Effects of different PEEP levels on respiratory mechanics and oxygenation after coronary artery bypass grafting.

OBJECTIVE: To compare the effects of different levels of positive end-expiratory pressure on respiratory mechanics and oxygenation indexes in the immediate postoperative period of coronary artery bypass grafting. METHODS: Randomized clinical trial in which 136 patients underwent coronary artery bypass grafting between January 2011 and March 2012 were divided into three groups and admitted to mechanical ventilation with different positive end-expiratory pressure levels: Group A, 5 cmH2O (n=44), Group B, 8 cmH2O (n=47) and Group C, 10 cmH2O (n=45). Data about respiratory mechanics were obtained from mechanical ventilator monitor and oxygenation indexes from arterial blood gas samples, collected twenty minutes after intensive care unit admission. Patients with chronic obstructive pulmonary disease and patients submitted to off-pump, emergency or combined operations were not included. For statistical analysis, we used Kruskal-Wallis, G and Chi-square tests, considering results significant when P<0.05. RESULTS: Groups were homogeneous in terms of demographic, clinical and surgical variables. Patients ventilated with positive end-expiratory pressure of 10 cmH2O (Group C) had best compliance (P=0.04) and airway resistance values, this, however, without statistical significance. They also had best oxygenation indexes, with statistical difference in all analyzed variables, and lower frequency of hypoxemia (P=0.03). CONCLUSION: Higher levels of positive end-expiratory pressure in immediate postoperative period of coronary artery bypass grafting improved pulmonary compliance values and increased oxygenation indexes, resulting in lower frequency of hypoxemia.

Factors associated to hypoxemia in patients undergoing coronary artery bypass grafting.

INTRODUCTION: Hypoxemia is a frequent pulmonary complication in the postoperative coronary artery bypass graft. Detection of factors associated with their occurrence may indicate patients at risk for this complication, which allows tracing specific therapeutic and consequently reduce morbidity and mortality. OBJECTIVE: To identify related factors to hypoxemia occurrence in immediate coronary artery bypass graft postoperative. METHODS: In this retrospective cohort study, we studied 100 patients submitted to elective om-pump artery bypass graft , between April 2010 and December 2011, at a reference university hospital for cardiac surgery in the state of Maranhão. It was considered hypoxemia gas exchange ratio less than or equal to 300 mmHg. Associated variables with perioperative hypoxemia were defined by the Student T test, G or Mann-Whitney tests, Chi-square, or Fisher's exact test and multiple linear regression. RESULTS: Among studied variables, high body mass index (P=0.036) and smoking (P=0.024) were significantly associated with hypoxemia in the immediate coronary artery bypass graft postoperative. Hypoxemia incidence in this period was 55% and did not affects mechanical ventilation duration and Intensive Care Unit lengh of stay. CONCLUSION: In this sample, body mass index and smoking were associated to hypoxemia. These data reinforce the importance of clinical assessment to identify patients at risk for this complication, considering its high incidence in immediate postoperative period.

Factors associated to hypoxemia in patients undergoing coronary artery bypass grafting / Fatores associados à ocorrência de hipoxemia em pacientes submetidos à revascularização miocárdica

INTRODUCTION: Hypoxemia is a frequent pulmonary complication in the postoperative coronary artery bypass graft. Detection of factors associated with their occurrence may indicate patients at risk for this complication, which allows tracing specific therapeutic and consequently reduce morbidity and mortality. OBJECTIVE: To identify related factors to hypoxemia occurrence in immediate coronary artery bypass graft postoperative. METHODS: In this retrospective cohort study, we studied 100 patients submitted to elective om-pump artery bypass graft , between April 2010 and December 2011, at a reference university hospital for cardiac surgery in the state of Maranhão. It was considered hypoxemia gas exchange ratio less than or equal to 300 mmHg. Associated variables with perioperative hypoxemia were defined by the Student T test, G or Mann-Whitney tests, Chi-square, or Fisher's exact test and multiple linear regression. RESULTS: Among studied variables, high body mass index (P=0.036) and smoking (P=0.024) were significantly associated with hypoxemia in the immediate coronary artery bypass graft postoperative. Hypoxemia incidence in this period was 55% and did not affects mechanical ventilation duration and Intensive Care Unit lengh of stay. CONCLUSION: In this sample, body mass index and smoking were associated to hypoxemia. These data reinforce the importance of clinical assessment to identify patients at risk for this complication, considering its high incidence in immediate postoperative period.

