Comparison of xylazine and medotomidine as premedicants for cats being anaesthetised with propofol-sevoflurane

The effects of premedicating cats with saline, xylazine or medetomidine before anaesthetising them with propofol-sevoflurane were compared. Twenty-four cats were randomly assigned to three groups of eight to receive either 0.25 ml of saline, 0.50 mg/kg of xylazine or 0.02 mg/kg of medetomidine intravenously, and anaesthesia was induced with propofol and maintained with sevoflurane. Medetomidine produced a greater reduction in the induction dose of propofol and fewer adverse postoperative effects than saline or xylazine. Hypoxaemia was observed after induction with propofol in the cats premedicated with saline and xylazine, but not in the cats given medetomidine. The cats treated with medetomidine and xylazine developed profound bradycardia. The blood pressure of the cats premedicated with saline and xylazine decreased, but the blood pressure of the cats premedicated with medetomidine was maintained. The cats premedicated with saline took longer to recover from anaesthesia than the other two groups.

Efeito da cadência de pedalada sobre as respostas metabólica e cardiovascular durante o exercício incremental e de carga constante em indivíduos ativos

The main purpose of this study was to analyze the effect of the pedaling cadence (500 × 100 rpm) on the heart rate (HR) and the blood lactate response during incremental and constant workload exercises in active individuals. Nine active male individuals (20.9 ± 2.9 years old; 73.9 ± 6.5 kg; 1.79 ± 0.9 m) were submitted to two incremental tests, and to 6-8 constant workload tests to determine the intensity corresponding to the maximal steady state lactate (MLSSintens) in both cadences. The maximal power (Pmax) attained during the incremental test, and the MLSSintens were significantly lower at 100 rpm (240.9 ± 12.6 W; 148.1 ± 154.W) compared to 50 rpm (263.9 ± 18.6 W; 186.1 ± 21.2 W), respectively. The HRmax did not change between cadences (50 rpm = 191.1 ± 8.8 bpm; 100 rpm = 192.6 ± 9.9 bpm). Regardless the cadence, the HRmax percentage (70, 80, 90, and 100%) determined the same lactate concentrations during the incremental test. However, when the intensity was expressed in Pmax percentage or in absolute power, the lactate and the HR values were always higher at highest cadences. The HR corresponding to MLSSintens was similar between cadences (50 rpm = 162.5 ± 9.1 bpm; 100 rpm = 160.4 ± 9.2 bpm). Based on these results, it can be conclude that regardless the cadence employed (50 × 100 rpm), the use of the HR to individualize the exercise intensity indicates similar blood lactate responses, and this relationship is also kept in the exercise of constant intensity performed at MLSSintens. On the other hand, the use of the Pmax percentages depend on the cadence used, indicating different physiological responses to a same percentage.

Comparação entre limiar anaeróbio determinado por variáveis ventilatórias e pela resposta do lactato sanguíneo em ciclistas

Many investigations have shown that the coincidence between the ventilatory thresholds and those thresholds using the lactate response does not happen all of the time, suggesting that there is no relationship between the cause-effect between these phenomena. Thus, the present study had as main purpose to compare and correlate the Oxygen consumption (V̇O 2), the power (W), and the heart rate (HR) values attained using protocols to determine the Ventilatory Threshold (VT) and the Individual Anaerobic Threshold (IAT). The sampling was constituted by eight State and National level cyclists (age: 27.88 ± 8.77 years; body mass: 65.19 ± 4.40 kg; height: 169.31 ± 5,77 cm). The IAT was determined starting from a three minutes 50 W warm up with progressive increases of 50 W.3min -1 up to achieving the voluntary exhaustion, when the blood was collected in the last 20 seconds of each phase, and during the recovering period. In order to determine the VT, it was used the same protocol used to determine the IAT, but without performing the blood collection. The VT was identified through the changes in the pulmonary ventilation, as well as of the ventilatory equivalent of the O 2 and CO 2. The t-Student test showed no significant statistical difference in any of the attained variables. The associations found were high and significant. The V̇O 2 (ml.kg -1.min. -1), P (W), and HR (bpm) corresponding to the VT and IAT, as well as the associations between variables were respectively: 48.00 ± 3.82 vs. 48.08 ± 3.71 (r = 0.90); 256.25 ± 32.04 vs. 246.88 ± 33.91 (r = 0.84); 173.75 ± 9.18 vs. 171.25 ± 12.02 (r = 0.97). According to the results attained, it can be concluded that the IAT and the VT produce similar V̇O 2, W, and HR values, favoring the adoption of the VT because it is a non-invasive method to determine the anaerobic threshold in cyclists.

