Orientador: Pedro Thadeu Galvão Vianna / Banca: Luiz Vicente Garcia / Banca: Luiz Antonio Vane / Banca: Rosa Beatriz Amorim / Banca: Angélica de Fátima de Assunção Braga / Resumo: Há fármacos que produzem pré-condicionamento farmacológico e, dentre estes, os anestésicos inalatórios são os mais estudados. Como exemplo, o isoflurano pode proteger o rim contra a lesão causada pela isquemiareperfusão, principalmente quando a anestesia inalatória é mantida por um período após a reperfusão. Os opióides parecem ser uma classe de fármacos capaz de produzir este pré-condicionamento. Há estudo mostrando que o remifentanil pode proteger o miocárdio contra a lesão produzida pela isquemia-reperfusão. Outro estudo mostrou que a lesão da isquemia e reperfusão renal pode ser atenuada em ratos submetidos à associação do isoflurano e do remifentanil e ao pré-condicionamento mecânico. O objetivo deste trabalho foi verificar se o isoflurano e a associação do isoflurano e do remifentanil usado após a isquemia-reperfusão podem causar proteção renal. 40 ratos machos, da raça Wistar foram distribuídos em quatro Grupos: Grupo Sham (n=10); Grupo IP (n=10), isoflurano usado durante o experimento e 90 minutos pós-reperfusão; Grupo IRP (n=10), associação do isoflurano com remifentanil usado durante o experimento e 90 minutos pós-reperfusão e Grupo Iso (n=10), isoflurano usado durante o experimento. Todos os animais foram anestesiados submetidos à intubação orotraqueal e colocados em ventilação mecânica (Ventilador Harvard Rodent 683). A veia jugular esquerda foi dissecada e um cateter foi introduzido para administração de fármacos e para a hidratação dos animais. A artéria carótida esquerda também foi dissecada e um cateter foi introduzido na sua luz com a finalidade de medida da pressão arterial (PAM) e de coleta de amostras de sangue. Todos os Grupos foram anestesiados com isoflurano na concentração inspirada entre 1,5 a 3 % e no Grupo IRP teve inicio a infusão de remifentanil na velocidade de 2 μg.kg-1.min-1. Após laparotomia... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: How we can protect our patients against ischemiareperfusion injury is a question we make every day in anesthesia. Some drugs may be having the answer. Drugs can make pharmacologic preconditioning may be a good way to answer the question. Remifentanil can protect heart cells against ischemiareperfusion (IR) injury. Isoflurane can protect the kidney against IR injury. Our work makes a question if the association can make any protection against ischemiareperfusion injury? 40 male Wistar rats were put in four groups Sham (n=10), Isoflurane (n=10) (Iso), isoflurane plus wemifentanil (IRP) and isoflurane before reperfusion (ISO) with 10 rats each one. All rats groups were anesthetized and put with mechanical ventilation (Harvard Rodent Ventilator 683) by tracheal intubation. Catheters were inserted in jugular internal vein, for fluid or drug administration, and carotid artery, for measure arterial blood pressure and blood samples. All groups were anesthetized with Isoflurane between 1.5 and 3% and the group IRP start after the venous catheterize remifentanil 2 mcg/kg/min. The right kidney was removed, in the group Sham the procedure were over. For the others groups a clamp were put in left renal artery (LRA) for 45 minutes. The group Iso end, the procedure after the clamp were retired. The group IRP and IP were anesthetized for plus 90 minutes and the procedure were over. In all groups body temperature were between 36-38°C. In the end of the procedure before the extubation, analgesia were performed with infiltration of bupivacaine at 0.25%. Free food and water for all animals. After 24 hours all rats were nefrectomized in the left side and sacrificed with thiopentone. The kidneys were send to histological examination, and score for tubular lesion were performed (0- 3). Flow Cytometry (FCM) were performed in the left kidney for all groups. Blood samples to analyze serum creatinine... (Complete abstract click electronic access below) / Doutor

Electroretinoraphic signals (ERGs) are affected when recorded under isoflurane anesthesia in the operating room. We explored the effect of isoflurane and propofol in ex vivo guinea pig retinal preparations using a multielectrode array to record simultaneously ERGs and retinal ganglion cell (RGC) activity. The viability and light-response characteristics of the model were documented. In the presence of isoflurane, the ERG and RGC activity was reduced in a dose-dependent manner, even at sub-clinical doses; the OFF responses were consistently more affected. Propofol had minimal effects: at subclinical doses, a small excitation was measured while a concentration a hundred times stronger than the clinical concentration was required to measure a significant decline in EGR and RGC signals. This study confirms the usefulness of the guinea pig model to study clinically relevant retinal issues and shows that propofol is a better anesthetic to use in the operating room when retinal investigations are required.

