232 resultados para minimum alveolar concentration


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PURPOSE: To measure the change in the minimum alveolar concentration of isoflurane (EtISO) associated with epidural nalbuphine and the postoperative analgesic requirements in dogs after ovariohysterectomy.METHODS: Twenty four healthy female dogs were randomly assigned to receive saline or nalbuphine at 0.3 or 0.6 mg/kg (n=8 for each group) administered via lumbosacral epidural catheter introduced cranially into the epidural canal. Changes in heart and respiratory rates and arterial blood pressure during surgery were recorded along with the corresponding EtISO. Immediately after tracheal extubation, analgesia, sedation, heart rate, respiratory rate, and arterial blood pressure were measured at predetermined intervals and every 60 min thereafter until the first rescue analgesic.RESULTS: A significant decrease in EtISO was associated with epidural nalbuphine at 0.3 mg/kg (26.3%) and 0.6 mg/kg (38.4%) but not with saline in ovariohysterectomized dogs. In the postoperative period, VAS and Colorado analgesic scores were lower for the dogs that received the higher nalbuphine dose, which only required supplemental analgesia 10 h following its administration, compared with dogs that received the lower dose.CONCLUSION: Epidural nalbuphine significantly reduces the intra-operative isoflurane requirement and provides prolonged postoperative analgesia after ovariohysterectomy in dogs.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The gastrointestinal tract is one of the first organs affected by hypoperfusion during hemorrhagic shock. The hemodynamics and oxygen transport variables during hemorrhagic shock and resuscitation can be affected by the anesthetics used. In a model of pressure-guided hemorrhagic shock in dogs, we studied the effects of three halogenated anesthetics - halothane, sevoflurane, and isoflurane - at equipotent concentrations on gastric oxygenation. Thirty dogs were anesthetized with 1.0 minimum alveolar anesthetic concentration (MAC) of either halothane, sevoflurane, or isoflurane. A gastric tonometer was placed in the stomach to determine mucosal gastric CO2 (PgCO(2)) and for the calculation of gastric-arterial PCO2 gradient (PCO2 gap). The dogs were splenectomized and hemorrhaged to hold mean arterial pressure at 40-50 mm Hg over 45 min and then resuscitated with the shed blood volume. Hemodynamics, systemic oxygenation, and PCO2 gap were measured at baseline, after 45 min of hemorrhage, and at 15 and 60 min after blood resuscitation. Hemorrhage induced reductions of mean arterial pressure and cardiac index, while systemic oxygen extraction increased (p < .05), without significant differences among groups (p > .05). Halothane group showed significant lower PCO2 gap values than the other groups (p < .05). After 60 min of shed blood replacement, all groups restored hemodynamics, systemic oxygenation, and PCO2 gap to the prehemorrhage levels (p > .05), without significant differences among groups (p > .05). We conclude that halothane is superior to preserve the gastric mucosal perfusion in comparison to isoflurane and sevoflurane, in dogs submitted to pressure-guided hemorrhagic shock at equipotent doses of halogenated anesthetics.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Background and Objectives - Inhalational anesthetics have a mild analgesic effect. The reduction of alveolar concentration (MAC) of potent volatile anesthesics by increasing plasma concentrations of opioids is desired in inhalational anesthesia. The purpose of this study was to determine the role of sufentanil in reducing sevoflurane and isoflurane MAC. Methods - Thirty eight adult patients of both genders, physical status ASA I or II, submitted to major abdominal procedures were randomly allocated into two groups. Group I (n = 24) received inahalational anesthesia with sevoflurane and Group II (n = 14) received inhalational anesthesia with isoflurane, both diluted in a mixture of N2O (1 liter) and O2 (0.5 liter). A semi-closed system with CO2 absorber and partial reinhalation was used. Ventilation was mechanically controlled. Sufentanil infusion was administered aiming at obtaining 0.5 ng.ml-1 of plasma concentration. Sufentanil plasma concentration was previously calculated by a computer software. End-tidal concentrations were obtained through a gas analyzer and measured at 15 minutes (M1), 30 minutes (M2), 60 minutes (M3), 90 minutes (M4) and 120 minutes (M5). Systolic and diastolic blood pressure (SBP and DBP) and heart rate (RR) were measured during the same periods with the addition of M0 (pre-anesthetic period). Hourly consumption of the inhalational anesthetic agent (IAC), extubation time (ET = time between admission to the recovery room and extubation) and stay in the post anesthesia recovery room (PA-RR) were also measured. Results - Type and duration of surgeries were similar for both groups. There were no statistically significant differences in MAC, SBP, DBP, RR, IAC, TE and PA-RR between groups. Systolic blood pressure in group I (sevoflurane) showed differences among periods F = 3.82 p < O.05; (M2 = M3)(M4 = M5) and M1 had a intermediate value. MAC in group I showed differences among periods F = 9.0 p < 0.05; M1 < M3. MAC in group II also showed differences among periods F = 13.03 p < O.05; M1 < (M2,M3,M4,M5). Conclusions - Both groups had similar behavior when associated to sufentanil in major abdominal surgeries. Group II showed a higher cardiac and circulatory stability.

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Objective: To evaluate the cardiorespiratory effects of continuous infusion of ketamine in hypovolemic dogs anesthetized with desflurane.Design: A prospective experimental study.Animals: Twelve mixed breed dogs allocated into 2 groups: saline (n=6) and ketamine (n=6).Interventions: After obtaining baseline measurements (time [T] 0) in awake dogs, hypovolemia was induced by the removal of 40 mL of blood/kg over 30 minutes. Anesthesia was induced and maintained with desflurane (1.5 minimal alveolar concentration) and 30 minutes later (T75) a continuous intravenous (IV) infusion of saline or ketamine (100 mu g/kg/min) was initiated. Cardiorespiratory evaluations were obtained 15 minutes after hemorrhage (T45), 30 minutes after desflurane anesthesia, and immediately before initiating the infusion (T75), and 5 (T80), 15 (T90), 30 (T105) and 45 (T120) minutes after beginning the infusion.Measurements and main results: Hypovolemia (T45) reduced the arterial blood pressures (systolic arterial pressure, diastolic arterial pressure [DAP] and mean arterial pressure [MAP]), cardiac (CI) and systolic (SI) indexes, and mean pulmonary arterial pressure (PAP) in both groups. After 30 minutes of desflurane anesthesia (T75), an additional decrease of MAP in both groups was observed, heart rate was higher than T0 at T75, T80, T90 and T105 in saline-treated dogs only, and the CI was higher in the ketamine group than in the saline group at T75. Five minutes after starting the infusion (T80), respiratory rate (RR) was lower and the end-tidal CO(2) (ETCO(2)) was higher compared with values at T45 in ketamine-treated dogs. Mean values of ETCO(2) were higher in ketamine than in saline dogs between T75 and T120. The systemic vascular resistance index (SVRI) was decreased between T80 and T120 in ketamine when compared with T45.Conclusions: Continuous IV infusion of ketamine in hypovolemic dogs anesthetized with desflurane induced an increase in ETCO(2), but other cardiorespiratory alterations did not differ from those observed when the same concentration of desflurane was used as the sole anesthetic agent. However, this study did not evaluate the effectiveness of ketamine infusion in reducing desflurane dose requirements in hypovolemic dogs or the cardiorespiratory effects of ketamine-desflurane balanced anesthesia.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)