Isoflurane is a volatile anesthetic agent commonly used in equine veterinary medicine for the induction and maintenance of general anesthesia. It is administered through inhalation and is valued for its rapid onset and recovery characteristics. Isoflurane acts on the central nervous system to produce a reversible loss of consciousness and sensation, facilitating various surgical and diagnostic procedures in horses. The agent is noted for its minimal metabolism by the liver, with the majority being exhaled unchanged, which is beneficial in reducing the burden on the equine liver. This page compiles peer-reviewed research studies and scholarly articles that explore the pharmacokinetics, physiological effects, and clinical applications of isoflurane in equine anesthesia.
Abass M, Picek S, Garzón JFG, Kühnle C, Zaghlou A, Bettschart-Wolfensberger R.In horses castration with primary intention healing is usually performed under balanced inhalation anaesthesia. To optimise analgesia, the use of local anaesthesia was tested. Objective: To investigate the effect of local mepivacaine before castration with first intention healing under balanced medetomidine-isoflurane anaesthesia and flunixin meglumine, morphine analgesia on perioperative cytokine levels and pain in horses. Methods: Prospective blinded clinical study. Methods: Twenty stallions were randomly assigned to control or mepivacaine groups. Flunixin meglumine was administered before s...
Hopster K, Wittenberg-Voges L, Geburek F, Hopster-Iversen C, Kästner SBR.Aim of this prospective experimental study was to assess effects of systemic hypoxemia and hypovolemia on global and gastrointestinal oxygenation and perfusion in anesthetized horses. Therefore, we anesthetized twelve systemically healthy warmblood horses using either xylazine or dexmedetomidine for premedication and midazolam and ketamine for induction. Anesthesia was maintained using isoflurane in oxygen with either xylazine or dexmedetomidine and horses were ventilated to normocapnia. During part A arterial oxygen saturation (SaO) was reduced by reducing inspiratory oxygen fraction in steps...
Hopster K, Wittenberg-Voges L, Kästner SBR.To investigate the effects of a xylazine infusion during isoflurane anesthesia on global perfusion parameters and gastrointestinal oxygenation and microperfusion, 8 adult warmblood horses were sedated with xylazine and anesthesia induced with midazolam and ketamine. Horses were mechanically ventilated during anesthesia. After 3 h of stable isoflurane anesthesia (FIso 1.3 Vol %), a xylazine infusion with 1 mg/kg body weight (BW) per hour was started for 1 h and then stopped. Before, during, and after xylazine infusion, heart rate (HR), arterial blood pressure (MAP), cardiac output (CO), central...
Hopster K, Neudeck S, Wittenberg-Voges L, Kästner SB.To compare alteration in intestinal blood flow in anaesthetized horses with changes in oral mucosa blood flow. Methods: Prospective, randomized clinical study. Methods: Eight warmblood horses. Methods: After induction with guaifenesin and ketamine, anaesthesia was maintained with isoflurane at 1.5 vol% in oxygen. The tissue blood flow was measured using laser Doppler flowmetry at the jejunum, colon, rectal mucosa, oesophageal mucosa and the oral mucosa. After three baseline measurements, blood flow was first increased by dobutamine infusion and thereafter decreased by increasing isoflurane con...
Sacks M, Ringer SK, Bischofberger AS, Berchtold SM, Bettschart-Wolfensberger R.To compare the effects of two balanced anaesthetic protocols (isoflurane-dexmedetomidine versus medetomidine) on sedation, cardiopulmonary function and recovery in horses. Methods: Prospective, blinded, randomized clinical study. Methods: Sixty healthy adult warm blood horses undergoing elective surgery. Methods: Thirty horses each were sedated with dexmedetomidine 3.5 μg kg (group DEX) or medetomidine 7 μg kg (group MED) intravenously. After assessing and supplementing sedation if necessary, anaesthesia was induced with ketamine/diazepam and maintained with isoflurane in oxygen/air and ...
Niimura Del Barrio MC, Bennett RC, Hughes JML.Influence of detomidine or romifidine constant rate infusion (CRI) on plasma lactate concentration and isoflurane requirements in horses undergoing elective surgery. Methods: Prospective, randomised, blinded, clinical trial. Methods: A total of 24 adult healthy horses. Methods: All horses were administered intramuscular acepromazine (0.02 mg kg) and either intravenous detomidine (0.02 mg kg) (group D), romifidine (0.08 mg kg) (group R) or xylazine (1.0 mg kg) (group C) prior to anaesthesia. Group D was administered detomidine CRI (10 μg kg hour) in lactated Ringer's solution (LRS), group...
