BRS estimation with sequence method improves with delayed time series, during supine position and orthostatism. Reduced BRS estimation error and recording time from this method could benefit studies with large populations or patients with low tolerance to orthostatism.

The inter beat interval (IBI) duration and systolic blood pressure (SBP) are cardiovascular variables related through several feedback mechanisms. We propose the analysis of diagonal lines in cross recurrence plots (CRPs) from IBI and SBP embedded within the same phase space to identify events where trajectories of both variables concur. The aim of the study was to describe the relationship between IBI and SBP of healthy subjects using CRP and diagonal analysis during baseline condition-supine position (SP)-and how the relationship changes during the physiological stress of active standing (AS). IBI and SBP time series were obtained from continuous blood pressure recordings during SP and AS (15 min each) in 19 young healthy subjects. IBI and SBP time series were embedded within a five-dimensional phase space using an embedding delay estimated from cross correlation between IBI and SBP. During SP, mean CRP showed high determinism (≥85%) and also brief but repeated events where both variables stay within a reduced space. Most quantitative recurrences analysis indexes of CRP increased significantly (p < 0.05) during AS. CRP analysis showed short diagonals indicating a very strong deterministic relationship between IBI and SBP with intermittent unlocking periods. The strength of IBI and SBP relationship increased during the physiological stress of AS. The CRP method allowed a rigorous quantitative description of the deterministic association between these two variables. Diagonal lines were intermittent and not always parallel, showing that there is not a defined and unique rhythm. This suggests the activation of different influences at different times and with different precedence between the heart rate and blood pressure in response to AS.

The assessment of spontaneous variability of blood pressure and heart rate is based on specific physiological hypotheses about dynamic features, for example, the baroreflex modulation of heart rate over time in daily life. Usually, arterial baroreflex control of heart rate is explored without delays between blood pressure and heart rate data points, within a narrow range of values, excluding the analysis of saturation regions or low-threshold changes. In this work, we examine the dynamic interactions between systolic blood pressure (SBP) and interbeat interval (IBI), in 15-min length time series and for the first time using the analysis of diagonals derived from a cross-recurrence plots in healthy persons and end-stage renal disease (ESRD) patients. We found that ESRD patients have stronger intermittent dynamical interactions between IBI and SBP, but they lose most of the dynamical interactions. Although healthy subjects exhibit a continuously changing order of precedence between IBI and SBP at different lags, ESRD patients preserve this changing order of precedence only for lags >0 beats. NEW & NOTEWORTHY This study is the first to compare the time-variant pattern of systolic blood pressure (SBP) and interbeat interval (IBI) coupling between ESRD patients and healthy volunteers through the analysis of diagonal in cross-recurrence plots, and in the face of an orthostatic challenge. Our results demonstrated alternant interactions on the order of precedence (IBI → SBP or SBP→ IBI) at different time delays. This pattern is different in resting position and during active standing for the two groups studied, and interestingly, some association patterns are lost in ESRD patients. These patterns of alternant interactions on the order of precedence could be related to autonomic neural activities and cardiovascular synchronization at different scales both in time and space. This could reflect physiological adaptive flexibility of cardiovascular regulation. Losing some association patterns in ESRD may be the result of chronic adjustments of many physiological mechanisms (including chronic sympathetic hyperactivity), which could increase cardiovascular vulnerability to hemodynamic challenges.

