Caracterización hemodinámica de pacientes con diagnóstico de hipertensión arterial y síndrome de apneas hipopneas obstructivas del sueño / Hemodynamic characterization of patients with diagnosis of arterial hypertension and obstructive sleep apnea hypopnea syndrome

Introducción. La hipertensión arterial (HTA) y el síndrome de apnea e hipopnea obstructiva del sueño (SAHOS) presentan alta prevalencia y relación. La HTA predispone a insuficiencia cardíaca, infarto de miocardio, insuficiencia renal y accidente cerebrovascular, mientras que el SAHOS es un problema sanitario emergente asociado a mayor morbimortalidad, por accidentes de tránsito y complicaciones cardiovasculares. El objetivo de este estudio es describir las características hemodinámicas de pacientes con diagnóstico de HTA y SAHOS. Material y métodos. Estudio observacional. Se incluyeron pacientes con diagnóstico reciente de HTA y SAHOS sin tratamiento. Se dividieron en tres categorías: HTA sin SAHOS, HTA con SAHOS y un grupo control de normotensos con SAHOS. Se realizó el diagnóstico mediante el registro de la presión arterial de consultorio y el monitoreo ambulatorio de la presión arterial. El patrón hemodinámico y el contenido de fluido torácico (CFT) fueron evaluados por cardiografía por impedancia (CGI) y se diagnosticó SAHOS por poligrafía respiratoria ambulatoria. Resultados. Los pacientes con HTA y SAHOS presentaron un patrón hemodinámico vasoconstrictor y valores superiores de TFC respecto de los normotensos con SAHOS y HTA sin SAHOS. Conclusión. Los resultados obtenidos sugieren mayor compromiso de los sistemas simpático y renina angiotensina aldosterona. Estos hallazgos brindan nuevas hipótesis para continuar esta línea de investigación con mayor número de pacientes.(AU)

Impedance cardiography in the evaluation of patients with arterial hypertension / Impedância cardiografica na avaliação de pacientes com hipertensão arterial

Arterial hypertension is responsible for high morbidity and mortality. Despite increasing awareness of the consequences of uncontrolled hypertension and the publication of several recommendations and guidelines, blood pressure control rates are suboptimal, and approximately half of the patients do not reach the targets. Defined as an increase in blood pressure, hypertension is characterized by hemodynamic abnormalities in cardiac output, systemic vascular resistance, or arterial compliance. Therefore, the approach to arterial hypertension can be improved by the knowledge of the hemodynamics underlying the blood pressure increase. Impedance Cardiography has emerged as a new strategy to customize therapy and monitor patients aiming to improve blood pressure control according to the hemodynamic profile, rather than a blind intensive care approach. This is a review of impedance cardiography evidence, its benefits, actual and future applications in the approach and management of arterial hypertension

Accuracy and Efficacy of Impedance Cardiography as a Non-Invasive Cardiac Function Monitor

PURPOSE: The most common method of monitoring cardiac output (CO) is thermodilution using pulmonary artery catheter (PAC), but this method is associated with complications. Impedance cardiography (ICG) is a non-invasive CO monitoring technique. This study compared the accuracy and efficacy of ICG as a non-invasive cardiac function monitoring technique to those of thermodilution and arterial pressure contour. MATERIALS AND METHODS: Sixteen patients undergoing liver transplantation were included. Cardiac index (CI) was measured by thermodilution using PAC, arterial waveform analysis, and ICG simultaneously in each patient. Statistical analysis was performed using intraclass correlation coefficient (ICC) and Bland-Altman analysis to assess the degree of agreement. RESULTS: The difference by thermodilution and ICG was 1.13 L/min/m², and the limits of agreement were −0.93 and 3.20 L/min/m². The difference by thermodilution and arterial pressure contour was 0.62 L/min/m², and the limits of agreement were −1.43 and 2.67 L/min/m². The difference by arterial pressure contour and ICG was 0.50 L/min/m², and the limits of agreement were −1.32 and 2.32 L/min/m². All three percentage errors exceeded the 30% limit of acceptance. Substantial agreement was observed between CI of thermodilution with PAC and ICG at preanhepatic and anhepatic phases, as well as between CI of thermodilution and arterial waveform analysis at preanhepatic phase. Others showed moderate agreement. CONCLUSION: Although neither method was clinically equivalent to thermodilution, ICG showed more substantial correlation with thermodilution method than with arterial waveform analysis. As a non-invasive cardiac function monitor, ICG would likely require further studies in other settings.