Cruz Benedetti IC, Nottrott K, Fourel I, Le Bris M, Mongellas E, Portier K.To compare the effects of a lidocaine constant rate infusion (CRI) combined with 1% isoflurane versus those of 2% isoflurane alone on cardiovascular variables in anaesthetized horses, and to estimate the sample size required to detect a difference in recovery quality. Methods: Prospective, randomized, blinded, crossover study. Methods: Twelve healthy experimental horses. Methods: Horses were anaesthetized twice using an intravenous (IV) administration of acepromazine, romifidine, diazepam and ketamine. Horses were placed in dorsal recumbency and ventilated mechanically. During the first 10 min...
Duke-Novakovski T, Ambros B, Feng C, Carr AP.To determine the accuracy of high-definition oscillometry (HDO) for arterial pressure measurement during injectable or inhalation anesthesia in horses. Methods: Prospective, clinical study. Methods: Twenty-four horses anesthetized for procedures requiring lateral recumbency. Methods: Horses were premedicated with xylazine, and anesthesia induced with diazepam-ketamine. Anesthesia was maintained with xylazine-ketamine-guaifenesin combination [TripleDrip (TD; n = 12) or isoflurane (ISO; n = 12)]. HDO was used to obtain systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures, and he...
Bailey PA, Hague BA, Davis M, Major MD, Zubrod CJ, Brakenhoff JE.The purpose of this study was to determine the incidence of post-anesthetic colic in non-fasted adult horses undergoing isoflurane inhalant anesthesia for an elective, non-abdominal procedure at a single referral center. Medical records were searched from May 1, 2012 to May 31, 2014. Inclusion criteria included non-fasted patients ≥ 2 years of age that were anesthetized for an elective, non-abdominal procedure. The incidence of post-anesthetic colic for this study population was 2.5%. None of the risk factors examined (season, age, gender, breed, surgeon, procedure, recumbency, butorphanol a...
Schier MF, Raisis AL, Secombe CJ, Hosgood G, Musk GC, Lester GD.OBJECTIVE To determine the effects of acepromazine maleate premedication on cardiovascular function before and after infusion of dobutamine hydrochloride for 30 minutes in isoflurane-anesthetized horses. ANIMALS 6 healthy adult horses. PROCEDURES Each horse was anesthetized once following premedication with acepromazine (0.02 mg/kg, IV) administered 30 minutes prior to anesthetic induction (ACP+ treatment) and once without premedication (ACP- treatment). Anesthesia was induced with IV administration of xylazine hydrochloride (0.8 mg/kg), ketamine hydrochloride (2.2 mg/kg), and diazepam (0.08 m...
Steffey EP, Pascoe PJ.To quantitate the dose- and time-related magnitude of the anesthetic sparing effect of, and selected physiological responses to detomidine during isoflurane anesthesia in horses. Methods: Randomized cross-over study. Methods: Three, healthy, young adult horses weighing 485 ± 14 kg. Methods: Horses were anesthetized on two occasions to determine the minimum alveolar concentration (MAC) of isoflurane in O and then to measure the anesthetic sparing effect (time-related MAC reduction) following IV detomidine (0.03 and 0.06 mg kg). Selected common measures of cardiopulmonary function, blood glucos...
Loughran CM, Raisis AL, Hosgood G, Secombe CJ, Lester GD.Cardiac output does not always increase with dobutamine administration in anaesthetised horses and information on peripheral perfusion is lacking. Objective: To determine the effect of intravenous (i.v.) dobutamine infusion with and without a concurrent 20 mL/kg bodyweight (bwt) bolus of crystalloid fluids on the cardiovascular function of acepromazine premedicated, hypotensive, isoflurane-anaesthetised horses. Methods: Randomised, cross-over experiment. Methods: A total of 6 horses aged 5-13 years, weighing 464-578 kg were premedicated with acepromazine 0.02 mg/kg bwt and then sedated with xy...
Benmansour P, Billinsky J, Duke-Novakovski T, Alcorn J.To determine blood remifentanil concentration in isoflurane-anesthetized horses during and after a 1h remifentanil and dexmedetomidine infusion. Methods: Prospective study. Methods: Six adult mixed breed horses with (mean±SD) bodyweight of 507±61kg and 14±4years of age. Methods: Following sedation with xylazine IV, anesthesia was induced with ketamine IV mixed with diazepam IV. Anesthesia was maintained with isoflurane in oxygen. After 52±7min for instrumentation, dexmedetomidine (0.25μgkg(-1) followed by 1.0μg(-1)kg(-1)h(-1)) and remifentanil infusions (6μgkg(-1)h(-1)) were administere...