This thesis determines and compares the sparing effect of ketamine on the minimum alveolar concentration (MAC) of isoflurane in rabbits and dogs using two methods in a crossover random design. One method determined the MAC of isoflurane and ketamine combined after previous determination of the MAC of isoflurane during the same day. The second method determined the MAC for the combination without prior determination of the MAC of isoflurane. The concentration of ketamine and norketamine in plasma were also determined in dogs. For the first method, the MAC of isoflurane in rabbits was 2.15 ± 0.09% (mean ± SD) and decreased to 1.63 ± 0.07% during ketamine administration (1 mg/kg bolus and a constant rate infusion [CRI] of 40 µg/kg/min). In dogs, the same ketamine dose decreased the MAC of isoflurane from 1.18 ± 0.14% to 0.88 ± 0.14%. Re-determination of MAC of isoflurane performed after stopping the CRI yielded a MAC value of 2.04 ± 0.11% in rabbits and of 1.09 ± 0.16% in dogs. MAC values of the isoflurane and ketamine combination determined for the second method were 1.53 ± 0.22% in rabbits and 0.79 ± 0.11% in dogs. MAC values of isoflurane after stopping the CRI of ketamine were 1.94 ± 0.25% in rabbits and 1.10 ± 0.17% in dogs. The MAC value obtained in dogs for the isoflurane and ketamine combination with the first method was significantly higher with respect to the MAC value obtained with the second method (0.88 ± 0.14 versus 0.79 ± 0.11%); whereas in rabbits, MAC values were similar. During ketamine administration in dogs, plasma concentrations of ketamine at MAC values were similar for the first and second method (824 ± 195.7 ng/mL and 729 ± 133.4 ng/mL, respectively). After stopping the CRI, plasma concentrations during isoflurane MAC were also similar for the two methods (407 ± 176.2 ng/mL and 347 ± 81.2 ng/mL, respectively). MAC values for the isoflurane and ketamine combination obtained with both methods were statistically different in dogs but not in rabbits, however these findings may be the result of the design of the study and tolerable experimental error derived from MAC studies rather than true species differences.

