBP measured from the tongue and thoracic limb in anaesthetized horses. Methods: Prospective clinical study. Methods: A group of eight client-owned healthy horses anaesthetized for scheduled procedures, American Society of Anesthesiologists classification I-II, weighing (mean ± standard deviation) 498 ± 91 kg and aged 7.8 ± 6.75 years. Methods: Animals were premedicated with intravenous (IV) romifidine (0.04-0.08 mg kg-1)...
Sandbaumhüter FA, Aerts JT, Theurillat R, Andrén PE, Thormann W, Jansson ET.The chiral drug ketamine has long-lasting antidepressant effects with a fast onset and is also suitable to treat patients with therapy-resistant depression. The metabolite hydroxynorketamine (HNK) plays an important role in the antidepressant mechanism of action. Hydroxylation at the cyclohexanone ring occurs at positions 4, 5, and 6 and produces a total of 12 stereoisomers. Among those, the four 6HNK stereoisomers have the strongest antidepressant effects. Capillary electrophoresis with highly sulfated γ-cyclodextrin (CD) as a chiral selector in combination with mass spectrometry (MS) was us...
Murillo C, Weng HY, Weil AB, Kreuzer M, Ko JC.This study aimed to investigate the use of electroencephalography (EEG) for detecting brain activity changes perioperatively in anesthetized horses subjected to surgery. Twelve adult horses undergoing various surgeries were evaluated after premedication with xylazine and butorphanol, induction with ketamine, midazolam, and guaifenesin, and maintenance with isoflurane. The frontal EEG electrodes were placed after the horse was intubated and mechanically ventilated. The EEG data were collected continuously from Stage (S)1-transition from induction to isoflurane maintenance, S2-during surgery, S3...
Bohner J, Painer J, Bakker D, Haw AJ, Rauch H, Greunz EM, Egner B, Goeritz F.Etorphine is widely used in zoological medicine for the immobilization of large herbivores. All reported immobilization protocols for kulans use etorphine as the primary immobilizing agent. However, etorphine can trigger severe side effects and is highly toxic for humans, its availability is occasionally limited for use in wildlife medicine. Therefore, two different alpha-2 agonist-based protocols for the general anesthesia of kulans were investigated and compared with the standard etorphine immobilization. In total, 21 immobilizations were performed within the scope of routine husbandry manag...
Alonso B, Carregaro A, Cuypers C, Michielsen A, Gasthuys F, Schauvliege S.To evaluate the effects of detomidine or romifidine on cardiovascular function, isoflurane requirements and recovery quality in horses undergoing isoflurane anaesthesia. Methods: Prospective, randomized, blinded, clinical study. Methods: A total of 63 healthy horses undergoing elective surgery during general anaesthesia. Methods: Horses were randomly allocated to three groups of 21 animals each. In group R, horses were given romifidine intravenously (IV) for premedication (80 μg kg), maintenance (40 μg kg hour) and before recovery (20 μg kg). In group D2.5, horses were given detomidine IV f...
Milnes EL, Skelding AM, Larouche CB, Ferro A, Delnatte P, Dutton C, Anderson NE.To compare ketamine-butorphanol-azaperone-medetomidine (KBAM) to detomidine-etorphine-acepromazine (DEA) for field anesthesia in captive Przewalski horses (Equus przewalskii). Methods: 10 adult Przewalski horses. Methods: A prospective randomized crossover trial was conducted. Each horse was immobilized once with KBAM (200 mg ketamine, 109.2 mg butorphanol, 36.4 mg azaperone, and 43.6 mg medetomidine) and once with DEA (40 mg detomidine premedication, followed 20 minutes later by 3.9 to 4.4 mg etorphine and 16 to 18 mg acepromazine). Both protocols were administered by IM remote dart injection...
