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.
Vermedal H, Valverde A, Sears W.The objective of this study was to investigate the effect of anesthesia duration on the quality of recovery in horses. The medical records of horses that were anesthetized and underwent surgery for elective and emergency soft tissue and orthopedic conditions from 2013 to 2019 were reviewed. Horses included in the study (N = 305) fulfilled the following requirements: all had the same premedication/induction protocol and the same balanced anesthesia for maintenance and were anesthetized by the same, experienced Board-certified anesthesiologist. A standardized anesthetic recovery score was comple...
Troya-Portillo L, López-Sanromán J, Villalba-Orero M, Santiago-Llorente I.Standing surgery under sedation reduces anesthetic-related mortality in horses. Medetomidine, alone and combined with morphine in a constant rate infusion (CRI), has been described for standing surgery but their cardiorespiratory, sedative and antinociceptive effects have never been compared. The addition of ketamine could improve analgesia in these procedures with minimal cardiorespiratory consequences. The objectives were to compare the cardiorespiratory effects, quality of sedation, antinociception and ataxia produced by administration of a medetomidine-based CRI with morphine, ketamine or ...
Neudeck S, Twele L, Kopp V, Kästner S.The aim was to determine the effects of vatinoxan on dexmedetomidine plasma concentrations and effects on cardiovascular and intestinal tissue pharmacodynamics. In a prospective randomized study, six horses were premedicated intravenously with dexmedetomidine 3.5 µg kg followed by a constant-rate infusion of 7 µg kg h (group DEX) and six horses with dexmedetomidine of the same dose (bolus and constant-rate infusion) combined with vatinoxan 130 µg kg followed by 40 µg kg h (group VAT). Anaesthesia was induced with ketamine and diazepam and maintained with isoflurane. Venous bloo...
Willette C, Aarnes TK, Lerche P, Ricco-Pereira C, Ballash GA, Bednarski RM.To assess anesthetic induction, recovery quality and cardiopulmonary variables after intramuscular (IM) injection of three drug combinations for immobilization of horses. Methods: Randomized, blinded, three-way crossover prospective design. Methods: A total of eight healthy adult horses weighing 470-575 kg. Methods: Horses were administered three treatments IM separated by ≥1 week. Combinations were tiletamine-zolazepam (1.2 mg kg), ketamine (1 mg kg) and detomidine (0.04 mg kg) (treatment TKD); ketamine (3 mg kg) and detomidine (0.04 mg kg) (treatment KD); and tiletamine-zolazepam (2.4 mg ...
Roşu O, Melega I, Evans AL, Arnemo JM, Küker S.Feral horses are immobilized for a variety of reasons including population control via contraceptives. Although opioid combinations have been successfully used for immobilization of feral horses, there is a need for combinations using drugs that are more readily available and present less of a human health hazard. We evaluated the chemical immobilization with physiological measurements and blood gas analyses of 91 free-ranging feral horses () remotely immobilized with a combination of 30 mg medetomidine and 775 mg ketamine in a single disposable 6 ml dart. During immobilization, heart rate, re...
Ellis JS, Mama KR, Rao S, Sadler RA, Marinkovich M, Clancy MM, Howard LL, Lamberski N, Kinney ME.Przewalski's horses () are an endangered equid species. Anesthesia administered by remote delivery is often needed to provide medical care. Behavioral and physiologic parameters were prospectively compared in 14 horses (8 females and 6 males, 3-18 yr) after a single-dart or staged two-dart anesthesia induction protocol with intramuscular medetomidine (0.06 mg/kg), butorphanol (0.05 mg/kg), thiafentanil (0.02 mg/kg), and ketamine (1 mg/kg). Seven horses were randomly assigned to receive all drugs in a single dart, and the other seven to receive medetomidine and butorphanol 10 min prior to thiaf...
Wiederkehr A, Barbarossa A, Ringer SK, Jörger FB, Bryner M, Bettschart-Wolfensberger R. To assess drug plasma levels, preanesthetic sedation, cardiopulmonary effects during anesthesia and recovery in horses anesthetized with isoflurane combined with medetomidine or xylazine. Prospective blinded randomized clinical study. Sixty horses undergoing elective surgery. Thirty minutes after administration of antibiotics, flunixine meglumine or phenylbutazone and acepromazine horses received medetomidine 7 μg kg (group MED) or xylazine 1.1 mg kg (group XYL) slowly intravenously (IV) and sedation was assessed 3 min later. Anesthesia was induced with ketamine/diazepam and maintained wi...
