Cardiac preload: hemodynamic physiology during thoracic surgery

Operations in pleural cavity have circulatory effects both in pulmonary and systemic circulations. Nevertheless studies of these effects have yielded conflicting results. The importance of good understanding of hemodynamic changes during the operation in pleural cavity consists in fact that they are one of the factors influencing postoperative course of operated patients.

Dominating changes in the hemodynamics are represented by an increase of the cardiac output after opening the pleura. Changes in the arterial pressure are clinically unimportant and decreased cardiac output cannot be explained by preload as the preload is almost constant during the whole operation procedure. Arterial pressures in the pulmonary circulation are also increased after opening of pleura but only in the hip position so it depends on the body position rather than on the operation itself.

As far as it is known, circulatory and ventilatory consequences of thoracotomy are influenced particularly by the position of the patient's body on the operation table. During operation performed on the lung hemodynamics are influenced particularly by the individual steps of the operation procedure and by the position of the body. The hemodynamics are also influenced by metabolic functions of lungs particularly by the increased turnover of catecholamines in the lungs (increased total peripheral resistance and arterial pressures).