Recent advances in autonomic function tests of the cardiovascular system in children

Recent advances in computer technology have made it possible to noninvasively determine fast and dynamic changes in autonomic nervous activity in humans. Power spectral analysis of heart rate variation, beat-to-beat blood pressure analysis, skin blood flow by the laser Doppler technique, sensitive sudorometry and direct measurement of sympathetic nervous discharge have been successfully applied in adults, but there are still only few studies reported in children and adolescents. This article reviews the usefulness of these autonomic function tests in the pediatric field including reliability and methodological limits. Power spectral analysis of heart rate variability seems to be a new potential method, but there have been only few studies in children. Orthostatic maneuvers with noninvasive beat-to-beat measurement of finger arterial pressure, especially during active standing, is useful for the evaluation of orthostatic intolerance in children as well as adults with autonomic failure. A new pharmacological method using multiple autonomic agents might indicate a more precise information including alpha- and beta-adrenoceptor sensitivity. It should be realized that a single test cannot identify impaired autonomic functions, and a combination of several autonomic tests should be employed. Moreover, age-related changes and racial differences in autonomic function should be considered when interpreting obtained results

Cardiovascular, respiratory and metabolic responses to temperature and hypoxia of the winter frog Rana catesbeiana

The objective of the present study was to determine the effects hypoxia and temperature on the cardiovascular and respiratory systems tems and plasma glucose levels of the winter bullfrog Rana calesbeiana. Body temperature was maintained at 10, 15, 25 and 35 degrees Celsius for measments of breathing frequency, heart rate, arterial blood pressure metabolic rate, plasma glucose levels, blood gases and acid-base status. Reducing body temperature from 35 to 10 degrees Celsius decreased (P<0.001) heart rate (bpm) from 64.0 ñ 3,1 (N =5) to 12.5 + 2.5 (N = 6) and blood pressure (mmHg) (P<0.05) from 41.9 ñ 2.1 (N = 5) to 33.1 ñ 2.1 (N = 6), whereas no significant changes were observed under hypoxia. Hypoxia-induced changes in breathing frequency and acid-base status were proportional to body ternperature, being pronounced at 25 degrees Celsius less so at l5 degrees Celsius, and absent at 10 degrees Celsius. Hypoxia at 35 degrees Celsius was lethal. Under normoxia, plasma glucose concentration (mg/dl) decreased (P<0.01 from 53.0 ñ 3.4 (N = 6) to 35.9 ñ 1.7 (N = 6) at body temperatures 35 and 10 degrees Celsius, respectively. Hypoxia had no significant effect on plasma glucose concentration at 10 and 15 degrees Celsius, but a 25 degrees Celsius there was a significant increase under conditions of 3 per cent inspired O2. The arterial PO2 and pH values were similar to those reported in previous studies on non-estivating Rana calesbeiana, but PaCO2 (37.5 ñ 1.9 mmHg, N = 5) was 3-fold higher, indicating increased plasma bicarbonate levels. The estivating bullfrog may be exposed not only to low temperatures but also to hypoxia. These animals show temperature-dependent responses that may be beneficial since during low body temperatures but also to hypoxia. These animals show temperature-dependent responses that may be beneficial since during low body temperatures the sensitivity of most physiological systems to hypoxia is reduced.

Aplicaciones clínicas de sistemas de indexación / Clinical applications of indexation systems

The clinical applications of standarized physiological functions such as cardiovascular, respiratory and renal systems are discussed

Preoptic-periventricular tissue (AV3V): central cholinergic-induced hydromineral and cardiovascular responses, and salt intake

The periventricular tissue of the anterior ventral portion of the third ventricle (AV3V) is an important area for the control of hydromineral balance and of cardiovascular function. The present work discusses the importance of the integrity of the AV3V for multiple responses to central cholinergic activation (water intake, hypertension, natriuresis, salivation) and for the control of salt intake.

Uso racional de la hemodilución / How to use hemodilution rationally

La pérdida perioperatoria excesiva de sangre ha sido siempre una complicación que pone en peligro de vida. Los médicos han intensificado los esfuerzos para minimizar las necesidades de productos sanguíneos, al aceptar un volumen globular más bajo para pacientes quirúrgicos. La hemodilución normovolémica aguda (HNA) consiste en la dilución del volumen eritrocítico (anemia dilucional) reemplazada por un sustituto libre de células, para mantener un volumen intravascular cercano a lo normal; pero sometiendo al sistema cardiovascular a adaptaciones para poder mantener su homeostasis. En esta revisión se considerarán los mecanismos y sus implicancias fisiológicas. Además se analizarán los distintos sustitutos y sus propiedades.