Fujiyama M, Jones T, Duke-Novakovski T.To evaluate perioperative stress-related hormones in isoflurane-anesthetized horses administered infusions of dexmedetomidine alone or with butorphanol or remifentanil, compared with ketamine-morphine. Methods: Randomized, prospective, nonblinded clinical study. Methods: A total of 51 horses undergoing elective surgical procedures. Methods: Horses were premedicated with xylazine, anesthesia induced with ketamine-diazepam and maintained with isoflurane and one of four intravenous infusions. Partial intravenous anesthesia (PIVA) was achieved with dexmedetomidine (1.0 μg kg hour; group D; 12 hor...
Douglas H, Hopster K, Cerullo M, Hopster-Iversen C, Stefanovski D, Driessen B.Flumazenil antagonises the actions of benzodiazepines. There has been no prior research specifically investigating this anaesthetic reversal agent for horses. Objective: To determine the effects of flumazenil administration in horses on (a) ventilatory parameters after midazolam-ketamine induction and maintenance with isoflurane in oxygen and on (b) the characteristics of recovery from general anaesthesia. Methods: Blinded, randomised, crossover experiment. Methods: Six horses were randomly assigned to receive high-dose flumazenil (F , 20 µg/kg), low-dose flumazenil (F , 10 µg/kg) and sali...
Gittel C, Schulz-Kornas E, Sandbaumhüter FA, Theurillat R, Vervuert I, Larenza Menzies MP, Thormann W, Braun C.To evaluate the pharmacokinetics and selected pharmacodynamic effects of a commercially available l-methadone/fenpipramide combination administered to isoflurane anaesthetized ponies. Methods: Prospective single-group interventional study. Methods: A group of six healthy adult research ponies (four mares, two geldings). Methods: Ponies were sedated with intravenous (IV) detomidine (0.02 mg kg) and butorphanol (0.01 mg kg) for an unrelated study. Additional IV detomidine (0.004 mg kg) was administered 85 minutes later, followed by induction of anaesthesia using IV diazepam (0.05 mg kg) and keta...
Alling CR, Cremer J, Liu CC, Lewin AC, Camacho-Luna P, Carter RT.To evaluate changes in intraocular pressure (IOP) with variable head position in healthy, anesthetized horses in hoisted inversion and to assess the influence of various cofactors (age, sex, body weight, body condition score, and neck length) on IOP changes during hoisting. Methods: Seventeen healthy adult horses without significant ocular abnormalities. Methods: Subjects were administered intravenous xylazine/butorphanol premedication and ketamine/midazolam induction with xylazine/ketamine boluses for anesthetic maintenance. While hoisted, IOP was measured in triplicate for each eye via rebou...
Duke-Novakovski T, Jimenez CP, Fujiyama M, Beazley SG.Various drugs administered to horses undergoing surgical procedures can release histamine. Histamine concentrations were evaluated in horses prepared for surgery and administered butorphanol or morphine intraoperative infusions. Methods: Prospective studies with one randomized. Methods: A total of 44 client-owned horses. Methods: In one study, anesthesia was induced with xylazine followed by ketamine-diazepam. Anesthesia was maintained with guaifenesin-xylazine-ketamine (GXK) during surgical preparation. For surgery, isoflurane was administered with intravenous (IV) morphine (group M: 0.15 mg ...
Trenholme HN, Barletta M, Quandt JE, Reed RA, Kleine SA, Hofmeister EH.Low arterial oxygen is a common complication in anesthetized horses and placing the animal in reverse Trendelenburg (RT) position may treat hypoxemia. The objective of this study was to assess the arterial partial pressure of oxygen (PaO) in horses placed in a 5-degree RT compared to horizontal (H) position. Client-owned healthy horses (n = 60) undergoing elective surgeries were enrolled in a randomized controlled clinical study. Horses were sedated with butorphanol, an α-adrenoceptor agonist, ± acepromazine and induced with ketamine combined with a benzodiazepine, propofol, or guaifenesin...
Louro LF, Milner PI, Bardell D.Opioid epidural analgesia has been shown to provide effective analgesia in horses. There is a lack of evidence regarding the effect of opioid epidural analgesia on quality of recovery in horses. Objective: Identify whether opioid epidural analgesia influences quality of recovery in horses undergoing general anaesthesia required for management of hindlimb synovial sepsis. Methods: Single-centre retrospective cross-sectional study. Methods: Data were obtained from the clinical records of horses which had undergone arthroscopic or tenoscopic surgery for management of hindlimb synovial sepsis over...