Heart Rate Variability Analysis Based on Photoplethysmographic Signals

An algorithm for extracting tachograms for Heart Rate Variability (HRV) analysis on the basis of Photoplethysmographic (PPG) signals (instead of electro cardiograms) has been proposed. The main feature of this proposal is to detect peaks from correlograms between a pattern waveform and a sliding time window in the PPG signal. Analysis was carried out with a set of two groups of patients (young and elderly).HRV variables were estimated using the publicly available Kubios HRV package. Results showed that both the sympathetic component of the autonomous nervous system (assessed by LF/HF) and the cardiovascular complexity (assessed by correlation dimension) are reduced with age. These results are supported by literature and may be taken as a support for the validity of the proposed algorithm. Since oximeters for getting PPG signals are affordable even in poor settings, this allows extending autonomic nervous system studies into remote areas of developing countries(AU)

Se propone un algoritmo para obtener tacogramas con la finalidad de realizar estudios de variabilidad de la frecuencia cardiaca, partiendo de registros de señales fotopletismográficas (PPG). La principal peculiaridad de esta propuesta lo es la detección de los picos en las ondas de la señal PPG a partir de un correlograma obtenido como una secuencia de correlaciones entre una onda patrón y una ventana deslizante de la señal PPG. Se realizó un análisis de variabilidad de frecuencia cardiaca sobre dos grupos de pacientes (jóvenes y de avanzada edad). Las variables de variabilidad de frecuencia cardiaca seleccionadas se obtuvieron a partir del programa Kubios HRV, de acceso público y gratuito. Los resultados mostraron que tanto el componente simpático del Sistema Nervioso Autónomo (evaluado a través de la variable LF/HF) como la complejidad cardiovascular (evaluada a través de la dimensión de correlación) disminuyeron con la edad. Estos resultados encuentran apoyo en datos de la literatura que apoyan así la validez del algoritmo propuesto. Por cuanto el oxímetro utilizado para obtener las señales PPG está al alcance de instituciones primarias de salud se hace posible de esta manera extender estudios del sistema nervioso autónomo hacia áreas remotas de países en desarrollo(AU)

De-noising of Impedance Cardiography Differential Signal and Detection of the Feature Points Based on Wavelet Transformation / 生物医学工程学杂志

Calculation of cardiac hemodynamic parameters is based on accurate detection of feature points in impedance cardiogram. According to these parameters, doctors can determine heart conditions, so it is very important to accurately detect the feature point of impedance differential signals. This article presents a process in which we used wavelet threshold method to de-noise signals, and then detected the feature points after six layers wavelet decomposition by using bior3. 7. The experimental data were collected from healthy persons in our laboratory and twenty two clinical patients in Chongqing Daping Hospital by using KF_ICG instrument. The results indicated that this method could precisely detect feature points whether it was from healthy people or clinical patients. This helps to achieve the application of noninvasive detection cardiac hemodynamic parameters in clinical treatments by using impedance method.

The Changes of Noninvasive Hemodynamic Parameters after Device-Guided Slow Breathing Exercise in Hypertensive Patients