Tünsmeyer J, Hopster K, Kästner SB.To investigate the use of the Narcotrend electroencephalogram (EEG) monitor for the assessment of anesthetic depth in horses undergoing xylazine balanced isoflurane anesthesia. Methods: Blinded experimental study. Methods: Seven healthy warm-blooded horses, aged 10.6 ± 5.9 years, weighing 535 ± 55 kg. Methods: Horses were anesthetized for a terminal surgical trial with xylazine, thiopentone, and guaiphenesin for induction and isoflurane and xylazine continuous rate infusion for maintenance. After surgery, an EEG was recorded and processed by the Narcotrend monitor. It displays an...
Dugdale AH, Taylor PM.To review the literature concerning mortality associated with general anaesthesia in horses and to assess whether there is evidence for a reduction in mortality over the 20 years since the Confidential Enquiry into Perioperative Equine Fatalities (CEPEF). Methods: PubMed, Scopus, Google Scholar. Search terms used: horse; pony; equine; anaesthesia; anesthesia; recovery; morbidity, and mortality. Conclusions: The most recent studies, in which isoflurane and sevoflurane have been more commonly used for anaesthesia maintenance, report fewer intraoperative cardiac arrests than older studies in whi...
Taylor AH, Seymour CJ.Horses may become hypoxaemic during anaesthesia despite a high inspired oxygen fraction (FiO2). A lower FiO2 is used commonly in human beings to minimise atelectasis and to improve lung function, and previously has been shown to be of potential benefit in horses in experimental conditions. Other studies suggest no benefit to using a FiO2 of 0.5 during clinically relevant conditions; however, low FiO2 (0.65) is commonly used in practice and in a large number of studies. The present study was performed to compare the effect of a commonly used FiO2 of 0.65 versus 0.90 on calculated respiratory in...
Risberg ÅI, Ranheim B, Krontveit RI, Lervik A, Haga HA.To compare cardiac index and oxygen extraction at equivalent depths of anaesthesia between isoflurane-anaesthetized horses and horses anesthetized with isoflurane and dexmedetomidine CRI. Methods: Sequential, blinded, randomized, balanced, crossover study. Methods: Eight horses weighing a mean ± standard deviation of 478 ± 58 kg. Methods: Horses were premedicated with 0.03 mg kg(-1) acepromazine intramuscularly (IM) and 8 μg kg(-1) dexmedetomidine intravenously (IV). Anaesthesia was induced with 2.5 mg kg(-1) ketamine and 0.1 mg kg(-1) midazolam IV and maintained with isofluran...
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...
Pakkanen SA, Raekallio MR, Mykkänen AK, Salla KM, de Vries A, Vuorilehto L, Scheinin M, Vainio OM.To investigate MK-467 as part of premedication in horses anaesthetized with isoflurane. Methods: Experimental, crossover study with a 14 day wash-out period. Methods: Seven healthy horses. Methods: The horses received either detomidine (20 μg kg(-1) IV) and butorphanol (20 μg kg(-1) IV) alone (DET) or with MK-467 (200 μg kg(-1) IV; DET + MK) as premedication. Anaesthesia was induced with ketamine (2.2 mg kg(-1) ) and midazolam (0.06 mg kg(-1) ) IV and maintained with isoflurane. Heart rate (HR), mean arterial pressure (MAP), end-tidal isoflurane concentration, end-tidal carbon ...
Villalba M, Santiago I, Gómez de Segura IA.The aim of this investigation was to determine the isoflurane-sparing effect and impact on arterial blood pressure and anaesthetic recovery of a constant rate infusion of medetomidine-propofol in horses. In a prospective, crossover, randomised study, six healthy horses (mean ± SD age, 13.7 ± 7.7 years; weight, 433 ± 51 kg) were anaesthetised twice with isoflurane and were randomly assigned to receive one of two treatments on each occasion, at least 2 weeks apart. The first treatment was saline (CTL group) and the second a medetomidine-propofol infusion (MP group; 1.25 µg/kg...
