The mechanism of lung injury in patients undergoing heart valves replacement with cardiopulmonary bypass / 中华麻醉学杂志

ABSTRACT

Objective To assess the mechanisms that contribute to lung injury in patients undergoing heart valve replacement with cardiopulmonary bypass (CPB) .Methods Eight HYHA grade Ⅱ-Ⅲ patients (4 males, 4 females) aged 47-67 years weighing 49.4-68.6 kg undergoing heart valve replacement with CPB were studied. The patients were premedicated with intramuscular morphine 0.1-0.2 mg?kg-1 and scopolamine 0.3 tng. Anesthesia was induced with midazolam 0.05-0.1 mg? kg-1 , fentanyl 15-20 ?g?kg-1 and pipecuronium 0.1 mg?kg-1 and maintained with intermittent Ⅳ boluses of midazolam 0.05 mg?kg-1 , fentanyl 10-30?g?kg-1 and pipecuronium 2 mg. Swan-Ganz catheter was placed via internal jugular vein after induction of anesthesia. Operation was performed under mild hypothermic (28-32℃) CPB. Blood samples were taken from radial and pulmonary artery for blood gas analysis and determination of neutrophil (PMN) counts, plasma TNFa and LPO concentrations and SOD activity prior to CPB (T0), 5 min after venae cava declamping (T1) and at the end of CPB (T2) and operation (T3 ) . The differences in the variables measured between pulmonary artery and vein were calculated to show the PMN entrapped, TNFa produced, SOD depleted and LPO released in the lungs. The alveolar-arterial oxygen tension difference (PA-aDO2) and intrapulmonary shunt( QS/QT)were calculated. Lung ischemia time was defined as the duration between occlusion and release of vena cava superior and inferior. Results The mean lung ischemia time was (97?21)min. MPAP, PVRI, PA-a.DO2 and QS/QT significantly increased after CPB, while PaO2/FiO2 and lung compliance significantly decreased compared with those before CPB (P