Development of a Software to Determine Disturbances in the Acid-Base Balance in Human Blood
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NOTA TÉCNICA Vol. 34, No. 2, Agosto 2013, pp. 175-191 Development of a Software to Determine Disturbances in the Acid-Base Balance in Human Blood A. Reyes-Lazalde∗ ABSTRACT ∗∗ M. Reyes-Monreal In intensive care units, one of the most frequent emergencies occurring ∗ M.E. Pérez-Bonilla in patients in critical condition is acid-base imbalance. The ability ∗ R. Reyes-Luna to proficiently manage such patients is achieved through many years of hospital practice. The correct quantification of such imbalances ∗ Laboratorio de Biología allows for the detection of complex alterations. Although this area Interactiva, Escuela de is fundamental for the clinical management of many patients, non- Biología, BUAP. Blvd. specialist doctors rarely receive the appropriate training. In addition, Valsequillo y Av. San Claudio, the learning required to master this area is difficult for doctors due Edificio 112-A, Col. Jardines to the level of mathematics involved. There are two online support de San Manuel. CP. 72570, programs available on the internet for determining blood pH based on Puebla, Pue. the Stewart Model, along with a spreadsheet for the patient’s collected ∗∗ Dirección General de data. Generally, the calculation of hydrogen ion concentration [H+] Innovación Educativa, BUAP. uses a table of equivalences between pH y [H+] for discontinuous values Blvd. Valsequillo y Av. San of pH, with the Davenport diagram used manually. However, none Claudio, Edificio 1AUB, Col. of these programs unite the methods of classic calculus, chemistry Jardines de San Manuel. CP. and physicochemistry. This study develops software for the teaching 72570, Puebla, Pue. and calculation of acid-base imbalance that combines all the relevant methods, such as the Henderson-Hasselbalch equation, the Siggard- Anderson modified excess base equation, the anion gap calculation, the computational implementation of the Davenport diagram, the calculus of [H+] for any value of pH, the calculus for the compensatory process, and the Stewart Model. The combined use of these methods is complementary, synergic and permits a preliminary diagnosis that interprets and understands both respiratory alterations and miniscule metabolic or mixed alterations. With this software, a doctor can identify acid-base imbalances and the occurrence of compensatory processes, such as the concentration of acid or base, in order to restore pH, while many simulations of clinical cases can be carried out in the classroom for medical training purposes. Keywords: acid-base, base excess, Stewart model, anion gap, medical education. 176 Revista Mexicana de Ingeniería Biomédica · volumen 34 · número 2 · Agosto, 2013 Correspondencia: RESUMEN Arturo Reyes Lazalde 15 Pte. No. 1102-A, Col. Álvaro En las unidades de cuidados intensivos, una de las emergencias más Obregón, Atlixco, Puebla, CP: frecuentes de los pacientes en estado crítico es el trastorno del equilibrio 74260. Tel. (01 222) 2295500 ácido-base sanguíneo. El manejo adecuado de estos pacientes se alcanza Ext. 7072 en la práctica hospitalaria después de varios años. La cuantificación Correo electrónico: correcta de estos desequilibrios permite detectar alteraciones complejas. [email protected] No obstante que el tema es fundamental para el manejo clínico de muchos pacientes, los médicos no especializados pocas veces cuentan Fecha de recepción: con este tipo de entrenamiento. Por otro lado, el aprendizaje del 23 de Noviembre de 2012 tema resulta difícil para los médicos debido a las matemáticas que Fecha de aceptación: están involucradas. En Internet existen dos programas online de apoyo 11 de Junio de 2013 para determinar el pH sanguíneo basados en el modelo de Stewart y una hoja de cálculo para el concentrado de datos del paciente. Generalmente, para el cálculo de hidrogeniones [H+] se utiliza una tabla de correspondencia entre el pH y [H+] para valores de pH discontinuos y el diagrama de Davenport es utilizado de manera manual. Sin embargo, ninguno de estos programas reúne los métodos de cálculo clásico, químico y fisicoquímico. En este trabajo se desarrolló un software para la enseñanza y el cálculo de las alteraciones ácido-base que conjunta todos los métodos como la ecuación de Henderson-Hasselbalch, la ecuación modificada de exceso de base de Siggard-Andersen, el cálculo de la brecha aniónica, la implementación en la computadora del diagrama de Davenport, el cálculo de [H+] para cualquier valor de pH, el cálculo de los procesos de compensación y el modelo de Steward. El uso conjunto de estos métodos es complementario, sinérgico y permite un diagnóstico preliminar que comprende alteraciones respiratorias y de manera minuciosa alteraciones metabólicas o mixtas, Con este