BACKGROUND: The device-guided breathing (DGB) exercise is a non-pharmacological treatment of high blood pressure (BP). Changes in hemodynamic variables after DGB remain to be defined. This study evaluated the hemodynamic effects of DGB in hypertensive patients. METHODS: Fifty-nine hypertensive individuals (male, 56%; age, 44 +/- 10 years) with systolic BP (SBP) in the range of 140 to169 mm Hg and diastolic BP (DBP) < 105 mm Hg were divided into two group: control group (n = 17) vs. DGB group (n = 42) who slowed respiratory rate by using 15 minutes daily DBG (RESPeRATE) over 8 weeks. Heart rate, BP and hemodynamic parameters including cardiac index (CI), thoracic fluid content (TFC), systemic vascular resistance index (SVRI) and total arterial compliance index (TACI) were measured using the ICG Monitor (CardioDynamics) at baseline and study end. RESULTS: Baseline characteristics were not different between the two groups. Office BP (SBP/DBP) was reduced from baseline to end value by 13.2 +/- 11.1/6.9 +/- 7.5 mm Hg in DGB group and 2.2 +/- 6.9/0.5 +/- 6.6 mm Hg in control group (p = 0.001, p = 0.004, respectively). Heart rate, CI, stroke index, and TFC were not changed in both groups. However, the SVRI was lower and the TACI was higher in DGB group than control group (SVRI: 2,728 +/- 599 vs. 3,141 +/- 714 dyne sec m2/cm5, p = 0.002; TACI: 0.845 +/- 0.194 vs. 0.761 +/- 0.184 mm Hg/mL/m2, p = 0.041). CONCLUSIONS: Daily device-guided breathing exercise for 8 weeks lowers the BP mediated by reducing the systemic vascular resistance and increasing the total arterial compliance without changes in heart rate and CI.

Applicability of the two-compartment coaxial cylindrical model for ambulatory measuring of cardiac output with spot-electrodes / 生物医学工程学杂志

The principle of ambulatory cardiac output (CO) measuring technique is introduced in this paper. Experimental studies about the applicability of the two-compartment coaxial cylindrical model for ambulatory measurement of cardiac output with spot-electrodes have been carried out with using our newly-developed multi-channel impedance mapping system. The key factors using a spot-electrode array instead of a conventional band-electrode array for non-invasive CO) measurement are elaborated. The variations of the electric impedance pulsatile component (deltaZ waveform) and the two kinds of typical modes of deltaZ distributions measured by six electrodes on the midsternal (midian) line from the medial portion at the level of clavicle to the portion above the xiphisternum are discussed. The applicability of the two-compartment coaxial cylindrical model for ambulatory measurement of CO with spot-electrodes is analyzed. Synthesizing the deltaZ distributions and their typical changing models on the midsternal (midian) line during blood inflowing into aorta is the optimal positions of a pair of spot-electrodes for voltage pick-up at the level of clavicle for the upper electrode and the position at the level of nipple for the lower electrode when spot-electrode is being used to measure non-invasive CO.

Bioimpedância transtorácica comparada à ressonância magnética na avaliação do débito cardíaco / Transthoracic impedance compared to magnetic resonance imaging in the assessment of cardiac output

FUNDAMENTO: A ressonância magnética cardíaca é considerada o método padrão-ouro para o cálculo de volumes cardíacos. A bioimpedância transtorácica cardíaca avalia o débito cardíaco. Não há trabalhos que validem essa medida comparada à ressonância. OBJETIVO: Avaliar o desempenho da bioimpedância transtorácica cardíaca no cálculo do débito cardíaco, índice cardíaco e volume sistólico, utilizando a ressonância como padrão-ouro. MÉTODOS: Avaliados 31 pacientes, com média de idade de 56,7 ± 18 anos, sendo 18 (58%) do sexo masculino. Foram excluídos os pacientes cuja indicação para a ressonância magnética cardíaca incluía avaliação sob estresse farmacológico. A correlação entre os métodos foi avaliada pelo coeficiente de Pearson, e a dispersão das diferenças absolutas em relação à média foi demonstrada pelo método de Bland-Altman. A concordância entre os métodos foi realizada pelo coeficiente de correlação intraclasses. RESULTADOS: A média do débito cardíaco pela bioimpedância transtorácica cardíaca e pela ressonância foi, respectivamente, 5,16 ± 0,9 e 5,13 ± 0,9 L/min. Observou-se boa correlação entre os métodos para o débito cardíaco (r = 0,79; p = 0,0001), índice cardíaco (r = 0,74; p = 0,0001) e volume sistólico (r = 0,88; p = 0,0001). A avaliação pelo gráfico de Bland-Altman mostrou pequena dispersão das diferenças em relação à média, com baixa amplitude dos intervalos de concordância. Houve boa concordância entre os dois métodos quando avaliados pelo coeficiente de correlação intraclasses, com coeficientes para débito cardíaco, índice cardíaco e volume sistólico de 0,78, 0,73 e 0,88, respectivamente (p < 0,0001 para todas as comparações). CONCLUSÃO: A bioimpedância transtorácica cardíaca mostrou-se acurada no cálculo do débito cardíaco quando comparada à ressonância magnética cardíaca.

