Emília Nozawa

Performance of two-dimensional Doppler echocardiography for the assessment of infarct size and left ventricular function in rats

Although echocardiography has been used in rats, few studies have determined its efficacy for estimating myocardial infarct size. Our objective was to estimate the myocardial infarct size, and to evaluate anatomic and functional variables of the left ventricle. Myocardial infarction was produced in 43 female Wistar rats by ligature of the left coronary artery. Echocardiography was performed 5 weeks later to measure left ventricular diameter and transverse area (mean of 3 transverse planes), infarct size (percentage of the arc with infarct on 3 transverse planes), systolic function by the change in fractional area, and diastolic function by mitral inflow parameters. The histologic measurement of myocardial infarction size was similar to the echocardiographic method. Myocardial infarct size ranged from 4.8 to 66.6% when determined by histology and from 5 to 69.8% when determined by echocardiography, with good correlation (r = 0.88; P < 0.05; Pearson correlation coefficient). Left ventricular diameter and mean diastolic transverse area correlated with myocardial infarct size by histology (r = 0.57 and r = 0.78; P < 0.0005). The fractional area change ranged from 28.5 +/- 5.6 (large-size myocardial infarction) to 53.1 +/- 1.5% (control) and correlated with myocardial infarct size by echocardiography (r = -0.87; P < 0.00001) and histology (r = -0.78; P < 00001). The E/A wave ratio of mitral inflow velocity for animals with large-size myocardial infarction (5.6 +/- 2.7) was significantly higher than for all others (control: 1.9 +/- 0.1; small-size myocardial infarction: 1.9 +/- 0.4; moderate-size myocardial infarction: 2.8 +/- 2.3). There was good agreement between echocardiographic and histologic estimates of myocardial infarct size in rats.

Structural and functional characteristics of rat hearts with and without myocardial infarct. Initial experience with doppler echocardiography

OBJECTIVE To assess by Doppler echocardiography the structural and functional alterations of rat heart with surgical induced extensive myocardial infarction. METHODS Five weeks after surgical ligature of the left coronary artery, 38 Wistar-EPM rats of both sexes, 10 of them with extensive infarction, undergone anatomical and functional evaluation by Doppler echocardiography and then euthanized for anatomopathological analysis. RESULTS Echocardiography was 100% sensible and specific to anatomopathological confirmed extensive miocardial infarction. Extensive infarction lead to dilatation of left ventricle (diastolic diameter: 0.89 cm vs.0.64 cm; systolic: 0. 72 cm vs. 0.33 cm) and left atrium (0.55 cm vs. 0.33 cm); thinning of left ventricular anterior wall (systolic: 0.14 cm vs. 0.23 cm, diastolic: 0.11 cm vs. 0.14 cm); increased mitral E/ A wave relation (6.45 vs. 1.95). Signals of increased end diastolic ventricle pressure, B point in mitral valve tracing in 62.5% and signs of pulmonary hypertension straightening of pulmonary valve (90%) and notching of pulmonary systolic flow (60%) were observed in animals with extensive infarction. CONCLUSION Doppler echocardiography has a high sensitivity and specificity for detection of chronic extensive infarction. Extensive infarction caused dilatation of left cardiac chambers and showed in Doppler signals of increased end diastolic left ventricular pressure and pulmonary artery pressure.

Assessment of factors that influence weaning from long-term mechanical ventilation after cardiac surgery

OBJECTIVE To analyze parameters of respiratory system mechanics and oxygenation and cardiovascular alterations involved in weaning tracheostomized patients from long-term mechanical ventilation after cardiac surgery. METHODS We studied 45 patients in their postoperative period of cardiac surgery, who required long-term mechanical ventilation for more than 10 days and had to undergo tracheostomy due to unsuccessful weaning from mechanical ventilation. The parameters of respiratory system mechanics, oxygenation and the following factors were analyzed: type of surgical procedure, presence of cardiac dysfunction, time of extracorporeal circulation, and presence of neurologic lesions. RESULTS Of the 45 patients studied, successful weaning from mechanical ventilation was achieved in 22 patients, while the procedure was unsuccessful in 23 patients. No statistically significant difference was observed between the groups in regard to static pulmonary compliance (p = 0.23), airway resistance (p = 0.21), and the dead space/tidal volume ratio (p = 0.54). No difference was also observed in regard to the variables PaO2/FiO2 ratio (p = 0.86), rapid and superficial respiration index (p = 0.48), and carbon dioxide arterial pressure (p = 0.86). Cardiac dysfunction and time of extracorporeal circulation showed a significant difference. CONCLUSION Data on respiratory system mechanics and oxygenation were not parameters for assessing the success or failure. Cardiac dysfunction and time of cardiopulmonary bypass, however, significantly interfered with the success in weaning patients from mechanical ventilation.