Bukoski A, Hodgson D, Downs J, LeBert C, Thombs L, Bailey J.To compare the cardiopulmonary effects of apneustic anesthesia ventilation (AAV) and conventional mechanical ventilation (CMV) in dorsally recumbent anesthetized horses. Methods: Randomized, crossover design. Methods: A total of 10 healthy adult horses from a university-owned herd. Methods: Following xylazine, midazolam and ketamine administration, horses were orotracheally intubated and positioned in dorsal recumbency. Anesthesia was maintained with isoflurane in oxygen [inspired oxygen fraction (FiO) = 0.3 initially, with subsequent titration to maintain PaO ≥ 85 mmHg (11.3 kPa)]. Horses ...
Ruíz-López P, Morgaz J, Quirós-Carmona S, Navarrete-Calvo R, Domínguez JM, Gómez-Villamandos RJ, Granados MM.Autonomic nervous system (ANS) activity can modify cardiovascular parameters in response to nociceptive stimuli or drugs in anesthetized animals. The aim of this study was to determine if a surgical nociceptive stimulus and morphine, ketamine, and dobutamine administration would modify ANS activity observed as a change in the mean parasympathetic tone activity (PTAm) in anesthetized horses. In 20 anesthetized horses, heart rate (HR), mean arterial pressure (MAP), and PTAm were monitored before and 1, 3, and 5 min after surgical incision, and before and 10 min after the administration of morphi...
Wilkens HL, Neudeck S, Kästner SBR.The present study aimed to investigate the effect of endotracheal intubation on nasal and tracheal endogenous NO concentrations, gas exchange and oxygenation in horses undergoing general anaesthesia. In many species a major part of physiological nitric oxide (NO) production takes place in the nasopharynx. Inhaled NO acts as a pulmonary vasodilator and regulates lung perfusion and endotracheal intubation bypasses the nasopharynx. Six horses were randomly assigned to either the "intubated" (INT) or the "non-intubated" (nINT) treatment group. Horses were premedicated with dexmedetomidine (5 μg...
Bennell AJ, Wright RJH, Malalana F, Senior JM.Catastrophic fractures or luxations (FoL) sustained during recovery from general anesthesia are a significant cause of mortality during equine anesthesia. There is a lack of evidence regarding potential risk factors for a FoL occurring in the immediate anesthetic recovery period. A single center, retrospective, case-matched study was performed to identify risk factors for sustaining a catastrophic FoL during recovery from general anesthesia. Clinical data were obtained for horses which sustained a catastrophic FoL when recovering from general anesthesia from January 2011 to June 2020 in a sing...
Midon M, Yamada DI, Zangirolami Filho D, Natalini CC, Escobar A, Clark-Price SC.This randomized double-blinded study evaluated the recovery from isoflurane anesthesia in horses receiving doxapram and xylazine. 6 horses were anesthetized 4 times (minimum of 2-week washout period). Anesthesia was performed with xylazine (0.6 mg/kg), ketamine (2.2 mg/kg), midazolam (0.1 mg/kg), and maintained with isoflurane for 90 minutes. At recovery, horses received one of the following randomized treatments: RX: xylazine (0.2 mg/kg), RXD1: xylazine (0.2 mg/kg) and doxapram (0.1 mg/kg), RXD2: xylazine (0.2 mg/kg) and doxapram (0.2 mg/kg), or RS: saline. Recoveries were rope-assisted and e...
Wise IK, Klöppel H, Leece EA.Ketamine-based total intravenous anaesthesia techniques are commonly used in equine practice for ponies requiring short procedures such as castration in field conditions. When a longer duration of recumbency than provided by the initial dose of anaesthetic agents is required, administration of supplementary 'top-up' doses of anaesthetic agents is required. Ideally, a single dose of anaesthetic agents would reliably achieve a longer duration of action whilst maintaining adequate anaesthetic, surgical and recovery qualities. Objective: This prospective, randomised and blinded study aimed to comp...
Hopster K, Driessen B.One of the biggest challenges in managing laminitis in horses remains the control of pain. The best analgesic approach is a multimodal approach, including nonsteroidal anti-inflammatory drugs, opioids, and/or constant rate infusions of α-2 agonists, ketamine, and lidocaine. Recent literature indicates that amitriptyline and soluble epoxide hydrolase inhibitor might be beneficial. Clinically oriented studies will be needed if they have a place in laminitis pain management. The systemic pain control can be combined with local techniques such as long-acting local anesthetics or epidural catheter...