Steblaj B, Schauvliege S, Pavlidou K, Gasthuys F, Savvas I, Duchateau L, Kowalczyk L, Moens Y.To compare pulmonary function and gas exchange in ponies during maintenance of anaesthesia with isoflurane or by a total intravenous anaesthesia (TIVA) technique. Methods: Experimental, cross-over study. Methods: Six healthy ponies weighing mean 286 (range 233-388) ± SD 61 kg, age 13 (9-16) ± 3 years. Methods: The ponies were anaesthetized twice, a minimum of two weeks apart. Following sedation with romifidine [80 μg kg(-1) intravenously (IV)], anaesthesia was induced IV with midazolam (0.06 mg kg(-1)) and ketamine (2.5 mg kg(-1), then maintained either with inhaled isoflurane (Fe'Iso = 1.1...
Duke-Novakovski T, Palacios-Jimenez C, Wetzel T, Rymes L, Sanchez-Teran AF.To examine the cardiopulmonary effects of two anesthetic protocols for dorsally recumbent horses undergoing carpal arthroscopy. Methods: Prospective, randomized, crossover study. Methods: Six horses weighing 488.3 ± 29.1 kg. Methods: Horses were sedated with intravenous (IV) xylazine and pulmonary artery balloon and right atrial catheters inserted. More xylazine was administered prior to anesthetic induction with ketamine and propofol IV. Anesthesia was maintained for 60 minutes (or until surgery was complete) using either propofol IV infusion or isoflurane to effect. All horses were admi...
Hopster K, Ambrisko TD, Stahl J, Schramel JP, Kästner SB.Previous studies showed an influence of xylazine on the LiDCO sensor in vitro and in standing horses, but did not prove that this interaction caused error in LiDCO measurements. Therefore, agreement of cardiac output (CO) measurements by LiDCO and bolus-thermodilution (BTD) was determined in horses receiving xylazine infusions. Methods: Prospective, experimental study. Methods: Eight Warmblood horses. Methods: All horses were premedicated with xylazine. Anaesthesia was induced with midazolam and ketamine and was maintained with isoflurane in oxygen. During six hours of anaesthesia CO measureme...
Pöppel N, Hopster K, Geburek F, Kästner S.To determine the influence of ketamine or xylazine constant rate infusions on isoflurane requirements, cardiovascular parameters and quality of anaesthesia in horses undergoing elective surgery. Methods: Prospective, matched paired clinical trial. Methods: Fifty four adult Warmblood horses. Methods: After premedication with acepromazine, xylazine and butorphanol, anaesthesia was induced with ketamine-midazolam and maintained with isoflurane alone (I), isoflurane with either 1 mg kg(-1) hour(-1) ketamine (IK) or same dose of xylazine (IX). End tidal concentration of isoflurane (Fe'Iso) was ...
Benmansour P, Husulak ML, Bracamonte JL, Beazley SG, Withnall E, Duke-Novakovski T.To examine the cardiopulmonary effects of infusions of remifentanil or morphine, and their influence on recovery of horses anesthetized with isoflurane and dexmedetomidine. Methods: Randomized crossover study with 7-day rest periods. Methods: Six adult horses (507 ± 61 kg). Methods: After the horses were sedated with xylazine, anaesthesia was induced with ketamine and diazepam, and maintained with isoflurane. After approximately 60 minutes, a dexmedetomidine infusion was started (0.25 μg kg(-1) then 1.0 μg(-1) kg(-1) hour(-1) ) in combination with either saline (group S), morphine (0.15 mg ...
Wiese AJ, Brosnan RJ, Barter LS.To compare effects of 2 acetylcholinesterase inhibitors on recovery quality of horses anesthetized with isoflurane. Methods: 6 horses in phase 1, 7 horses in phase 2A, and 14 horses in phase 2B. Methods: The study comprised 3 phases (2 randomized, blinded crossover phases in horses undergoing orthopedic procedures and 1 prospective dose-determining phase). In phase 1, horses were anesthetized with isoflurane and received neostigmine or saline (0.9% NaCl) solution prior to anesthetic recovery. Phase 2A was a physostigmine dose-determining phase. In phase 2B, horses were anesthetized with isoflu...
Posner LP, Kasten JI, Kata C.To document the suitability of intravenous propofol and ketamine following sedation with xylazine for routine anaesthetic induction in horses. Retrospective. 100 client-owned horses. Anaesthetic records were evaluated to determine: signalment, anaesthetic drug and dosages, need for additional induction agents, notation of any adverse events, duration of anaesthesia and recovery characteristics (rough or smooth, and rapid or prolonged). Horses were sedated with xylazine 0.99±(0.2) mg/kg intravenous and 23 horses were also administered butorphanol 0.02±(0.001) mg/kg intravenous. Horses were an...
