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Browsing by Author "Cavalcanti, Ruben Lundgren"

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    Effects of a convertible to-and-fro and circle anesthetic system on cardiopulmonary variables in isoflurane anesthetized horses
    Natalini, Claudio Corrêa; Polydoro, Alexandre da Silva D. S.; Cavalcanti, Ruben Lundgren; Branquinho, Luciana Queiroga; Crosignani, Nadia; Serpa, Priscila B. S.; Schallenberger, Rodrigo Gonçalves; Pellin de Molnar, Bruna Favieiro; Carregaro, Adriano; Futema, Fábio (Universidade Federal do Rio Grande do Sul, 2018-03-30)
    Six healthy adult horses two male and four female, mean body weight of 424 + 44.1kg, were anesthetized with xylazine, ketamine/diazepam and isoflurane for 60 minutes using a convertible to-and-fro and circle system. Variables analyzed were arterial blood pH, carbon dioxide partial pressure (PaCO2) and oxygen partial pressure (PaO2), respiratory rate(RR), and blood pressure. The horses were allowed to breath spontaneously, and were positioned in right lateral recumbency. The arterial O2 values were significantly higher during isoflurane anesthesia when compared to the baseline values, and significantly lower after induction with ketamine/diazepam although arterial hypoxemia were not present. The arterial PCO2 values were significantly higher from baseline values during isoflurane anesthesia occurring arterial hypercapnia and mild respiratory acidosis. The arterial pH changes paralleled the changes in PaCO2. Respiratory rate values were significantly lower during isoflurane anesthesia when compared to baseline values. All values remained within accepted range for lateral recumbent spontaneously breathing anesthetized horses. There were no significant differences between the circle and the to-and-fro system, demonstrating that either system is safe to maintain isoflurane anesthesia in adult horses.
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    Effects of Detomidine Constant Rate Infusion on Blood Glucose and Lactate in Sevoflurane Anesthetized Horses
    Serpa, Priscila B. S.; Natalini, Claudio Corrêa; Cavalcanti, Ruben Lundgren; Nogueira Estrella, Jose Pedro; Pellin de Molnar, Bruna Favieiro; Bezerra, Daniele Pankowski; Pires, Ananda da Rocha D. R.; Fernandes, Viviane Conde (Universidade Federal do Rio Grande do Sul, 2012-01-01)
    Background: The drugs that promote sedation, analgesia, and anesthesia, as inhalatory agents, phenothiazines, benzodiazepines, alpha-2 adrenergic agonists, and opioids, can promote different kinds of side effects. The concept of a balanced anesthesia in equine was developed in order to minimize adverse effects inherent to anesthesia, creating a combination of lower doses of these drugs in comparison with the doses of each one used alone. Alpha-2-adrenoceptor agonists such as xylazine, detomidine, and others, are drugs used for standing sedation, analgesia, and reduction of volatile anesthetic requirement in the equine as well as an agent used to maintenance of arterial blood pressure during anesthesia. Alpha-2 agonists works stimulating receptors of autonomic neurons inducing reduction of heart rate, cardiac output and vascular resistance, hypertension, behavioral changes, and inhibition of insulin secretion. This reduction in insulin levels increases blood glucose concentration in horses due to its lower utilization in insulin-dependent tissues, as muscular and adipose tissues. Muscular tissue is capable to maintain a constant lactate production even in a well oxygenated environment in order to maintain its cellular activity, especially in cases when glucose is not available. To evaluate the effect on blood glucose and lactate, horses were submitted to one hour of detomidine constant rate infusion during sevoflurane inhalatory anesthesia with controlled ventilation, in order to assess blood concentration of glucose and lactate Materials, Methods & Results: Four adult horses were studied. Detomidine 20 μg.kg-1 was used as premedication followed by an association of ketamine and diazepam intravenously as anesthetic induction. After intubation, sevoflurane was vaporized at approximately 2.3 V%. Mechanical ventilation was established. After stabilization, an intravenous continuous rate infusion (CRI) of detomidine 5 μg.kg.h-1 was started. Venous blood samples were collected before premedication, prior to detomidine continuous infusion, 20, 40, and 60 min after beginning of infusion, in order to determination of glucose and lactate serum concentrations. After 60 min of detomidine infusion, the horses were allowed to recovery. There was statistical significant hyperglycemia in the horses under CRI of detomidine. There was no significant increase in blood lactate, despite of the hyperlactatemia in some animals. Discussion: Detomidine CRI of 5 μg.kg.h-1 does increase blood glucose levels over normal values but not to levels that could be toxic to tissues, mainly CNS. With low levels of serum insulin, body tissues, mainly muscular and adipose tissues, are unable to capture this available blood glucose and these cells depend on lactate metabolism. The lactate serum concentrations below normal range observed in studied horses suggest that all lactate produced by the tissues is being utilized in the energetic metabolism. In according to many authors, lactate is produced and utilized for mitochondrias as energetic source even in fully oxygenated tissues, which seems to be what happened in this experiment. The present study helps to understand energetic metabolism in horses under general inhaled anesthesia with detomidine CRI, a selective alpha-2-adrenoceptor agonist. In order to better evaluate energetic metabolism during inhaled anesthesia under detomidine influence, other studies are suggested, as prolonged anesthesia duration to evaluate a longer adrenergic stimulus induced by detomidine. Besides, other investigations with detomidine CRI in horses submitted to surgical procedures could provide different responses in energetic metabolism.