Las matemáticas y el corazón / Mathematics and the heart

El modelado matemático en las ciencias biomédicas es especialmente difícil, debido a la gran cantidad de variables que el proceso biológico implica, a la dificultad de observación y experimentación y a la escasez de herramientas matemáticas capaces de incorporar a todas estas variables. A pesar de estas dificultades, hay modelos matemáticos de algunos fenómenos biológicos. Los que existen son modelos reduccionistas, modelos estructurales y modelos de intregración. Los modelos teóricos en biología se diseñan con propósitos claramente definidos y pueden abarcar los distintos niveles del fenómeno biológicos, desde el molecular hasta el organismo intacto. Definir claramente las variables que conforman los niveles y las relaciones entre ellas, permite estructurar un modelo útil. El corazón, tanto sano como enfermo, es un órgano susceptible a ser modelado matemáticamente por sus aspectos observables y medibles, como son la periodicidad, los patrones de activación, las relaciones entre variables conocidas y la estructura. Se mencionan algunos ejemplos. El modelado matemático del corazón puede servir para orientar a la investigación hacia elementos faltantes, para integrar los conocimientos existentes y como apoyo de la terapéutica

Neuropeptide control of the cardiovascular system in fish and reptiles

Accumulating evidence shows the involvement of neuropeptides in cardiovascular control in mammals as well as non-mammalian species. Our own immunohistochemical studies indicate a sparse innervation only in cyclostomes, holostean fish and lungfish, a more extensive variation and distribution in elasmobranchs and teleosts, and a rich and varied innervation of the cardiovascular system in crocodiles and lizards. Vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), gastrin releasing peptide (GRP) and tachykinins are present in most vertebrate groups. VIP is vasodilatory in the Atlantic cod (Gadus morhua) as in most mammalian species, but increases gut vascular resistance in the spiny dogfish (Squalus acanthias). NPY potentiates the effect of noradrenaline on skate (Raja rhina) coronary vessels, suggesting an interaction between adrenergic mechanisms and NPY early in evolution, but studies in the spiny dogfish and the crocodile also demonstrate different mechanisms for the action of NPY and adrenaline in some species. Bombesin/GRP increases flow to the gut in the spiny dogfish by an increase in somatic vascular resistance, while visceral resistance remains unchanged. In the caiman (Caiman crocodylus crocodylus) bombesin causes a shunting of blood from the lung to the gut. Substance P and other tachykinins in general increase flow to the gut, and on some occasions also increase somatic blood flow. Flow in the anastomosis of the crocodile (Crocodylus porosus) gut is increased by substance P. The results presented here are a review of several published and unpublished studies.

Cardiovascular effects of adrenomedullin in teleost fishes

Adrenomedullin is a fifty-two-amino acid polypeptide that was first discovered in pheochromocytoma cells, and later in the normal adrenal medullae, lungs, kidneys, and blood. In mammals, adrenomedullin has vasodepressive effects, mainly by decreasing peripheral vascular resistance. I investigated the effects of adrenomedullin in fish to see if this novel neuropeptide would have an effect in lower vertebrates, or if its actions were limited to the higher vertebrates. Bolus injections of adrenomedullin resulted in a reduction of heart rate and dorsal aortic pressure in the rainbow trout Oncorhynchus mykiss. However, adrenomedullin had no effect in the Atlantic cod, Gadus morhua. The effects of adrenomedullin in trout appear to be due to a direct action on the peripheral vasculature, as pre-treatment of celiac artery strips with tetrodotoxin had no effect on the ability of adrenomedullin to relax the strip.

