[Role of endogenous nitric oxide (NO) in pulmonary vascular adaptation to one-lung ventilation during thoracic surgery]

To determine whether endogenous production of nitric oxide (NO) increases during one-lung lung ventilation (OLV) and to observe its possible influence on pulmonary vascular resistance (PVR). The experimental group consisted of 19 patients undergoing chest surgery with OLV, with monitoring by Swan-Ganz catheter. Hemodynamic parameters were measured and peripheral venous blood samples were taken at the start of surgery and 10 minutes after starting OLV. The control group consisted of 13 patients with comparable clinical characteristics undergoing chest surgery with conventional lung ventilation. In this group samples of peripheral venous blood were taken at the start of surgery and at a moment comparable to the sampling of the experimental group. NO was assessed by quantitative colorimetry as the concentration of nitrites in venous blood. Nitrite concentration in the experimental group was higher during OLV (12.7 +/- 10.1 muMol/ml) than initially (7.1 +/- 5.4 muMol/ml) (p < 0.05). Nitrite concentration was similar at the two moments sampled in the control group (8.7 +/- 2.8 muMol/ml at the start of surgery and 8.1 +/- 3.2 muMol/ml in the second sample taken). Mean percent increase in nitrite concentration in the experimental group was 93.7 +/- 117%; mean percent change in the control group was 3.9 +/- 23% (p < 0.001). PVR during OLV (134 +/- 45 din.s.cm-5) is lower than at the start of surgery (163 +/- 37 din.s.cm-5, p < 0.05). During OLV endogenous production of NO, measured as nitrite concentration in plasma, increases. PVR decreases, possibly because of the increase in nitrite concentration.