Effects of lung surgery and one-lung ventilation on pulmonary arterial pressure, venous admixture and immediate postoperative lung function.

We studied 17 patients, with unilateral lesions in lung or thoracic wall, during thoracotomy performed in the full lateral position. Balanced anaesthesia was used with pethidine and 50% nitrous oxide, in oxygen. The procedure included a period of one-lung ventilation (OLV). Haemodynamic and gas exchange measurements were performed before and after pleurotomy, during OLV, after re-expansion of the lung and after closure of the thoracic wall. The function of each lung was assessed separately during the first and last stages. Mean venous admixture was 9-12% before and after OLV and 31% during OLV. There was a positive correlation between venous admixture and pulmonary arterial pressure during OLV. End-tidal PCO2, carbon dioxide elimination and compliance of the operated side were reduced significantly at the end of the procedure; this is consistent with reduced blood flow and increased water content in that lung.