Cardiovascular measurements in animals in the milligram range

The study of microscopic animals should be intensified because: most of the world's animal biomass consists of very small animals; life as a small animal is both qualitatively and quantitatively very different from that of a large animal; and almost all animals are very small as they begin their development. Fortunately, developing technology now allows us to make quantitative measurements in microscopic animals. This paper describes new techniques for measuring cardiovascular variables such as blood pressure, stroke volume, heart rate and cardiac output in animals weighing as little as a few mg. Non-invasive techniques such as videomicroscopy can be used for determining heart stroke volume in small animals. Impedance measurement is another non-invasive or minor invasive technique for determining rates of heart beat, gill or lung ventilation and limb movement as well as giving qualitative information on changes in blood flow. Pulsed Doppler technology can be used to obtain blood flow velocity in small vessels. Invasive techniques depend on servo-null micropressure systems that record pressure through glass microelectrodes that are implanted into the vessel or heart lumen. This allows stable pressure recordings for up to 5-6 h in animals weighing as little as a few mg. Microinjectors can be used for intravascular injections of vasoactive drugs (or blood withdrawals). Newly emerging techniques for in vivo cardiovascular measurements allow us to understand the function of the cardiovascular system in a larger portion of the world's animal biomass, as well as in the immature and as yet poorly understood early developmental stages of animals.

Aplicaciones anestesiológicas del óxido nítrico y sus inhibidores / Anesthesiological applications of nitric oxid and its inhibitors

El Oxido Nítrico, un gas inestable con características de radical libre, es sintetizado por bacterias como también lo es por los macrófagos humanos. Inicialmente, fue conocido como Factor de Relajación Endotelial, ahora clasificado como neurotransmisor No-típico no sólo debido a sus características estructurales, sino a su peculiar mecanismo de acción. En esta breve revisión, nosotros pondremos énfasis a las aplicaciones anestesiológicas del Oxido Nítrico y sus inhibidores

Evaluation of cardiovascular autonomic functions compared with clinical response in patients with malignant lymphomas before and after chemotherapy

54 patients presented with malignant lymphoma [20 cases with Hodgkin's disease, 11 with low grade non-HodgKin's lymphoma and 23 with high grade non-Hodgkin's lymphoma] were studied. All had advanced disease [stage II B, III and IV], requiring combination chemotherapy which included the use of vinca alkaloids. Clinical assessment and standard cardiovascular autonomic function tests were carried out prior to and following completion of chemotherapy treatment and 8 weeks after whenever possible. At presentation forty patients 40/54 [74%] had abnormal cardiovascular autonomic function tests and there was no correlation with the presence or absence of mediastinal disease. Significant improvement in autonomic scores at the end of treatment were recorded in 26/40 [65%] patients despite the use of drugs with known neurocardiac toxicity, but others 14/40 [35%] showed residual abnormalities of cardiovascular autonomic functions despite clinical resolution of the disease. After 8 weeks from completion of chemotherapy treatment autonomic scores showed further improvement in four patients [complete remission was achieved]. It was suggested that subclinical autonomic dysfunction is common in patients with malignant lymphoma and probably it may represent a paraneoplastic syndrome rather than toxic effects of the drugs used, but its pathogenesis and prevalence of which deserve further study. This phenomenon may predispose the patients with lymphoma to develop other autonomic dysfunction in gastrointestinal and genitourinary tract and should be considered during the evaluation of neurotoxicity of chemotherapy regimens used

Respuesta cardiovascular al ejercicio a gran altura en trabajadores crónicamente expuestos a hipoxia hipobárica intermitente / Cardiovascular response to exercise at high altitude in chronically exposured workers to intermittent hypobaric hypoxia

The isottonic work perfomance was assessed in 34 workers aged 35 ñ 5.8 years old that had working of four days at 4500 m over the sea level and resting periods of other four days at the sea level during at least two years. Subjects were assessed in one occasion at the sea level, and at the first and fourth day of the working shift at 4500 m over the sea level. resting arterial oxygen saturation in theses three periods was 97 ñ 1.1, 88 ñ 18 and 91 ñ 1.1 percent respectively (p<0.01) and markedly decreased during maximal and submaximal exercise at 4500 m over sea level. Evercise duration in the three periods was 931 ñ 210, 775 ñ 105 and 778 ñ 105 seg respectively (p<0.001). Heart rate in the resting period was at least 10 percent higher and maximal and submaxilmal rates were lower at the high altitude. No differences in blood pressure or packed red cell volume were observed. Exercise duration correlated inversely with age (r=-0.49 p=0.03) and directly with maximal heart rate (r=0.44 p=0.009) at the sea level. No correlation between aerobic capacity and other measured parameters was observed. These results show no differences in the cardiovascular response to exercise between the first and fourth day of stay at high altitude in workers chronically exposed to intermittent hypobaric hypoxia

Microneurografia: técnica para estudo da regulaçäo cardiovascular pelo sistema nervoso simpático em humanos / Microneurography: technique to study cardiovascular regulation through the sympathetic nervous system in humans

