Cardiovascular and respiratory changes during slow-wave sleep in rats are associated with electrocorticogram desynchronization

In awake rats a single recurrent larger tidal volume (deep breaths) occurs at regular intervals, followed by oscillations in arterial pressure and heart rate. In the present study we recorded the changes in blood pressure, heart rate and ventilation during the wakefulness-sleep cycle identified by electrocorticographic records in order to determine whether the deep breaths and cardiovascular oscillations were associated with changes in the electrocorticogram. During several episodes of slow-wave sleep (SWS) in 7 rats the deep breaths and oscillations in arterial pressure and heart rate were preceded by SWS desynchronization. The interval between deep breaths during SWS was 71 ± 4 s, the period between initial desynchronization and the generation of deep breaths was 3.98 ± 0.45 s and the duration of SWS desynchronization was 11 ± 0.65 s. Hypotension (-16 ± 1 mmHg) and tachycardia (+15 ± 5 bpm) were observed during deep breaths in the SWS state. These data indicate that the oscillations in arterial pressure and heart rate during SWS are associated with deep breaths, which in turn are preceded by desynchronization of the electrocorticogram in this state of sleep

Cardio respiratory activity in high-anxious vs. low-anxious professional music students before and during performance

Questionnaire studies indicate that high-anxious musicians may suffer from hyperventilation symptoms before and/or during performance. Reported symptoms include amongst others shortness of breath, fast or deep breathing, dizziness and thumping heart. However, no study has yet tested if these self-reported symptoms reflect actual cardio respiratory changes. Disturbances in breathing patterns and hyperventilation may contribute to the often observed poorer performance of anxious musicians under stressful performance situations. The main goal of this study is to determine if music performance anxiety is manifest physiologically in specific correlates of cardio respiratory activity. We studied 74 professional music students divided into two groups (i.e. high-anxious and lowanxious) based on their self-reported performance anxiety in three distinct situations: baseline, private performance (without audience), public performance (with audience). We measured a) breathing patterns, end-tidal carbon dioxide (EtCO2, a good non-invasive estimator for hyperventilation), ECG and b) self-perceived emotions and self-perceived physiological activation. The poster will concentrate on the preliminary results of this study. The focus will be a) on differences between high-anxious and low-anxious musicians regarding breaths per minute and heart rate and b) on the response coherence between self-perceived palpitations and actual heart rate.

Chronic intermittent hypoxia alters glutamatergic control of sympathetic and respiratory activities in the commissural NTS of rats

Costa-Silva JH, Zoccal DB, Machado BH. Chronic intermittent hypoxia alters glutamatergic control of sympathetic and respiratory activities in the commissural NTS of rats. Am J Physiol Regul Integr Comp Physiol 302: R785-R793, 2012. First published December 28, 2011; doi:10.1152/ajpregu.00363.2011.-Sympathetic overactivity and altered respiratory control are commonly observed after chronic intermittent hypoxia (CIH) exposure. However, the central mechanisms underlying such neurovegetative dysfunctions remain unclear. Herein, we hypothesized that CIH (6% O-2 every 9 min, 8 h/day, 10 days) in juvenile rats alters glutamatergic transmission in the commissural nucleus tractus solitarius (cNTS), a pivotal site for integration of peripheral chemoreceptor inputs. Using an in situ working heart-brain stem preparation, we found that L-glutamate microinjections (1, 3, and 10 mM) into the cNTS of control rats (n = 8) evoked increases in thoracic sympathetic nerve (tSN) and central vagus nerve (cVN) activities combined with inhibition of phrenic nerve (PN) activity. Besides, the ionotropic glutamatergic receptor antagonism with kynurenic acid (KYN; 250 mM) in the cNTS of control group (n = 7) increased PN burst duration and frequency. In the CIH group (n = 10), the magnitude of L-glutamate-induced cVN excitation was smaller, and the PN inhibitory response was blunted (P < 0.05). In addition, KYN microinjections into the cNTS of CIH rats (n = 9) did not alter PN burst duration and produced smaller increases in its frequency compared with controls. Moreover, KYN microinjections into the cNTS attenuated the sympathoexcitatory response to peripheral chemoreflex activation in control but not in CIH rats (P < 0.05). These functional CIH-induced alterations were accompanied by a significant 10% increase of N-methyl-D-aspartate receptor 1 (NMDAR1) and glutamate receptor 2/3 (GluR2/3) receptor subunit density in the cNTS (n = 3-8, P < 0.05), evaluated by Western blot analysis. These data indicate that glutamatergic transmission is altered in the cNTS of CIH rats and may contribute to the sympathetic and respiratory changes observed in this experimental model.

