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: 0.89cm vs.0.64cm; systolic: 0.72cm vs. 0.33cm) and left atrium (0.55cm vs. 0.33cm); thinning of left ventricular anterior wall (systolic: 0.14cm vs. 0.23cm, diastolic: 0.11cm vs. 0.14cm); 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.Universidade Federal de São Paulo (UNIFESP) Escola Paulista de MedicinaUNIFESP, EPMSciEL

Efeitos da posição sentada na força de músculos respiratórios durante o desmame de pacientes sob ventilação mecânica prolongada no pós-operatório de cirurgia cardiovascular

The purpose was to study the effects of sitting position, in ventilatory and hemodynamic parameters, in patients under prolonged mechanical ventilation, in the postoperative of cardiovascular surgery. Participated 40 postoperative cardiovascular patients, intubated and mechanically ventilated, were randomized into control group (n=17) and intervention group (n=23). Hemodynamic parameters, arterial blood gases, respiratory muscle strength and ventilometry, were measured in two moments: first and second evaluation, with 30-minute interval between measurements. In the control group, both evaluations were performed at head of the bed elevated at 30°. In the sitting group, the first evaluation was developed at 30° and the second, (30 minutes after transfer to the armchair) in the sitting position (90°). The mean age of patients was 64.7±11.2 years. There were no differences regarding the hemodynamic parameters, blood gas analysis, forced vital capacity, minute ventilation and tidal volume. However, a significant increase in maximal inspiratory pressure (MIP) in the intervention group was observed (pO objetivo do estudo foi investigar os efeitos da posição sentada, nos parâmetros ventilatórios e hemodinâmicos, em pacientes com suporte ventilatório mecânico prolongado, estáveis hemodinamicamente. Participaram do estudo 40 pacientes que foram randomizados em grupo controle (n=17) e grupo intervenção (n=23). Foram mensurados parâmetros hemodinâmicos, gasometria arterial, força muscular respiratória e ventilometria, realizados em dois momentos: primeira e segunda avaliação, com intervalo de 30 minutos entre as medidas. No grupo controle, as duas avaliações foram realizadas no leito, com a cabeceira elevada a 30°. No grupo intervenção, a primeira avaliação foi realizada no leito (30°) e a segunda, 30 minutos após transferência para a poltrona, na posição sentada (90°). A idade média da amostra foi de 64,7±11,2 anos. O resultado do estudo demonstrou que não houve diferenças em relação às variáveis, hemodinâmicas, gasométricas, capacidade vital forçada, volume minuto e volume de ar corrente. Entretanto, ocorreu aumento significativo da pressão inspiratória máxima (PImáx) no grupo intervenção (

Benefícios da ventilação não-invasiva após extubação no pós-operatório de cirurgia cardíaca Benefits of non-invasive ventilation after extubation in the postoperative period of heart surgery

OBJETIVO: Demonstrar os benefícios da utilização da ventilação não-invasiva (VNI) no processo de interrupção da ventilação mecânica, no pós-operatório de cirurgia cardíaca. MÉTODOS: Estudo prospectivo, randomizado e controlado, com 100 pacientes submetidos a cirurgia de revascularização do miocárdio ou cirurgia valvar. Os pacientes foram admitidos na Unidade de Terapia Intensiva (UTI), sob ventilação mecânica e randomizados posteriormente em grupo estudo (n= 50) que utilizou VNI com dois níveis pressóricos após a extubação por 30 minutos, e grupo controle (n= 50) que fez uso apenas de cateter nasal de O2. Foram analisadas as variáveis antropométricas, os tempos correspondentes à anestesia, cirurgia e circulação extracorpórea, bem como o tempo necessário para a supressão da ventilação mecânica invasiva. As variáveis gasométricas e hemodinâmicas também foram avaliadas antes e após a extubação. RESULTADOS: Os grupos controle e estudo evoluíram de forma semelhante e não apresentaram diferença estatisticamente significante na análise das variáveis, exceto para a PaO2. A utilização da VNI por 30 minutos após a extubação promoveu melhora na PaO2 quando comparados os grupos, com p= 0,0009, mas não apresentou diferença estatisticamente significante na PaCO2 (p=0,557). CONCLUSÃO: O uso da VNI por 30 minutos após extubação produziu melhora na oxigenação do pacientes em pósoperatório imediato de cirurgia cardíaca.<br>OBJECTIVE: to show the benefits of the use of non-invasive positive pressure ventilation (NPPV) in the process of weaning from mechanical ventilation in the immediate postoperative period of heart surgery. METHODS: A prospective, randomized and controlled study was performed involving 100 consecutive patients submitted to coronary artery bypass grafting or valve surgery. The subjects were admitted into the Intensive Care Unit (ICU) under mechanical ventilation and randomized in a study group (n=50), which used NPPV with bilevel pressure for 30 minutes after extubation, and a control group (n=50) which only used a nasal O2 catheter. Anthropometric variables and the times of the intra-operative periods corresponding to anesthesia, surgery and cardiopulmonary bypass, as well as the time required for weaning from invasive mechanical ventilation were analysed. The arterial blood gases and hemodynamic variables were also assessed before and after extubation. RESULTS: The evolution was similar for the control and study groups without statistically significant differences of the variables analyzed except for the PaO2. On comparing the groups, the PaO2 improved significantly (p = 0.0009) with the use of NPPV for 30 minutes after extubation, but there was no statistically significant difference in the PaCO2 (p = 0.557). CONCLUSION: The use of NPPV for 30 minutes after extubation improved oxygenation in the immediate postoperative period of heart surgery

