Técnicas de titulación ácido-base: consideraciones metrológicas / Acid-base titration techniques: metrological considerations / Técnicas de titulação ácido-base: considerações metrológicas

Resumen Se evaluaron diferentes sistemas de medición para titulaciones ácido-base, con el propósito de determinar cuál presenta mejores características metrológicas. Estos sistemas incluyen volumetrías y gravimetrías, las cuales se combinaron con diferentes métodos de detección del punto de equivalencia: (i) potenciometría, (ii) indicador ácido-base y (iii) conductividad electrolítica. Este artículo propone una nueva aproximación para la estimación de la incertidumbre de medición asociada a la detección del punto de equivalencia. Los resultados indicaron que, para la determinación del punto de equivalencia, las incertidumbres más bajas se obtienen mediante el método potenciométrico en comparación con el método conductimétrico cuyo sesgo es hasta 78 veces mayor. Sin embargo, se encontró que el método potenciométrico es fuertemente dependiente de la resolución del instrumento y/o la cantidad de agente titulante que se adiciona en la cercanía al punto de equivalencia. También se encontró que la incertidumbre disminuye cerca del 40% empleando métodos gravimétricos en comparación con los volumétricos. Al realizar la evaluación del sesgo de los sistemas de medición acorde con la guía ISO 33:2015, los resultados mostraron que, de los métodos evaluados, el método gravimétrico con detección potenciométrica presentó las mejores características metrológicas, pues se obtuvieron sesgos e incertidumbres menores.

Abstract Different measurement systems for acid-base titrations were evaluated to determine which one had the best metrological characteristics. These systems included volumetric and gravimetric titrations, which were combined with different detection systems: (i) potentiometry, (ii) acid-base indicator, and (iii) electrolytic conductivity. This article proposes a new approach for estimating the measurement uncertainty associated with the detection of the equivalence point. The results showed that, for the determination of the equivalence point, the lowest uncertainties were obtained by the potentiometric method in comparison with the conductometric method, whose bias was 78 times higher. The potentiometric method, however, was strongly dependent on the instrument resolution and/or the titrant amount that is added close to the equivalence point. It was also found that uncertainty decreases about 40% using gravimetric methods as compared to volumetric methods. When performing bias evaluation of the measurement systems according to the ISO 33:2015 guide, results showed that, among the evaluated methods, the gravimetric method with potentiometric detection presented the best metrological characteristics, with the lowest biases and uncertainties.

Resumo Foram avaliados diferentes sistemas de medida para titulações ácido-base, a fim de determinar quais possuem as melhores características metrológicas. Estes sistemas incluem titulações e gravimétricas, que foram combinadas com diferentes sistemas de detecção do ponto de equivalência: (i) potenciometria, (ii) indicador ácido-base e (iii) condutividade electrolítica. Este artigo propõe uma nova abordagem para estimar a incerteza de medição associada à detecção do ponto de equivalência. Os resultados indicaram que, para a determinação do ponto de equivalência, as incertezas mais baixas são obtidas pelo método potenciométrico enquanto que a incerteza do método condutométrico é até 78 vezes maior que a obtida pela potenciometria. Além disso, a potencimetria é altamente dependente da resolução do instrumento e/ou da quantidade de titulante para ser adicionado na proximidade com o ponto de equivalência. Também verificou-se que a incerteza diminui em torno de 40% utilizando métodos gravimétricos. De acordo à guia de norma ISO 33:2015, os resultados mostraram que os métodos de titulação ácido-base avaliados gravimetricamente com detecção potenciométrica proporcionaram as melhores características de metrologia, porque obtiveram os menores distorções e incertezas.

