National Institute on Drug Abuse Clinical Trials Network Meeting Report: Managing Patients Exposed to Xylazine-Adulterated Opioids in Emergency, Hospital and Addiction Care Settings.

Used as a veterinary sedative and not approved for human use, xylazine has been increasingly linked with opioid overdose deaths in the United States. A growing number of people have been exposed to xylazine in the illicit opioid supply (especially fentanyl) or in other drugs, particularly in some areas of the Northeast. Xylazine is an α-2 adrenergic agonist that decreases sympathetic nervous system activity. When combined with fentanyl or heroin, it is purported to extend the duration of the opioid's sedative effect and to cause dependence and an associated withdrawal syndrome; however, data to support these concerns are limited. Despite the escalating frequency of detection of xylazine in people with nonfatal and fatal opioid overdose, direct links to these outcomes have not been identified. Because the strongest causal link is to fentanyl coexposure, ventilatory support and naloxone remain the cornerstones of overdose management. Xylazine is also associated with severe tissue injury, including skin ulcers and tissue loss, but little is known about the underlying mechanisms. Nonetheless, strategies for prevention and treatment are emerging. The significance and clinical effects of xylazine as an adulterant is focused on 4 domains that merit further evaluation: fentanyl-xylazine overdose, xylazine dependence and withdrawal, xylazine-associated dermal manifestations, and xylazine surveillance and detection in clinical and nonclinical settings. This report reflects the Proceedings of the National Institute on Drug Abuse Center for the Clinical Trials Network convening of clinical and scientific experts, federal staff, and other stakeholders to describe emerging best practices for treating people exposed to xylazine-adulterated opioids. Participants identified scientific gaps and opportunities for research to inform clinical practice in emergency departments, hospitals, and addiction medicine settings.

Comparison of the sedative effects of alfaxalone and methadone with or without midazolam in dogs.

This blinded, randomized, prospective study evaluated the sedative and physiologic effects of a combination of alfaxalone and methadone with or without midazolam in adult dogs. Sixteen dogs received methadone (0.5 mg/kg body weight) and alfaxalone (1 mg/kg body weight), either with or without midazolam (0.5 mg/kg body weight), by intramuscular injection. Quality of sedation, heart rate, respiratory rate, systolic arterial pressure, rectal temperature, arterial oxygen saturation of hemoglobin, and dose of alfaxalone required for endotracheal intubation were recorded. Sedation score increased over time in both groups; however, dogs premedicated with methadone and alfaxalone appeared significantly less sedated than dogs premedicated with midazolam at 15, 20, and 25 minutes post-injection (P = 0.04). Dogs receiving methadone and alfaxalone were almost 5 times more likely to show excitement than those receiving midazolam (P = 0.03). We concluded that adding midazolam to an intramuscular combination of methadone and alfaxalone cannot be recommended in healthy dogs.

Comparaison des effets sédatifs de l'alfaxalone et de la méthadone avec ou sans midazolam chez le chien. Cette étude prospective randomisée à l'aveugle a évalué les effets sédatifs et physiologiques d'une association d'alfaxalone et de méthadone avec ou sans midazolam chez le chien adulte. Seize chiens ont reçu par voie intramusculaire (IM) méthadone (0,5 mg/kg) et alfaxalone (1 mg/kg) (MA) ou méthadone et alfaxalone à les même dosages plus midazolam (0,5 mg/kg) (MMA). La qualité de la sédation, la fréquence cardiaque, la fréquence respiratoire, la pression artérielle systolique, la température rectale, la saturation artérielle en oxygène de l'hémoglobine et la dose d'alfaxalone requise pour l'intubation endotrachéale ont été enregistrées. Le score de sédation augmentait avec le temps dans les deux groupes, cependant, les chiens ayant reçu la combinaison MMA semblaient significativement moins sous sédation que les chiens ayant reçu la combinaison MA 15, 20, et 25 minutes après l'injection (P = 0,04). Les chiens recevant MMA étaient presque cinq fois plus susceptibles de montrer de l'excitation que ceux recevant du MA (P = 0,03). Nous avons conclu que l'ajout de midazolam à une combinaison IM de méthadone et d'alfaxalone ne peut pas être recommandé chez les chiens en santé.(Traduit par les auteurs).

Clinical use of a low-dose medetomidine infusion in healthy dogs undergoing ovariohysterectomy.