Knowledge of the absorption of inhalation anaesthetic agents is essential if one is to safely administer them. Despite many years of research in linear science, no model has been described that can reliably predict inhalation agent uptake. To date no published investigation has looked for non¬linearity in the absorption process. The aim if this research project was to determine if the absorption of anaesthetic agents is non-linear, using isoflurane and enflurane as examples. To detect non-linearity, four conditions must be met: <ul> <li>Sensitivity to initial conditions, </li> <li>Fractal Dimension of the attract or, </li> <li>Invariant probability distribution of the attractor, and</li> <li>Detection of an underlying dynamical process. <br></li></ul> Ten measured time series for both isoflurane and enflurane absorption were measured. These were then compared with ten noise signals, with similar standard deviations, means and number of points in the series. Calculated Lyapunov exponents tested sensitivity to initial conditions. The dimension of the attractor was calculated using the following statistics, each giving an approximation of the fractal dimension. Approximate entropy, information entropy, correlation dimension and fractal dimension (box counting method). The Invariant probability distribution of the attractor was tested for using non-linear forecasting. Detection of an underlying dynamical process was determined by the method of surrogate data. Each of the four conditions required have been met with statistical significance ( p< 0.05) and acceptable statistical power (>0.8). It is therefore concluded that the absorption of both isoflurane and enflurane are non-linear processes. The implications and implementations in anaesthesia practice are discussed. / Thesis (PhD (Anaesthesiology))--University of Pretoria, 2005. / Anaesthesiology / unrestricted

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2009-2010 / Cette étude résume certains concepts liés à l’anesthésie générale, détaille les mécanismes d’action de l’isoflurane, un anesthésiant volatil, et aborde le phénomène du burst-suppression. Elle vise principalement la compréhension de l’impact de l’isoflurane, à des doses amenant le burst-suppression, sur l’inhibition dans le réseau thalamo-cortical. Nous effectuons des enregistrements intracellulaires de neurones corticaux in vivo et de potentiels de champs locaux à différentes doses d’anesthésiants chez le chat. Conjointement à ces enregistrements, nous appliquons des drogues en iontophorèse en péri-synaptique des neurones enregistrés et nous stimulons les noyaux thalamiques projetant dans les aires corticales enregistrées. Nous suggérons que l’isoflurane amène une diminution de l’inhibition corticale, via une plus grande recapture du glutamate par les glies, ce qui diminue l’activation des interneurones corticaux. / This study summarizes some concepts about general anesthesia, details the mechanisms of action of the volatile anesthetic isoflurane and describes the phenomenon of burst-suppression. It aims at understanding the impact of isoflurane, under doses sufficient to induce burst-suppression, on inhibition in the thalamo-cortical network. We performed intracellular recordings of cortical neurons in vivo and local field potentials under different doses of anesthesia in cats. Additionally, we applied drugs in iontophoresis in the perisynaptic space of the recorded neurons and we stimulated thalamic nuclei projecting to the areas where recordings were performed. We suggest that isoflurane diminishes the cortical inhibition, by an increase of the glutamate uptake by glial cells leading to a diminished activation of cortical interneurons.

L'infarctus du myocarde, une des causes majeures de mortalité à travers le monde, engendre une mort irréversible du muscle cardiaque suite à une ischémie. Cette ischémie, c'est-à-dire une privation de dioxygène et de nutriments, déclencher un stress réticulaire qui perturbe l'équilibre calcique de la cellule cardiaque. Plusieurs pompes et canaux calciques situés à la membrane plasmique ou réticulaire sont des intervenants clés dans le maintien de l'homéostasie calcique. Parmi eux, il existe des canaux de fuites calciques passives, comme les TRPs, et peu d'informations sont actuellement connus à propos de leur rôle précis au cours de l'infarctus du myocarde.TRPV1 est un canal cationique non sélectif qui est activé par la capsaïcine, le pH et la chaleur nocive (>42°C). Dans le muscle squelettique, nous avions démontré que TRPV1 est situé dans la partie longitudinale du réticulum sarcoplasmique et qu'il répond à différentes stimulations physiologiques et pharmacologiques (Lotteau et al., 2013). Ici, nous nous interrogeons sur un éventuel rôle similaire de TRPV1 dans la physiologie cardiaque. Des analyses biochimiques et des mesures de calcium intracellulaire furent réalisées sur des cardiomyocytes issus de souris WT et KO TRPV1. Nos résultats in vitro montrent