RENAL SODIUM EXCRETORY FUNCTION DURING ACUTE OXYGEN ADMINISTRATION

To evaluate the effect of O2 administration and O2 removal on renal Na + excretion, 12 hypoxemic eucapnic patients affected by chronic obstru ctive pulmonary disease (COPD) and 9 normal subjects were studied. Aft er 1 h in the supine position, O2 was administered for 3 h by a tight- fitting face-mask. Urine and blood samples for renal Na+ excretion eva luation were taken at times 0, 60 and 180 min. After O2 removal both t he blood and the urine samples were taken again for a further 3 h. In normal subjects, urinary Na+ excretion did not vary after both O2 admi nistration and removal. On the contrary, in patients affected by COPD renal Na+ excretion significantly increased during O2 administration ( from basal values of 0.08 +/- 0.01 to 0. 17 +/- 0.O2 mEq/min at 180 mi n, p < 0.05), and returned to baseline levels (0.13 +/- 0.03 mEq/min) after 3 h from O2 removal. The basal fractional excretion of filtered Na+ was significant lower in hypoxemic patients than in normal subject s (0.72 +/- 0.3% in patients with COPD vs. 0.95 +/- 0.7% in normal sub jects, p < 0.05), while, at the end of O2 administration, it became hi gher in patients with COPD than in controls (1.62 +/- 0.4% in patients with COPD vs. 0.89 +/- 0.5 in control subjects, p < 0.001). In conclu sion, our findings showed an oxygen-related increase of both the urina ry Na+ excretion and the fractional excretion of filtered sodium in pa tients affected by COPD.