Grady SE, Lescun TB, Moore GE, Cooper BR, Davern AJ, Brunner TJ, Taylor SD.The objective was to compare the analgesic efficacy of ketorolac tromethamine (KT) and two other nonsteroidal anti-inflammatory drugs (NSAIDs), including flunixin meglumine (FM) and phenylbutazone (PB), using a heart bar shoe (HBS) model of reversible foot lameness in horses. Nine adult horses were used in a blinded, randomized, placebo-controlled crossover study. After induction of left front limb lameness using a modified HBS model, one of three NSAIDs (KT, 2.0 mg/kg IV; FM, 1.1 mg/kg IV; PB, 4.4 mg/kg IV) or saline (placebo) was administered IV as a single dose. Lameness was assessed eve...
Gehlen H, Loschelder J, Merle R, Walther M.The effects of a standard protocol for euthanasia on heart rate variability (HRV) as a consequence of stress response were analyzed in this prospective clinical study. The HRV was determined in 40 horses undergoing euthanasia due to various reasons, at different locations, and with/without owner presence. For euthanasia, horses were sedated with xylazine or a combination of xylazine and butorphanol. General anesthesia was induced using diazepam and ketamine. Afterwards, horses were euthanized with pentobarbital. The ECG data were taken by a Telemetric ECG at three time points (sedation, anesth...
Hector RC, Rezende ML, Mama KR, Hess AM.Post-anaesthetic sedation is administered to horses to improve recovery quality from inhalant anaesthesia and reduce the risk of catastrophic injury. A single dose of dexmedetomidine for this purpose has not been evaluated clinically. Objective: To determine whether dexmedetomidine improves recovery quality from sevoflurane anaesthesia compared to a previously studied dose of romifidine. Methods: Prospective, randomised, masked clinical trial. Methods: Ninety-nine, adult, client-owned horses anaesthetised for elective procedures completed the trial. Anaesthetic protocol was standardised. Horse...
Smith MC, Bass L, Damone J, Mama K, Rao S.The ideal field anaesthetic protocol for castration will offer an adequate duration and depth of anaesthesia using a single injection without compromising safety or recovery quality. Objective: The objective of this study was to compare intravenous (IV) xylazine and detomidine as sedatives in combination with midazolam and ketamine for induction of anaesthesia in horses undergoing field castration. Methods: Randomised, blinded, clinical study. Methods: Fifty-seven male Quarter Horses were randomly assigned to receive xylazine (group X) (1.1 mg/kg bwt) or detomidine (group D) (0.03 mg/kg bwt)...
Carregaro AB, Ueda GI, Censoni JB, Bisetto SP, Alonso BB, Reginato GM.The aim of this study was to compare the effects of methadone combined with detomidine or acepromazine on the quality of sedation and its influence over dissociative anesthesia in healthy horses. In a crossover design, seven horses were administered with 0.1 mg/kg methadone and 0.02 mg/kg detomidine intravenously (group MD) or 0.1 mg/kg methadone and 0.05 mg/kg acepromazine intravenously (group MA). Subsequently, anesthesia was induced with a combination of 2.2 mg/kg ketamine and 0.1 mg/kg midazolam intravenously. Descriptive scales and footages were used to evaluate the quality of sedat...
Rossi H, Raekallio M, Määttä M, Tapio H, Hanifeh M, Junnila J, Rajamäki MM, Mykkänen A.Pneumonia is one of the potential complications of general anaesthesia in horses. Anaesthesia is known to increase neutrophils in bronchoalveolar lavage fluid (BALF) of horses after lateral recumbency, but studies after dorsal recumbency are lacking. Our primary aim was to determine when lung inflammation reaches its maximum and how rapidly BALF cytology returns to baseline after anaesthesia in dorsal recumbency. A secondary aim was to investigate the possible effect of vatinoxan, a novel drug, on the BALF cytology results. Six healthy experimental horses were enrolled in this observational cr...
Peña-Cadahia C, Manso-Díaz G, Santiago-Llorente I, Villalba-Orero M.A 2-day-old filly was referred to the hospital with abdominal pain and constipation. The foal presented tachycardia, tachypnea, hypoxemia, hyperlactatemia, and abdominal distension. Meconium impaction was diagnosed, and the filly underwent abdominal surgery. Diazepam and butorphanol were administered for anesthesia premedication, but sedative effects were mild. Xylazine was used to enhance sedation and ketamine was subsequently administered for induction. The foal showed swallow reflex and head movement when intubation was attempted. Consequently, isoflurane on oxygen was provided via an anest...