Louro LF, Robson K, Hughes J, Loomes K, Senior M.In equine anaesthesia, the recovery period is critical, accounting for most anaesthesia-related fatalities reported. Horses may recover unassisted or may be assisted, for example, using a head and tail rope recovery method. Objective: To compare the impact of head and tail rope and unassisted recovery method on quality of recovery in horses undergoing colic surgery under general anaesthesia (GA). Methods: Single centre retrospective cross-sectional study, with prospective model performance analysis. Methods: Clinical data were obtained from horses undergoing emergency exploratory laparotomy ov...
Dmitrović P, Vanaga J, Dupont J, Franck T, Gougnard A, Detilleux J, Kovalcuka L, Salciccia A, Serteyn D, Sandersen C.Controversy continues to surround the use of opioids in equine anaesthesia, with variable effects reported. This blinded clinical study aimed to investigate the influence of a low-dose fentanyl continuous rate infusion (CRI) on isoflurane requirements, parasympathetic tone activity (PTA), and anaesthetic parameters in horses during general anaesthesia. All of the twenty-two horses included in the research underwent a standard anaesthetic protocol. Eleven horses in the fentanyl group (Group F) received a loading dose of fentanyl at 6 µg/kg, followed by a CRI of 0.1 µg/kg/min during anaesthesi...
Jarosinski SK, Simon BT, Hatfield R, Matthews NS, Arnold CE.The purpose of this prospective, blinded, randomized clinical trial was to compare the effects of low dose detomidine to xylazine on recovery quality and duration in a castration procedure. Horses were administered either detomidine [0.015 mg/kg body weight (BW)] or xylazine (1.1 mg/kg BW) intravenously (IV) before IV induction with ketamine (2.2 mg/kg BW) and diazepam (0.05 mg/kg BW). Two anesthesiologists who were unaware of treatment allocation scored the recoveries using a simple descriptive scale (with a low number representing the most desirable recovery) and recoveries were timed. Horse...
Kälin I, Henze IS, Ringer SK, Torgerson PR, Bettschart-Wolfensberger R.Medetomidine partial intravenous anaesthesia (PIVA) has not been compared to xylazine PIVA regarding quality of recovery. This clinical retrospective study compared recoveries following isoflurane anaesthesia balanced with medetomidine or xylazine. The following standard protocol was used: sedation with 7 µg·kg medetomidine or 1.1 mg·kg xylazine, anaesthesia induction with ketamine/diazepam, maintenance with isoflurane and 3.5 µg·kg·h medetomidine or 0.7 mg·kg·h xylazine, and sedation after anaesthesia with 2 µg·kg medetomidine or 0.3 mg·kg xylazine. Recovery was timed and, using vi...
Balko JA, Fogle C, Stuska SJ, Fogle JE, Posner LP.Butorphanol-azaperone-medetomidine (BAM™) has not been evaluated in horses. Objective: The objective of this study was to evaluate BAM™ for chemical restraint of feral horses. Methods: Retrospective and prospective descriptive studies. Methods: Data were collected retrospectively from medical records of 28 feral horses immobilised with BAM™ over a 6-year period. Prospectively, 0.0125 mL/kg bwt of BAM™ (butorphanol 27.3 mg/mL, azaperone 9.1 mg/mL and medetomidine 10.9 mg/mL) intramuscularly (im) was administered to eight stallions via dart, and once recumbent, 1.0 mg/kg bwt ketamin...
Cunneen A, Pratt S, Perkins N, McEwen M, Truchetti G, Rainger J, Farry T, Kidd L, Goodwin W.To evaluate the use of ketamine-medetomidine-midazolam total intravenous infusion as part of a balanced anaesthetic technique for surgical castration in horses. Five healthy Standardbred cross colts were premedicated with IV acepromazine (0.01-0.02 mg/kg), medetomidine (7 µg/kg) and methadone (0.1 mg/kg) and anaesthesia induced with IV ketamine (2.2 mg/kg) and midazolam (0.06 mg/kg). Horses were anaesthetised for 40 min with an IV infusion of ketamine (3 mg/kg/h), medetomidine (5 µg/kg/h) and midazolam (0.1 mg/kg/h) while routine surgical castration was performed. Cardiorespiratory variables...