VO2MAX : uma proposta de teste de campo para jogadores de futebol

Universidade Estadual de Campinas . Faculdade de Educação Física

Online monitoring of pulse pressure variation to guide fluid therapy after cardiac surgery

BACKGROUND: The arterial pulse pressure variation induced by mechanical ventilation (Delta PP) has been shown to be a predictor of fluid responsiveness. Until now, Delta PP has had to be calculated offline (from a computer recording or a paper printing of the arterial pressure curve), or to be derived from specific cardiac output monitors, limiting the widespread use of this parameter. Recently, a method has been developed for the automatic calculation and real-time monitoring of Delta PP using standard bedside monitors. Whether this method is to predict reliable predictor of fluid responsiveness remains to be determined. METHODS: We conducted a prospective clinical study in 59 mechanically ventilated patients in the postoperative period of cardiac surgery. Patients studied were considered at low risk for complications related to fluid administration (pulmonary artery occlusion pressure <20 mm Hg, left ventricular ejection fraction >= 40%). All patients were instrumented with an arterial line and a pulmonary artery catheter. Cardiac filling pressures and cardiac output were measured before and after intravascular fluid administration (20 mL/kg of lactated Ringer`s solution over 20 min), whereas Delta PP was automatically calculated and continuously monitored. RESULTS: Fluid administration increased cardiac output by at least 15% in 39 patients (66% = responders). Before fluid administration, responders and nonresponders were comparable with regard to right atrial and pulmonary artery occlusion pressures. In contrast, Delta PP was significantly greater in responders than in nonresponders, (17% +/- 3% vs 9% +/- 2%, P < 0.001). The Delta PP cut-off value of 12% allowed identification of responders with a sensitivity of 97% and a specificity of 95%. CONCLUSION: Automatic real-time monitoring of Delta PP is possible using a standard bedside rnonitor and was found to be a reliable method to predict fluid responsiveness after cardiac surgery. Additional studies are needed to determine if this technique can be used to avoid the complications of fluid administration in high-risk patients.

Influence of ventilatory settings on static and functional haemodynamic parameters during experimental hypovolaemia

Background and objective The influence of ventilatory settings on static and functional haemodynamic parameters during mechanical ventilation is not completely known. The purpose of this study was to evaluate the effect of positive end-expiratory pressure, tidal volume and inspiratory to expiratory time ratio variations on haemodynamic parameters during haemorrhage and after transfusion of shed blood. Methods Ten anaesthetized pigs were instrumented and mechanically ventilated with a tidal volume of 8 ml kg(-1), a positive end-expiratory pressure of 5 cmH(2)O and an inspiratory to expiratory ratio of 1 : 2. Then, they were submitted in a random order to different ventilatory settings (tidal volume 16 ml kg(-1), positive end-expiratory pressure 15 cmH(2)O or inspiratory to expiratory time ratio 2: 1). Functional and static haemodynamic parameters (central venous pressure, pulmonary artery occlusion pressure, right ventricular end-diastolic volume and pulse pressure variation) were evaluated at baseline, during hypovolaemia (withdrawal of 20% of estimated blood volume) and after an infusion of withdrawn blood (posttransfusion). Results During baseline, a positive end-expiratory pressure of 15cmH(2)O significantly increased pulmonary artery occlusion pressure from 14.6 +/- 1.6 mmHg to 17.4 +/- 1.7 mmHg (P<0.001) and pulse pressure variation from 15.8 +/- 8.5% to 25.3 +/- 9.5% (P<0.001). High tidal volume increased pulse pressure variation from 15.8 8.5% to 31.6 +/- 10.4% (P<0.001), and an inspiratory to expiratory time ratio of 2: 1 significantly increased only central venous pressure. During hypovolaemia, high positive end-expiratory pressure influenced all studied variables, and high tidal volume strongly increased pulse pressure variation (40.5 +/- 12.4% pre vs. 84.2 +/- 19.1 % post, P<0.001). The inversion of the inspiratory to expiratory time ratio only slightly increased filling pressures during hypovolaemia, without without affecting pulse pressure variation or right ventricle end-diastolic volume. Conclusion We concluded that pulse pressure variation measurement is influenced by cyclic variations in intrathoracic pressure, such as those caused by augmentations in tidal volume. The increase in mean airway pressure caused by positive end-expiratory pressure affects cardiac filling pressures and also pulse pressure variation, although to a lesser extent. Inversion of the inspiratory to expiratory time ratio does not induce significant changes in static and functional haemodynamic parameters. Eur J Anaesthesiol 26:66-72 (c) 2009 European Society of Anaesthesiology.