Tokushige H, Araki M, Kusano K, Arima D, Ito H, Yamazaki Y, Urayama S, Kambayashi Y, Tateno O, Ohta M.This study compares clinical characteristics between induction with thiopental/guaifenesin and propofol/ketamine in Thoroughbred racehorses anesthetized with sevoflurane and medetomidine. Clinical records of 214 horses that underwent arthroscopic surgery between 2015 and 2016 were retrospectively retrieved. Horses were premedicated with medetomidine and midazolam to sedate at the adequate level for smooth induction, and then induced with either thiopental (4.0 mg/kg) and guaifenesin (100 mg/kg) in Group TG (n=91) or propofol (1.0 mg/kg) and ketamine (1.0 mg/kg) in Group PK (n=123). Anesthesia ...
Theurillat R, Sandbaumhüter FA, Gittel C, Larenza Menzies MP, Braun C, Thormann W.An enantioselective assay for the determination of methadone and its main metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine in equine plasma based on capillary electrophoresis with highly sulfated γ-cyclodextrin as chiral selector and electrokinetic analyte injection is described. The assay is based on liquid/liquid extraction of the analytes at alkaline pH from 0.1 mL plasma followed by electrokinetic sample injection of the analytes from the extract across a buffer plug without chiral selector. Separation occurs cationically at normal polarity in a pH 3 phosphate buffer containin...
Harðardóttir H, Murison PJ, Blissitt K, Olason S, Clutton RE.Ketamine at 2.2 mg/kg given i.v. is often used to induce anaesthesia for surgical procedures in horses under field conditions. Commonly, additional doses are needed to complete the surgery. We hypothesised that surgical conditions would be improved when 5 mg/kg of ketamine was used to induce anaesthesia, while induction and recovery qualities would not differ from those when 2.2 mg/kg ketamine was used. Objective: To compare the anaesthetic effects of two ketamine doses (5 and 2.2 mg/kg) during field anaesthesia for castration of horses. Methods: Prospective, randomised, blinded, clinical stud...
Pratt S, Cunneen A, Perkins N, Farry T, Kidd L, McEwen M, Rainger J, Truchetti G, Goodwin W.There is no information directly comparing midazolam with guaifenesin when used in combination with an alpha-2 agonist and ketamine to maintain anaesthesia via i.v. infusion in horses. Objective: To compare ketamine-medetomidine-guaifenesin with ketamine-medetomidine-midazolam for total intravenous anaesthesia (TIVA) in young horses anaesthetised for computerised tomography. Methods: Prospective, randomised, blinded, crossover trial. Methods: Fourteen weanlings received medetomidine 7 μg/kg bwt i.v. and anaesthesia was induced with ketamine 2.2 mg/kg bwt i.v. On two separate occasions hors...
Sage AM, Keating SC, Lascola KM, Schaeffer DJ, Clark-Price SC.To evaluate cardiopulmonary and recovery characteristics of horses administered total intravenous anesthesia (TIVA) with xylazine and ketamine combined with midazolam or propofol. Methods: Randomized crossover study. Methods: A group of eight adult horses, aged 7-22 years, weighing 493-740 kg. Methods: Horses were administered xylazine (1 mg kg) intravenously (IV), and anesthesia was induced with ketamine (2.2 mg kg) IV. Anesthesia was maintained for 45 minutes via IV infusion of xylazine (0.016 mg kg minute) and ketamine (0.03 mg kg minute) combined with midazolam at 0.002 mg kg minute (MKX),...
Jarrett MA, Bailey KM, Messenger KM, Prange T, Gaines B, Posner LP.OBJECTIVE To evaluate quality of recovery from general anesthesia in horses after induction with propofol and ketamine versus midazolam and ketamine. DESIGN Prospective randomized crossover study. ANIMALS 6 healthy adult horses. PROCEDURES Horses were premedicated with xylazine (1.0 mg/kg [0.45 mg/lb], IV), and general anesthesia was induced with midazolam (0.1 mg/kg [0.045 mg/lb], IV) or propofol (0.5 mg/kg [0.23 mg/lb], IV), followed by ketamine (3.0 mg/kg [1.36 mg/lb], IV). Horses were endotracheally intubated, and anesthesia was maintained with isoflurane. After 60 minutes, horses were giv...
Aarnes TK, Lerche P, Bednarski RM, Hubbell JAE.This study evaluated use of midazolam, ketamine, and xylazine (MKX) for total intravenous (IV) anesthesia (TIVA) in horses. Medical records of 46 horses undergoing a clinical procedure using MKX for TIVA were reviewed. Age, breed, procedure, heart rate (HR), respiratory rate (RR), pre-anesthetic drugs, induction drugs, and total volume of MKX were recorded. Duration of anesthesia, time to standing, number of attempts to stand, and recovery score were also recorded. All horses were premedicated with an alpha-2 adrenoceptor agonist and anesthesia was induced with ketamine and midazolam. Duration...