Myocardial infarction scar plication in the rat: cardiac mechanics in an animal model for surgical procedures

BACKGROUND The immediate effects of surgical reduction of left ventricle cavity on cardiac mechanics have not been well defined. METHODS Cardiac mechanics were analyzed before and after myocardial infarction scar plication in 11 isolated infarcted rat hearts. RESULTS Despite a decrease in myocardial stiffness, an increase in chamber stiffness was noted after myocardial infarction scar plication. Systolic function was favored in more than one way. For the same diastolic pressures, maximal developed pressures were higher after myocardial infarction scar plication, and the slope of the systolic pressure-volume relationship was steeper afterwards as compared with before; this means that Frank-Starling recruitment is accentuated in smaller cavities. In addition, the developed net forces needed to generate these pressures were clearly lower afterward than before, indicating reduced ventricular afterload. CONCLUSIONS The study results show that diastolic function is harmed and systolic function is favored by myocardial infarction scar plication. We suggest that preoperative evaluation of the degree of diastolic dysfunction and impairment of the Frank-Starling mechanism may help to identify patients who may have a poor postoperative outcome due to diastolic or systolic dysfunction.

Manobra de recrutamento alveolar na reversão da hipoxemia no pós-operatório imediato em cirurgia cardíaca

JUSTIFICATIVA Y OBJETIVOS: Evaluar los efectos de la maniobra de reclutamiento alveolar en la oxigenacion y volumen corriente exhalado en pacientes con hipoxemia en el postoperatorio inmediato de intervencion quirurgica cardiaca. METODO: Estudio prospectivo, consecutivo. Entre 469 intervenciones quirurgicas cardiacas entre febrero a abril de 2006, fueron incluidos en el protocolo 40 pacientes (8,5%), que en la primera evaluacion en la admision de la unidad de terapia intensiva quirurgica presentaban relacion PaO2/FiO2 < 200. En ese grupo de pacientes se aplico prospectivamente protocolo estandarizado de maniobras de reclutamiento alveolar con presion en las vias aereas de 20 cmH2O en la vigencia de relacion PaO2/FiO2 < 200, 30 cmH2O en la relacion PaO2/FiO2 < 150, y 40 cmH2O cuando la relacion PaO2/FiO2 se mantuviese inferior a 150 despues de la maniobra de reclutamiento con presion n la vias aereas de 30 cmH2O. La presion aplicada por medio del ventilador mecanico fue en la modalidad de presion positiva continua en las vias aereas, por tres veces, con una duracion promedio de 30 segundos cada una. Los parametros de oxigenacion y volumen corriente exhalado fueron comparados antes e inmediatamente despues de las maniobras de reclutamiento. RESULTADOS: De los 40 pacientes estudiados, 30 respondieron favorablemente a la maniobra de reclutamiento con presion de 20 cmH2O y en 10 hubo necesidad de 30 cmH2O. Ninguna vez fue necesario aplicar maniobra de reclutamiento con presion de 40 cmH2O. Despues de la aplicacion de la maniobra de reclutamiento hubo una mejoria significativa de la oxigenacion caracterizada por aumento de la relacion PaO2/FiO2 (p = 0,001), saturacion periferica de oxigeno (p = 0,004); y del volumen corriente exhalado (p = 0,038). CONCLUSIONES: Las maniobras de reclutamiento alveolar fueron efectivas en la correccion de la hipoxemia y aumento del volumen corriente exhalado en pacientes bajo ventilacion mecanica en el postoperatorio inmediato de intervencion quirurgica cardiaca.BACKGROUND AND OBJECTIVES To evaluate the effects of the alveolar recruitment maneuver on oxygenation and exhaled tidal volume, in patients with hypoxemia, in the immediate postoperative period of cardiac surgery. METHODS This is a prospective, consecutive study. Among the 469 cardiac surgeries performed from February to April 2006, 40 patients (8.5%) who, at the time of admission to the surgical intensive care unit, presented PaO2/FIO2 < 200, were included in the protocol. A standard prospective protocol of alveolar recruitment maneuvers with pressure of 20 cmH2O in the upper airways in the presence of the ratio PaO2/FIO2 < 200, 30 cmH2O with PaO2/FIO2 < 150, and 40 cmH2O when Pa2O2/FIO2 remained below 150 after recruitment maneuver with pressure of 30 cmH2O, was applied to this group of patients. Continuous positive pressure was applied to the airways with a mechanical ventilator, 3 times, for approximately 30 seconds each. Parameters of oxygenation and exhaled tidal volume were compared before and immediately after the recruitment maneuvers. RESULTS Of the 40 patients in the study, 30 showed good responses to recruitment maneuvers with 20 cmH2O, and 10 cases required 30 cmH2O. It was not necessary to apply pressure of 40 cmH2O. There was a significant improvement in oxygenation after the recruitment maneuvers, demonstrated by an increase in PaO2/FIO2 (p = 0.001), peripheral oxygen saturation (p = 0.004), and exhaled tidal volume (p = 0.038). CONCLUSIONS Alveolar recruitment maneuvers were successful on correcting hypoxemia and increasing the exhaled tidal volume in patients on mechanical ventilation in the immediate postoperative period of cardiac surgery.

