Christof M. Strang

One-lung ventilation induces hyperperfusion and alveolar damage in the ventilated lung: an experimental study

BACKGROUND One-lung ventilation (OLV) increases mechanical stress in the lung and affects ventilation and perfusion (V, Q). There are no data on the effects of OLV on postoperative V/Q matching. Thus, this controlled study evaluates the influence of OLV on V/Q distribution in a pig model using a gamma camera technique [single-photon emission computed tomography (SPECT)] and relates these findings to lung histopathology after OLV. METHODS Eleven anaesthetized and ventilated pigs (V(T)=10 ml kg(-1), Fio2=0.40, PEEP=5 cm H2O) were studied. After lung separation, OLV and thoracotomy were performed in seven pigs (OLV group). During OLV and in a two-lung ventilation (TLV), control group (n=4) ventilation settings remained unchanged. SPECT with (81m)Kr (ventilation) and (99m)Tc-labelled macro-aggregated albumin (perfusion) was performed before, during, and 90 min after OLV/TLV. Finally, lung tissue samples were harvested and examined for alveolar damage. RESULTS OLV affected ventilation and haemodynamic variables, but there were no differences between the OLV group and the control group before and after OLV/TLV. SPECT revealed an increase of perfusion in the dependent lung compared with baseline (49-56%), and a corresponding reduction of perfusion (51-44%) in non-dependent lungs after OLV. No perfusion changes were observed in the control group. This resulted in increased low V/Q regions and a shift of V/Q areas to 0.3-0.5 (10(-0.5)-10(-0.3)) in dependent lungs of OLV pigs and was associated with an increased diffuse alveolar damage score. CONCLUSIONS OLV in pigs results in a substantial V/Q mismatch, hyperperfusion, and alveolar damage in the dependent lung and may thus contribute to gas exchange impairment after thoracic surgery.

Anesthetic considerations in patients with previous thoracic surgery.

Purpose of the review This review presents an overview of the different problems and challenges after thoracic surgery. It covers the pathophysiological changes that may occur regularly in the early and late period following surgery. In addition, surgical complications with anesthesiological implications for diagnosis, treatment and prevention are discussed, and consequences for anesthesia in further major and thoracic surgical procedures are shown. Recent findings During the last decade, complications in the early period following surgery after thoracotomy have increasingly moved into the focus caused by their high morbidity and mortality. These problems, such as hemorrhagia and bronchopleural fistulas, are important because they call for a prompt revision or even an emergency operation. The therapy of acute bleeding follows general anesthesiological guidelines whereas the bronchopleural fistula demands methods to prevent aspiration pneumonia as a first priority. In the late period following surgery, typical cardiac and pulmonary modifications can be described that persist and have anesthesiological implications in the case of further surgery. Recent literature, however, lacks clear recommendations regarding anesthesiological management and practice for these cases. Summary Current literature presents no general recommendations on how to manage patients after recent thoracic surgery. Therefore it is necessary to find an individual strategy to handle possible complications and well known pathophysiological changes. Knowledge and understanding of the etiology, the pathophysiology and the risk factors of the perioperative period, allows prevention and target intervention aimed at reducing morbidity and mortality following surgery.

Improved ventilation―perfusion matching with increasing abdominal pressure during CO2-pneumoperitoneum in pigs

Background: CO2‐pneumoperitoneum (PP) is performed at varying abdominal pressures. We studied in an animal preparation the effect of increasing abdominal pressures on gas exchange during PP.