Santos M, Fuente M, Garcia-Iturralde R, Herran R, Lopez-Sanroman J, Tendillo FJ.Recovery from inhalant anaesthesia in the horse is a critical and difficult period to manage; however, several factors could help to obtain a calm recovery period including choice of anaesthetic and analgesic procedure used and the conditions under which anaesthetic maintenance and recovery occur. Objective: The objective of this study was to evaluate and compare the quality of recovery in horses administered saline, xylazine, detomidine or romifidine during recovery from isoflurane anaesthesia. Methods: Six mature and healthy horses were premedicated with i.v. xylazine and butorphanol, and an...
Dzikiti TB, Hellebrekers LJ, van Dijk P.Physiological parameters, metabolic parameters and stress-related hormones are evaluated in horses anaesthetized with isoflurane in oxygen combined with lidocaine intravenously. Two groups of horses anaesthetized with isoflurane (six horses in each group) were studied: a lidocaine group (IL), which received intravenous lidocaine and a control group (C), which received intravenous saline. Horses in both groups were premedicated with detomidine (i.v.), and anaesthesia was induced with midazolam-ketamine (i.v.). The lidocaine group received intravenous lidocaine as a loading dose of 2.5 mg kg(-1)...
Haga HA, Dolvik NI.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...
Muir WW.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 ...
Klöppel H, Leece EA.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(-...
Lankveld DP, Bull S, Van Dijk P, Fink-Gremmels J, Hellebrekers LJ.Ketamine is widely used in equine anaesthesia. Beside its anaesthetic and analgesic properties, ketamine possesses a cytokine-modulating activity. However, to date, no data are available regarding the inhibitory effect of ketamine on the cytokine response in horses. In horses, cytokines such as tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) play a pivotal role in the pathogenesis of equine endotoxaemia following gastrointestinal disorders. Hence, the objective of this study was to assess the influence of ketamine on LPS-induced TNF-alpha and IL-6 formation in an equine macro...
Ringer SK, Kalchofner K, Boller J, Fürst A, Bettschart-Wolfensberger R.To compare the effects of two balanced anaesthetic protocols on end-tidal isoflurane (Fe'ISO), cardiopulmonary performance and quality of recovery in horses. Methods: Prospective blinded randomized clinical study. Methods: Sixty-nine client-owned horses, American Society of Anesthesiologists category I and II, undergoing elective surgery. Methods: The horses were premedicated with acepromazine (0.03 mg kg(-1)) IM 30-60 minutes before induction of anaesthesia and were randomly assigned to one of two treatments: in group L (37 horses) xylazine (1 mg kg(-1)) and in group M (31 horses) medetomidin...
Voulgaris DA, Hofmeister EH.To identify anesthesia-related variables which may independently predict time to standing in horses anesthetized with ketamine/diazepam/isoflurane. Methods: Retrospective case series. Methods: Three hundred and eighty-one horses. Methods: Case records were searched for the years 2000-2003 and 381 horses older than 12 months which weighed at least 200 kg were identified. Data were extracted from the records, and only horses that were anesthetized with xylazine, ketamine, diazepam and isoflurane were included in the analysis. Multiple linear regression was used to relate time to standing with de...
Kerr CL, McDonell WN, Young SS.The purpose of this study was to compare and evaluate sedation with intravenous xylazine (1.1 mg/kg bodyweight [BW]) versus intravenous romifidine (100 micrograms/kg BW) followed by induction of anesthesia with intravenous diazepam (0.04 mg/kg BW) and ketamine (2.2 mg/kg BW). Twelve healthy horses were used in a blinded, randomized, cross-over design. Heart rate, presence of 2nd degree atrioventricular heart blocks (2 degrees AVB), respiratory rate, arterial blood pressures, blood gases, packed cell volume, total serum proteins, and duration of anesthesia and recumbency were recorded. Inductio...