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, oxigenation 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

Aplicação da ventilação não-invasiva em insuficiência respiratória aguda após cirurgia cardiovascular Application of noninvasive ventilation in acute respiratory failure after cardiovascular surgery

OBJETIVOS: Verificar as respostas ventilatória, de oxigenação e hemodinâmica de pacientes com insuficiência respiratória aguda (IResp) hipoxêmica submetidos a aplicação de ventilação mecânica não-invasiva (VMNI) no pós-operatório de cirurgia cardiovascular, buscando variáveis preditoras de sucesso, e comparar as diferentes modalidades de VMNI. MÉTODOS: No total, 70 pacientes com IResp hipoxêmica foram randomizados em uma das três modalidades de VMNI: pressão positiva contínua em vias aéreas (CPAP) e ventilação com dois níveis pressóricos (PEEP + PS e BiPAP®). Foram analisadas variáveis ventilatórias, de oxigenação e hemodinâmicas nos períodos pré-aplicação, 3, 6 e 12 horas após iniciado o protocolo. RESULTADOS: Foram excluídos 13 pacientes. Dos pacientes restantes, 31 evoluíram para independência do suporte ventilatório, constituindo o grupo sucesso, e 26 necessitaram de intubação orotraqueal, sendo considerados insucesso. Idade e níveis iniciais de freqüência cardíaca (FC) e de freqüência respiratória (FR) apresentaram valores elevados no grupo insucesso (p = 0,042, 0,029 e 0,002, respectivamente). O grupo insucesso apresentou maior número de intercorrências intra-operatórias (p = 0,025). As variáveis de oxigenação elevaram-se somente no grupo sucesso. Dentre as modalidades de VMNI, evoluíram como sucesso 57,9% dos pacientes no grupo ventilador, 57,9% no bi-nível e 47,3% no CPAP. Variáveis de oxigenação e FR apresentaram melhora somente nos grupos com dois níveis pressóricos. CONCLUSÃO: Pacientes com IResp hipoxêmica no pós-operatório de cirurgia cardiovascular apresentaram melhora da oxigenação, da FR e da FC durante a aplicação de VMNI. Em pacientes mais idosos e com valores iniciais de FR e de FC mais elevados, a VMNI não foi suficiente para reverter o quadro de IResp. Modalidades com dois níveis pressóricos apresentaram resultados superiores.<br>OBJECTIVE: To examine ventilatory response, oxygenation-related, and hemodynamics of patients with hypoxemic acute respiratory failure (ARF) submitted to noninvasive mechanical ventilation (NIV) during the postoperative phase of cardiovascular surgery in order to identify predictive variables of success, and to compare the different types of NIV. METHODS: Seventy patients with hypoxemic ARF were randomized to one of three modalities of NIV - continuous positive airway pressure (CPAP) and ventilation with two pressure levels (PEEP + SP and BiPAP®). Ventilation, oxygenation-related, and hemodynamics variables were analyzed at pre-application, and 3, 6, and 12 hours after the protocol began. RESULTS: Thirteen patients were excluded. Thirty-one patients progressed to independence from ventilatory support and comprised the success group, and 26 required orotracheal intubation and were considered the nonsuccess group. Age, initial heart rate (HR), and respiratory rate (RR) showed elevated levels in the nonsuccess group (p=0.042, 0.029, and 0.002, respectively). A greater number of intraoperative complications were seen in the nonsuccess group (p=0.025). Oxygenation variables increased only in the success group. Among the NIV types, 57.9% of patients in the ventilator group, 57.9% in the two-pressure levels group, and 47.3% in the CPAP group progressed with success. Oxygenation and RR variables showed improvement only in the groups with two pressure levels. CONCLUSION: Patients with hypoxemic ARF in the postoperative stage after cardiovascular surgery showed better oxygenation, RR, and HR during NIV application. In older patients and those with higher baseline RR and HR values, NIV was not sufficient to reverse ARF. The two-pressure level modes showed better results