Total plasma clearance of infused norepinephrine in non-azotemic diabetes mellitus.

The total plasma clearance of norepinephrine (NE) was assessed during steady state NE infusion at two different dose rates in 27 patients with non-azotemic diabetes mellitus as compared with 27 normal subjects. Lower NE dose rates were required in diabetics than in normal subjects (P less than 0.001) to induce similar increases in blood pressure. However, plasma NE levels during NE infusion correlated closely (r = 0.79 and 0.78; P less than 0.001) with concomitant dose rates, and this relationship was similar in both study groups. Moreover, the plasma NE clearance did not differ between low and high dose rates of NE infusion, and was similar in diabetics and normal subjects (6.0 +/- 3.1 and 5.1 +/- 2.6 liter/min, respectively). It correlated inversely with the pre-infusion plasma NE (r = -0.38 and -0.53; P less than 0.05);this relationship was also similar in the two groups. The correlation relating plasma NE to NE infusion rates as well as the plasma NE clearance did not differ between the 13 diabetics without and the 14 with signs of peripheral neuropathy or between the 17 patients with normal and the 10 patients with high blood pressure. These findings suggest that the kinetics of circulating NE are usually unaltered in non-azotemic diabetes mellitus. An increased pressor responsiveness to NE, in the presence of normal plasma NE concentrations and clearance rates, may be a setting predisposing for the development of hypertension in diabetic patients.