INTRODUÇÃO: A hipoxemia é uma complicação pulmonar frequente no pós-operatório de revascularização miocárdica. A detecção de fatores associados a sua ocorrência pode indicar pacientes de risco para essa complicação, o que possibilita traçar terapêuticas específicas e, consequentemente, diminuir a morbi-mortalidade. OBJETIVO: Identificar fatores relacionados à ocorrência de hipoxemia no pós-operatório imediato de revascularização miocárdica. MÉTODOS: Nesta coorte retrospectiva, foram estudados 100 pacientes que se submeteram à cirurgia eletiva de revascularização miocárdica com uso de circulação extracorpórea, no período de abril de 2010 a dezembro de 2011, no Hospital Universitário de referência para cirurgia cardíaca no estado do Maranhão. Considerou-se hipoxemia índice de troca gasosa menor ou igual a 300 mmHg. A associação das variáveis perioperatórias com a ocorrência de hipoxemia foi definida por meio dos testes t de Student ou Mann Whitney, Qui-quadrado, teste G, ou Exato de Fisher, além de regressão linear múltipla. RESULTADOS: Dentre as variáveis estudadas, o índice de massa corpórea elevado (P=0,036) e o tabagismo (P=0,024) apresentaram associação estatisticamente significante com a ocorrência de hipoxemia no pós-operatório imediato de revascularização miocárdica. A incidência de hipoxemia no pós-operatório imediato foi 55%. A ocorrência de hipoxemia não interferiu nos tempos de ventilação mecânica e de estadia na Unidade de Terapia Intensiva. CONCLUSÃO: Nesta amostra, houve associação entre o índice de massa corpórea e o tabagismo com a ocorrência de hipoxemia. Esses dados reforçam a importância da avaliação clínica para identificação do paciente de risco para ocorrência dessa complicação, já que esta apresenta elevada incidência no pós-operatório imediato.

Effects of different PEEP levels on respiratory mechanics and oxygenation after coronary artery bypass grafting / Efeitos de diferentes níveis de PEEP na mecânica respiratória e oxigenação após revascularização do miocárdio

OBJECTIVE: To compare the effects of different levels of positive end-expiratory pressure on respiratory mechanics and oxygenation indexes in the immediate postoperative period of coronary artery bypass grafting. METHODS: Randomized clinical trial in which 136 patients underwent coronary artery bypass grafting between January 2011 and March 2012 were divided into three groups and admitted to mechanical ventilation with different positive end-expiratory pressure levels: Group A, 5 cmH2O (n=44), Group B, 8 cmH2O (n=47) and Group C, 10 cmH2O (n=45). Data about respiratory mechanics were obtained from mechanical ventilator monitor and oxygenation indexes from arterial blood gas samples, collected twenty minutes after intensive care unit admission. Patients with chronic obstructive pulmonary disease and patients submitted to off-pump, emergency or combined operations were not included. For statistical analysis, we used Kruskal-Wallis, G and Chi-square tests, considering results significant when P<0.05. RESULTS: Groups were homogeneous in terms of demographic, clinical and surgical variables. Patients ventilated with positive end-expiratory pressure of 10 cmH2O (Group C) had best compliance (P=0.04) and airway resistance values, this, however, without statistical significance. They also had best oxygenation indexes, with statistical difference in all analyzed variables, and lower frequency of hypoxemia (P=0.03). CONCLUSION: Higher levels of positive end-expiratory pressure in immediate postoperative period of coronary artery bypass grafting improved pulmonary compliance values and increased oxygenation indexes, resulting in lower frequency of hypoxemia.

OBJETIVO: Comparar os efeitos de diferentes níveis de pressão expiratória positiva final na mecânica respiratória e nos índices de oxigenação no pós-operatório imediato de revascularização do miocárdio. MÉTODOS: Ensaio clínico randomizado no qual 136 pacientes submetidos à revascularização do miocárdio, entre janeiro de 2011 e março de 2012, foram distribuídos em três grupos e admitidos na ventilação mecânica com diferentes níveis de pressão expiratória positiva final: Grupo A, 5 cmH2O (n=44), Grupo B, 8 cmH2O (n=47) e Grupo C, 10 cmH2O (n=45), sendo os dados da mecânica respiratória obtidos do monitor do ventilador mecânico e os índices de oxigenação por meio de gasometria arterial coletada vinte minutos após a admissão na unidade de terapia intensiva. Não foram incluídos pacientes com doença pulmonar obstrutiva crônica, cirurgias associadas, de emergência ou sem circulação extracorpórea. Para análise estatística, empregaram-se os testes de Kruskal-Wallis, Teste G e Qui-quadrado, considerando os resultados significantes quando P<0,05. RESULTADOS: Os grupos apresentaram-se homogêneos em relação às variáveis demográficas, clínicas e cirúrgicas. Os pacientes ventilados com pressão expiratória positiva final de 10 cmH2O (Grupo C) apresentaram os melhores valores de complacência (P=0,04) e de resistência das vias aéreas, esta, porém sem significância estatística. Apresentaram, ainda, os melhores índices de oxigenação, com diferença estatística em todas as variáveis estudadas, além de menor frequência de hipoxemia (P=0,03). CONCLUSÃO: Níveis mais elevados de pressão expiratória positiva final no pós-operatório imediato de revascularização do miocárdio incrementaram os valores de complacência pulmonar e melhoraram os índices de oxigenação, resultando acarretando em menor frequência de hipoxemia.