Head-down tilt as a physiological diuretic in normal controls and in patients with fluid-retaining states.

The effect of the sitting, supine, supine with legs elevated 10 degrees, and 10 degrees head-down tilt postures on renal fluid and electrolyte handling was investigated in 14 patients with hypoalbuminaemic fluid-retaining states and in 14 normal individuals. Basal (sitting) urine volume, creatinine clearance, and urinary electrolyte levels were significantly lower in patients than in controls. In patients the values of these variables increased progressively from the sitting to the supine to the legs elevated to the head-down postures. The percentage rise was higher in patients than in controls, to the extent that, in the head-low position, only creatinine clearance values remained lower in patients than in controls. The head-down posture acts as a physiological diuretic, enhancing diuresis by improving renal function in normal individuals and in patients with ascites and oedema due to hypoalbuminaemia; it also corrects the abnormal fluid and sodium retention in these patients.