Descripción anatómica, clínica y sobrevida de los pacientes con atresia pulmonar que han sido llevados a angioplastia con stent en el ductus arterioso persistente en el periodo 2009-2014 / Anatomical and clinical description and survival of patients with pulmonary atresia subjected to angioplasty with ductal stent in the period 2009-2014

Resumen Objetivo: describir las características anatómicas, la evolución clínica y la sobrevida de los pacientes con atresia pulmonar que han sido llevados a angioplastia con stent en ductus arterioso persistente y determinar si existen diferencias significativas en la saturación al inicio y final del procedimiento y a las 6, 12 y 24 horas posprocedimiento. Materiales y métodos: estudio analítico, descriptivo tipo cohorte. La población de estudio se tomó de las bases de datos del servicio de Cardiología pediátrica de una institución especializada en la ciudad de Bogotá, Colombia. Se incluyeron pacientes con diagnóstico de atresia pulmonar sometidos a angioplastia, en tanto que se excluyeron aquellos con cirugía cardiovascular previa. El análisis estadístico se realizó en STATA® 12,0, mediante estadística descriptiva, curvas de Kaplan-Meier y ANOVA de medidas repetidas. Resultados: se identificaron 237 pacientes con atresia pulmonar. Se seleccionaron 30 de los cuales se excluyeron 5. En total se construyó una cohorte de 25 pacientes que fueron llevados a angioplastia, 52% con atresia pulmonar con comunicación interventricular. Edad promedio 12,2 días, peso 2.698 g, diámetro del DAP 3,8 mm (DE = 1,1), índice de McGoon media 1,35. El implante del stent fue exitoso en todos los pacientes; sin embargo 2 fallecieron en la sala de procedimientos y uno durante las 6 horas siguientes. Las complicaciones más frecuentes fueron paro cardiorrespiratorio (n = 2), trombosis del stent (n = 2) y bacteriemia (n = 2). La mortalidad a 30 días fue del 28% (n = 7); durante el tiempo total fue del 36% (n = 9). Por medio del ANOVA no se encontraron diferencias significativas en los promedios de saturación en los cinco tiempos de interés. Conclusiones: la atresia pulmonar es una patología compleja que requiere intervención invasiva para el mantenimiento de la capacidad circulatoria de los pacientes. Este estudio muestra que a pesar de una intervención efectiva, la mortalidad a los 30 días es elevada. No se encontraron diferencias en los tiempos de saturación, lo que sugiere que mantiene la saturación de los pacientes de una forma no distinta que con la prostaglandina E (PGE1) pero garantiza la permeabilidad del ductus.

Abstract Objective: the aim of this study is to describe the anatomical characteristics, the clinical progression, and survival of patients with pulmonary atresia subjected to angioplasty with a stent in patent ductus arteriosus (PDA), and to determine if there are significant difference in the saturation at the beginning and the end of the procedure, and at 6, 12, and 24 hours after the procedure. Materials and methods: An analytical and descriptive cohort study was conducted on a population taken from the database of a Paediatric Cardiology Department of a specialised institution in the city of Bogota, Colombia. Patients with pulmonary atresia subjected to angioplasty were included, and those with previous cardiovascular were excluded. The statistical analysis was performed using STATA® 12.0, by means of descriptive statistics, Kaplan-Meier curves and repeated measurements ANOVA. Results: A total of 237 patients with pulmonary atresia were identified. Of the 30 that were selected, 5 were excluded, leaving a total of 25 patients that were subjected to angioplasty. Interventricular communication was observed in 52%. The mean age was 12.2 days, with a mean weight of 2.698 g, a mean PDA diameter of 3.8 mm (SD = 1.1), and a mean McGoon index of 1.35. Although the stent implant was successful in all patients, two died in the procedures room, and another one during the following 6 hours. The most common complications were, cardiorespiratory arrest in 2 patients, thrombosis of the stent in 2, and bacteraemia in two patients. The mortality at 30 days was 28% (7), and 36% (9) during the total time. Using ANOVA, no significant differences were found in the saturation means at the five times of interest. Conclusions: Pulmonary atresia is a complicated condition that requires invasive intervention in order to maintain the circulatory capacity of the patients. This study shows that, despite an effective intervention, the 30-day mortality is elevated. No differences were, found in the saturation times, which suggest that saturation is maintained in the patients in a way not unlike that with prostaglandin E (PGE1), but ensures the patency of the ductus.