Comparative study of pressure- and volume-controlled ventilation on pulse pressure variation in a model of hypovolaemia in rabbits

Background and objective: Dynamic indices represented by systolic pressure variation and pulse pressure variation have been demonstrated to be more accurate than filling pressures in predicting fluid responsiveness. However, the literature is scarce concerning the impact of different ventilatory modes on these indices. We hypothesized that systolic pressure variation or pulse pressure variation could be affected differently by volume-controlled ventilation and pressure-controlled ventilation in an experimental model, during normovolaemia and hypovolaemia. Method: Thirty-two anaesthetized rabbits were randomly allocated into four groups according to ventilatory modality and volaemic status where G1-ConPCV was the pressure-controlled ventilation control group, G2-HemPCV was associated with haemorrhage, G3-ConVCV was the volume-controlled ventilation control group and G4-HemVCV was associated with haemorrhage. In the haemorrhage groups, blood was removed in two stages: 15% of the estimated blood volume withdrawal at M1, and, 30 min later, an additional 15% at M2. Data were submitted to analysis of variance for repeated measures; a value of P < 0.05 was considered to be statistically significant. Results: At MO (baseline), no significant differences were observed among groups. At M1, dynamic parameters differed significantly among the control and hypovolaemic groups (P < 0.05) but not between ventilation modes. However, when 30% of the estimated blood volume was removed (M2), dynamic parameters became significantly higher in animals under volume-controlled ventilation when compared with those under pressure-controlled ventilation. Conclusions: Under normovolaemia and moderate haemorrhage, dynamic parameters were not influenced by either ventilatory modalities. However, in the second stage of haemorrhage (30%), animals in volume-controlled ventilation presented higher values of systolic pressure variation and pulse pressure variation when compared with those submitted to pressure-controlled ventilation.

Organisation et modulation du réseau neuronal de la respiration chez la lamproie.

Les mécanismes neuronaux contrôlant la respiration sont présentement explorés à l’aide de plusieurs modèles animaux incluant le rat et la grenouille. Nous avons utilisé la lamproie comme modèle animal nous permettant de caractériser les réseaux de neurones du tronc cérébral qui génèrent et modulent le rythme respiratoire. Nous avons d’abord caractérisé une nouvelle population de neurones, dans le groupe respiratoire paratrigéminal (pTRG), une région du tronc cérébral essentielle à la genèse du rythme respiratoire chez la lamproie. Les neurones de cette région sont actifs en phase avec le rythme respiratoire. Nous avons montré que ces neurones possèdent une arborisation axonale complexe, incluant des projections bilatérales vers les groupes de motoneurones du tronc cérébral qui activent les branchies ainsi que des connexions reliant les pTRG de chaque côté du tronc cérébral. Ces résultats montrent que le pTRG contient un groupe de cellules qui active les motoneurones respiratoires des deux côtés et qui pourrait être impliqué dans la synchronisation bilatérale du rythme respiratoire. Nous avons ensuite étudié les mécanismes neuronaux par lesquels le rythme respiratoire est augmenté en lien avec l’effort physique. Nous avons montré que la région locomotrice du mésencéphale (MLR), en plus de son rôle dans la locomotion, active les centres respiratoires pendant la nage, et même en anticipation. Les neurones de la MLR projetant vers les centres locomoteurs et respiratoires sont ségrégés anatomiquement, les neurones localisés plus dorsalement étant ceux qui possèdent des projections vers les centres respiratoires. Nous avons aboli la contribution de la partie dorsale de la MLR aux changements respiratoires en injectant des bloqueurs des récepteurs glutamatergiques localement, sur des préparations semi-intactes. Nous avons montré que lors d’épisodes de nage, une majeure partie de l’effet respiratoire est abolie par ces injections, suggérant un rôle prépondérant des neurones de cette région dans l’augmentation respiratoire pendant la locomotion. Nos résultats confirment que le rythme respiratoire est généré par une région rostrolatérale du pons de la lamproie et montrent que des connexions des centres locomoteurs arrivent directement à cette région et pourraient être impliquées dans l’augmentation respiratoire reliée à l’effort physique.