Alveolar recruitment maneuver to reverse hypoxemia in the immediate postoperative period of cardiac surgery

JUSTIFICATIVA Y OBJETIVOS: Evaluar los efectos de la maniobra de reclutamiento alveolar en la oxigenacion y volumen corriente exhalado en pacientes con hipoxemia en el postoperatorio inmediato de intervencion quirurgica cardiaca. METODO: Estudio prospectivo, consecutivo. Entre 469 intervenciones quirurgicas cardiacas entre febrero a abril de 2006, fueron incluidos en el protocolo 40 pacientes (8,5%), que en la primera evaluacion en la admision de la unidad de terapia intensiva quirurgica presentaban relacion PaO2/FiO2 < 200. En ese grupo de pacientes se aplico prospectivamente protocolo estandarizado de maniobras de reclutamiento alveolar con presion en las vias aereas de 20 cmH2O en la vigencia de relacion PaO2/FiO2 < 200, 30 cmH2O en la relacion PaO2/FiO2 < 150, y 40 cmH2O cuando la relacion PaO2/FiO2 se mantuviese inferior a 150 despues de la maniobra de reclutamiento con presion n la vias aereas de 30 cmH2O. La presion aplicada por medio del ventilador mecanico fue en la modalidad de presion positiva continua en las vias aereas, por tres veces, con una duracion promedio de 30 segundos cada una. Los parametros de oxigenacion y volumen corriente exhalado fueron comparados antes e inmediatamente despues de las maniobras de reclutamiento. RESULTADOS: De los 40 pacientes estudiados, 30 respondieron favorablemente a la maniobra de reclutamiento con presion de 20 cmH2O y en 10 hubo necesidad de 30 cmH2O. Ninguna vez fue necesario aplicar maniobra de reclutamiento con presion de 40 cmH2O. Despues de la aplicacion de la maniobra de reclutamiento hubo una mejoria significativa de la oxigenacion caracterizada por aumento de la relacion PaO2/FiO2 (p = 0,001), saturacion periferica de oxigeno (p = 0,004); y del volumen corriente exhalado (p = 0,038). CONCLUSIONES: Las maniobras de reclutamiento alveolar fueron efectivas en la correccion de la hipoxemia y aumento del volumen corriente exhalado en pacientes bajo ventilacion mecanica en el postoperatorio inmediato de intervencion quirurgica cardiaca.BACKGROUND AND OBJECTIVES To evaluate the effects of the alveolar recruitment maneuver on oxygenation and exhaled tidal volume, in patients with hypoxemia, in the immediate postoperative period of cardiac surgery. METHODS This is a prospective, consecutive study. Among the 469 cardiac surgeries performed from February to April 2006, 40 patients (8.5%) who, at the time of admission to the surgical intensive care unit, presented PaO2/FIO2 < 200, were included in the protocol. A standard prospective protocol of alveolar recruitment maneuvers with pressure of 20 cmH2O in the upper airways in the presence of the ratio PaO2/FIO2 < 200, 30 cmH2O with PaO2/FIO2 < 150, and 40 cmH2O when Pa2O2/FIO2 remained below 150 after recruitment maneuver with pressure of 30 cmH2O, was applied to this group of patients. Continuous positive pressure was applied to the airways with a mechanical ventilator, 3 times, for approximately 30 seconds each. Parameters of oxygenation and exhaled tidal volume were compared before and immediately after the recruitment maneuvers. RESULTS Of the 40 patients in the study, 30 showed good responses to recruitment maneuvers with 20 cmH2O, and 10 cases required 30 cmH2O. It was not necessary to apply pressure of 40 cmH2O. There was a significant improvement in oxygenation after the recruitment maneuvers, demonstrated by an increase in PaO2/FIO2 (p = 0.001), peripheral oxygen saturation (p = 0.004), and exhaled tidal volume (p = 0.038). CONCLUSIONS Alveolar recruitment maneuvers were successful on correcting hypoxemia and increasing the exhaled tidal volume in patients on mechanical ventilation in the immediate postoperative period of cardiac surgery.