Lower mini-sternotomy in congenital heart disease: just a cosmetic improvement?

OBJECTIVES: Lower mini-sternotomy represents a minimally invasive surgical technique that has been utilized for the repair of a wide variety of congenital heart defects with excellent surgical and cosmetic outcomes. However, clinical improvements provided for this technique beyond cosmetic results are controversial. The aim of our study is to report our results with lower mini-sternotomy for the repair of congenital heart malformations and compare them with a matched group with a full median sternotomy approach. METHODS: From 2010 through 2013, 105 consecutive congenital patients (81 paediatric) underwent lower mini-sternotomy at our centre (Group 1). We analysed in-hospital and follow-up outcomes, and compare them with an age-sex-diagnosis-type of surgery-matched group (Group 2). Both groups were managed following the same clinical protocols. RESULTS: In Group 1, age at the time of surgery was 12 ± 17 years (range from 0.2 to 64.6 years). In this group, 81 patients were paediatric and 62 were female. Operative techniques were atrial septal defect (n = 72), ventricular septal defect (n = 24) and atrioventricular canal repairs (n = 9). There were no deaths or major in-hospital complications. Two adult patients required conversion to full median sternotomy. For a medium follow-up of 1.5 years (range from 1 month to 5 years), there were no deaths, reinterventions or reoperations and no significant residual defects were found. Compared with Group 2, patients in Group 1 had longer cardiopulmonary bypass times (58.71 ± 19.08 vs 45.39 ± 20.45, P < 0.001) and cross-clamp times (32.75 ± 13.11 vs 23.22 ± 13.93, P < 0.001), higher rate of early extubation (96 vs 85%, P = 0.018) and lower rate of postoperative complications (11.6 vs 22.3%, P = 0.034). CONCLUSIONS: At our centre, lower mini-sternotomy represents a safe alternative for the repair of congenital heart defects in paediatric and adult populations. Cardiopulmonary bypass and cross-clamp times were longer in the mini-sternotomy group. However, these patients showed earlier extubation and less postoperative complications when compared with patients with a full sternotomy approach. Combined with improved cosmetic outcomes, lower mini-sternotomy could represent the technique of choice for these populations.

Valve-sparing tetralogy of Fallot repair with intraoperative dilation of the pulmonary valve.

Deleterious long-term effects of pulmonary regurgitation after tetralogy of Fallot (TOF) repair have become evident during the last two decades. Subsequently, different groups have developed strategies aimed at preserving the pulmonary valve function. However, the results of these approaches are not well known. From July 2009 through March 2012, 38 patients underwent primary repair of TOF at the authors' institution. Of these, 12 children (7 boys) underwent attempted pulmonary valve-sparing surgery with intraoperative dilation of the pulmonary valve. The technical details as well as the echocardiographic preoperative and follow-up data for this repair were recorded, with a special focus on the feasibility of the technique and the effects on pulmonary valve function. No patient in the series died. At repair, the median age was 6 months (range 3.4-126 months), and the median weight was 7.6 kg (range 4.7-47 kg). Intraoperative dilation of the pulmonary valve was technically feasible for all the patients. Two patients had unsuccessful dilation and underwent a transannular patch procedure. During a median follow-up period of 22 months (range 6-30 months), the pulmonary valve diameter and z-score improved significantly. Moreover, the annular size normalized, whereas the mean right ventricular outflow tract (RVOT) gradient remained at the mild level (median, 24 mmHg; range 12-36 mmHg). At the most recent follow-up evaluation, three patients showed moderate pulmonary regurgitation. Intraoperative dilation of the pulmonary valve in patients undergoing TOF repair is feasible and provides good relief of obstruction. Moreover, the pulmonary valve annulus grows through the follow-up period. Longer follow-up studies are needed to evaluate the exact role of this strategy in this population.