Comparison of hemodynamic, clinicopathologic, and gastrointestinal motility effects and recovery characteristics of anesthesia with isoflurane and halothane in horses undergoing arthroscopic surgery

Objective - To compare hemodynamic, clinicopathologic, and gastrointestinal motility effects and recovery characteristics of halothane and isoflurane in horses undergoing arthroscopic surgery. Animals - 8 healthy adult horses. Procedure - Anesthesia was maintained with isoflurane or halothane (crossover study). At 6 intervals during anesthesia and surgery, cardiopulmonary variables and related derived values were recorded. Recovery from anesthesia was assessed; gastrointestinal tract motility was subjectively monitored for 72 hours after anesthesia. Horses were administered chromium, and fecal chromium concentration was used to assess intestinal transit time. Venous blood samples were collected for clinicopathologic analyses before and 2, 24, and 48 hours after anesthesia. Results - Compared with halothane-anesthetized horses, cardiac index, oxygen delivery, and heart rate were higher and systemic vascular resistance was lower in isoflurane-anesthetized horses. Mean arterial blood pressure and the dobutamine dose required to maintain blood pressure were similar for both treatments. Duration and quality of recovery from anesthesia did not differ between treatments, although the recovery periods were somewhat shorter with isoflurane. After isoflurane anesthesia, gastrointestinal motility normalized earlier and intestinal transit time of chromium was shorter than that detected after halothane anesthesia. Compared with isoflurane, halothane was associated with increases in serum aspartate transaminase and glutamate dehydrogenase activities, but there were no other important differences in clinicopathologic variables between treatments. Conclusions and clinical relevance - Compared with halothane, isoflurane appears to be associated with better hemodynamic stability during anesthesia, less hepatic and muscle damage, and more rapid return of normal intestinal motility after anesthesia in horses undergoing arthroscopic procedures.

Central nitric oxide modulates hindquarter vasodilation elicited by AMPA receptor stimulation in the NTS of conscious rats

Microinjection of S-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) in the nucleus of the solitary tract (NTS) of conscious rats causes hypertension, bradycardia, and vasoconstriction in the renal, mesenteric, and hindquarter vascular beds. In the hindquarter, the initial vasoconstriction is followed by vasodilation with AMPA doses >5 pmol/100 nl. To test the hypothesis that this vasodilation is caused by activation of a nitroxidergic pathway in the NTS, we examined the effect of pretreatment with the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 10 nmol/100 nl, microinjected into the NTS) on changes in mean arterial pressure, heart rate, and regional vascular conductance (VC) induced by microinjection of AMPA (10 pmol/100 nl in the NTS) in conscious rats. AMPA increased hindquarter VC by 18 ± 4%, but after pretreatment with L-NAME, AMPA reduced hindquarter VC by 16 ± 7% and 17 ± 9% (5 and 15 min after pretreatment, P < 0.05 compared with before pretreatment). Pretreatment with L-NAME reduced AMPA-induced bradycardia from 122 ± 40 to 92 ± 32 beats/min but did not alter the hypertension induced by AMPA (35 ± 5 mmHg before pretreatment, 43 ± 6 mmHg after pretreatment). Control injections with D-NAME did not affect resting values or the response to AMPA. The present study shows that stimulation of AMPA receptors in the NTS activates both vasodilatatory and vasoconstrictor mechanisms and that the vasodilatatory mechanism depends on production of nitric oxide in the NTS. Copyright © 2006 the American Physiological Society.