Eight healthy dogs undergoing elective ovariohysterectomy were anesthetized with a standard protocol and received a low-dose medetomidine constant rate infusion during surgery. Cardiorespiratory parameters, including non-invasive cardiac output, were measured at various times. This protocol resulted in acceptable and stable cardiovascular performance, allowed low isoflurane concentrations, and provided smooth recoveries.

Utilisation clinique d'une infusion d'une faible dose de médétomidine chez les chiennes en santé subissant une ovariohystérectomie. Huit chiennes en santé subissant une ovariohystérectomie non urgente ont été anesthésiées à l'aide d'un protocole standard et ont reçu une infusion constante d'une faible dose de médétomidine durant la chirurgie. Les paramètres cardiorespiratoires, incluant le débit cardiaque non effractif, ont été mesurés à divers moments. Ce protocole a produit un rendement cardiovasculaire acceptable et stable et a permis de faibles concentrations d'isoflurane et des réveils sans problème.(Traduit par Isabelle Vallières).

Pharmacokinetics and pharmacodynamics of intranasal and intramuscular administration of naloxone in working dogs administered fentanyl.

BACKGROUND: Working dogs exposed to narcotics might require reversal in the field. OBJECTIVE: To explore the pharmacokinetic and pharmacodynamic effects of naloxone administered intramuscularly (IM) or intranasally (IN) to reverse fentanyl sedation in working dogs. ANIMALS: Ten healthy, working dogs aged 1.7 ± 1 year and weighing 26 ± 3 kg. METHODS: In this randomized, controlled cross-over study dogs received either 4 mg of naloxone IN or IM 10 minutes after fentanyl (0.3 mg IV) administration. Sedation was assessed at baseline and 5 minutes after fentanyl administration, then at 5, 10, 15, 20, 25, 30, 60 and 120 minutes after reversal with naloxone. Blood samples for naloxone detection were obtained at 0, 5, 10, 30, 60 and 120 minutes. Pharmacokinetic parameters and sedation scores were compared between IM and IN naloxone groups. RESULTS: There was a significant increase in sedation score from baseline (0.25 [-4 to 1] IM; 0 [-2 to 1] IN) after fentanyl administration (11 [5-12] IM; 9.25 [4-11] IN), followed by a significant reduction at 5 (0.5 [-0.5 to 1.5] IM; 1.25 [-1.5 to 4.5] IN) through 120 minutes (-0.5 [-2 to 1] IM; 0 [-4.5 to 1] IN) after reversal with naloxone. Route of administration had no significant effect on sedation score. Maximum plasma concentration was significantly lower after IN administration (11.7 [2.8-18.8] ng/mL IN, 36.7 [22.1-56.4] ng/mL IM, P < .001) but time to reach maximum plasma concentration was not significantly different from IM administration. CONCLUSION AND CLINICAL IMPORTANCE: Although IM administration resulted in higher naloxone plasma concentrations compared to IN, reversal of sedation was achieved via both routes after administration of therapeutic doses of fentanyl.

Comparison of Mean Arterial Blood Pressure and Heart Rate Changes in Response to Three Different Randomized Isotonic Crystalloid Boluses in Hypotensive Anesthetized Dogs.

The aim of this prospective, randomized, nonblinded, controlled clinical trial was to compare mean arterial blood pressure (MAP) and heart rate (HR) during an intravenous bolus of three different balanced isotonic crystalloid solutions in euvolemic, anesthetized dogs with hypotension. Thirty healthy dogs (American Society of Anesthesiologists Physical Status I-II) weighing at least 15 kg that presented for elective orthopedic or dental surgical procedures at the Ryan Veterinary Hospital for Small Animals of the University of Pennsylvania were included in this study. Anesthetized hypotensive patients (defined as a MAP ≤ 65 mmHg), were administered an infusion of Lactated Ringer's solution (LRS), Plasma-Lyte (PLYTE) or Canadian Plasma-Lyte (PLYTECA), selected at random. The infusion was administered over 15 min via a volumetric fluid pump. Differences in oscillometric MAP and HR between time points and across treatments were evaluated by mANOVA. Intravenous isotonic crystalloid infusions over 15 min did not significantly change MAP or HR in hypotensive dogs under general anesthesia. Neither LRS, PLYTE nor PLYTECA exacerbated hypotension or caused tachycardia.

Anesthetic management of a white rhinoceros (Ceratotherium simum) undergoing an emergency exploratory celiotomy for colic.