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...
Fantoni DT, Marchioni GG, Ida KK, Belo JN, Zoppa AL, Silva LC, Ambrósio AM.To assess the cardiopulmonary effects of ephedrine and phenylephrine for management of isoflurane-induced hypotension in horses. Methods: Prospective randomized clinical study. Methods: Fourteen isoflurane-anesthetized horses undergoing digital palmar neurectomy. Methods: Ephedrine (EPH group; 0.02 mg kg(-1) minute(-1); n = 7) or phenylephrine (PHE group; 0.002 mg kg(-1) minute(-1); n = 7) was administered to all horses when mean arterial pressure (MAP) was <60 mmHg. The infusions were ended when the target MAP was achieved, corresponding to a 50% increase over the pre-infusion MAP (baseline)....
Crumley MN, McMurphy RM, Hodgson DS, Kreider SE.To compare the effects of 2 fractions of inspired oxygen, 50% and > 95%, on ventilation, ventilatory rhythm, and gas exchange in isoflurane-anesthetized horses. Methods: 8 healthy adult horses. Methods: In a crossover study design, horses were assigned to undergo each of 2 anesthetic sessions in random order, with 1 week separating the sessions. In each session, horses were sedated with xylazine hydrochloride (1.0 mg/kg, IV) and anesthesia was induced via IV administration of diazepam (0.05 mg/kg) and ketamine (2.2 mg/kg) Anesthesia was subsequently maintained with isoflurane in 50% or > 95% o...
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...
Guedes A, Knych H, Tucker L, Almeida DC, Baldo CF, Wendt-Hornickle E, Allweiler S.This study determined the pharmacokinetics and compared the clinical effects of xylazine and dexmedetomidine in horses recovering from isoflurane anesthesia. Six healthy horses aged 8.5 ± 3 years and weighing 462 ± 50 kg were anesthetized with isoflurane for 2 hr under standard conditions on two occasions one-week apart. In recovery, horses received 200 μg/kg xylazine or 0.875 μg/kg dexmedetomidine intravenously and were allowed to recover without assistance. These doses were selected because they have been used for postanesthetic sedation in clinical and research studies. Serial ...
Meyer RE, Short CE.The correlation between end-tidal partial pressure of CO2 (PETCO2) and arterial (PaCO2) was determined for spontaneously breathing ponies under halothane or isoflurane anesthesia. The PETCO2 was useful as a trend indicator of PaCO2 during the first 60 minutes of halothane or isoflurane anesthesia when PaCO2 values were less than 60 to 70 mm of Hg. Halothane anesthesia lasting greater than 90 minutes was associated with PaCO2 values in excess of 60 to 70 mm of Hg, a large arterial- to end-tidal PCO2 difference (PaCO2-PETCO2) and a significant increase in alveolar dead space. These effects were ...
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...
Risberg ÅI, Ranheim B, Krontveit RI, Lervik A, Haga HA.To compare cardiac index and oxygen extraction at equivalent depths of anaesthesia between isoflurane-anaesthetized horses and horses anesthetized with isoflurane and dexmedetomidine CRI. Methods: Sequential, blinded, randomized, balanced, crossover study. Methods: Eight horses weighing a mean ± standard deviation of 478 ± 58 kg. Methods: Horses were premedicated with 0.03 mg kg(-1) acepromazine intramuscularly (IM) and 8 μg kg(-1) dexmedetomidine intravenously (IV). Anaesthesia was induced with 2.5 mg kg(-1) ketamine and 0.1 mg kg(-1) midazolam IV and maintained with isofluran...
Auer U, Moens Y.The production of a central eye to ease surgical access for intraocular surgery is generally dependent on the depth of anesthesia. The aim of this study was to evaluate the eyeball position under muscle relaxation with rocuronium during general anesthesia. Methods: Twenty horses, body weight 480 ± 62 kg; age 12.6 ± 6.2 years (mean ± SD) were anesthetised for various ophthalmic surgeries. Horses were premedicated with acepromazine, xylazine, and butorphanol intravenously and anesthesia induced with ketamine and diazepam. Anesthesia was maintained with isoflurane in 100% oxyge...