Articaine and mepivacaine efficacy in postoperative analgesia for lower third molar removal: a double-blind, randomized, crossover study

Objective: Comparison of the clinical efficacy of 4% articaine in relation to 2% mepivacaine, both with 1:100,000 epinephrine, in the prevention of postoperative pain after lower third molar removal. Study design: Twenty patients underwent removal of bilateral lower third molars under local anesthesia (articaine or mepivacaine) in 2 separate appointments, in a double-blind, randomized, and crossed manner. Objective and subjective parameters were recorded for paired comparison of postoperative courses. Results: Duration of analgesia provided by articaine and mepivacaine was 198.00 ± 25.86, and 125.40 ± 13.96 min, respectively (P = .02), whereas the duration of anesthesia was 273.80 ± 15.94 and 216.85 ± 20.15 min, respectively (P = .06). Both solutions exerted no important effects upon arterial pressure, heart rate, or oxygen saturation (P > .05). Conclusions: Articaine provides a longer period of analgesic effect and a tendency for a longer period of anesthesia as compared to mepivacaine. The presence of a vasoconstrictor agent in local anesthetic solutions does not seem to influence hemodynamic parameters during lower third molar removal in healthy subjects. © 2006 Mosby, Inc. All rights reserved.

Cardiopulmonary effects of buprenorphine in horses

Objective - To investigate the effects of buprenorphine on cardiopulmonary variables and on abdominal auscultation scores in horses. Animals - 6 healthy adult horses. Procedures - Horses were restrained in stocks and allocated to 2 treatments in a randomized crossover design, with 1-week intervals between each treatment. Saline (0.9% NaCl) solution was administered IV as a control, whereas buprenorphine (10 μg/kg, IV) was administered to the experimental group. Cardiopulmonary data were collected for 120 minutes after buprenorphine or saline solution administration. Abdominal auscultation scores were monitored for 2 and 12 hours after drug administration in the control and experimental groups, respectively. Results - Following control treatment, horses remained calm while restrained in the stocks and no significant changes in cardiopulmonary variables were observed throughout the study. Buprenorphine administration caused excitatory phenomena (restlessness and head shaking). Heart rate, cardiac index, and arterial blood pressure were significantly increased after buprenorphine administration until the end of the observational period (120 minutes). Minimal changes were found in arterial blood gas tensions. Abdominal auscultation scores decreased significantly from baseline for 4 hours after buprenorphine administration. Conclusions and Clinical Relevance - Buprenorphine induced excitement and hemodynamic stimulation with minimal changes in arterial blood gas tensions. These effects may impact the clinical use of buprenorphine in horses. Further studies are indicated to investigate the effects of buprenorphine on gastrointestinal motility and fecal output.

Is 44-hour better than 24-hour ambulatory blood pressure monitoring in hemodialysis?

The aim of this study is to evaluate if hemodialysis (HD) patients with similar blood pressure (BP) in the whole inter-HD period could have different target organ lesions and survival if the behavior of BP differs from the first to the second day of the inter-HD period. The present study compares 44-hour ambulatory BP monitoring (ABPM) patterns in 45 HD patients. Three BP patterns emerged: group A (n = 15) had similar BPs throughout (138 ± 11/88 ± 12 in the first 22 h vs. 140 ± 11/87 ± 12 mm Hg in the second 22-hour period); group B (n = 15) had a significant systolic BP rise from the first to the second period (132 ± 15/80 ± 12 vs. 147 ± 12/86 ± 13 mm Hg, p < 0.05); group C (n = 15) had significantly higher BPs (p < 0.05) than the other 2 groups throughout the whole inter-HD period, with no significant change between the 2 halves (172 ± 14/108 ± 12 vs. 173 ± 18/109 ± 14 mm Hg). Ventricular mass and survival during the 30-month follow-up period were statistically significantly better in group A, intermediate in group B and worse in group C. The data suggest that a 44-hour ABPM is more accurate than a 24-hour one in evaluating organ lesion and prognosis in HD patients. Copyright © 2006 S. Karger AG.