OBSERVATIONS: A 26-year-old male white rhinoceros (Ceratotherium simum), weighing approximately 2000 kg was anesthetized for an exploratory celiotomy. Sedation was achieved with intramuscular butorphanol (0.04 mg kg(-1)) and detomidine (0.025 mg kg(-1)) and induction of anesthesia with intravenous glyceryl guaiacolate (50 g) and three intravenous boluses of ketamine (200 mg, each); the trachea was then intubated and anesthesia maintained with isoflurane in oxygen using a circle breathing system. Positioning in dorsal recumbency for the surgery and later in sternal recumbency for the recovery represented challenges that added to the prolonged anesthesia time and surgical approach to partially correct an impaction. The rhinoceros recovered uneventfully after 10.4 hours of recumbency. CONCLUSIONS: Anesthetic management for an exploratory celiotomy with a midline approach is possible in rhinoceroses, although planning and extensive staff support is necessary to adequately position the patient.

Prevalence of and covariates associated with the oculocardiac reflex occurring in dogs during enucleation.

OBJECTIVE: To determine the prevalence of and covariates associated with the oculocardiac reflex (OCR) occurring in dogs during enucleations. SAMPLE: 145 dogs that underwent enucleation at 2 veterinary teaching hospitals between January 2010 and June 2015. PROCEDURES: Information was collected from the medical records of included dogs regarding age and body weight at hospital admission, breed (for classification of brachycephalic status), and whether they had received anticholinergic drugs or a retrobulbar nerve block (RNB) prior to enucleation. An OCR was considered to have occurred if there was a sudden decrease of ≥ 30% in heart rate from the baseline value (mean heart rate prior to the sudden decrease) during surgery in the absence of intraoperative administration of opioids or α2-adrenoceptor agonists. Associations were explored between the collected data and the prevalence of OCR by means of binomial logistic regression. RESULTS: 4.8% (7/145) of dogs had an OCR noted during enucleation. Dogs that received a preoperative RNB (n = 82) had significantly lower odds of an OCR being observed than dogs that received no preoperative RNB (OR, 0.12). No association with OCR was identified for age or brachycephalic conformation or for preoperative administration of anticholinergic drugs. CONCLUSIONS AND CLINICAL RELEVANCE: These findings suggested that preoperative administration of an RNB, but not preoperative administration of anticholinergic drugs, was associated with a lower prevalence of OCR in dogs during enucleations.

Comparison between cerebrospinal fluid and serum lactate concentrations in neurologic dogs with and without structural intracranial disease.

The objectives of this study were to investigate the relationship between cerebrospinal fluid lactate and serum concentrations in dogs with clinical signs of central nervous system disease and to establish if cerebrospinal fluid lactate (CSF) concentrations are higher in dogs with structural intracranial disease (Group Pos-MRI) compared to dogs that have clinical signs of intracranial disease but no structural brain disease (Group Neg-MRI) based on magnetic resonance imaging (MRI) findings. Using a prospective study canine blood and cerebrospinal fluid were collected in 24 dogs with neurological signs after undergoing brain MRI. Dogs were divided in 2 groups. No significant difference between serum lactate (1.57 ± 0.9 mmol/L) and CSF lactate concentration (1.34 ± 0.3 mmol/L) was detected. There was a direct correlation between CSF and serum lactate concentration (R = 0.731; P = 0.01). No significant difference was found in CSF lactate concentration between the 2 groups of dogs (P = 0.13).

Les objectifs de la présente étude étaient d'examiner la relation entre les concentrations de lactate du liquide céphalo-rachidien (LCR) et du sérum chez des chiens présentant des signes cliniques de pathologie du système nerveux central et établir si les concentrations de lactate du LCR sont plus élevées chez les chiens avec une maladie intracrânienne structurale (Groupe Pos-IRM) comparativement à des chiens avec des signes cliniques de maladie intracrânienne mais sans maladie structurale du cerveau (Groupe Nég-IRM) sur la base des trouvailles en imagerie par résonnance magnétique (IRM). Utilisant une étude prospective, du sang canin et du LCR ont été prélevés chez 24 chiens avec des signes neurologiques après un examen par IRM du cerveau. Les chiens ont été séparés en deux groupes. Aucune différence significative ne fut détectée entre les concentrations de lactate sérique (1,57 ± 0,9 mmol/L) et de lactate du LCR (1,34 ± 0,3 mmol/L). Il y avait une corrélation directe entre les concentrations de lactate du LCR et du sérum (R = 0,731; P = 0,01). Aucune différence significative dans la concentration de lactate du LCR ne fut trouvée entre les deux groupes de chiens (P = 0,13).(Traduit par Docteur Serge Messier).