BACKGROUND: Cardiac magnetic resonance imaging is considered the gold-standard method for the calculation of cardiac volumes. Transthoracic impedance cardiography assesses the cardiac output. No studies validating this measurement, in comparison to that obtained by magnetic resonance imaging, are available. OBJECTIVE: To evaluate the performance of transthoracic impedance cardiography in the calculation of the cardiac output, cardiac index and stroke volume using magnetic resonance imaging as the gold-standard. METHODS: 31 patients with a mean age of 56.7 ± 18 years were assessed; of these, 18 (58%) were males. Patients whose indication for magnetic resonance imaging required pharmacologic stress test were excluded. Correlation between methods was assessed using the Pearson's coefficient, and dispersion of absolute differences in relation to the mean was demonstrated using the Bland-Altman's method. Agreement between methods was analyzed using the intraclass correlation coefficient. RESULTS: The mean cardiac output by transthoracic impedance cardiography and by magnetic resonance imaging was 5.16 ± 0.9 and 5.13 ± 0.9 L/min, respectively. Good agreement between methods was observed for cardiac output (r = 0.79; p = 0.0001), cardiac index (r = 0.74; p = 0.0001) and stroke volume (r = 0.88; p = 0.0001). The analysis by the Bland-Altman plot showed low dispersion of differences in relation to the mean, with a low amplitude of agreement intervals. Good agreement between the two methods was observed when analyzed by the intraclass correlation coefficient, with coefficients for cardiac output, cardiac index and stroke volume of 0.78, 0.73 and 0.88, respectively (p < 0.0001 for all comparisons). CONCLUSION: Transthoracic impedance cardiography proved accurate in the calculation of the cardiac output in comparison to cardiac magnetic resonance imaging.

Evaluación hemodinámica no invasiva con cardiografía de impedancia: aplicaciones en falla cardíaca y en hipertensión arterial / Non-invasive hemodynamic evaluation with impedance cardiography: applications in heart failure and hypertension

La cardiografía de impendancia (CGI) representa un método no invasivo para la evaluación del estado hemodinámico latido a latido. Aunque se introdujo por primera vez hace más de 40 años, la CGI ha mostrado un resurgimiento en la última década, a partir de una serie de estudios clínicos que han demostrado su precisión en la estimación del volumen latido, tanto contra el "gold-standard" invasivo (termodilución), como contra los métodos de referencia no invasivos (ecocardiografía). Diversos estudios demuestran la utilidad de esta técnica en el manejo del paciente con falla cardíaca y en el enfoque diagnóstico y terapéutico de la hipertensión arterial, por lo cual constituyen actualmente dos de las aplicaciones clínicas más importantes de la CGI. En falla cardiaca, los cambios en el volumen de líquido del tórax y del gasto cardíaco evaluados por CGI, han demostrado ser predictores de descompensación aguda, incluso semanas antes del inicio de la sintomatología respiratoria; además, permiten identificar el origen cardiogénico o respiratorio de la disnea cuando el examen físico y los demás paraclínicos no son concluyentes. En los pacientes con hipertensión arterial no controlada o resistente, la CGI permite realizar una mejor caracterización del fenotipo hipertensivo y elegir la estrategia farmacológica más específica para intervenir la alteración hemodinámica predominante (resistencia vascular vs. gasto cardiaco elevado). En este artículo se realiza una revisión de los principios biofísicos de la CGI y su utilidad en la evaluación no invasiva del estado hemodinámico, así como una evaluación crítica de la literatura que da soporte a su aplicación clínica en el tratamiento de la falla cardíaca y la hipertensión arterial.