Sandbaumhüter FA, Thormann W.Glucuronidation catalyzed by uridine-5'-diphospho-glucuronosyl-transferases (UGTs) is the most important reaction in phase II metabolism of drugs and other compounds. O-glucuronidation is more common than N-glucuronidation. The anesthetic, analgesic and antidepressive drug ketamine is metabolized in phase I by cytochrome P450 enzymes to norketamine, hydroxynorketamine (HNK) diastereomers and dehydronorketamine (DHNK). Equine urine samples collected two hours after ketamine injection were treated with β-glucuronidase and analyzed with three enantioselective capillary electrophoresis assays. Co...
Sandbaumhüter FA, Vimercati S, Thormann W, Mevissen M.The anesthetic ketamine is often combined with analgesics and benzodiazepines in equine medicine. Therefore, drug-drug interactions are possible. Enzyme kinetics for ketamine N-demethylation were determined using equine CYP3A94, CYP3A95 and CYP3A97, and the effect of medetomidine, diazepam and methadone on the ketamine metabolism was studied in vitro. Ketamine was incubated with the CYPs or equine liver microsomes (ELM) alone or in presence of medetomidine, diazepam and/or methadone for different times. Norketamine levels were determined using enantioselective capillary electrophoresis (CE) wi...
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...
Muir WW, Skarda RT, Sheehan W.A combination of intramuscular xylazine plus intravenous guaifenesin and ketamine hydrochloride was evaluated as a method for chemical restraint and casting of the adult horse. This drug combination provided safe and rapid induction of the horse and uneventful recovery from lateral recumbency. Cardiopulmonary function remained within base-line values for the adult horse, although cardiac output, arterial blood pressure, and arterial partial pressure of oxygen were decreased from base-line values. Xylazine, guaifenesin, and ketamine hydrochloride provided safe induction to general anesthesia wi...
Wettstein D, Moens Y, Jaeggin-Schmucker N, Böhm SH, Rothen HU, Mosing M, Kästner SB, Schatzmann U.To evaluate pulmonary and cardiovascular effects of a recruitment maneuver (RM) combined with positive end-expiratory pressure (PEEP) during total intravenous anesthesia in ponies. Methods: 6 healthy adult Shetland ponies. Methods: After premedication with detomidine (10 microg/kg, IV), anesthesia was induced with climazolam (0.06 mg/kg, IV) and ketamine (2.2 mg/kg, IV) and maintained with a constant rate infusion of detomidine (0.024 mg/kg/h), climazolam (0.036 mg/kg/h), and ketamine (2.4 mg/kg/h). The RM was preceded by an incremental PEEP titration and followed by a decremental PEEP titrati...
Gómez de Segura IA, De Rossi R, Santos M, López San-Roman J, Tendillo FJ, San-Roman F.To determine the analgesic, sedative, and cardiopulmonary effects of epidural ketamine in the horse. Methods: Six healthy horses (three males and three females) weighing between 350 and 450 kg. Methods: Three doses of ketamine were selected (0.5, 1, 2 mg/kg). Two months before the beginning of experiments, the carotid artery was exteriorized, and 1 week before experiments began, an epidural catheter was placed percutaneously in all animals with the tip located 12 cm cranially in the midsacrum. One week later, either saline (control) or one of three doses of ketamine was injected epidurally. Ea...
Duke T, Filzek U, Read MR, Read EK, Ferguson JG.During an 8-year period of clinic improvements, an increased incidence of postanesthetic myopathy (PAM) was observed in horses undergoing anesthesia. A request was made for an independent anesthesiologist to examine possible reasons for this increase. Routine methods used for anesthesia were then compared with new methods introduced by the anesthesiologist. Methods: Investigative observations were conducted from October 1999 to April 2000. Following premedication with xylazine or detomidine, anesthesia was induced with diazepam or guiaifenesin followed by ketamine. Maintenance of anesthesia wa...
McMurphy RM, Young LE, Marlin DJ, Walsh K.To compare cardiopulmonary responses during anesthesia maintained with halothane and responses during anesthesia maintained by use of a total intravenous anesthetic (TIVA) regimen in horses. Methods: 7 healthy adult horses (1 female, 6 geldings). Methods: Each horse was anesthetized twice. Romifidine was administered IV, and anesthesia was induced by IV administration of ketamine. Anesthesia was maintained for 75 minutes by administration of halothane (HA) or IV infusion of romifidine, guaifenesin, and ketamine (TIVA). The order for TIVA or HA was randomized. Cardiopulmonary variables were mea...