Effect of blood collection by the push-pull technique from an indwelling catheter versus direct venipuncture on venous blood gas values before and after administration of alfaxalone or propofol in dogs.

OBJECTIVE To compare the effect of blood collection by a push-pull technique from an indwelling IV catheter versus direct venipuncture on venous blood gas values before and after administration of alfaxalone or propofol to dogs. DESIGN Prospective randomized clinical study. ANIMALS 30 healthy client-owned dogs that weighed ≥ 10 kg (22 lb) and were anesthetized for elective surgical procedures. PROCEDURES All dogs were premedicated with methadone (0.5 mg/kg [0.2 mg/lb], IM), and 20 to 30 minutes later, anesthesia was induced with either alfaxalone (1 to 3 mg/kg [0.5 to 1.4 mg/lb], IV to effect; n = 15) or propofol (2 to 6 mg/kg [0.9 to 2.7 mg/lb], IV to effect; 15). Immediately prior to premedication and after anesthesia induction, paired blood samples were collected from the cephalic veins; 1 by direct venipuncture and 1 by use of a push-pull technique from a 20-gauge catheter. All blood samples underwent venous blood gas analysis immediately after collection. Results were compared between sample collection techniques before and after anesthesia induction and between anesthesia induction protocols. RESULTS All results were within established reference ranges. For many variables, statistically significant but clinically irrelevant differences were detected between samples collected by direct venipuncture and those collected by the push-pull technique but not between the 2 anesthesia induction protocols. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated the push-pull technique was an acceptable method for collection of blood samples from dogs for venous blood gas analysis that could be used instead of direct venipuncture for patients with patent IV catheters.

Influence of prior determination of baseline minimum alveolar concentration (MAC) of isoflurane on the effect of ketamine on MAC in dogs.

The objective of this study was to determine if prior measurement of the minimum alveolar concentration (MAC) of isoflurane influences the effect of ketamine on the MAC of isoflurane in dogs. Eight mixed-breed dogs were studied on 2 occasions. Anesthesia was induced and maintained using isoflurane. In group 1 the effect of ketamine on isoflurane MAC was determined after initially finding the baseline isoflurane MAC. In group 2, the effect of ketamine on isoflurane MAC was determined without previous measure of the baseline isoflurane MAC. In both groups, MAC was determined again 30 min after stopping the CRI of ketamine. Plasma ketamine concentrations were measured during MAC determinations. In group 1, baseline MAC (mean ± SD: 1.18 ± 0.14%) was decreased by ketamine (0.88 ± 0.14%; P < 0.05). The MAC after stopping ketamine was similar (1.09 ± 0.16%) to baseline MAC and higher than with ketamine (P < 0.05). In group 2, the MAC with ketamine (0.79 ± 0.11%) was also increased after stopping ketamine (1.10 ± 0.17%; P < 0.05). The MAC values with ketamine were different between groups (P < 0.05). Ketamine plasma concentrations were similar between groups during the events of MAC determination. The MAC of isoflurane during the CRI of ketamine yielded different results when methods of same day (group-1) versus separate days (group-2) are used, despite similar plasma ketamine concentrations with both methods. However, because the magnitude of this difference was less than 10%, either method of determining MAC is deemed acceptable for research purposes.