que: (a) TRPV1 est exprimé dans les cellules cardiaques; (b) une activation de TRPV1 engendre une réduction de la concentration calcique réticulaire et que (c) TRPV1 pourrait être une cible directe de l'isoflurane.Dans la mesure où TRPV1 peut être modulé par de nombreuses molécules pharmacologiques, il pourrait constituer une cible thérapeutique pour réduire la taille d'infarctus. De nombreuses études antérieures ont déjà mis en évidence un rôle cardioprotecteur de TRPV1 dans le système nerveux entourant le cœur. Le but de cette étude est de décrire le fonctionnement des canaux TRPV1 dans des cardiomyocytes adultes / Acute myocardial infarction (MI), a leading cause of morbidity and mortality worldwide, is the irreversible death of heart muscle secondary to ischemia. This ischemia, i.e. oxygen and nutrients deprivation, triggers a reticular stress disrupting the Ca2+ balance of the cardiac cell. Several Ca2+ pumps and channels located at the sarcolemma or at the reticulum membrane are key players in this maintenance of Ca2+ homeostasis. Among them, we find passive leak channels, such as TRPs and little is known about their precise role in MI.TRPV1 represents a non-selective cation channel that is activated by capsaicin, pH and noxious heat. In skeletal muscle, we previously demonstrated that TRPV1 is located in the longitudinal part of the SR and respond to pharmacological and physiological activations (Lotteau et al., 2013). We questioned here whether TRPV1 might have a similar role in heart physiology. Biochemical analysis and intracellular Ca2+ measurements were performed on cardiomyocytes from wild-type and TRPV1-KO mice. Our in vitro results show that: (i) TRPV1 is expressed in cardiac cells; (ii) an increase in intracellular calcium concentration ([Ca2+]i) is elicited under TRPV1 activation; (iii) TRPV1 could be a direct target of isoflurane. In parallel, our in vivo results indicate that a pharmacological preconditioning by isoflurane decrease the infarct size, probably though activation of TRPV1. According to the fact that TRPV1 activity can be modulated by a lot of pharmacological molecules, TRPV1 may serve as therapeutic target to reduce the infarct size. Most of published data have already evidenced this TRPV1 cardioprotective role in the peripheral heart system. The aim of the present work is to describe how TRPV1 channels behave in adult cardiomyocytes

A novel in vitro membrane oxygenator circuit was developed to test gas exchange where particular elements could be examined whilst keeping other variables constant. The circuit comprises two membrane oxygenators connected to form a continuous blood circuit resembling venous and arterial blood conditions. The effects of Isoflurane, a volatile anaesthetic, on oxygen transfer were investigated. RBC resistance to nitric oxide diffusion (DNO) was tested in this circuit by haemolysis and addition of the haemoglobin-based-oxygen-carrier (HBOC) Oxyglobin. The circuit was primed with equine blood flowing at 2.5 l/min. The oxygenator was ventilated with 5 l/min air/oxygen/N2 mix providing a range of FiO2. The deoxygenator received 5 l/min 5% CO2 in N2 with 0.2-0.3 l/min CO2. Isoflurane 1%, NO 4000-16000 ppb and CO 0.03% were added to the oxygenator gas. Uptake of O2, CO2, CO and NO were calculated by gas inlet and outlet concentrations and flow rates. Arterial and venous oxygen dissociation curve (aODC and vODC) comparisons were made. Isoflurane uptake by the circuit blood was evident and 1% Isoflurane did not affect oxygen uptake (p=0.981), aODC or vODC (p=0.311 and p=0.751). Haemolysis did not affect O2 or CO2 transfer but increased DNO (p<0.001). 250ml free Hb solution addition to the circuit increased DNO by 91% (p<0.0001). Addition of 250ml Oxyglobin increased DNO by 143% from 7.41±2.77 to 17.97±1.83 ml/min/mmHg. Oxyglobin caused a right shift of aODC and vODC (p<0.0001) but NO-bound Oxyglobin caused a left vODC shift (p<0.0001). Conclusion: Isoflurane administered via a membrane oxygenator does not affect O2 uptake or carriage in the blood. RBC surroundings provide significant resistance to DNO in circuit tests. Significant uptake of NO by Oxyglobin supports the potential of HBOCs to scavenge endothelial NO in vivo, causing vasoconstriction.