Impedance cardiography (ICG) represents a non-invasive method for hemodynamic assessment in a beat-to-beat basis. Since its introduction more than forty years ago, a renewed interest in the use of this technique during the last decade has been noticed, mainly as a result of a series of clinical studies showing its precision in the estimation of stroke volume either against invasive gold standard (i.e. thermodilution) or against non-invasive reference methods (i.e. echocardiography). On the other hand, ICG has demonstrated to be useful for the management of heart failure patients and for the diagnostic and therapeutic approach to hypertension, which currently constitute two of the major applications of ICG. In heart failure patients, changes in thoracic fluid content and cardiac output tracked by ICG have shown to be predictors of acute decompensation even weeks before respiratory symptoms appear; also allowing identification of a cardiac vs. respiratory origin of dyspnea when physical examination and laboratory tests are not conclusive. In the particular case of patients with uncontrolled or severe hypertension, ICG makes possible a better characterization of hypertensive phenotype leading to a more specific choice of pharmacological agents to treat the primary hemodynamic alteration (i.e elevated peripheral resistance vs. elevated cardiac output). The present review, provides a review of the biophysical principles of ICG and its precision in measuring stroke volume and present a critical assessment of the literature supporting its clinical application in the management of heart failure and arterial hypertension.

Avaliação hemodinâmica na insuficiência cardíaca: papel do exame físico e dos métodos não invasivos / Hemodynamic assessment in heart failure: role of physical examination and noninvasive methods / Evaluación hemodinámica en la insuficiencia cardíaca: papel del examen físico y de los métodos no invasivos

Entre as doenças cardiovasculares, a insuficiência cardíaca (IC) apresenta elevada taxa de internação hospitalar, morbidade e mortalidade, consumindo grandes recursos financeiros do sistema de saúde no Brasil e em outros países. A correta determinação das pressões de enchimento do ventrículo esquerdo, por avaliação invasiva ou não invasiva, é fundamental para o adequado tratamento dos pacientes com IC crônica descompensada, considerando que a congestão é o principal fator determinante dos sintomas e da hospitalização. O exame físico tem se mostrado inadequado para prever o padrão hemodinâmico. Vários estudos sugerem que a concordância em achados de exame físico por diferentes médicos é pequena e que, por fim, as próprias alterações fisiológicas adaptativas na IC crônica mascaram importantes aspectos do exame físico. Como a avaliação clínica falha em prever a hemodinâmica e pelo fato de a utilização do cateter de Swan-Ganz de rotina não ser recomendada para esse fim em pacientes com IC, métodos de avaliação hemodinâmica não invasivos, como o BNP, o ecocardiograma e a bioimpedância cardiográfica, vêm sendo crescentemente utilizados. O presente trabalho tem por objetivo realizar, para o clínico, uma revisão da função de cada uma dessas ferramentas, na definição da condição hemodinâmica em que se encontram os pacientes com IC descompensada, visando a um tratamento mais racional e individualizado.

Among the cardiovascular diseases, heart failure (HF) has a high rate of hospitalization, morbidity and mortality, consuming vast resources of the public health system in Brazil and other countries. The correct determination of the filling pressures of the left ventricle by noninvasive or invasive assessment is critical to the proper treatment of patients with decompensated chronic HF, considering that congestion is the main determinant of symptoms and hospitalization. Physical examination has shown to be inadequate to predict the hemodynamic pattern. Several studies have suggested that agreement on physical findings by different physicians is small and that, ultimately, adaptive physiological alterations in chronic HF mask important aspects of the physical examination. As the clinical assessment fails to predict hemodynamic aspects and because the use of Swan-Ganz catheter is not routinely recommended for this purpose in patients with HF, noninvasive hemodynamic assessment methods, such as BNP, echocardiography and cardiographic bioimpedance, are being increasingly used. The present study intends to carry out, for the clinician, a review of the role of each of these tools when defining the hemodynamic status of patients with decompensated heart failure, aiming at a more rational and individualized treatment.