A microneurografia é um método eficaz e seguro para o registro intraneural direto da atividade nervosa simpática para o músculo e para pele em humanos. A técnica e suas aplicaçöes para o estudo da funçäo autonômica seräo discutidos neste artigo. Será abordada a regulaçäo da atividade nervosa simpática em diferentes situaçöes clínicas e/ou estímulos, tais como hipertensäo arterial essencial, hipertensäo experimental por mineralocorticóide, exercício, estresse mental, teste do gelo, hiperinsulinemia e ingestäo oral de álcool

Insuficiência cardíaca congestiva / Congestive cardiac failure

A presente revisao aborda os principais mecanismos fisiopatológicos e os sintomas e sinais característicos da insuficiência cardíaca crônica ou congestiva. Considerando-se que esta é uma síndrome de natureza complexa, e que causa desarranjo funcional em múltiplos sistemas biológicos, até os dias de hoje persistem dúvidas a respeito da importância relativa de vários mecanismos fisiopatológicos responsabilizados pelas suas manifestaçoes clínicas. Assim sendo, o tema é objeto de intensa investigaçao, de natureza multidisciplinar, no sentido de melhor se conhecer, nos diferentes níveis de organizaçao biológica (molecular, celular, organismo, sistemas), os processos fisiológicos implicados na gênese desta síndrome.

Atualizaçäo da classificaçäo de afogamento: avaliaçäo de 2304 casos em 20 anos / Up-to-dating of drowning classification: evaluation of 2304 cases in 20 years

O objetivo do estudo foi atualizar a classificaçao de afogamento utilizada durante 20 anos pelo Centro de Recuperaçao de Afogados (CRA - Rio de Janeiro), para que seja possível determinar de forma mais precisa o tratamento e o prognóstico desta condiçao clínica, de acordo com sua gravidade. Foi realizado um estudo retrospectivo de casos de afogamento ocorridos durante 20 anos (1972-1991), numa área restrita de 20km, entre as praias de Sao Conrado e Flamengo, no Rio de Janeiro. A área estudada representa aproximadamente 30 por cento de todos os casos que ocorrem nesta cidade. De um total de 41.279 resgates realizados nas praias pelos guarda-vidas, 2.304 casos necessitaram de atendimento médico no Centro de Recuperaçao de Afogados. A idade média foi de 22,75 anos (DP = 11,48) 98,7 por cento ocorreram em água do mar e 74,2 por cento eram do sexo masculino. Para a atualizaçao da classificaçao foram avaliados estatisticamente cinco parâmetros clínicos: ausculta pulmonar, necessidade de assistência ventilatória, status cardiovascular, nível de consciência e a presença de apnéia ou parada cardiorrespiratória. Todos estes parâmetros foram avaliados por médicos no primeiro atendimento. A revisao destes 2.304 casos de afogamento permitiu estabelecer uma atualizaçao (1992) da classificaçao de afogamento que vinha sendo utilizada há 20 anos pelos médicos do Centro de Recuperaçao de Afogados, a qual resultou na divisao abaixo, onde sao demonstradas sua freqüência, a mortalidade geral e no CRA e a necessidade de internaçao por mais de 12 horas.

Anestesia en el anciano

En los ultimos años y con el advenimiento de modernas técnicas y aparatos de anestesia, más los conocimientos a fondo de diversas enfermedades, el índice de la vía a aumentado a alrededor de 74 años en el hombre y 78 años en la mujer, por lo tanto existe un incremento en la supervivencia, dejando en apenas 2 por ciento las muertes debidas a accidentes anestésicos quirúrgicos. Los pacientes de la tercera edad (sobre 70 años), tienen cambios anatómicos y fisiológicos importantes, sobre todo el sistema cardiovascuar con una clara disminución en el flujo sanguineo, aumento de la rigidez miocárdica hipertrofias ventriculares, aumento de la tensión arterial, etc. el aparato respiratorio al igual que el sistema renal hepático, endócrino, sufren modificación con la senectud. el sistema nervioso es tan sensible en los ancianos que amerita un trato especial al usar las drogas anestésicas. Al llegar a esta época de la vida, se deven tener en consideración estos cambios al administrar anestésicos, es por eso que el paciente geriátrico debe tener un trato especial y un conocimiento adecuado de dosis y drogas por parte del anestesiologo.