Cardiovascular responses produced by central injection of hydrogen peroxide in conscious rats

Reactive oxygen species (ROS) have been shown to modulate neuronal synaptic transmission and may play a role on the autonomic control of the cardiovascular system. In this study we investigated the effects produced by hydrogen peroxide (H 2O 2) injected alone or combined with the anti-oxidant agent N-acetil-l-cysteine (NAC) or catalase into the fourth brain ventricle (4th V) on mean arterial pressure and heart rate of conscious rats. Moreover the involvement of the autonomic nervous system on the cardiovascular responses to H 2O 2 into the 4th V was also investigated. Male Holtzman rats (280-320 g) with a stainless steel cannula implanted into the 4th V and polyethylene cannulas inserted into the femoral artery and vein were used. Injections of H 2O 2 (0.5, 1.0 and 1.5 μmol/0.2 μL, n = 6) into the 4th V produced transient (for 10 min) dose-dependent pressor responses. The 1.0 and 1.5 μmol doses of H 2O 2 also produced a long lasting bradycardia (at least 24 h with the high dose of H 2O 2). Prior injection of N-acetyl-l-cysteine (250 nmol/1 μL/rat) into the 4th V blockade the pressor response and attenuated the bradycardic response to H 2O 2 (1 μmol/0.5 μL/rat, n = 7) into the 4th V. Intravenous (i.v.) atropine methyl bromide (1.0 mg/kg, n = 11) abolished the bradycardia but did not affect the pressor response to H 2O 2. Prazosin hydrochloride (1.0 mg/kg, n = 6) i.v. abolished the pressor response but did not affect the bradycardia. The increase in the catalase activity (500 UEA/1 μL/rat injected into the 4th V) also abolished both, pressor and bradycardic responses to H 2O 2. The results suggest that increased ROS availability into 4th V simultaneously activate sympathetic and parasympathetic outflow inducing pressor and bradycardic responses. © 2006 Elsevier Inc. All rights reserved.

Mensuração da energia despendida no jejum e no aporte calórico (MEL) em parturientes

This research aims to measure the energy spending in parturient women of low gestation risk. Participants were selected randomly and submitted to fasting (n=15; Group I) or honey ingestion (n = 15; Group II). Data were collected by means of capillary blood values and heart frequency monitoring. The paired t-test with a 5% significance level and Tukey's method were used in statistical analysis. The results showed that honey ingestion did not promote an overload in the mother's glucose; the lactate response demonstrated that the substrate offered was well used; the cardiorespiratory rate demonstrated good performance for both groups; the total energy spent during labor demonstrated that carbohydrate ingestion exerts significant influence, improving maternal anaerobic performance; the group which remained in fasting presented, immediately after labor, higher levels of lactate, showing the organism's efforts to compensate for the energy spent.

Parâmetros fisiológicos do desempenho de cavalos de alta performance hidratados voluntariamente com água ou solução isotônica contendo carboidrato

During eight weeks, in summer, four endurance trained high performance horses were worked in resistence exercise, recieving two different types of hydratatio, water or an isotonic solution containing carbohydrates, with the objective to compare their performance physiological parameters. Only the RT (rectal temperature), HR (heart rate), RR (respiratory rate), weight, total protein, glucose, the electrolytes K, Ca and the muscular enzyme CK presented distance effect. The others parameters evaluated, there weren't any identified effects of treatment and of the interaction between distance and treatments, with a significancy level of 5%, and it was concluded that the isotonic solution containing carbohydrate didn't have any significant influence on the animal's performance when compared to water.