Entre las enfermedades cardiovasculares, la insuficiencia cardíaca (IC) presenta una elevada tasa de ingreso hospitalario, morbilidad y mortalidad, consumiendo enormes recursos financieros del sistema de sanidad en Brasil, y de otros países. La correcta determinación de las presiones en el llenado del ventrículo izquierdo, por evaluación invasiva o no invasiva, es fundamental para el adecuado tratamiento de los pacientes con IC crónica descompensada, considerando que la congestión es el principal factor determinante de los síntomas y del ingreso. El examen físico ha sido inadecuado para prever el estándar hemodinámico. Varios estudios sugieren que la concordancia en los hallazgos del examen físico por diferentes médicos es pequeña y que, las propias alteraciones fisiológicas adaptativas en la IC crónica, disimulan los importantes aspectos del examen físico. Como la evaluación clínica falla a la hora de prevenir la hemodinámica, y también por el hecho de que la utilización del catéter de Swan-Ganz de rutina no se recomiende con ese fin en los pacientes con IC, los métodos de evaluación hemodinámica no invasivos, como el PNB, el ecocardiograma y la bioimpedancia cardiográfica, están en aumento. Este trabajo pretende realizar, a favor del médico, una revisión de la función de cada una de esas herramientas, para definir la condición hemodinámica en que están los pacientes con IC descompensada, objetivando un tratamiento más racional e individualizado.

Optimal electrode array for ambulatory measuring of cardiac output based on the electrical impedance method / 生物医学工程学杂志

Principle of ambulatory cardiac output (CO) measuring technique is introduced in this paper. A lot of experimental studies of the current distribution on the thorax under the condition that the current injection electrodes were adhered to different positions were carried out by using a developed multi-channel impedance mapping system. The static impedance contour maps (Zo-map) and its pulsatile component contour maps (deltaZ-map) under different measuring conditions were analyzed, and the applicability of a two-compartment coaxial cylindrical model using a spot-electrode array instead of the conventional band-electrode array for ambulatory CO measurement, as well as the optimal spot-electrode array, were discussed. Based on the experimental results and the daily use of the ambulatory CO measuring technique, the optimal spot-electrode array meeting the condition of the two-compartment coaxial cylindrical model was determined as that a pair of spot-electrodes for current injection was located on the positions behind the ears and on the right lower abdomen, and a pair of spot-electrodes for voltage pick-up places on the medial portion at the level of clavicle and on the portion above the xiphisternum.

Single center experience with intrathoracic impedance monitoring / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The Medtronic InSync Sentry is the first available cardiac resynchronization therapy defibrillator (CRT-D) which can monitor fluid status by measuring intrathoracic impedance. This study was designed to observe the effectiveness of intrathoracic impedance monitoring on detecting aggravation of heart failure.</p><p><b>METHODS</b>We retrospectively analyzed the clinical data of 14 consecutive patients. Patients were regularly followed up every 3 - 6 months after the implantation. At each visit, interrogation of the device was done. Patients were instructed to inform the researcher on hearing the device alert, and to take extra 40 milligrams of furosemidum if they had aggravated symptoms later. If the symptoms could not be relieved, they were asked to see a doctor. Data about heart failure hospitalization were collected from the medical record.</p><p><b>RESULTS</b>During 18 - 48 months follow-up, a total of 7 patients encountered 28 alert events. On one hand, alert events appeared before all deteriorated symptoms and heart failure hospitalizations. On the other hand, there were 23 alerts followed by deterioration of heart failure symptoms, and 2 alerts related to 2 hospitalizations caused by pulmonary infection in one patient. Only 5 patients were hospitalized 10 times for deterioration of cardiac function.</p><p><b>CONCLUSION</b>The function of intrathoracic impedance monitoring is reliable in predicting deterioration of heart failure.</p>

Temas de atualização e revisão em clínica médica: impedância cardiográfica: o avanço tecnológico na tomada de decições / Themes of updating and revision in medical clinic: impedance cardiography: technological advance in taking decisions