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    Hemodynamic and Respiratory Effects of Positive End-expiratory Pressure during a Pulmonary Distress Model in Isoflurane Anesthetized Swine
    Cavalcanti, Ruben Lundgren; Serpa, Priscila B. S.; Natalini, Claudio Corrêa (Universidade Federal do Rio Grande do Sul, 2014-10-24)
    Background: Several pulmonary and hemodynamic complications may occur during mechanical ventilation of the lungs. The use of a positive end-expiratory pressure (PEEP) can improve oxygenation and prevent atelectasis, although this method can cause important hemodynamic side effects. Mostly, these hemodynamic effects are due to increased airway pressure that is transferred to the intrapleural space, increasing the intrathoracic pressure, which decreases venous return to the heart. Cardiac output is significantly reduced with high PEEP levels which in turn precludes the improvement effects on blood oxygenation. The aim of this study was to evaluate hemodynamic and respiratory effects of different levels of carbon dioxide insufflations associated with different levels of PEEP under conventional two-lung ventilation in isoflurane anesthetized pigs. Materials, Methods & Results: Twelve juvenile pigs were anesthetized with ketamine and midazolam, and end tidal isoflurane 2.0 V% for maintenance. Animals were submitted to tension pneumothorax through an acute intrathoracic insufflation with carbon dioxide at 0, 5, and 10 mmHg. Mechanical lung ventilation with 100% oxygen was started with zero PEEP then increased to 5 and 10 cmH2O. Ventilatory, respiratory and hemodynamic parameters were measured, as well as blood gases. Tension pneumothorax of 10 mmHg, with both PEEP levels, induced a significant decrease in cardiac index, stroke volume, right ventricular stroke work index, dynamic compliance, arterial pH, arteriovenous oxygen difference, arterial blood pressure, in addition to significance increase in heart rate. Moreover, tension pneumothorax of 5 or 10 mmHg combined with 5 or 10 cmH2O PEEP produced a significant increase in alveolar-arterial oxygen difference, a significant decrease in arterial oxygen content, and arterial partial pressure of O2. Central venous pressure, mean pulmonary arterial pressure, physiologic dead space, and arterial partial pressure of CO2 significantly increased with tension pneumothorax of 5 or 10 cmH2O when 5 or 10 mmHg PEEP was used. Arterial oxygenation improved significantly when 10 cmH2O PEEP was applied to 5 or 10 mmHg tension pneumothorax. Discussion: In this study, a thoracoscopic trocar was used to produce the acute respiratory function impairment. All animals showed the hemodynamic effects of an increased intrapleural pressure (IPP), such as hypotension and decreased SpO2. The major change observed was the increased shunt fraction, due to increased physiologic dead space. The hemodynamic changes observed were mainly due to compression of the large thoracic vessels as well as lung compression. When PEEP was applied without increased IPP, the hemodynamic depressive effects were less important. Levels of ETCO2 in our study did not present a significant increase, demonstrating that recruitment maneuvers are not always effective when there is a concomitant increased IPP. Dead space and V/Q mismatch significantly increased, demonstrating an important respiratory depressant effect. We have demonstrated in this study that while arterial oxygenation and tissue oxygen extraction is improved when high PEEP strategy is used in a swine tension pneumothorax model, the mechanical ventilation of the lungs with low PEEP or high PEEP strategy produced significant depression of the hemodynamic function during tension pneumothorax.