Gozalo-Marcilla M, Gasthuys F, Schauvliege S.To review the literature with regard to the use of different intravenous agents as supplements to inhalational anaesthesia in horses. These drugs include lidocaine, ketamine, opioids and α2 -agonists. The Part 1 of this review will focus in the use of lidocaine and ketamine. Methods: Pubmed & Web of Science. Search terms: horse, inhalant anaesthesia, balanced anaesthesia, partial intravenous anaesthesia, lidocaine, ketamine. Conclusions: Different drugs and their combinations can be administered systemically in anaesthetized horses, with the aim of reducing the amount of the volatile agen...
Grosenbaugh DA, Muir WW.To determine and compare cardiorespiratory and recovery effects of sevoflurane, isoflurane, and halothane in horses. Methods: 8 clinically normal horses (4 mares, 4 geldings), 5 to 12 years old. Methods: Inhalation anesthesia was maintained for 90 minutes with sevoflurane, isoflurane, or halothane. Anesthesia depth was maintained at 1.5 minimum alveolar concentration of halothane, isoflurane, and sevoflurane, then was reduced at 30 and 60 minutes. A surgical plane of anesthesia was reinduced by administration of ketamine or thiopental or by increasing the fractional inspired concentration of s...
Muir WW, Skarda RT, Milne DW.The cardiopulmonary effects resulting from the combination of xylazine and ketamine hydrochloride were evaluated in the adult horse. Xylazine (1.1 mg mg/kg) administered intravenously prior to or simultaneously with ketamine hydrochloride (2.2 mg/kg; intravenous) provided excellent analgesia and light anesthesia in all horses. Cardiac output, arterial blood pressure, pulmonary arterial pressure, central venous pressure, and pulmonary arterial wedge pressure remained within normal limits for the adult horse. Evidence of respiratory acidosis developed with time during the anesthetic period. Indu...
Valverde A.Balanced anesthetic techniques are commonly used in equine patients, and include the combination of a volatile anesthetic with at least one injectable anesthetic throughout the maintenance period. Injectable anesthetics used in balanced anesthesia include the α2-agonists, lidocaine, ketamine, and opioids, and those with muscle-relaxant properties such as benzodiazepines and guaifenesin. Administration of these injectable anesthetics is best using constant-rate infusions based on the pharmacokinetics of the drug, which allows steady-state concentrations and predictable pharmacodynamic actions....
Haga HA, Dolvik NI.To determine whether the bispectral index (BIS) can be used as an indicator of degree of CNS depression in isoflurane-anesthetized horses. Methods: 10 Standardbred and 6 Norwegian cold-blooded trotter stallions admitted for routine castration. Methods: A 2-channel referential electrode configuration was used to record EEG for calculation of BIS by the EEG monitor. The BIS was calculated before (awake) and after (sedated) administration of detomidine (0.01 mg/kg of body weight, IV) and butorphanol (0.01 mg/kg, IV). Anesthesia was induced with ketamine hydrochloride (2.5 mg/kg, IV) and diazepam ...
Kaka JS, Klavano PA, Hayton WL.Ketamine HCl was administered IV to xylazine HCl-treated horses. The plasma concentration of ketamine was measured several times after administration of the drug and these data were used to develop a two-compartment pharmacokinetic model. The distribution and the elimination phase half-lives averaged 2.9 and 42 minutes. The volume of the central compartment averaged 212 ml/kg of body weight and the volume of the peripheral compartment was approximately threefold larger. The total body clearance of ketamine averaged 26.6 ml/minute/kg. Plasma protein binding of ketamine averaged 50% over the con...