A impedância cardiográfica é uma tecnologia baseada nas leis de Ohm, que nos permite avaliar, de forma não invasiva e com alta acurácia (1), parâmetros hemodinâmicos, através das diferentes propriedades elétricas dos tecidos, como músculo, osso, gordura e sangue. Pode ser utilizada em nível hospitalar ou ambulatorial e aplicada em diversas doenças, principalmente na hipertensão arterial resistente e insuficiência cardíaca. É capaz de identificar a causa da dispneia na sala de emergência, predizer a descompensação por insuficiência cardíaca e titular doses do tratamento medicamentoso nesta síndrome. Mais recentemente, tem sido utilizada na otimização dos marcapassos cardíacos.

The impedance cardiography (ICG) isa technology based on Ohm's laws, whick allows to assess hemodynamic parameters, in a non-invasive and with high accuracy, through the different electrical properties of tissues such as muscle, bone, fat and blood. Can be used in hospital or outpatient and applied in various diseases, especially in resistant hypertension and heart failure. Is is able to identify the cause of dyspnea in the emergency room, to predict decompensated heart failure and titration of doses of the drug in this syndrome. More recently, it has been used in optimization of cardiac pacemakers.

Noninvasive Cardiac Output Measurement in Shock Patients

PURPOSE: Invasive determination of cardiac output (CO) is possible via a pulmonary artery catheter but catheter implantation has risks. Clinicians can assess CO safely using a non-invasive cardiac output device such as a commercially available doppler system (ultrasonic cardiac output monitor, USCOM, USCOM Ltd, Australia) or using impedance cardiography (ICG). The purpose of this study was to investigate the consistency of hemodynamic measurements between ICG and USCOM in shock patients. METHODS: From June 2007 to October 2007, we prospectively evaluated 21 patients with shock, who visited our emergency center. We measured CO and systemic vascular resistance (SVR) using ICG and USCOM on arrival, and at 30, 60, 90, and 120 minutes. RESULTS: The mean difference in CO between ICG and USCOM was 1.08+/-2.13 L/min. The percent limits of agreement (LOA) were -60.0 to 84.7% between ICG and USCOM. The correlation coefficient for CO between ICG and USCOM was 0.76 (p<0.01). CO values measured by ICG and USCOM were 4.3+/-1.7 vs 5.9+/-3.9 initially, 4.8+/-2.2 vs 6.0+/-3.9 at 30 min, 4.3+/-1.6 vs 5.1+/-2.9 at 60 min, 4.2+/-1.6 vs 4.9+/-2.7 at 90 min, and 4.1+/-1.6 vs 5.0+/-2.9 at 120 min, respectively. Statistical significance was observed within each modalities (p=0.03) but we did not find statistical significances between the two modalities. SVR (dynes*sec/cm5) values were measured by ICG and USCOM on arrival, and at 30, 60, 90, and 120 minutes. No statistical significance was seen within and between study groups. CONCLUSION: ICG and USCOM do not show clinically acceptable agreement.

Paddle-skin Coupling Material Usage in Emergency Institutes in South Korea

PURPOSE: While the use of coupling material (CM) during defibrillation is known to decrease transthoracic impedance more so than other materials elsewhere, the situation in Korea is unclear. The study assessed the use of paddleskin CM during defibrillation in South Korean emergency institutes (EIs) and measured the impedances. METHODS: From October 15 to October 19, 2009, 112 EIs (all of regional emergency medical centers (EMCs), specialized care centers, and local EMCs) were surveyed. Institute members were queried about their current use of paddleskin CMs during defibrillation. Indications for use were studied by means of a World Wide Web search, descriptions on the CM packaging, and telephone conversations with CM manufacturers and related people. Impedance measurements were recorded from April 13 to August 3, 2009. RESULTS: During defibrillation, 27 different CMs were used in the 108 EIs. Only nine institutes used CMs directly for defibrillation. Impedence of nine CMs could not be measured. The impedance values were 1.69, 1.71, 2.00, and 6.12 ohm for four CMs used for defibrillation; 6.66 and 11.94 ohm for two CMs used for electrodes; 9.71, 9.82, 11.57, 13.68, 13.89, 14.36, 18.31, and 19.66 ohm for eight CMs used for ultrasonography; and 14.05, 17.71, 35.44, and 41.15 ohm for four other CMs. CONCLUSION: More education and public information about the use of CMs for defibrillation are needed.