No abstract

Impaired baroreflex sensitivity (BRS) is partially responsible for erratic blood pressure fluctuations in End-Stage Renal Disease (ESRD) patients on chronic hemodialysis (HD), which is related to autonomic nervous dysfunction. The sequence method with delayed signals allows for the measurement of BRS in a non-invasive fashion and the investigation of alterations in this physiological feedback system that maintains BP within healthy limits. Our objective was to evaluate the modified delayed signals in the sequence method for BRS assessment in ESRD patients without pharmacological antihypertensive treatment and compare them with those of healthy subjects. We recruited 22 healthy volunteers and 18 patients with ESRD. We recorded continuous BP to obtain a 15-min time series of systolic blood pressure and interbeat intervals during the supine position (SP) and active standing (AS) position. The time series with delays from 0 to 5 heartbeats were used to calculate the BRS, number of data points, number of sequences, and estimation error. The BRS from the ESRD patients was smaller than in healthy subjects (p < 0.05). The BRS estimation with the delayed sequences also increased the number of data points and sequences and decreased the estimation error compared to the original time series. The modified sequence method with delayed signals may be useful for the measurement of baroreflex sensitivity in ESRD patients with a shorter recording time and maintaining an estimation error below 0.01 in both the supine and active standing positions. With this framework, it was corroborated that baroreflex sensitivity in ESRD is decreased when compared with healthy subjects.

RESUMENNumerosos autores recomiendan la realización de análisis toxicológico, prácticamente en todos los casos forenses, especialmente, cuando tras el examen macroscópico no aparece suficientemente aclarada la causa de la muerte.La ausencia de lesiones patognomónicas en la mayoría de las intoxicaciones avalan la recomendación anterior; sin embargo, en algunos casos los hallazgos en la autopsia son indicativos del agente causal. Así vemos como la coloración rojo cereza de las livideces cadavéri-cas van a ser muy sugestivas de intoxicación por monóxi-do de carbono o cianuro.Palabras clave: Intoxicacion por gases, monóxido de carbono, suicidio. Cuad Med Forense 2007; 13(47):65-69 ABSTRACTSeveral authors recommend to perform a toxicological analysis in practically every forensic autopsy, specifically when the macroscopical examination does not reveal sufficiently the cause of death.The absence of pathognomonic findings in the majority of poisonings support this recommendation. However; in some cases autopsy findings are indicative of the causative agent. For instance, the red cherry coloration from livor mortis are suggestive of a carbon monoxide or cyanide poisoning.

RESUMEN Los procesos de descomposición cadavérica dificultan, de forma muy importante, la labor del Médico Forense en el esclarecimiento de la causa de la muerte. Podemos decir, que esta dificultad es directamente proporcional al tiempo transcurrido entre la muerte y el hallazgo del cuerpo o de la práctica de la autopsia. En ocasiones, sin embargo, aparecen los fenómenos conservadores del cadáver que, de forma natural, retrasan o impiden el desarrollo de la putrefacción favoreciendo la investigación Forense. Los procesos naturales conservadores del cadáver son la momificación, saponificación y corificación. En el caso que presentamos se presentó denuncia en el Juzgado transcurridos diez meses de la muerte, procediéndose entonces a la exhumación y posterior autopsia. El cuerpo se encontraba saponificado parcialmente lo que ayudó en la investigación forense.

El trasplante de órganos es una de las aportaciones modernas más importantes de la Medicina a la sociedad, y en el curso de este procedimiento interactúan con frecuencia los médicos del equipo de trasplantes (MET) y los médicos forenses (MF), estableciéndose en ocasiones cuestiones o controversias poco comprendidas por el otro colectivo. Así, vemos que algunos MET piensan que aunque el número de negativas judiciales en la extracción de órganos sea pequeño, su trascendencia en el número de receptores es importante, pudiéndose establecer dudas sobre la justificación ética a que una posible sobreprotección de los procedimientos judiciales impida salvar vidas. También se da la circunstancia contraria: algunos MF opinan que el explante de órganos puede imposibilitar la determinación de la causa de la muerte en determinados casos. No son pocos, sin embargo, los facultativos de ambos equipos que opinan que los objetivos de la donación de órganos y la recolección de pruebas forenses no son mutuamente excluyentes. La comprensión de los problemas que se plantean, a una y otra parte, unido a un afán de colaboración adecuado, pueden disminuir el número de negativas. También, la inclusión del MF en los MET podría suponer una significativa mejora en el proceso, tanto médico como judicial, de la extracción y el trasplante de órganos, disminuyendo la negativa judicial de explante de órganos. Palabras clave: Muertes judiciales. Autopsia forense. Trasplante de órganos de cadáver. Especialista en Medicina Legal.