L'objectif de la présente étude était de déterminer si une mesure antérieure de la concentration alvéolaire minimum (MAC) d'isoflurane influence l'effet de la kétamine sur la MAC d'isoflurane chez les chiens. Huit chiens de race croisée ont été examinés à deux occasions. L'anesthésie fut induite et maintenue à l'aide d'isoflurane. Dans le groupe 1, l'effet de la kétamine sur la MAC d'isoflurane fut déterminé après avoir initialement trouvé la MAC de base de l'isoflurane. Dans le groupe 2, l'effet de la kétamine sur la MAC d'isoflurane fut déterminé sans mesure préalable de la MAC de base de l'isoflurane. Dans les deux groupes la MAC fut déterminée de nouveau 30 min après l'arrêt de la CRI de kétamine. Les concentrations de kétamine plasmatiques furent mesurées durant les déterminations de MAC.Dans le groupe 1, la MAC de base (moyenne ± SD : 1,18 ± 0,14 %) fut diminuée par la kétamine (0,88 ± 0,14 %; P < 0,05). La MAC après l'arrêt de la kétamine était similaire (1,09 ± 0,16 %) à la MAC de base et plus élevée qu'avec la kétamine (P < 0,05). Dans le groupe 2, la MAC avec kétamine (0,79 ± 0,11 %) était également augmentée après l'arrêt de la kétamine (1,10 ± 0,17 %; P < 0,05). Les valeurs de MAC avec la kétamine étaient différentes entre les groupes (P < 0,05). Les concentrations plasmatiques de kétamine étaient similaires durant la détermination des MAC.La MAC d'isoflurane durant la CRI de kétamine a donné des résultats différents lorsque les méthodes d'un jour unique (le groupe 1) versus des jours séparés (le groupe 2) étaient utilisées, malgré des concentrations plasmatiques de kétamine similaires avec les deux méthodes. Toutefois, étant donné que l'ampleur de cette différence était de moins de 10 %, chacune des deux méthodes pour déterminer la MAC est considérée comme acceptable à des fins de recherche.(Traduit par Docteur Serge Messier).

Effects of high-volume, rapid-fluid therapy on cardiovascular function and hematological values during isoflurane-induced hypotension in healthy dogs.

The objective of this study was to determine the effects of the administration of a high volume of isotonic crystalloid at a rapid rate on cardiovascular function in normovolemic, isoflurane-anesthetized dogs during induced hypotension.Using a prospective study, 6 adult dogs were induced to general anesthesia and cardiovascular and hematological values were measured while the dogs were maintained at 3 hemodynamic states: first during light anesthesia with 1.3% end-tidal isoflurane (ETI); then during a hypotensive state induced by deep anesthesia with 3% ETI for 45 min while administered 1 mL/kg body weight (BW) per minute of isotonic fluids; and then decreased to 1.6% ETI while receiving 1 mL/kg BW per minute of fluids for 15 min. End-tidal isoflurane (ETI) at 3.0 ± 0.2% decreased arterial blood pressure (ABP), cardiac index (CI), and stroke volume index (SVI), and increased stroke volume variation (SVV) and central venous pressure (CVP). Fluid administration during 3% ETI decreased only SVV and systemic vascular resistance index (SVRI), while CVP increased progressively. Decreasing ETI to 1.6 ± 0.1% returned ABP and SVI to baseline (ETI 1.3 ± 0.1%), while CI and heart rate increased and SVV decreased. There was significant progressive clinical hemodilution of hemoglobin (Hb), packed cell volume (PCV), total protein (TP), colloid osmotic pressure (COP), arterial oxygen content (CaO(2)), and central-venous oxygen content (CcvO(2)).High-volume, rapid-rate administration of an isotonic crystalloid was ineffective in counteracting isoflurane-induced hypotension in normovolemic dogs at a deep plane of anesthesia. Cardiovascular function improved only when anesthetic depth was reduced. Excessive hemodilution and its adverse consequences should be considered when a high volume of crystalloid is administered at a rapid rate.

Prior determination of baseline minimum alveolar concentration (MAC) of isoflurane does not influence the effect of ketamine on MAC in rabbits.

The objective of this study was to compare the effect on the minimum alveolar concentration (MAC) of isoflurane when ketamine was administered either after or without prior determination of the baseline MAC of isoflurane in rabbits. Using a prospective randomized crossover study, 8 adult, female New Zealand rabbits were allocated to 2 treatment groups. Anesthesia was induced and maintained with isoflurane. Group 1 (same-day determination) had the MAC-sparing effect of ketamine [1 mg/kg bodyweight (BW) bolus followed by a constant rate infusion (CRI) of 40 µg/kg BW per min, given by intravenous (IV)], which was determined after the baseline MAC of isoflurane was determined beforehand. A third MAC determination was started 30 min after stopping the CRI. Group 2 (separate-day determination) had the MAC-sparing effect of ketamine determined without previous determination of the baseline MAC of isoflurane. A second MAC determination was started 30 min after stopping the CRI. In group 1, the MAC of isoflurane (2.15 ± 0.09%) was significantly decreased by ketamine (1.63 ± 0.07%). After stopping the CRI, the MAC was significantly less (2.04 ± 0.11%) than the baseline MAC of isoflurane and significantly greater than the MAC during the CRI. In group 2, ketamine decreased isoflurane MAC (1.53 ± 0.22%) and the MAC increased significantly (1.94 ± 0.25%) after stopping the CRI. Minimum alveolar concentration (MAC) values did not differ significantly between the groups either during ketamine administration or after stopping ketamine. Under the study conditions, prior determination of the baseline isoflurane MAC did not alter the effect of ketamine on MAC. Both methods of determining MAC seemed to be valid for research purposes.