Curva de aprendizaje para ventana ecográfica de la vena cava inferior, en residentes de medicina de emergencias

INTRODUCCIÓN. El ultrasonido es fundamental en la medicina de emergencias, no se conoce cual debería ser la curva de aprendizaje para obtener las competencias técnicas y operativas; ACEP recomienda por cada ventana ecográfica realizar 25 repeticiones. No existe una curva de aprendizaje para ventana de VCI en la población de residentes colombianos. OBJETIVO: Determinar la curva de aprendizaje necesaria para obtener una proporción mayor al 80% de éxitos en la toma de la ventana ecográfica de la VCI, usando la escala de calificación para el aseguramiento de la calidad sugerida por ACEP, en residentes de I a III año de medicina de emergencias. METODOLOGÍA: Estudio experimental no comparativo, que evaluó la proporción de éxito en función del las tomas repetidas de la VCI por ultrasonido, mediciones que se tomaron luego de participar en una capacitación teórica y demostrativa de la técnica propuesta; se calificaron los videos según la escala publicada por ACEP. El análisis estadístico se realizó con un modelo logístico multinivel para la proporción del éxito, agrupado por repetición y agrupado por sujeto. RESULTADOS: Se obtuvo información de 8 residentes, cada uno realizo 25 repeticiones a 3 modelos sanos con asignación aleatoria. Se realizó la curva de aprendizaje obteniendo en 11 repeticiones una proporción de 0.80 (rango 0.54 a 0.92) y en 21 repeticiones una proporción de 0.9 (rango 0.75 a 0.96), datos ajustados por numero de repetición y residente. CONCLUSIÓN: La curva de aprendizaje para la ventana ecográfica de la VCI es de 11 y 21 repeticiones para obtener el 80% y 90% de éxito en residentes de medicina de emergencias de I a III año de la universidad del rosario.

Estado neurológico e cardiorrespiratório de filhotes de cães nascidos de parto normal ou de cesariana sob anestesia geral inalatória com sevofluorano

A anestesia obstétrica possibilita um procedimento mais seguro para a mãe e para os fetos. em medicina veterinária, no entanto, a literatura científica a respeito do assunto é deficiente. Este trabalho teve como objetivo avaliar o grau de depressão neurológica, hemodinâmica e respiratória fetais provocado pelo agente anestésico, em que as mães foram submetidas ao parto normal ou à cesariana, utilizando-se sevofluorano como agente de manutenção anestésica, comparando-o com o parto normal. Foram realizados seis partos normais (GN) e seis cesarianas (GC), avaliando-se um total de 36 filhotes. As cesarianas foram realizadas utilizando-se acepromazina, propofol e sevofluorano (GC) e os neonatos foram avaliados clinicamente ao primeiro, quinto e décimo minuto de nascimento, nos dois grupos. Observou-se maior depressão respiratória nos filhotes nascidos de cesariana. Contudo, apesar dessa depressão, o protocolo anestésico empregado não comprometeu de maneira importante a viabilidade e a saúde das mães e dos filhotes, demonstrando ser seguro em cadelas gestantes.

Estudo clínico e cardiorrespiratório em cadelas gestantes com parto normal ou submetidas à cesariana sob anestesia inalatória com sevofluorano

Estudaram-se as alterações hemodinâmicas e respiratórias em cadelas, decorrentes do parto normal e da cesariana, utilizando-se sevofluorano como agente de manutenção anestésica. Foram acompanhados seis partos normais e seis cesarianas, sendo as últimas realizadas sob anestesia geral utilizando-se acepromazina, propofol e sevofluorano. Durante o parto normal, ao nascimento de cada filhote, as gestantes foram monitoradas (temperatura retal, pressão arterial não-invasiva, freqüências respiratória e cardíaca, tempo de reperfusão capilar e gasometria). Durante a cesariana foram avaliadas as mesmas características citadas para o parto normal, acrescentando-se a temperatura esofágica e a pressão arterial invasiva, ao longo de todo o período anestésico, além da qualidade da recuperação anestésica. Os valores das variáveis: freqüência cardíaca, pressão arterial, freqüência respiratória, tempo de reperfusão capilar e o pH do sangue arterial no grupo submetido à cesariana foram menores que os das cadelas de partos normais, evidenciando a relativa depressão cardiorrespiratória produzida pelo procedimento anestésico. O protocolo anestésico empregado não comprometeu a viabilidade e a saúde das parturientes e dos filhotes e é seguro em cadelas gestantes, podendo ser utilizado nas operações cesarianas.