Principios de la evaluación hemodinámica no invasiva con cardiografía de impedancia / Principles of non-invasive hemodynamic assessment with impedance cardiography

La cardiografía de impedancia es una técnica no invasiva que permite una determinación rápida, continua y reproducible del gasto cardiaco latido a latido. Mide los cambios en la resistencia eléctrica del tórax que se producen por las variaciones en el volumen sanguíneo en la aorta durante el ciclo cardiaco. La medición continua del cambio en la impedancia o las fluctuaciones del volumen sanguíneo durante la sístole y la diástole, permite determinar el volumen latido, el gasto cardiaco, la contractilidad miocárdica y el contenido total de fluido del tórax. Entre las ventajas de esta técnica se incluyen su fácil implementación y asequibilidad, así como la posibilidad de ser realizada por prácticamente cualquier miembro del equipo de salud. La precisión de la cardiografía de impedancia ha sido validada en numerosos estudios en diferentes escenarios clínicos: hipertensión arterial, falla cardiaca, hipertensión pulmonar, optimización de la terapia de resincronización cardiaca y en pacientes críticos, situaciones en las que provee información sobre el estado hemodinámico sin los riesgos de otras técnicas invasivas o mínimamente invasivas. Es además un método de fácil aplicación y costo-efectivo para el diagnóstico y seguimiento de la respuesta a las intervenciones terapéuticas en múltiples patologías. La técnica representa así un cambio en los paradigmas del monitoreo hemodinámico.

Impedance cardiography (ICG) is a non-invasive technique that allows a rapid, continuous and reproducible beat-to-beat cardiac output estimation. This technique measures thoracic electrical resistance changes produced by variations in the blood volume in the aorta during the cardiac cycle. Continuous measurement of impedance changes or fluctuations of blood volume during systole and diastole allow the determination of stroke volume, cardiac output, myocardial contractility, and total thoracic fluid content. Between the advantages of this technique are included its easy implementation and accessibility, as well as the possibility of its measurement by practically any member of the health team. Impedance cardiography accuracy has been validated in several clinical scenarios such as arterial hypertension, heart failure, pulmonary hypertension, optimization of cardiac resynchronization therapy, and in critically ill patients, situations where it provides information about the hemodynamic state without the risks and costs of other invasive or minimally invasive techniques. It is also an easy to use, cost-effective method for the diagnosis and follow-up of the response to therapeutic interventions in multiple clinical scenarios. Thus, this technology represents a change in the paradigms of hemodynamic monitoring.

A comparison of hemodynamics in elderly patients that were administered thiopental sodium or propofol to induce general anesthesia / 대한마취과학회지

BACKGROUND: Thiopental sodium and propofol are commonly used to induce anesthesia. This study was conducted to compare the hemodynamic effects of propofol and thiopental sodium during the induction of general anesthesia in elderly patients. METHODS: Forty patients undergoing general anesthesia were randomly divided into two groups. In group T, thiopental sodium was used to induce anesthesia, whereas propofol was used in group P. Hemodynamic changes in the mean blood pressure, heart rate, cardiac index (as determined using a NICCOMO monitor) and bispectral index (BIS) during induction were then compared between the two groups. In addition, the dosage of induction agent, time required until loss of response to verbal order (LOV) and eyelid reflex were compared between groups. RESULTS: The mean blood pressure was significantly lower in group P than in group T during the 1-5 min following LOV and during the 2, 3 min following intubation (P < 0.05). However, the heart rate did not differ significantly between the two groups. The cardiac index also did not differ significantly between groups, except during the first 3 min following LOV. Finally, the BIS value were significantly lower than the baseline values in both groups during induction. CONCLUSIONS: In elderly patients, the heart rate, cardiac index and BIS value did not differ significantly between the two groups. But the mean blood pressure was significantly lower in propofol than in thiopental sodium.