Steffey EP, Zinkl J, Howland D.The potential toxicity to horses of 7.33 +/- 0.87 SD minimal alveolar concentration hours of isoflurane anesthesia was evaluated by sequential determination of blood cell counts, electrolyte concentrations, and certain blood chemical values. Minimal or no serious toxicosis was observed for up to 7 days after anesthesia was terminated.
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...
Thomasy SM, Mama KR, Whitley K, Steffey EP, Stanley SD.In order to evaluate its potential as an adjunct to inhalant anaesthesia in horses, the pharmacokinetics of fentanyl must first be determined. Objective: To describe the pharmacokinetics of fentanyl and its metabolite, N-[1-(2-phenethyl-4-piperidinyl)maloanilinic acid (PMA), after i.v. administration of a single dose to horses that were awake in Treatment 1 and anaesthetised with isoflurane in Treatment 2. Methods: A balanced crossover design was used (n = 4/group). During Treatment 1, horses received a single dose of fentanyl (4 microg/kg bwt, i.v.) and during Treatment 2, they were anaesthet...
Hopster K, Wittenberg-Voges L, Kästner SBR.To investigate the effects of a xylazine infusion during isoflurane anesthesia on global perfusion parameters and gastrointestinal oxygenation and microperfusion, 8 adult warmblood horses were sedated with xylazine and anesthesia induced with midazolam and ketamine. Horses were mechanically ventilated during anesthesia. After 3 h of stable isoflurane anesthesia (FIso 1.3 Vol %), a xylazine infusion with 1 mg/kg body weight (BW) per hour was started for 1 h and then stopped. Before, during, and after xylazine infusion, heart rate (HR), arterial blood pressure (MAP), cardiac output (CO), central...
Hopster K, Ambrisko TD, Stahl J, Schramel JP, Kästner SB.Previous studies showed an influence of xylazine on the LiDCO sensor in vitro and in standing horses, but did not prove that this interaction caused error in LiDCO measurements. Therefore, agreement of cardiac output (CO) measurements by LiDCO and bolus-thermodilution (BTD) was determined in horses receiving xylazine infusions. Methods: Prospective, experimental study. Methods: Eight Warmblood horses. Methods: All horses were premedicated with xylazine. Anaesthesia was induced with midazolam and ketamine and was maintained with isoflurane in oxygen. During six hours of anaesthesia CO measureme...
Posner LP, Kasten JI, Kata C.To document the suitability of intravenous propofol and ketamine following sedation with xylazine for routine anaesthetic induction in horses. Retrospective. 100 client-owned horses. Anaesthetic records were evaluated to determine: signalment, anaesthetic drug and dosages, need for additional induction agents, notation of any adverse events, duration of anaesthesia and recovery characteristics (rough or smooth, and rapid or prolonged). Horses were sedated with xylazine 0.99±(0.2) mg/kg intravenous and 23 horses were also administered butorphanol 0.02±(0.001) mg/kg intravenous. Horses were an...
Pakkanen SA, Raekallio MR, Mykkänen AK, Salla KM, de Vries A, Vuorilehto L, Scheinin M, Vainio OM.To investigate MK-467 as part of premedication in horses anaesthetized with isoflurane. Methods: Experimental, crossover study with a 14 day wash-out period. Methods: Seven healthy horses. Methods: The horses received either detomidine (20 μg kg(-1) IV) and butorphanol (20 μg kg(-1) IV) alone (DET) or with MK-467 (200 μg kg(-1) IV; DET + MK) as premedication. Anaesthesia was induced with ketamine (2.2 mg kg(-1) ) and midazolam (0.06 mg kg(-1) ) IV and maintained with isoflurane. Heart rate (HR), mean arterial pressure (MAP), end-tidal isoflurane concentration, end-tidal carbon ...
Niimura Del Barrio MC, Bennett RC, Hughes JML.Influence of detomidine or romifidine constant rate infusion (CRI) on plasma lactate concentration and isoflurane requirements in horses undergoing elective surgery. Methods: Prospective, randomised, blinded, clinical trial. Methods: A total of 24 adult healthy horses. Methods: All horses were administered intramuscular acepromazine (0.02 mg kg) and either intravenous detomidine (0.02 mg kg) (group D), romifidine (0.08 mg kg) (group R) or xylazine (1.0 mg kg) (group C) prior to anaesthesia. Group D was administered detomidine CRI (10 μg kg hour) in lactated Ringer's solution (LRS), group...