Luna SP, Taylor PM, Wheeler MJ.Six Welsh gelding ponies (weight 246 +/- 6 kg) were premedicated with 0.03 mg/kg of acepromazine intravenously (i.v.) followed by 0.02 mg/kg of detomidine i.v. Anaesthesia was induced with 2 mg/kg of ketamine i.v. Ponies were intubated and lay in left lateral recumbency. On one occasion anaesthesia was maintained for 2 h using 1.2% halothane in oxygen. The same group of ponies were anaesthetized 1 month later using the same induction regime and anaesthesia was maintained with a combination of detomidine, ketamine and guaiphenesin, while the ponies breathed oxygen-enriched air. Electrocardiogra...
Ekström PM, Short CE, Geimer TR.This study was done to compare the electroencephalographic (EEG) response evoked by orthopedic surgery in halothane- and isoflurane-anesthetized horses. Eight horses scheduled for bilateral arthroscopic surgery of the stifle were premedicated with detomidine (20 micrograms/kg) intravenously and five minutes later induced to anesthesia with ketamine (2.2 mg/kg) intravenously. Anesthesia was maintained with either halothane or isoflurane. Assignment of inhalation anesthetic was done randomly. The multiple of minimal alveolar concentration (MAC) of halothane required for anesthesia was significan...
Larenza MP, Knobloch M, Landoni MF, Levionnois OL, Kronen PW, Theurillat R, Schatzmann U, Thormann W.The pharmacokinetics of ketamine and norketamine enantiomers after administration of intravenous (IV) racemic ketamine (R-/S-ketamine; 2.2 mg/kg) or S-ketamine (1.1 mg/kg) to five ponies sedated with IV xylazine (1.1mg/kg) were compared. The time intervals to assume sternal and standing positions were recorded. Arterial blood samples were collected before and 1, 2, 4, 6, 8 and 13 min after ketamine administration. Arterial blood gases were evaluated 5 min after ketamine injection. Plasma concentrations of ketamine and norketamine enantiomers were determined by capillary electrophoresis and wer...
Gozalo-Marcilla M, Steblaj B, Schauvliege S, Duchateau L, Gasthuys F.Twenty adult healthy horses undergoing elective surgery were involved in this prospective, blinded, clinical study. Horses were randomly allocated to receive a constant rate infusion (CRI) of morphine or dexmedetomidine. After induction, anaesthesia was maintained with isoflurane in oxygen/air and mechanical ventilation applied. The end-tidal isoflurane concentration (FÉISO) was initially set at 0.9% and adjusted by the anaesthetist, to maintain a light surgical plane of anaesthesia, according to an objective flow-chart. The cardiopulmonary function was only minimally different between groups...
Casoni D, Spadavecchia C, Wampfler B, Thormann W, Levionnois OL.Intravenous anaesthetic drugs are the primary means for producing general anaesthesia in equine practice. The ideal drug for intravenous anaesthesia has high reliability and pharmacokinetic properties indicating short elimination and lack of accumulation when administered for prolonged periods. Induction of general anaesthesia with racemic ketamine preceded by profound sedation has already an established place in the equine field anaesthesia. Due to potential advantages over racemic ketamine, S-ketamine has been employed in horses to induce general anaesthesia, but its optimal dose remains und...
Theurillat R, Knobloch M, Schmitz A, Lassahn PG, Mevissen M, Thormann W.CE with multiple isomer sulfated beta-CD as the chiral selector was assessed for the simultaneous analysis of the enantiomers of ketamine and metabolites in extracts of equine plasma and urine. Different lots of the commercial chiral selector provided significant changes in enantiomeric ketamine separability, a fact that can be related to the manufacturing variability. A mixture of two lots was found to provide high-resolution separations and interference-free detection of the enantiomers of ketamine, norketamine, dehydronorketamine, and an incompletely identified hydroxylated metabolite of no...
Young LE, Bartram DH, Diamond MJ, Gregg AS, Jones RS.General anaesthesia was maintained in 40 horses by the continuous intravenous infusion of a mixture of 500 ml 10% guaifenesin solution, 1 g ketamine and 500 mg xylazine. The median duration of infusion was 65 mins (interquartile range 51-95 mins). Anaesthesia was characterised by active palpebral reflexes, variable degrees of nystagmus and occasional swallowing. Swallowing was considered to be undesirable in horses undergoing laryngeal surgery, but the infusion produced satisfactory conditions for all other surgical procedures performed. Arterial blood pressure was well maintained in all cases...
