Venous plasma noradrenaline increases with age: correlation to total blood volume and long-term smoking habits.

Venous plasma noradrenaline (NA), cardiac index, total blood volume, and other haemodynamic parameters were measured in 12 young (median age of 29, range 21-37 years) and 10 elderly (median age of 68, range 55-85 years) healthy male subjects in the resting supine and sitting positions. Cardiac index was equal in the two groups and did not correlate to plasma NA. Plasma NA was significantly elevated in the elderly subjects in the sitting position (2.47 +/- 0.28 vs. 1.80 +/- 0.13 nmol l-1, P = 0.038). Elevated plasma NA levels were confined to elderly long-term smokers. Sitting plasma NA was significantly correlated to total blood volume corrected for body weight, r = -0.720, P = 0.0002, but with no difference in blood volume between smokers and non-smokers. It is concluded, that long-term smoking may result in elevated plasma NA levels seen in elderly subjects. It is suggested, that this is a compensatory mechanism to vascular dilation induced by chronic smoking.