Marcilla MG, Schauvliege S, Duchateau L, Gasthuys F.To evaluate the cardiopulmonary effects of two different constant rate infusions (CRI) of dexmedetomidine (1 and 1.75 microg kg(-1 )hour(-1)) in experimental ponies. Methods: Six healthy ponies (mean 306 +/- SD 71 kg, 7.0 +/- 1.6 years). Methods: Prospective, randomized, experimental study. Methods: After premedication with intravenous (IV) dexmedetomidine (3.5 microg kg(-1)), anaesthesia was induced (T0) with ketamine (2.2 mg kg(-1) IV) and midazolam (0.06 mg kg(-1) IV) and maintained with isoflurane (Fe'ISO 1.50%) in 55% oxygen for 150 minutes. Normocapnia was maintained using artificial ven...
Benmansour P, Husulak ML, Bracamonte JL, Beazley SG, Withnall E, Duke-Novakovski T.To examine the cardiopulmonary effects of infusions of remifentanil or morphine, and their influence on recovery of horses anesthetized with isoflurane and dexmedetomidine. Methods: Randomized crossover study with 7-day rest periods. Methods: Six adult horses (507 ± 61 kg). Methods: After the horses were sedated with xylazine, anaesthesia was induced with ketamine and diazepam, and maintained with isoflurane. After approximately 60 minutes, a dexmedetomidine infusion was started (0.25 μg kg(-1) then 1.0 μg(-1) kg(-1) hour(-1) ) in combination with either saline (group S), morphine (0.15 mg ...
Creighton CM, Lemke KA, Lamont LA, Horney BS, Doyle AJ.To compare the effect of xylazine bolus versus medetomidine constant rate infusion (MCRI) on serum cortisol and glucose concentrations, urine production, and anesthetic recovery characteristics in dorsally recumbent, spontaneously breathing, isoflurane-anesthetized horses. Methods: Prospective, randomized crossover study. Methods: 10 healthy 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 maintain...
Taylor AH, Seymour CJ.Horses may become hypoxaemic during anaesthesia despite a high inspired oxygen fraction (FiO2). A lower FiO2 is used commonly in human beings to minimise atelectasis and to improve lung function, and previously has been shown to be of potential benefit in horses in experimental conditions. Other studies suggest no benefit to using a FiO2 of 0.5 during clinically relevant conditions; however, low FiO2 (0.65) is commonly used in practice and in a large number of studies. The present study was performed to compare the effect of a commonly used FiO2 of 0.65 versus 0.90 on calculated respiratory in...
Steffey EP, Pascoe PJ.To quantitate the dose- and time-related magnitude of the anesthetic sparing effect of, and selected physiological responses to detomidine during isoflurane anesthesia in horses. Methods: Randomized cross-over study. Methods: Three, healthy, young adult horses weighing 485 ± 14 kg. Methods: Horses were anesthetized on two occasions to determine the minimum alveolar concentration (MAC) of isoflurane in O and then to measure the anesthetic sparing effect (time-related MAC reduction) following IV detomidine (0.03 and 0.06 mg kg). Selected common measures of cardiopulmonary function, blood glucos...
Wagner AE, Mama KR, Steffey EP, Hellyer PW.To determine whether infusion of xylazine (XYL) and ketamine (KET) for 30 minutes after isoflurane administration in horses would result in improved quality of recovery from anesthesia, without detrimental cardiopulmonary changes. Methods: Randomized, blinded experimental trial. Methods: Seven healthy adult horses aged 6.4 +/- 1.9 years and weighing 506 +/- 30 kg. Methods: Horses were anesthetized twice, at least 1 week apart. On both occasions, anesthesia was induced by the administration of XYL, diazepam, and KET, and maintained with isoflurane for approximately 90 minutes, the last 60 minut...
Bailey PA, Hague BA, Davis M, Major MD, Zubrod CJ, Brakenhoff JE.The purpose of this study was to determine the incidence of post-anesthetic colic in non-fasted adult horses undergoing isoflurane inhalant anesthesia for an elective, non-abdominal procedure at a single referral center. Medical records were searched from May 1, 2012 to May 31, 2014. Inclusion criteria included non-fasted patients ≥ 2 years of age that were anesthetized for an elective, non-abdominal procedure. The incidence of post-anesthetic colic for this study population was 2.5%. None of the risk factors examined (season, age, gender, breed, surgeon, procedure, recumbency, butorphanol a...