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Ocular hypertension has been identified as the fundamental risk factor in glaucoma which is the leading cause for irreversible blindness in the world. Understanding the different factors that affect IOP is of utmost importance in clinical management as IOP is considered as the fundamental factor in assessing the efficiency of glaucoma medications. Several studies have attempted to assess factors that could affect IOP including age, body position, blood pressure, anesthetics commonly used during eye operations, etc. However, in most of these studies IOP is measured under anesthesia using rodent models and these anesthetics could affect the IOP measurements directly or indirectly. The use of tonometry in such experiments also includes certain limitations like acquiring IOP at discrete moments in time, human error while handling the instrument and stress induced spikes in IOP while handling awake animals. This study uses a wireless continuously monitoring device to eliminate these limitations while also acquiring IOP at a higher rate. Anesthesia induction is known to lower body temperature. However, previous studies on the effects of various anesthetic agents fail to take into account this drop in body temperature which could potentially lead to erroneous results. This thesis focuses on studying the effects of two commonly used anesthetic agents, isoflurane and ketamine while accounting for loss in body temperature. The effects of changing body temperature on intraocular pressure was also studied to help understand the effects of these factors accurately. There was a statistically significant drop (p<0.001) in intraocular pressure post isoflurane induction with no heat support across several animals. The addition of heat support in the next set of experiments resulted in an almost steady pressure throughout the experiment. Since the body temperature was maintained constant throughout the experiment, there was no statistically significant difference (p>0.05) among IOP’s for the awake and anesthetized condition. This conclusion was then confirmed by obtaining a direct effect of changing body temperature on IOP. There was a rise in IOP while the animal was placed on a 42 degree Celsius heating pad and a drop in IOP while the animal was placed on a 20 degree Celsius surface with no heat support. The corresponding changes in body temperature were confirmed using a rectal thermometer. There were no significant changes in the IOP measured by the sensor while measuring pressure with the iCare tonolab. Applanation tonometry however produced an average mean intraocular pressure increase of 2.11 ± 1.62 mmHg.

A clinical trial was undertaken using three different inhalant anaesthetic agents and one intravenous anaesthetic agent in dogs undergoing routine desexing surgery. Healthy adult dogs undergoing either ovariohysterectomy or castration were assessed as to their demeanour, with the more excitable dogs being placed in groups receiving premedication with acepromazine and morphine. All dogs were then randomly assigned an anaesthetic agent for induction of general anaesthesia. The agents were the inhalants halothane, isoflurane and sevoflurane, and the intravenous agent propofol. Inhalant inductions were undertaken using a tight fitting mask attached to a standard anaesthetic machine with a rebreathing circuit, with the maximum dose of inhalant available from a standard vaporiser. Propofol inductions were undertaken via intravenous catheter. Dogs induced with propofol were randomly assigned one of the three inhalant agents for maintenance. Those induced by inhalant agent were maintained using the same agent. The surgical procedure was undertaken in standard fashion, as was recovery from anaesthesia. All dogs received the non-steroidal anti-inflammatory agent meloxicam. Data collection was divided into three stages: induction, maintenance, and recovery from anaesthesia. Variables measured at induction of anaesthesia were time to intubation, number of intubation attempts, tolerance of mask, quality of induction and quality of transfer to the maintenance stage. Standard variables for monitoring of anaesthesia were recorded throughout the maintenance of anaesthesia. Variables measured at recovery were time to righting, time to standing and quality of recovery. The mean time to intubation when using the newer inhalant sevoflurane (196.2 � 14.8sec, mean � SE) was not significantly different to that for halothane (221.4 � 14.0sec) or isoflurane (172.4 � 15.0sec). Time to intubation with isoflurane was significantly faster than with halothane. Mean time to intubation with propofol (85.4 � 7.7sec) was significantly faster than that for any of the three inhalants. Choice of inhalant had no effect on quality of induction. The use of premedication significantly improved the quality of induction. The use of propofol for induction likewise significantly improved the quality of induction. Standard cardiorespiratory variables measured during the maintenance phase of anaesthesia remained within normal clinical ranges for all three inhalants, and were therefore not further analysed. Choice of inhalant agent had no significant effect on the time to righting or standing in recovery. The use of propofol for induction had no effect on these variables. Animals placed in groups receiving premedication had significantly longer times to righting and standing. The oesophageal temperature at the end of the procedure had a significant effect on times to righting and standing, with lower temperatures contributing to slower recoveries. Independent of procedure time, male dogs had shorter times to righting than female dogs.