software, el médico puede determinar desordenes del equilibrio ácido-base, la existencia de procesos compensatorios así como la concentración de ácido o de base para restaurar el pH y en el módulo de enseñanza se pueden realizar numerosas simulaciones de casos clínicos para el entrenamiento médico. Palabras clave: ácido-base, exceso de base, modelo de Stewart, brecha aniónica, educación médica. INTRODUCTION Compensatory physiological processes and Acid-base alterations commonly present in mixed acid-base imbalances may complicate patients found in intensive care units [1]. Various diagnosis and, consequently, the patient’s organs are involved in the regulation of acid-base treatment [3]. For this reason, the correct and for this reason intensivist doctors are experts quantification of this imbalance, which permits in the diagnosis and management of complicated the detection of complex metabolic alterations, alterations in acid-base balance [2]. In clinical is very important [4,5]. Consequently, the ability practice, when the acid-base imbalances in the to diagnose and manage acid-base alterations patient are severe, inappropriate and not rapidly rapidly and effectively is fundamental for the corrected, they can lead to the death of the treatment of seriously ill patients. The patient. doctor relies on laboratory data such as pH Reyes-Lazalde et al. Development of a Software to Determine Disturbances in the Acid-Base Balance in Human Blood 177 and blood gases (various apparatus measure that is executable, easy to use, does not − the concentration of bicarbonate [HCO3 ]), ion require an internet connection or another type concentration, glucose and routine tests such of software, and includes all the available as blood chemistry and complete blood count, calculation methods. amongst others. There are three specific methods for the If the doctor needs to carry out more quantification of acid-base distortions: (1) advanced studies with this data in order to the classic, (2) the chemical, and (3) the determine a complex metabolic alteration or physicochemical [2,8]. The first is based in the − a compensatory process, it is important that concentration of bicarbonate [HCO3 ], the second it is processed by a program designed to in base excess (BE)[9], and the third in strong ion calculate this data. Otherwise, it is necessary difference (SID)[10,11,12,13]. to use a scientific calculator and record the The classic method uses the Henderson- corresponding mathematical operations. In Hasselbalch (H-H) equation; which has a clinical these conditions, the simultaneous solution of value in two senses: (1) it determines whether various equations could become impossible. the laboratory results are correct, and (2) if the There is a vacuum of software for both the laboratory data are incomplete, this equation quantification of acid-base alterations and the males it possible to obtain the missing data teaching of it. In 1990, Siggaard-Andersen y - for example if the pH value and arterial Siggaard-Andersen [6] reported a program for pressure of carbon dioxide (PaCO2) are known, − PC that is executable using DOS version 2.11. it is possible to calculate [HCO3 ][14]. However, This program determined the partial oxygen with this method, it is not possible to precisely pressure (PaO2), which is the concentration measure metabolic imbalances. To resolve of O2 and acid-base state. However, this is this restriction, chemical and physicochemical not currently available and there exists no methods have been used and, in this sense, are update. There are only two programs for complementary. The former uses the standard the calculation of blood acid-base available base excess equation (SBE)[15], while the second on the internet, both of which correspond uses the Stewart Model[16]. to the Stewart Model: (1) The program The chemical method uses the SBE and developed by Figge y Fencl (www.figgefencl.org), orients the doctor in their administration of which has a teaching application and whose doses of acids or bases, depending on the case, computer process 3.0 can be found on their to restore the blood pH. The physicochemical webpage, which, to be used, requires the editor method uses the Stewart Model and permits Visual Basic, which is associated with Excel. the identification of respiratory and metabolic To achieve this requires both computational alterations (specifically metabolic alterations knowledge, 2) the program developed by Watson caused by illnesses of the liver, digestive system to which, however, access is not always available or kidney). On the other hand, the classic (www.med.sc.edu:96/watson/Acidbase/Acidbase. method is not able to specify the cause of a htm). metabolic alteration. Stewart proposed a system Huerta-Torrijos et al., developed an Excel formed of three independent variables: SID, spreadsheet