Purohit RC, Mysinger PW, Redding RW.A continuous series of electroencephalograms (EEG) was obtained from each of 6 mature horses which had been given xylazine and ketamine hydrochloride IV. Electrocardiograms and respiratory rates were also obtained. The EEG of the unsedated standing adult horse displayed a dominant fast activity in the range of 25-35 Hz, 5-30 microV superimposed over slower 1-4 Hz, 10-50 microV activity with occasional 10-14 Hz, 10-40 microV spindle-type activity. The xylazine-sedated horse displayed hypersynchronous EEG patterns, with the dominant activity being 1-3 Hz, 10-70 microV with overlying mixed freque...
Knobloch M, Portier CJ, Levionnois OL, Theurillat R, Thormann W, Spadavecchia C, Mevissen M.Ketamine is widely used as an anesthetic in a variety of drug combinations in human and veterinary medicine. Recently, it gained new interest for use in long-term pain therapy administered in sub-anesthetic doses in humans and animals. The purpose of this study was to develop a physiologically based pharmacokinetic (PBPk) model for ketamine in ponies and to investigate the effect of low-dose ketamine infusion on the amplitude and the duration of the nociceptive withdrawal reflex (NWR). A target-controlled infusion (TCI) of ketamine with a target plasma level of 1 microg/ml S-ketamine over 120 ...
Waterman AE, Robertson SA, Lane JG.The metabolism and distribution of ketamine and its two major metabolites (norketamine and dehydronorketamine) was investigated in 10 horses undergoing airway surgery. Following premedication with xylazine (1.1 mg kg-1 intravenously) anaesthesia was induced by the rapid injection of ketamine at a dose of 2.2 mg kg-1 intravenously. Anaesthesia was maintained with halothane vaporized in oxygen and nitrous oxide (50:50). Serially collected blood samples were analysed by a sensitive gas liquid chromatographic technique. Plasma ketamine concentrations declined biexponentially with a rapid initial d...
Mircica E, Clutton RE, Kyles KW, Blissitt KJ.To identify the incidence of adverse effects caused by morphine 100-170 micro g kg-1 administration during surgery in horses. Methods: Retrospective case record analysis (1996-2000). Methods: Eighty-four healthy (ASA 1 or 2) horses, mean age 5.5 +/- 3.1 (SD) years (2 months to 16 years), mean weight 524 +/- 14 kg (100-950). Methods: Physiological data and evidence of complications were collected from the anaesthetic records of all animals anaesthetized with romifidine, ketamine, diazepam and halothane and undergoing laryngeal surgery or orchiectomy at the Royal (Dick) School of Veterinary Stud...
Mössner LD, Schmitz A, Theurillat R, Thormann W, Mevissen M.To identify and characterize cytochrome P450 enzymes (CYPs) responsible for the metabolism of racemic ketamine in 3 mammalian species in vitro by use of chemical inhibitors and antibodies. Methods: Human, canine, and equine liver microsomes and human single CYP3A4 and CYP2C9 and their canine orthologs. Methods: Chemical inhibitors selective for human CYP enzymes and anti-CYP antibodies were incubated with racemic ketamine and liver microsomes or specific CYPs. Ketamine N-demethylation to norketamine was determined via enantioselective capillary electrophoresis. Results: The general CYP inhibit...
Enderle AK, Levionnois OL, Kuhn M, Schatzmann U.To compare isoflurane alone or in combination with systemic ketamine and lidocaine for general anaesthesia in horses. Methods: Prospective, randomized, blinded clinical trial. Methods: Forty horses (ASA I-III) undergoing elective surgery. Methods: Horses were assigned to receive isoflurane anaesthesia alone (ISO) or with ketamine and lidocaine (LKI). After receiving romifidine, diazepam, and ketamine, the isoflurane end-tidal concentration was set at 1.3% and subsequently adjusted by the anaesthetist (unaware of treatments) to maintain a light plane of surgical anaesthesia. Animals in the LKI ...
Dobson A, Gleed RD, Meyer RE, Stewart BJ.The distribution of blood flow to the lungs was measured with labelled microspheres injected into horses before and during anaesthesia. Anaesthesia was induced with glycerol guaiacolate ether and ketamine, and maintained with the spontaneous breathing of halothane in oxygen. In a preliminary group of six horses, flow distribution was observed during anaesthesia in sternal, dorsal and right lateral recumbency. In two other groups, each of four horses, the flow distribution with time during either sternal or right lateral recumbency was observed. A small, constant proportion of the 15 micron dia...