L'objectif de la présente étude était de comparer l'effet de la concentration alvéolaire minimale (MAC) d'isoflurane lorsque de la kétamine était administrée soit après ou sans détermination préalable de la MAC de base d'isoflurane chez les lapins. Au moyen d'une étude prospective aléatoire croisée, huit lapines adultes de race Nouvelle-Zélande ont été réparties dans deux groupes de traitement. Une anesthésie a été induite et maintenue avec de l'isoflurane. Le groupe 1 (détermination le même jour), a eu l'effet atténuant sur la MAC de la kétamine [bolus de 1 mg/kg de poids corporel (BW) suivi d'une infusion à taux constant (CRI) de 40 µg/kg BW par minute, administré par voie intraveineuse (IV)], déterminé après que la MAC de base de l'isoflurane fut déterminée préalablement. Une troisième détermination de la MAC a débuté 30 min après l'arrêt de la CRI. Le groupe 2 (détermination lors de jours distincts) a eu l'effet atténuant de la kétamine déterminé sans détermination préalable de MAC de base de l'isoflurane. Une deuxième détermination de la MAC fut débutée 30 min après l'arrêt de la CRI. Dans le groupe 1, la MAC d'isoflurane (2,15 ± 0,09 %) était significativement réduite par la kétamine (1,63 ± 0,07 %). Après l'arrêt de la CRI, la MAC était significativement moindre (2,04 ± 0,11 %) que la valeur de MAC de base d'isoflurane et significativement plus élevée que la MAC durant la CRI. Dans le groupe 2, la kétamine diminua la MAC d'isoflurane (1,53 ± 0,22 %) et la MAC augmenta de manière significative (1,94 ± 0,25 %) après l'arrêt de la CRI. Les valeurs de MAC n'ont pas différé significativement entre les groupes durant soit l'administration de kétamine ou après l'arrêt de kétamine. Dans les présentes conditions expérimentales, la détermination préalable de la MAC de base d'isoflurane n'a pas altéré l'effet de la kétamine sur la MAC. Les deux méthodes pour déterminer la MAC ont semblé être valides pour des besoins de recherche.(Traduit par Docteur Serge Messier).

Comparison of cardiac output determined by arterial pulse pressure waveform analysis method (FloTrac/Vigileo) versus lithium dilution method in anesthetized dogs.

OBJECTIVE: To compare the determination of cardiac output (CO) via arterial pulse pressure waveform analysis (FloTrac/Vigileo) versus lithium dilution method. DESIGN: Prospective study. SETTING: University teaching hospital. ANIMALS: Six adult dogs. INTERVENTIONS: Dogs were instrumented for CO determinations using lithium dilution (LiDCO) and FloTrac/Vigileo methods. Direct blood pressure, heart rate, arterial blood gases, and end-tidal isoflurane (ETIso) and CO(2) concentrations were measured throughout the study while CO was manipulated with different depth of anesthesia and rapid administration of isotonic crystalloids at 60 mL/kg/h. MEASUREMENTS AND MAIN RESULTS: Baseline CO measurements were obtained at 1.3% ETIso and were lowered by 3% ETIso. Measurements were obtained in duplicate or triplicate with LiDCO and averaged for comparison with corresponding values measured continuously with the FloTrac/Vigileo method. For 30 comparisons between methods, a mean bias of -100 mL/kg/min and 95% limits of agreement between -311 and +112 mL/kg/min (212 mL/kg/min) was determined. The mean (mL/kg/min) of the differences of LiDCO-Vigileo=62.0402+-0.8383 × Vigileo, and the correlation coefficient (r) between the 2 methods 0.70 for all CO determinations. The repeatability coefficients for the individual LiDCO and FloTrac/Vigileo methods were 187 and 400 mL/kg/min, respectively. Mean LiDCO and FloTrac/Vigileo values from all measurements were 145 ± 68 mL/kg/min (range, 64-354) and 244 ± 144 mL/kg/min (range, 89-624), respectively. The overall mean relative error was 48 ± 14%. CONCLUSION: The FloTrac/Vigileo overestimated CO values compared with LiDCO and the relative error was high, which makes this method unreliable for use in dogs.