Níveis de sedação determinados pela clonidina e midazolam na medicação pré-anestésica: avaliação clínica e eletroencefalográfica bispectral

JUSTIFICATIVA E OBJETIVOS: Verificar o efeito sedativo da clonidina, um a2-agonista, e do midazolam, um benzodiazepínico, quando utilizados na medicação pré-anestésica, empregando-se avaliação clínica e eletroencefalográfica bispectral. MÉTODO: Após aprovação institucional e consentimento escrito fornecido, 45 pacientes de 18 a 65 anos, estado físico ASA I, foram aleatoriamente distribuídos nos grupos placebo (P), clonidina (C) ou midazolam (M), em que receberam, respectivamente placebo, 150 µg de clonidina ou 15 mg de midazolam por via oral, 60 minutos antes da indução da anestesia (n = 15 por grupo). A monitorização constituiu-se de eletrocardiograma (D II), pressão arterial não invasiva, freqüência cardíaca, saturação de pulso de oxigênio, freqüência respiratória, temperatura axilar e da sala de cirurgia e eletroencefalograma bispectral para determinação do índice bispectral (BIS). Esses atributos e a escala de sedações (1 - ansioso, 2 - calmo, 3 - sonolento, 4 - dormindo com reflexo, 5 - dormindo sem reflexo) foram obtidos aos 0 (M0), 15 (M15), 30 (M30), 40 (M40), 50 (M50) e 60 (M60) minutos após a medicação. RESULTADOS: Nos grupos não houve alteração significante dos parâmetros respiratórios, hemodinâmicos e de temperatura. Houve diferença significante entre os grupos na ES (M60: M=C>P) e no BIS (M50 e M60: M=C>P). CONCLUSÕES: Nas condições utilizadas, a clonidina e o midazolam determinaram níveis de sedação adequados e semelhantes na medicação pré-anestésica de pacientes estado físico ASA I, quando avaliados pela escala de sedação e pelo índice bispectral, sem determinarem alterações hemodinâmicas e respiratórias.

Estudo comparativo entre parto normal e a anestesia para a cesariana em cães: estudo clínico e cardiorrespiratório na mãe e no feto

Pós-graduação em Medicina Veterinária - FMVZ

Avaliações clínicas e laboratoriais da intoxicação experimental por veneno de sapo em cães

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Postoperative pain control in cats: clinical trials with pre-emptive lidocaine epidural co-administered with morphine or methadone

To evaluate the effectiveness of epidural lidocaine in combination with either methadone or morphine for postoperative analgesia in cats undergoing ovariohysterectomy. Under general anesthesia, 24 cats that underwent ovariohysterectomy were randomly allocated into three treatments groups of eight each. Treatment 1 included 2% lidocaine (4.0 mg/kg); treatment 2 included lidocaine and methadone (4.0 mg/kg and 0.3 mg/kg, respectively); and treatment 3 included lidocaine and morphine (4.0 mg/kg and 0.1 mg/kg, respectively). All drugs were injected in a total volume of 0.25 ml/kg via the lumbosacral route in all cats. During the anesthetic and surgical periods, the physiological variables (respiratory and heart rate, arterial blood pressure and rectal temperature) were measured at intervals of time zero, 10 mins, 20 mins, 30 mins, 60 mins and 120 mins. After cats had recovered from anesthesia, a multidimensional composite pain scale was used to assess postoperative analgesia at 2, 4, 8, 12, 18, and 24 h after epidural. The time to first rescue analgesic was significantly (P <0.05) prolonged in cats that received both lidocaine and methadone or lidocaine and morphine treatments compared with those that received the lidocaine treatment. All cats that received lidocaine treatment alone required rescue analgesic within 2 h of epidural injections. All treatments had significant cardiovascular and respiratory changes but they were within acceptable range for healthy animals during the surgical period. The two combinations administered via epidural allowed ovariohysterectomy with sufficient analgesia in cats, and both induced prolonged postoperative analgesia.