Greene SA, Thurmon JC, Tranquilli WJ, Benson GJ.Eight ponies were anesthetized with a solution containing 50 mg of guaifenesin, 1 mg of ketamine, and 0.5 mg of xylazine X ml-1 of 5% dextrose in water. Anesthesia was induced by IV injection (1.1 ml X kg-1), followed by continuous IV infusion at 2.75 ml X kg-1 X hr-1. Heart rate, rate-pressure product, mean pulmonary artery pressure, and standard bicarbonate were not significantly changed throughout the study. Systolic, diastolic, and mean arterial pressures and left ventricular stroke work index were significantly decreased at 5 and 15 minutes after a bolus of the anesthetic solution was inj...
Haga HA, Lykkjen S, Revold T, Ranheim B.To evaluate the effect of intratesticular administration of lidocaine on cardiovascular responses and cremaster muscle tension during castration of isoflurane-anesthetized stallions. Methods: 28 healthy stallions (mean +/- SD age, 4.2 +/- 2.8 years) with no testicular abnormalities that were scheduled for castration. Methods: Each horse was given acepromazine (20 microg/kg, IM), romifidine (50 microg/kg, IV), and butorphanol (20 microg/kg, IV). Anesthesia was induced with ketamine (2.5 mg/kg, IV) and midazolam (50 microg/kg, IV) and maintained with isoflurane (1.7% end-tidal concentration). Af...
Matthews NS, Hartsfield SM, Cornick JL, Williams JD, Beasley A.Six combinations of injectable anesthetic agents were administered to six adult horses in a Latin square design. The drug combinations were xylazine-ketamine, xylazine-butorphanol-ketamine, xylazine-tiletamine-zolazepam, xylazine-butorphanol-tiletamine-zolazepam, detomidine-ketamine, and detomidine-butorphanol-ketamine. Measured variables were heart rate, respiratory rate, systolic blood pressure, arterial pH (pHa), PaCO2, PaO2, recumbency time, and number of attempts necessary to stand. Quality of induction and recovery, muscle relaxation, and response to stimulus were evaluated subjectively....
Robinson EP, Natalini CC.Intercoccygeal, or caudal, epidural injection of local anesthetics is a convenient method of producing analgesia and local anesthesia of the tail and perineal structures in conscious standing horses. This technique has been further developed to provide long duration analgesia and anesthesia by placement of catheters into the epidural space of horses. More recently, opioid, alpha-2 adrenergic agonists, ketamine and other analgesic agents have been administered by caudal epidural injection, providing pain relief in both conscious, standing and anesthetized, recumbent horses. This chapter describ...
Müller TM, Hopster K, Bienert-Zeit A, Rohn K, Kästner SBR.Standing surgery, especially dental procedures, are commonly performed in horses. This leads to an increasing demand for reliable sedation protocols. Therefore, it was the purpose of this study to investigate the influence of butorphanol, midazolam or ketamine on romifidine based sedation in horses during cheek tooth removal. Methods: Forty horses presented for tooth extraction were divided in four groups using matched pair randomization. Group R was sedated with romifidine (bolus 0.03 mg/kg, followed by a constant rate infusion (CRI) 0.05 mg/kg/h) and group RB with romifidine (same dose) an...
Love EJ, Taylor PM, Clark C, Whay HR, Murrell J.In the UK butorphanol has a marketing authorisation for administration to horses for sedation in combination with detomidine, and at a higher dose (0.1 mg/kg bwt), for the alleviation of pain. There is only a limited number of clinical studies designed to examine the analgesic effects of butorphanol administration following surgery. Objective: To investigate the effect of premedication with butorphanol on post operative pain following castration under general anaesthesia in ponies. Objective: Ponies receiving butorphanol would experience less pain after castration than ponies that did not rece...
