Non-invasive ECG recording and QT interval correction assessment in anesthetized rats and mice / Eletrocardiograma não invasivo e avaliação da correção do intervalo QT em roedores anestesiados

Rats and mice are the most common species used in experimental cardiac electrophysiology studies. Electrocardiogram (ECG) recording shows paramount importance for monitoring arrhythmias and cardiac function in several disease models, including QT syndrome. However, the lack of standardized reference values and QT correction formula for different animal species and lineages represent a challenge for ECG interpretation. The aim of this study is to provide an improved method for ECG recording, establishing reference range values and determine the QT formulas with higher correlation to heart rate (HR). A total of 10 Wistar rats, 10 Swiss mice, 10 C57BL/6 mice and 10 FVB/NJ mice were used in the study. Animals were submitted to anesthesia with isoflurane and ECG recording was performed using a six-channel non-invasive electrocardiograph. QT was corrected using the following formulas: Bazzett, Fridericia, Mitchell, Hodges, Van der Water and Framingham. Normal range values for ECG parameters were established in all animals studied. Pearsons' correlation defined Hodges formula as the most suitable for QT correction. This study demonstrated an improved method of ECG recording with reference values for Swiss, FVB/NJ, C57BL/6 mice, and Wistar rats. Hodges' formula was the most effective formula for QT correction in rodents, whereas Bazett's and Friderica formulas were ineffective for such animals. The present work contributes to arrhythmias investigation in experimental cardiology and may reduce misinterpretations in rodents' ECG.(AU)

Ratos e camundongos são as espécies mais comumente utilizadas em estudos experimentais de eletrofisiologia cardíaca. O registro do eletrocardiograma (ECG) é de suma importância para o monitoramento de arritmias e função cardíaca em vários modelos de patologias. No entanto, a falta de valores de referência padronizados e a fórmula de correção do QT para diferentes espécies e linhagens animais representam um desafio para a interpretação do ECG. O objetivo deste estudo é fornecer um método melhorado para o registro de ECG, estabelecendo valores de referência e determinar as fórmulas QT com maior correlação com a freqüência cardíaca (FC). Um total de 10 ratos Wistar, 10 camundongos Swiss, 10 camundongos C57BL/6 e 10 camundongos FVB/NJ foram utilizados no estudo. Os animais foram submetidos à anestesia com isoflurano e o registro de ECG foi realizado com eletrocardiógrafo não invasivo de seis canais. O QT foi corrigido usando as seguintes fórmulas: Bazzett, Fridericia, Mitchell, Hodges, Van der Water e Framingham. Os valores da normalidade para os parâmetros do ECG foram estabelecidos em todos os animais estudados. A correlação de Pearson definiu a fórmula de Hodges como a mais adequada para a correção do QT. Este estudo demonstra um método melhorado de registro de ECG com valores de referência para camundongos Swiss, FVB/NJ, C57BL/6 e Wistar. A fórmula de Hodges foi a mais eficaz para correção de QT em roedores, enquanto as fórmulas de Bazett e Friderica apresentaram valores mais baixos de correlação. O presente trabalho contribui para a investigação de arritmias em cardiologia experimental e pode reduzir interpretações erradas no ECG de roedores.(AU)

Consistency of indirect calorimetry and HB coefficient method for measuring energy expenditure of pa-tients with sepsis / 中华临床营养杂志