Brosnan RJ, Steffey EP, LeCouteur RA, Farver TB, Imai A.To test the hypothesis that isoflurane-anesthetized horses during controlled ventilation and spontaneous ventilation exhibit temporal changes in cerebral hemodynamics, as measured by intracranial pressure and cerebral perfusion pressure, that reflect temporal changes in systemic arterial pressure. Methods: 6 healthy adult horses. Methods: Horses were anesthetized in left lateral recumbency with 1.57% isoflurane in O2 for 5 hours in 2 experiments by use of either controlled ventilation (with normocapnia) or spontaneous ventilation (with hypercapnia) in a randomized crossover design. Intracrania...
Knych HK, Steffey EP, Mama KR, Stanley SD.To verify the isoflurane anesthetic minimum alveolar concentration (MAC)-sparing effect of a previously administered target plasma fentanyl concentration of 16 ng/mL and characterize an anticipated further sparing in isoflurane MAC associated with higher target plasma fentanyl concentrations. Methods: 8 horses. Methods: Horses were assigned 2 of 3 target plasma fentanyl concentrations (16, 24, and 32 ng/mL), administered in ascending order. Following determination of baseline MAC, horses received a loading dose of fentanyl followed by a constant rate infusion; MAC determination was performed i...
Brosnan RJ, Steffey EP, Escobar A.To test the hypothesis that hypercapnic hyperpnea produced using endotracheal insufflation with 5-10% CO(2) in oxygen could be used to shorten anesthetic recovery time in horses, and that recovery from sevoflurane would be faster than from isoflurane. Methods: Randomized crossover study design. Methods: Eight healthy adult horses. Methods: After 2 hours' administration of constant 1.2 times MAC isoflurane or sevoflurane, horses were disconnected from the anesthetic circuit and administered 0, 5, or 10% CO(2) in balance O(2) via endotracheal tube insufflation. End-tidal gas samples were collect...
Pöppel N, Hopster K, Geburek F, Kästner S.To determine the influence of ketamine or xylazine constant rate infusions on isoflurane requirements, cardiovascular parameters and quality of anaesthesia in horses undergoing elective surgery. Methods: Prospective, matched paired clinical trial. Methods: Fifty four adult Warmblood horses. Methods: After premedication with acepromazine, xylazine and butorphanol, anaesthesia was induced with ketamine-midazolam and maintained with isoflurane alone (I), isoflurane with either 1 mg kg(-1) hour(-1) ketamine (IK) or same dose of xylazine (IX). End tidal concentration of isoflurane (Fe'Iso) was ...
Alonso BB, La Rosa L, Carregaro AB, Gasthuys F, Schauvliege S.To examine the influence of detomidine or romifidine on recovery quality from isoflurane anesthesia, 78 anesthetic records were reviewed, from horses that had received romifidine (group R) during premedication [80-120 μg kg IV], anesthetic maintenance (40 μg kg hour IV), and recovery (20 μg kg IV) or detomidine (group D), at doses of 10-20 μg kg IV, 5 μg kg hour IV, and 2.5 μg kg IV, respectively. Duration of the different recovery phases, the number of attempts to sternal and standing, scores for transition to standing (TrSta), balance and coordination once standing (BC), and fina...
Bienert A, Bartmann CP, von Oppen T, Poppe C, Schiemann V, Deegen E.Isofluorane is a modern, only slightly depressive inhalation anaesthetic with excellent pharmacologic characteristics in use in equine medicine. In contrast to halothane, isofluorane is hardly broken down in the liver, but is eliminated by the lung. It low solubility in blood permits excellent control of anaesthesia. However, due to its swift elimination from the organism there is heightened risk of premature recovery from isofluorane anaesthesia. In this study the recovery phases of 96 horses were monitored for its duration and the animals' physical coordination. The horses were divided into ...
Hopster K, Wittenberg-Voges L, Geburek F, Hopster-Iversen C, Kästner SBR.Aim of this prospective experimental study was to assess effects of systemic hypoxemia and hypovolemia on global and gastrointestinal oxygenation and perfusion in anesthetized horses. Therefore, we anesthetized twelve systemically healthy warmblood horses using either xylazine or dexmedetomidine for premedication and midazolam and ketamine for induction. Anesthesia was maintained using isoflurane in oxygen with either xylazine or dexmedetomidine and horses were ventilated to normocapnia. During part A arterial oxygen saturation (SaO) was reduced by reducing inspiratory oxygen fraction in steps...
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...
