Alterations of the pulmonary microcirculation after open heart surgery. Correlation between the pulmonary vascular dynamics and ultrastructural changes after the operation.

Resumo

The study of pulmonary hemodynamics after mitral valve replacement in 30 patients, during the first 18 post-operative hours, did show elevated pulmonary vascular resistance from the pre-operative levels in the majority of them. This rise varied directly, with the bypass time and was associated with increased right ventricular work, intrapulmonary shunt and more severe ultrastructural lesions of the alveolar-capillary membrane. The pulmonary vascular resistance had tendency to lower to the pre-operative values at the end of 18 hours. The microscopic changes, very similar with the observed on shock lung, fat emboli and in all non-hemodynamic pulmonary edemas, may well be due to excessive and prolonged stimulation of catecholamines, microemboli and hypoxia. The control of perfusion pressure, better synthetic surfaces and oxygenators, and the use of assisted ventilation with positive end-expiratory pressure must be investigate to precise their exact role on the alterations of the pulmonary microcirculation after open heart surgery.