Maniobra de reclutamiento alveolar en la reversión de la hipoxemia en el postoperatorio inmediato en cirugía cardiaca

JUSTIFICATIVA Y OBJETIVOS: Evaluar los efectos de la maniobra de reclutamiento alveolar en la oxigenacion y volumen corriente exhalado en pacientes con hipoxemia en el postoperatorio inmediato de intervencion quirurgica cardiaca. METODO: Estudio prospectivo, consecutivo. Entre 469 intervenciones quirurgicas cardiacas entre febrero a abril de 2006, fueron incluidos en el protocolo 40 pacientes (8,5%), que en la primera evaluacion en la admision de la unidad de terapia intensiva quirurgica presentaban relacion PaO2/FiO2 < 200. En ese grupo de pacientes se aplico prospectivamente protocolo estandarizado de maniobras de reclutamiento alveolar con presion en las vias aereas de 20 cmH2O en la vigencia de relacion PaO2/FiO2 < 200, 30 cmH2O en la relacion PaO2/FiO2 < 150, y 40 cmH2O cuando la relacion PaO2/FiO2 se mantuviese inferior a 150 despues de la maniobra de reclutamiento con presion n la vias aereas de 30 cmH2O. La presion aplicada por medio del ventilador mecanico fue en la modalidad de presion positiva continua en las vias aereas, por tres veces, con una duracion promedio de 30 segundos cada una. Los parametros de oxigenacion y volumen corriente exhalado fueron comparados antes e inmediatamente despues de las maniobras de reclutamiento. RESULTADOS: De los 40 pacientes estudiados, 30 respondieron favorablemente a la maniobra de reclutamiento con presion de 20 cmH2O y en 10 hubo necesidad de 30 cmH2O. Ninguna vez fue necesario aplicar maniobra de reclutamiento con presion de 40 cmH2O. Despues de la aplicacion de la maniobra de reclutamiento hubo una mejoria significativa de la oxigenacion caracterizada por aumento de la relacion PaO2/FiO2 (p = 0,001), saturacion periferica de oxigeno (p = 0,004); y del volumen corriente exhalado (p = 0,038). CONCLUSIONES: Las maniobras de reclutamiento alveolar fueron efectivas en la correccion de la hipoxemia y aumento del volumen corriente exhalado en pacientes bajo ventilacion mecanica en el postoperatorio inmediato de intervencion quirurgica cardiaca.BACKGROUND AND OBJECTIVES To evaluate the effects of the alveolar recruitment maneuver on oxygenation and exhaled tidal volume, in patients with hypoxemia, in the immediate postoperative period of cardiac surgery. METHODS This is a prospective, consecutive study. Among the 469 cardiac surgeries performed from February to April 2006, 40 patients (8.5%) who, at the time of admission to the surgical intensive care unit, presented PaO2/FIO2 < 200, were included in the protocol. A standard prospective protocol of alveolar recruitment maneuvers with pressure of 20 cmH2O in the upper airways in the presence of the ratio PaO2/FIO2 < 200, 30 cmH2O with PaO2/FIO2 < 150, and 40 cmH2O when Pa2O2/FIO2 remained below 150 after recruitment maneuver with pressure of 30 cmH2O, was applied to this group of patients. Continuous positive pressure was applied to the airways with a mechanical ventilator, 3 times, for approximately 30 seconds each. Parameters of oxygenation and exhaled tidal volume were compared before and immediately after the recruitment maneuvers. RESULTS Of the 40 patients in the study, 30 showed good responses to recruitment maneuvers with 20 cmH2O, and 10 cases required 30 cmH2O. It was not necessary to apply pressure of 40 cmH2O. There was a significant improvement in oxygenation after the recruitment maneuvers, demonstrated by an increase in PaO2/FIO2 (p = 0.001), peripheral oxygen saturation (p = 0.004), and exhaled tidal volume (p = 0.038). CONCLUSIONS Alveolar recruitment maneuvers were successful on correcting hypoxemia and increasing the exhaled tidal volume in patients on mechanical ventilation in the immediate postoperative period of cardiac surgery.