A Clinic Study Of ALI/ARDS Following Valve Replacement Under Cardiopulmonary Bypass

ALI/ARDS after open heart operation under cardiopulmonary bypass (CPB) is one of critical postoperative complications, which impacts the prognosis of open heart operation severely. The incidence of ALI/ARDS following CPB is 0.4%-2.0%, with a high mortality of 40-60%. The mechanism of ARDS is complicated. The typical clinic manifestations include refractory hypoxia, dyspnea and respiratory distress, pulmonary infiltration in chest X-ray, and multiple organ failure present in the late phase. So far, the mechanism of ALI/ARDS has not been clearly elucidated, and there are no standard diagnostic criteria on ALI/ARDS. This study focuses on investigating the clinic characteristics and the risk factors of ARDS, aiming to gain insights into the mechanism of ALI/ARDS and providing scientific evidences for early diagnosis and treatment of ALI/ARDS following CPB.Methods:Preparation was performed in the first part of the study. Microsoft Access XP, VB6.0, Microsoft SQL and SPSS 10.0 software were used to create the minitype professional database of ALI/ARDS following CPB. Case-controlled studies were performed in the second and the third part of the study. In the second part of the study, the professional database of ALI/ARDS was used to collect the clinic data of patients underwent valve replacement from January 2003 to August 2004. The clinic data of the patients suffering prolonged mechanical ventilation (PMV) from January 1996 to March 2004 in our ICU were collected by this database. SPSS 10.0 software was used to statistics the characteristics of perioperative blood gas. Multivariable Linear regression model was used to determine the risk factors of PMV after CPB. In the third part of the study, the clinic data of 69 cases of patients underwent ARDS in our ICU from January 1996 to March 2004 were collected by this database. Binary Logistic Regression analysis was used to detect the risk factors of mortality after ARDS. 1:6 matched Controlled patients underwent similar operation procedures during the same period were involved to analysis the risk factors of ARDS. A clinic study was conducted in the fourth part of this study. To investigate the PMNactivation and lung injury after open heart operation under CPB, Bronchoalveolar lavage (BAL) technique was used to collect the samples of Bronchoalveolar lavage fluid (BALF) preoperatively, IntraCPB, postoperatively from March 2004 to May 2004. The peripheral blood samples were collected simultaneously. The related clinic data were also collected. Results:1. Results of the first part of the studyA minitype professional database of ALI/ARDS following CPB was created by our work team based on Microsoft Access XP software, VB6.0, Microsoft SQL. And it works well in collecting the clinic data of the patients underwent open heart operation, by which satisfactory results reached.2. Results of the second part of the study(1) Postoperative cardiac enzymes increased significantly (P = 0.000) after open heart operation under CPB. Postoperative level of T-Bil, D-Bil, BUN raised significantly (P = 0.000). And the postoperative peripheral WBC count increased significantly (P=0.000). It showed that CPB caused noticeable injury to major organs such as: heart, liver and renal. And the peripheral PMN were sequestrated and activated significantly.(2) CPB led to various degrees acute lung injuries. The patients' postoperative oxygen index (PaO2/FiO2) decreased, oxygen gradient between alveolar and artery increased, and intrapulmonary shunt increased significantly. Injury to the pulmonary oxygenation function occurred frequently. The incidence of PaO2/FiO2<300 at 2h, 6h, 12h, 24h, 48h, 72h after operation were 31.1%, 23.4%, 30.2%, 23.8%, 20.6%, 15.4% respectively. Monitoring the dynamic shifts of blood gas plays an important role during perioperative treatment for the patients underwent open heart operations(3) PaO2, PaO2/FiO2 and A-aDO2 at FiO2 of 1.0 mechanical ventilation were higher than breathe air (P=0.00), but there were no significant differences in Qs/Qt (P=0.288). There was no significant correlation in PaO2 under different FiO2 and ventilation manner(P = 0.647). And significant correlation present in PaO2/FiO2, A-aDO2, Qs/Qt (P = 0.000). PaO2/FiO2 is a valuable predictor of pulmonary oxygenation function under different FiO2 and ventilation manner.(4) Multivariate liner regress analysis showed that the duration of mechanical ventilation is related with the preoperative cardiac function, CPB time, the level ofpostoperative myocardial enzyme, PaO2/FiO2 and the quantity of postoperative drainage. It is suggested that efforts be made to improve cardiac function before operation, active management of the concomitant disease, shorten the CPB time, prevent anesthesiology and operative accidents, carefully homeostasis during the operation procedures.3. Results of the third part of the study(1) Most of this cohort of the patients had concomitant diseases or risk factors, including: concomitant diseases in 62.3% of the patients, special history in 55.1%, perioperative accidents or preoperative misdiagnosis in 13.04%.