Diabetic orthostatic hypotension: the role of total exchangeable sodium and nephropathy.

The purpose of this report was to examine the influence of nephropathy and sodium balance on the orthostatic blood pressure and renin (PRA) responses of diabetic patients with orthostatic hypotension (OH). Four groups of similar age were studied: non-diabetic controls (n = 7), diabetics free of OH and other diabetic complications (n = 7), diabetics with OH but no nephropathy (n = 6), and diabetics with OH and nephropathy (24-hr urine protein greater than 400 mg, n = 6). In the diabetics with OH, mean systolic BP fell 49 and 47 mmHg on standing in the groups without and with nephropathy respectively. NaE (expressed as % predicted by leanness index) differed significantly between the groups and was 100 +/- 2 in the controls, 109 +/- 3 in the diabetics free of complications, 102 +/- 2 in the diabetics with OH free of nephropathy, and 121 +/- 6 in diabetics with OH and nephropathy (p less than 0.05 compared to diabetics with OH and no nephropathy). Both supine (r = 0.68, p less than 0.02) and upright (r = 0.78, p less than 0.005) mean arterial pressure correlated with NaE in diabetics with OH but not in the other groups. Upright PRA was greatest in diabetics with OH but no nephropathy and lowest in diabetics with OH and nephropathy. These findings suggest that the presence of nephropathy markedly influences sodium balance in diabetics with OH and has a substantial influence on orthostatic BP and PRA responses.