Characterization of heart rate variability in end-stage renal disease patients after kidney transplantation with recurrence quantification analysis.

Heart rate variability (HRV) is a noninvasive approach to studying the autonomic modulation of heart rate in experimental settings, such as active standing sympathetic stimulation. It is known that patients with end-stage renal disease during active standing have few changes in HRV dynamics, which are improved after hemodialysis. However, it is unknown whether the response to active standing is recovered after definitive treatment with kidney transplantation. This work aims to assess the change in HRV dynamics in the supine position and active standing through time and frequency-based metrics, as well as recurrence plot quantitative analysis (RQA). We studied HRV dynamics by obtaining 5-minute electrocardiographic recordings from kidney transplant recipients who underwent an active standing test. The mean duration of heartbeats and their standard deviation diminished in active standing, compared with the supine position. Also, the low-frequency component of HRV and the presence of diagonal and vertical structures in RQA were predominant. A larger estimated glomerular filtration rate was significantly correlated with broader HRV in the supine position and during active standing. The narrower HRV during active standing may indicate a sympathetic response to external stimuli, which is expected in a functional cardiovascular system, and may be influenced by renal function.

Evidencia del uso de metilxantinas en las exacerbaciones de la EPOC / Evidence for the use of methylxantines in exacerbations of COPD

Introducción: A las metilxantinas se les atribuyen efectos broncodilatadores, entre otros. Se recomiendan en la enfermedad pulmonar obstructiva crónica (EPOC) estable, cuando el tratamiento con β2 agonistas y anticolinérgicos no es suficiente para mejorar los síntomas, en los estadios más avanzados de la enfermedad y en las exacerbaciones. Objetivo: Conocer la evidencia que respalda el uso de metilxantinas en las exacerbaciones de la EPOC y otros beneficios, además de su efecto broncodilatador. Métodos: Búsqueda computarízada en Medline y EMBASE de estudios controlados aleatorízados que compararon las metilxantinas (teofilina oral, aminofilina o doxofilina intravenosa) contra placebo para la exacerbación aguda de la EPOC en enfermos atendidos en urgencias y en su hospitalización inmediata. Resultados: De 1,356 estudios de EPOC, sólo cinco cumplieron con los criterios de inclusión para el análisis. La evidencia obtenida fue la siguiente: Con respecto a la función pulmonar (VEF1, la mayoría de los estudios no encontraron mejoría significativa, sólo en uno se obtuvo mejoría al tercer día de tratamiento; otro estudio mostró disminución de la PaCO2 y ligero aumento del pH a las 12 h, en el grupo de aminofilina vs placebo. No hubo diferencias significativas en los días de hospitalización, calidad de vida y escalas de disnea. Las náuseas y el vómito fueron más frecuentes en el grupo de metilxantinas. Conclusiones: El uso basado en evidencias de metilxantinas en las exacerbaciones de la EPOC requiere de protocolos perfectamente estructurados, controlados y aleatorizados que muestren resultados estadísticamente significativos.

Introduction: Methylxantines are used for stable chronic obstructive pulmonary disease (COPD), when there is need for an additional drug besides β2 agonists and anticholinergics, in the more advanced stages of the disease and during acute exacerbations. Among other effects, methylxantines are said to have bronchodilator properties. Objective: To review the evidence supporting the use of methylxantines during acute exacerbations of COPD , and the presence of other beneficial properties besides their bronchodilator effects. Method: Medline and EMBASE computer search for aleatorized controlled studies comparing methylxantines (oral theophylline, intravenous aminophylline or doxophylline) vs placebo. Results: Only five of 1,356 published studies fulfilled the inclusion criteria. The evidence showed no significant improvement in FEV1 only one study showed a 70 vs 40 mL improvement on day 3; there was also decrease in the PCO2 and slight increase in the pH 12 hours after the use of aminophylline. There was no significant improvement in length of stay, quality of life nor dyspnoea scales. Nausea and vomiting were more frequent in the methylxantine group. Conclusions: We need properly structured protocols with statistically significant results, to define the evidence based place for the use of methylxantines in the treatment of acute exacerbations of COPD.