Signal processing and machine learning algorithm to classify anaesthesia depth.

BACKGROUND: Poor assessment of anaesthetic depth (AD) has led to overdosing or underdosing of the anaesthetic agent, which requires continuous monitoring to avoid complications. The evaluation of the central nervous system activity and autonomic nervous system could provide additional information on the monitoring of AD during surgical procedures. METHODS: Observational analytical single-centre study, information on biological signals was collected during a surgical procedure under general anaesthesia for signal preprocessing, processing and postprocessing to feed a pattern classifier and determine AD status of patients. The development of the electroencephalography index was carried out through data processing and algorithm development using MATLAB V.8.1. RESULTS: A total of 25 men and 35 women were included, with a total time of procedure average of 109.62 min. The results show a high Pearson correlation between the Complexity Brainwave Index and the indices of the entropy module. A greater dispersion is observed in the state entropy and response entropy indices, a partial overlap can also be seen in the boxes associated with deep anaesthesia and general anaesthesia in these indices. A high Pearson correlation might be explained by the coinciding values corresponding to the awake and general anaesthesia states. A high Pearson correlation might be explained by the coinciding values corresponding to the awake and general anaesthesia states. CONCLUSION: Biological signal filtering and a machine learning algorithm may be used to classify AD during a surgical procedure. Further studies will be needed to confirm these results and improve the decision-making of anaesthesiologists in general anaesthesia.

Decisión Making, Stress Assessed by Physiological Response and Virtual Reality Stimuli / Toma de Decisiones, Estrés Valorado mediante la Respuesta Fisiológica y Estímulos en Realidad Virtual

Abstract Many decisions must be made under stress; therefore, stress and decision-making are intrinsically related not only at the behavioral level but also at the neural level. Additionally, virtual reality tools have been proposed as a method to induce stress in the laboratory. This review focuses on answering the following research question: Does stress assessed by physiological variables of a subject under virtual reality stimuli increase the chances of error in decision-making? The reviewed studies were consulted in the following databases: PubMed, IEEE Xplore, and Science Direct. The analysis of the consulted literature indicates that the stress induced in the laboratory using virtual reality tools and the physiological response of the central and autonomous nervous system are complementary subjects and allow the design of training and support systems for the decision-making process.

Resumen Muchas decisiones deben tomarse bajo estrés, por lo tanto, el estrés y la toma de decisiones están intrínsecamente relacionados, no solo a nivel conductual sino también a nivel neural. Además, las herramientas de realidad virtual se han propuesto como un método para inducir estrés en el laboratorio. El presente trabajo de revisión temática se centra en responder la siguiente pregunta de investigación: ¿El estrés evaluado mediante variables fisiológicas de un sujeto bajo estímulos de realidad virtual aumenta las posibilidades de error en la toma de decisiones? Los estudios revisados fueron consultados en las siguientes bases de datos: PubMed, IEEE Xplore y Science Direct. El análisis de la literatura consultada indica que el estrés inducido en el laboratorio, por medio de herramientas de realidad virtual, y la respuesta fisiológica del sistema nervioso central y autónomo son temas que se complementan y permiten el diseño de sistemas de soporte y entrenamiento para el proceso de toma de decisiones.

Penetrating cardiac trauma in stab wounds: A study of diagnostic accuracy of the cardiac area.

BACKGROUND: Stab wounds (SW) to the thorax raises suspicion for cardiac injuries; however, the topographic description is variable. The present study aims to evaluate different topographical descriptions within the thorax and establish their diagnostic value in penetrating cardiac trauma by SW. METHODS: Medical records of all patients admitted to our center with thoracic SW from January 2013 to June 2016 were included in this study. Diagnostic value potential was measured using different areas of the thorax described in the literature. RESULTS: In this study, we analyzed 306 cases. Thirty-eight (12.4%) patients had a cardiac injury managed surgically. Death by cardiac injury occurred in seven (18.4%) patients. The cardiac area defined between the right mid-clavicle line until the left anterior axillary line, and between 2nd and 6th intercostal spaces was the more accurate. It has sensitivity of 97.3%, specificity 72%, positive predictive value 33%, negative predictive value 99.4% and accuracy 75.1% for penetrating cardiac trauma. ROC was 0.894 IC 95% (0.760-0.901). CONCLUSION: Among the thoracic areas, topographical limits between the right mid-clavicle line and the left anterior axillary line, and between 2nd and 6th intercostal spaces are the more accurate and are highly indicative of cardiac injury in patients with SW to the thorax.

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Letter to the Editor

Ensayo clínico cruzado y aleatorizado para comparar dos modelos farmacocinéticos de propofol usando índices de entropía / Randomized cross-over clinical trial comparing two pharmacokinetic models of propofol using entropy indices

Introduction: There are two different pharmacokinetic models (Marsh and Schnider) for the administration of total intravenous anesthesia with propofol, the parameter differences could have some impact over the depth of anesthesia. Objective: To determine if there is a significant difference in the variability of depth of anesthesia suggesting that one model is superior in achieving a more stable and predictable depth of anesthesia during surgery. Methods: A cross-over clinical trial was conducted on 16 healthy patients programmed for upper or lower limb ambulatory orthopedic surgery. Patients were randomly assigned to (i) effect site target controlled infusion of propofol with Marsh model at a target concentration of 2.5 μg/ml for 20 min, a 20 min washout, then propofol was administered with Schnider model at the same effect site target for the reminder of the surgery, or (ii) the reverse sequence. Differences in variability of depth of anesthesia, were assessed by comparing records of spectral entropy indices during surgery through an unpaired t-test. Results: There was no evidence of significant difference in the mean variances of either spectral entropy indices between the two models (p-value: 0.57 for State Entropy, p-value: 0.51 for Response Entropy). Conclusion: The study suggests that both pharmacokinetic models are equivalent in terms of stability of depth of anesthesia. It is important to keep testing determinants of the efficacy of the models in different types of population because their behavior according to individual characteristics of patients or variables such as cost-effectiveness could end up tilting the scale.

Introducción: Hay dos modelos farmacocinéticos diferentes para la administración de la anestesia total intravenosa con propofol (Marsh y Schnider), las diferencias entre los parámetros podrían tener algún impacto sobre la profundidad anestésica. Objetivo: Comparar la variabilidad de la profundidad anestésica durante administración de infusión de propofol con los modelos de Marsh y Schnider para determinar si hay diferencias significativas que sugieran que uno de los modelos es superior en lograr una profundidad anestésica más estable y predecible. Métodos: Estudio clínico cruzado, controlado y aleatorizado llevado a cabo en 16 pacientes programados para cirugía ambulatoria de ortopedia. Los pacientes fueron asignados aleatoriamente a i) infusión controlada por objetivo de propofol con el modelo de Marsh a una concentración objetivo en sitio de efecto de 2.5μg/ml durante 20 minutos, 20 minutos de periodo de lavado, seguido de infusión de propofol con modelo de Schnider a la misma concentración objetivo; o ii) la secuencia inversa. La diferencia en variabilidad de profundidad anestésica fue evaluada mediante la comparación de registros de índices de entropía con una prueba t no pareada. Resultados: No se encontró evidencia de diferencias significativas de la varianza media en los índices de entropía espectral asociada a los modelos (valor-p: 0.57 para entropía de estado, valor-p: 0.51 para entropía de respuesta). Conclusión: El estudio sugiere que ambos modelos son equivalentes en términos de estabilidad de profundidad anestésica. Es importante continuar estudiando la eficacia de los modelos en diferentes tipos de población, dado que su comportamiento según características individuales de los pacientes o variables cómo costo-efectividad podrían inclinar la balanza.