(2) Typical manifestations of ARDS after CPB included refractory hypoxia, stunned response to routine treatments, companying higher airway pressure, lower pulmonary compliance, and chest X-ray changes. In the early phase, the patients were ventilated mechanically; neuromuscular blockade and sedation were needed to maintain the patients' cooperation. And lack of respiratory distress under mechanical ventilation, higher airway pressure and lower pulmonary compliance present outstandingly. We experienced that monitor respiratory dynamics and blood gas continuously was helpful to make the early diagnosis and provide prompt treatment for the patients underwent ARDS.(3) Binary Logistic regress analysis showed that poor preoperative cardiac function, prolonged CPB time, large quantity of postoperative chest drainage and occurrence of multiple organ failure were the risk factors of mortality after ARDS. Preoperative renal dysfunction, fat and large body weight (BW), preoperative coexisting diseases, perioperative accidents, excessive postoperative drainage and large quantity of transfusion are independent risk factors of ARDS.4. Results of the fourth part of the study(1) The postoperative concentration of total protein in BALF increased significantly compared with preoperative concentration (preoperative TPC 0.715±0.200 g/L, postoperative TPC 1.578±0.758 g/L, p=0.000). The WBC count in BALF also increased (preoperative WBC 14.250±4.979×106/L, postoperative WBC 71.07±24.59 ×106/L, P=0.000), and the ratio of PMN in the classification of WBC increased as well (preoperative ratio 0.070±0.032, postoperative ratio 0.376±0.181, P=0.000).(2) The concentration of NE, MPO, MDA and sLPI in BALF at post-CPB were higher than those at pre-CPB. They were at the highest level at 4h after operation (P value equal0.000, 0.000, 0.000, 0.001 respectively). On the contrary, the concentrations of -SH at post-CPB in BALF were lower than that at pre-CPB. They were lowest at 4h after operation (P=0.000).(3) The postoperative concentrations of NE, MPO, MDA and vWF in plasma were increased significantly, compared with preoperative concentrations (P=0.000), whereas the postoperative concentration of sLPI and -SH in plasma decreased significantly (P value equal to 0.014 and 0.000).(4) There presented positive correlation between NE and sLPI in BALF (r=0.429, P=0.004), while negative correlation between NE and sLPI in plasma presented (r=-0.323, P=0.025). Negative correlation presented between NE in BALF and PaO2/FiO2 (r=-0.395, P=0.034), between NE in plasma and PaO2/FiO2 (r=-0.600, P=0.000), between vWF in plasma and PaO2/FiO2 (r=-0.698, P=0.000). Whereas, a positive correlation presented between sLPI in plasma and PaO2/FiO2 (r=0.629, P=0.000). These results illustrated that the level of NE both in BALF and in plasma was related with pulmonary oxygenation function and was implicated to the lung injury. The level of vWF was also related with pulmonary oxygenation function. sLPI was a protective factor to pulmonary oxygenation function.Conclusion:1. Accuracy of perioperative clinic data is secured by the minitype professional ALI/ARDS database based on Microsoft Access Software and the laborious workload is also alleviated. Furthermore, it is convenient to perform later statistics.2. Although the inflammatory injury to cardiopulmonary bypass often remains at subclinical levels, it can lead to major organ dysfunction and multiple organ failure. Various degree depression in pulmonary oxygenation function present commonly after open heart operation under CPB. PaO2/FiO2 is a valuable index to assess pulmonary oxygenation function at different FiO2 or under different ventilation manner.3. The preoperative cardiac function, CPB time, the effects of intraoperative myocardial protection, the status of pulmonary function and the quantity of chest drainage are the independent risk factors of prolonged mechanical ventilation.4. ARDS following CPB present typical manifestations within 72h after CPB. And coexisting diseases and risk factors present in most of ARDS patients. Typical manifestations include refractory hypoxia, stunned response to routine treatments,companying higher airway pressure, lower pulmonary compliance and chest X-ray changes. In the patients underwent mechanical ventilation, muscle paralysis and sedation, higher airway pressure and lower pulmonary compliance present obviously instead of respiratory distress.5. Poor preoperative cardiac function, prolonged CPB time, larger quantity of postoperative chest drainage and occurrence of multiple organ failure were the independent risk factors of mortality of ARDS. Preoperative renal dysfunction, large BW, preoperative concomitant diseases, perioperative accidents, excessive postoperative drainage and large quantity of transfusion are independent risk factors of ARDS.6. BAL is a safe and effective method in the study on the lung injury following valve replacement. It offers important and direct evidences on the early diagnosis and management lung injury following CPB. The mechanisms involved in lung injury following CPB include neutrophil sequestration and degranulation both in peripheral blood and alveolar, and a large quantity of inflammatory mediators such as proteases. sLPI is an important protective factor against inflammatory injury.