Browsing by Author "Nogueira Estrella, Jose Pedro"

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    Blood Gas Tension Changes in Dogs Anesthetized with Two Different Oxygen Flow Rates Using a Nonrebreathing Bain Anesthetic System
    Natalini, Claudio Corrêa; Futema, Fábio; Serpa, Priscila B. S.; Nogueira Estrella, Jose Pedro; Pires, Jefferson da Silva D. S. (Universidade Federal do Rio Grande do Sul, 2010-01-01)
    Background: The non-rebreathing anesthetic system is one of the most used in veterinary medicine in small animals due to the low resistance to breathing. The Bain System is constructed with one corrugated external hose, one internal conducting duct for fresh gases, an optional pop-off valve and two connections (one for the breathing bag and the other for the patient). According to the literature recommendations, this system requires an oxygen flow rate between 130-200 mL/kg/min. This present work aims to evaluate the arterial blood gases tension changes in dogs anesthetized with two different oxygen flow rates (100 mL/kg/min or 200 ml/kg/min) using a nonrebreathing Bain System, in adult healthy dogs. Materials, Methods & Results: Fourteen adult healthy mongrel dogs (10 males and 4 females) ranging from 3.5 to 4.5 years old, with average body weight of 12.5 + 0.81 kg, were submitted to preanesthetic medication with acepromazine maleate (0.1 mg/kg IM) and fentanyl citrate (5 mcg/kg IM) and after 15 min induction of anesthesia was performed using sodium thiopental (9 mg/ kg, IV). An anesthetic state using the Bain System was maintained using oxygen 100 mL/kg/min and isoflurane 1.5 V% in group I and oxygen 200 mL/kg/min and isoflurane 1.5V% in group II. Heart and respiratory rates, oxygen saturation, arterial pH, blood gases and bicarbonate were the variables analyzed after induction and before intubation (T0), immediately after intubation (T1), at 10 min of anesthesia (T2), at 20 min of anesthesia (T3), at 30 min of anesthesia (T4), at 40 min of anesthesia (T5), at 50 min of anesthesia (T6), and after 60 min of anesthesia in the end of the procedure (T7). The results indicated that animals submitted to both protocols showed a significant decrease in arterial pH values from T1 to T7 in relation to T0. The differences found between the values from times T1 to T7 were statistically significant between them. The values of PaCO2 demonstrated statistically significant differences from T1 to T7 in both protocols. Protocol I showed statistically significant difference between T0 with respect to the times T1 to T7. For the parameter PaO2 there were statistically significant differences between protocols in T0 and not from T0 in comparison with T1 to T7 in both protocols. However, there were no significant differences between protocols due to inhalation of pure O2, that even using different flows causes an increase in PaO2The values of heart rate showed significant differences from T1 to T7 between protocols I, and protocol II. The values of base excess, O2 saturation and respiratory rate showed no statistically significant between protocols and time points. Discussion: Oxygen flow rate is the mean by which the CO2 is eliminated from nonrebrathing systems. Higher flow rates than those used in circle anesthetic systems are recommended in order to avoid carbon dioxide rebreathing within the nonrebrathing system. In our study we did demonstrate that the use of oxygen flow rate of 200 mL/kg/min with a Bain system kept the blood gas values and pH within acceptable range in healthy dogs submitted to general anesthesia with isoflurane 1.5V%. A lower flow rate of 100 mL/kg did produce arterial hypercapnia and academia of respiratory origin. The explanation for such result is probably due to the physical property of the inhalant anesthetic carrier gas flow. The use of higher flow rates will force exhaled carbon dioxide through the pop off valve, reducing its absorption. According to our findings a flow rate of 200 mL/kg/min should be recommended for the Bain system in dogs.
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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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    Use of Calcium Chloride as an Adjuvant in Cardiopulmonary Cerebral Resuscitation (CPCR) in Dogs
    Natalini, Claudio Corrêa; Nogueira Estrella, Jose Pedro; Polydoro, Alexandre da Silva D. S.; Futema, Fábio; Serpa, Priscila B. S. (Universidade Federal do Rio Grande do Sul, 2011-01-01)
    Background: Treatment of cardiopulmonary arrest has been a source of discussion in both medicine as in veterinary with an emphasis on the use of solutions with calcium because of its importance as an ion essential for heart's functionality. Only a few studies have showed the use of Ca 2+ in CPCR. Based on this, the present study aimed to evaluate the use of calcium chloride as an adjuvant therapy in CPCR in dogs. Materials, Methods & Results: Eighteen cases of CPCR from the hospital routine of HCV-UFRGS were studied. Cases were selected from those in which occurred a cardiopulmonary arrest with reversal to a ventricular asystole in dogs. These animals were divided into two groups. In nine animals from the group called EPI, epinephrine was administered intravenously at a dose of 0.1 mg.kg -1 or by pulmonary route in a dose of 0.2 mg.kg -1. In the remaining nine animals, named EPIC group, the protocol was similar to the previous group, with the addition of the administration of calcium chloride 10% immediately after administration of epinephrine. In EPI group, the overall rate of success was 55.6%, and three of the cases treated showed reversion to normal sinus rhythm asystole. In the remaining six cases, four progressed to nonresponsive transient ventricular tachycardia (VT) and death, and two progressed to junctional rhythm. In the EPIC group, the overall rate of success was 22.2%. Four animals had VF from an asystole, in which in two of them were reversed by electric defibrillation, and in two of them the reversal was not obtained. In the other five treated animals, a ventricular tachycardia was developed followed by an irreversible cardiac arrest. Discussion: The incidence and prevalence of cardiac arrest diagnosed in animals in both hospitals and outpatients are still scarce data. However when it comes to patients under anesthesia, the success rate of CPCR are low compared to medicine. Calcium ion is indispensable in order to generate activation of the cardiac myofilaments to produce contraction of the heart. Cardiopulmonary arrest leads to a series of physiological changes that decrease the ability of the myocardium to maintain their automaticity and, in turn, generate a cardiac pacemaker, as well as its contractility. Several studies show that such these changes could be because of a severe hypocalcemia, found in both humans and dogs. Despite of the recent consensus against its use, calcium chloride in CPCR can increase the intracellular levels of this ion, which can cause inhibition of cellular respiration and energy production in mitochondrias, triggering an enzymatic proteolytic reaction, leading to cell death. However there is a clear exception in cases where the patient is in a framework of hypocalcemia. The EPI group has reached better rates of success; however, in the EPIC group was observed a reversal of asystole to VF, a fact that did not occur in group EPI. The treatment for VF is electric defibrillation, with a better prognosis when compared to asystole. Although the EPI group has obtained the best result and epinephrine rather is the best treatment of choice to CPCR, the EPIC group demonstrated that the use of calcium chloride may be an alternative to try to transform a VF in an asystole, with the possibility of using electric defibrillator in patients unresponsive to epinephrine alone.