Creighton CM, Lemke KA, Lamont LA, Horney BS, Riley CB.To compare the effects of xylazine bolus versus medetomidine constant rate infusion (MCRI) on cardiopulmonary function and depth of anesthesia in dorsally recumbent, spontaneously breathing, isoflurane-anesthetized horses. Methods: Prospective, randomized crossover study. Methods: 10 healthy adult Standardbreds. Methods: Horses were premedicated with xylazine or medetomidine IV. Anesthesia was induced with diazepam and ketamine and maintained with isoflurane for 150 minutes. For the xylazine treatment, end-tidal isoflurane concentration was maintained at 1.7%, and xylazine (0.2 mg/kg [0.09 mg/...
Keates HL, van Eps AW, Pearson MR.To compare anaesthesia induced with either alfaxalone or ketamine in horses following premedication with xylazine and guaifenesin. Methods: Randomized blinded cross-over experimental study. Methods: Six adult horses, five Standardbreds and one Thoroughbred; two mares and four geldings. Methods: Each horse received, on separate occasions, induction of anaesthesia with either ketamine 2.2 mg kg(-1) or alfaxalone 1 mg kg(-1) . Premedication was with xylazine 0.5 mg kg(-1) and guaifenesin 35 mg kg(-1) . Incidence of tremors/shaking after induction, recovery and ataxia on recovery were scored. Time...
Kalchofner KS, Picek S, Ringer SK, Jackson M, Hässig M, Bettschart-Wolfensberger R.To determine, in mildly hypercapnic horses under isoflurane-medetomidine balanced anaesthesia, whether there is a difference in cardiovascular function between spontaneous ventilation (SV) and intermittent positive pressure ventilation (IPPV). Methods: Prospective randomized clinical study. Methods: Sixty horses, undergoing elective surgical procedures under general anaesthesia: ASA classification I or II. Methods: Horses were sedated with medetomidine and anaesthesia was induced with ketamine and diazepam. Anaesthesia was maintained with isoflurane and a constant rate infusion of medetomidine...
Hopster K, Hopster-Iversen C, Geburek F, Rohn K, Kästner SB.The aim of this study was to assess the effect of duration of anaesthesia and concentration of isoflurane on global perfusion as well as intestinal microperfusion and oxygenation. Nine Warmblood horses were premedicated with xylazine; anaesthesia was induced with midazolam and ketamine, and maintained with isoflurane. Horses were ventilated to normocapnia. During 7 h of anaesthesia, mean arterial blood pressures (MAP), heart rate, central venous pressure, pulmonary artery pressure, expiratory isoflurane concentration (ETIso) and cardiac output using lithium dilution were measured; cardiac in...
Sandbaumhüter FA, Thormann W.Glucuronidation catalyzed by uridine-5'-diphospho-glucuronosyl-transferases (UGTs) is the most important reaction in phase II metabolism of drugs and other compounds. O-glucuronidation is more common than N-glucuronidation. The anesthetic, analgesic and antidepressive drug ketamine is metabolized in phase I by cytochrome P450 enzymes to norketamine, hydroxynorketamine (HNK) diastereomers and dehydronorketamine (DHNK). Equine urine samples collected two hours after ketamine injection were treated with β-glucuronidase and analyzed with three enantioselective capillary electrophoresis assays. Co...
Bettschart-Wolfensberger R, Kalchofner K, Neges K, Kästner S, Fürst A.To examine the clinical suitability of medetomidine-propofol infusions for total intravenous anaesthesia in horses. Methods: Fifty client-owned horses of mixed breed, age [mean +/- SD (range)] 6.6 +/- 4.4 (0.04-18) years, mass 478 +/- 168.3 (80-700) kg presented for a range of operations requiring general anaesthesia. Methods: Pre-anaesthetic medication was intravenous (IV) medetomidine 7 mug kg(-1). Anaesthesia was induced with IV ketamine (2 mg kg(-1)) and diazepam (0.02 mg kg(-1)). After endotracheal intubation, O2 was delivered (FiO2 > 0.85). Positive pressure ventilation was initiated if ...
