Effect of Body Positions on Hemodynamics and Gas Exchange in Anesthetized Pigs Shortly After Pneumonectomy
Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan, Republic of China.Shock (Augusta, Ga.) (Impact Factor: 3.05). 03/2010; 34(5):482-7. DOI: 10.1097/SHK.0b013e3181dc0812
Positional changes are thought to affect hemodynamics, respiratory mechanics, and gas exchange after pneumonectomy. The objective of this study was to compare hemodynamic and respiratory parameters and gas exchange in different positions before and after pneumonectomy. Twenty pigs were anesthetized and mechanically ventilated. Seven received right-side pneumonectomy, seven received left-side pneumonectomy, and six were anesthetized but did not receive surgery and served as controls. Hemodynamic and respiratory parameters and blood gas values were measured in different positions (supine and right and left lateral decubitus). Minute mechanical ventilation was controlled throughout. Pneumonectomy resulted in significant reductions in MAP, accompanied by significant decreases in cardiac index, stroke volume index, global ejection fraction, and global end-diastolic volume index. Mean pulmonary arterial pressure and pulmonary vascular resistance index increased. PaCO2, airway resistance, and peak airway pressure increased, whereas PaO2 and lung compliance decreased. Hemodynamic and respiratory parameters and gas exchange were also significantly affected by changes in position with pneumonectomy. Mean arterial pressure, cardiac index, stroke volume index, global ejection fraction, and global end-diastolic volume index were significantly lower in the supine than in the right or left lateral decubitus position. PaO2 was significantly higher in a lateral position, with the remaining lung uppermost. Our findings suggest that avoiding the supine positioning after pneumonectomy may facilitate improvements in hemodynamics and a decreased risk of hypoxemia. The optimal position for gas exchange after pneumonectomy is a lateral position, with the remaining lung in the uppermost position.
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- "It is interesting that positional effects are different in animals with normal lung, post-pneumonectomy, and post-thoracotomy. In our previous study, PaO2 did not change in different positions in pigs with normal lung. In post-pneumonectomized pigs, the PaO2 significantly changed in different positions with the best PaO2 in the position with remained lung uppermost (operated side lowermost). "
ABSTRACT: Thoracotomy is a common procedure. However, thoracotomy leads to lung atelectasis and deteriorates pulmonary gas exchange in operated side. Therefore, different positions with operated side lowermost or uppermost may lead to different gas exchange after thoracotomy. Besides, PEEP (positive end-expiratory pressure) influence lung atelectasis and should influence gas exchange. The purpose of this study was to determine the physiological changes in different positions after thoracotomy. In addition, we also studied the influence of PEEP to positional effects after thoracotomy. There were eight pigs in each group. Group I received left thoracotomy with zero end-expiratory pressure (ZEEP), and group II with PEEP; group III received right thoracotomy with ZEEP and group IV with PEEP. We changed positions to supine, LLD (left lateral decubitus) and RLD (right lateral decubitus) in random order after thoracotomy. PaO2 was decreased after thoracotomy and higher in RLD after left thoracotomy and in LLD after right thoracotomy. PaO2 in groups II and IV was higher than in groups I and III if with the same position. In group I and III, PaCO2 was increased after thoracotomy and was higher in LLD after left thoracotomy and in RLD after right thoracotomy. In groups II and IV, there were no PaCO2 changes in different positions after thoracotomy. Lung compliance (Crs) was decreased after thoracotomy in groups I and III and highest in RLD after left thoracotomy and in LLD after right thoracotomy. In groups II and IV, there were no changes in Crs regardless of the different positions. There were significant changes with regards to pulmonary gas exchange, hemodynamics and Crs after thoracotomy. The best position was non-operated lung lowermost Applying PEEP attenuates the positional effects.
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ABSTRACT: Pneumonectomy is a major surgery. Severe hypoxemia sometimes occurs after pneumonectomy. Effective gas exchange depends on perfect pulmonary ventilation (V˙(A)) and perfusion (Q˙) matching. The effect of position on V˙(A)/Q˙ matching after pneumonectomy is not clear. We therefore conducted this study to examine the effects of supine, left lateral decubitus (LLD), and right lateral decubitus (RLD) positions on V˙(A)/Q˙ matching and gas exchange after pneumonectomy in a porcine model. Twelve pigs were anesthetized and mechanically ventilated; six pigs received right pneumonectomy and six pigs received left pneumonectomy. The positions of the pigs were changed to supine, LLD, and RLD in random order after pneumonectomy. We applied intravenous and aerosolized high-resolution fluorescent microsphere technique (FMT) to mark V˙(A) and Q˙ in conjunction with arterial blood gas analysis to study these variables at different positions. Mechanical ventilation was kept constant throughout. Different positions after pneumonectomy lead to significant changes in heterogeneity and matching of V˙(A)/Q˙. In right pneumonectomized pigs, the highest PaO(2), lowest V˙(A)/Q˙heterogeneity, and highest matching of V˙(A)/Q˙ was in RLD. In left pneumonectomized pigs, the highest PaO(2), lowest V˙(A)/Q˙ heterogeneity, and highest matching of V˙(A)/Q˙ was in LLD. The lateral position with the remaining lung uppermost leads to the highest V˙(A)/Q˙ matching and best gas exchange after pneumonectomy.
Article: What's New in Shock, November 2010?
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