Objective To evaluate the difference and correlation of 24 h energy expenditure in patients with sepsis by indirect calorimetry (IC) and HB coefficient equation. Methods A prospective comparative study including 60 patients with sepsis who was suitable for nutritional support and respiratory indirect calorimetry in the intensive care unit (ICU) from January to October 2015 was conducted. Resting energy expenditure (REE) was measured simultaneously by respiratory indirect calorimetry and HB coefficient (Harris-Benedict formula×stress coefficient) in 60 patients with sepsis at 0 day, 3 day, 7 day, and 14 day after nutritional support, and the differences in dynamic REE were compared between the two methods. The consistency of REE by indirect calorimetry (IC) and HB coefficient equation was evaluated by Bland-Altman. The correlation of IC and HB methods was determined by Pearson analysis. The linear regression equation was determined by linear regression analysis. Results Within 2 weeks after nutritional support, 188 times of measures by IC method and HB method respectively were finished in all patients with sepsis. The dynamic REE in respiratory indirect calorimetry group was significantly higher than that in HB coefficient method group (P<0. 05). The average bias of REE between the IC method and the HB method was (1930. 9±597. 7) kJ/24 h. For the consistency boundaries was over large and beyond the scope of clinical acceptance, there was a bias between the two methods and they could not directly substituted. There was a linear correlation of REE between the IC method and the HB coefficient (r =0. 757, P =0. 000). The equation associated with the HB coefficient method is fitted using a oneway regression: Y=1. 17X+ 834. 11 (kJ/24 h), and X was the 24 h energy expenditure measured by the HB coefficient method. Conclusion The energy metabolism of patients with sepsis is not obvious in the first 2 weeks. The HB coefficient method significantly underestimates the 24 h energy expenditure of patients with sepsis. The prediction equation can be used to correct the HB coefficient method and improve the HB coefficient method to predict the energy expenditure of patients with sepsis.

Consistency of indirect calorimetry and HB coefficient method for measuring energy expenditure of patients with sepsis / 中华临床营养杂志

Objective@#To evaluate the difference and correlation of 24 h energy expenditure in patients with sepsis by indirect calorimetry (IC) and HB coefficient equation.@*Methods@#A prospective comparative study including 60 patients with sepsis who was suitable for nutritional support and respiratory indirect calorimetry in the intensive care unit (ICU) from January to October 2015 was conducted. Resting energy expenditure (REE) was measured simultaneously by respiratory indirect calorimetry and HB coefficient (Harris-Benedict formula×stress coefficient) in 60 patients with sepsis at 0 day, 3 day, 7 day, and 14 day after nutritional support, and the differences in dynamic REE were compared between the two methods. The consistency of REE by indirect calorimetry (IC) and HB coefficient equation was evaluated by Bland-Altman. The correlation of IC and HB methods was determined by Pearson analysis. The linear regression equation was determined by linear regression analysis.@*Results@#Within 2 weeks after nutritional support, 188 times of measures by IC method and HB method respectively were finished in all patients with sepsis. The dynamic REE in respiratory indirect calorimetry group was significantly higher than that in HB coefficient method group (P<0.05). The average bias of REE between the IC method and the HB method was (1 930.9±597.7)kJ/24 h. For the consistency boundaries was over large and beyond the scope of clinical acceptance, there was a bias between the two methods and they could not directly substituted. There was a linear correlation of REE between the IC method and the HB coefficient (r=0.757, P=0.000). The equation associated with the HB coefficient method is fitted using a one-way regression: Y=1.17X+ 834.11 (kJ/24 h), and X was the 24 h energy expenditure measured by the HB coefficient method.@*Conclusion@#The energy metabolism of patients with sepsis is not obvious in the first 2 weeks. The HB coefficient method significantly underestimates the 24 h energy expenditure of patients with sepsis. The prediction equation can be used to correct the HB coefficient method and improve the HB coefficient method to predict the energy expenditure of patients with sepsis.

Validation and discussion of the time response correction formula for radiation detectors / 中华放射医学与防护杂志

Objective To validate and discuss the time response correction formula for four types of dosimeters (6150AD6 + 6150AD-b,FH40G + FHZ672E-10,451P ionization chamber and AT1123).Methods The ambient dose equivalent rates shown by survey meters were recorded separately when X-ray emission time was 500,200,100 and 50 ms.The corrected values were obtained by the formula of circuit having a capacitance C and asistance R in series.Results Therewas no correlation between the value measured by AT1123 dosimeter and the time of irradiation.The values by other three kinds of dosimeters obviously varied with the time of irradiation.Conclusions It is not required to make the time response correction for the measured value of ATl123 dosemeter,whereas the values measured by the other three dosimeters could be corrected by the time response correction formula.