Hopster K, Müller C, Hopster-Iversen C, Stahl J, Rohn K, Kästner S.To compare cardiovascular effects and recovery quality and duration of total intravenous anaesthesia (TIVA) with xylazine-ketamine-midazolam or dexmedetomidine-ketamine-midazolam. Methods: Prospective, randomized experimental cross-over trial. Methods: Eight adult warmblood horses. Methods: After sedation with acepromazine and either xylazine [0.5 mg kg(-1) , intravenously (IV)] or dexmedetomidine (3.5 μg kg(-1) IV) anaesthesia was induced with ketamine and midazolam and maintained with a constant rate infusion (CRI) of xylazine (1 mg kg(-1) hour(-1) ) [XKM] or dexmedetomidine (7 μg...
Yamashita K, Wijayathilaka TP, Kushiro T, Umar MA, Taguchi K, Muir WW.The anesthetic and cardiopulmonary effects of midazolam, ketamine and medetomidine for total intravenous anesthesia (MKM-TIVA) were evaluated in 14 horses. Horses were administered medetomidine 5 microg/kg intravenously as pre-anesthetic medication and anesthetized with an intravenous injection of ketamine 2.5 mg/kg and midazolam 0.04 mg/kg followed by the infusion of MKM-drug combination (midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.1 mg/ml). Nine stallions (3 thoroughbred and 6 draft horses) were castrated during infusion of MKM-drug combination. The average duration of anesthesia wa...
Larenza MP, Peterbauer C, Landoni MF, Levionnois OL, Schatzmann U, Spadavecchia C, Thormann W.To evaluate pharmacokinetics of ketamine and norketamine enantiomers after constant rate infusion (CRI) of a subanesthetic dose of racemic ketamine or S-ketamine in ponies. Methods: Five 6-year-old Shetland pony geldings that weighed between 101 and 152 kg. Methods: In a crossover study, each pony received a CRI of racemic ketamine (loading dose, 0.6 mg/kg; CRI, 0.02 mg/kg/min) and S-ketamine (loading dose, 0.3 mg/kg; CRI, 0.01 mg/kg/min), with a 1-month interval between treatments. Arterial blood samples were collected before and at 5, 15, 30, 45, and 60 minutes during drug administration and...
Edner A, Nyman G, Essén-Gustavsson B.To study in horses (1) the relationship between cardiovascular variables and muscle perfusion during propofol-ketamine anaesthesia, (2) the physiological effects of a single intravenous (IV) detomidine injection, (3) the metabolic response of muscle to anaesthesia, and (4) the effects of propofol-ketamine infusion on respiratory function. Methods: Prospective experimental study. Methods: Seven standardbred trotters, 5-12 years old, 416-581 kg. Methods: Anaesthesia was induced with intravenous (IV) guaifenesin and propofol (2 mg kg) and maintained with a continuous IV infusion of propofol (0.15...
Elfenbein JR, Robertson SA, MacKay RJ, KuKanich B, Sanchez L.Prolonged drug infusions are used to treat horses with severe signs of pain, but can be associated with altered gastrointestinal transit. The purpose of this study was to determine the effects of prolonged constant rate infusions (CRI) of lidocaine (L), butorphanol (B), and ketamine (K) alone and in combination on gastrointestinal transit, behavior, and thermal nociceptive threshold in healthy horses. Methods: Eight healthy adult horses were used in a randomized, cross-over, blinded, prospective experimental trial. Interventions were saline, L, K, B, LK, LB, BK, and LBK as an intravenous CRI f...
Aleman M, Davis E, Williams DC, Madigan JE, Smith F, Guedes A.An intravenous (IV) overdose of pentobarbital sodium is the most commonly used method of euthanasia in veterinary medicine. However, this compound is not available in many countries or rural areas resulting in usage of alternative methods such as intrathecal lidocaine administration after IV anesthesia. Its safety and efficacy as a method of euthanasia have not been investigated in the horse. Objective: To investigate changes in mean arterial blood pressure and electrical activity of the cerebral cortex, brainstem, and heart during intrathecal administration of lidocaine. Our hypothesis was th...
Larenza MP, Landoni MF, Levionnois OL, Knobloch M, Kronen PW, Theurillat R, Schatzmann U, Thormann W.The arterial pharmacokinetics of ketamine and norketamine enantiomers after racemic ketamine or S-ketamine i.v. administration were evaluated in seven gelding ponies in a crossover study (2-month interval). Methods: Anaesthesia was induced with isoflurane in oxygen via a face-mask and then maintained at each pony's individual MAC. Racemic ketamine (2.2 mg kg(-1)) or S-ketamine (1.1 mg kg(-1)) was injected in the right jugular vein. Blood samples were collected from the right carotid artery before and at 1, 2, 4, 8, 16, 32, 64, and 128 min after ketamine administration. Ketamine and norketamine...
