Relationship between autonomic function and progression of renal disease in diabetic proteinuria: clinical correlations and implications for blood pressure control.

The objective of this study was to test the relationship between neurologic and microvascular complications of type 1 diabetes mellitus. It was hypothesized that the mechanisms operative in autonomic dysfunction seen in diabetic patients with microangiopathy play a role in the rapidity of progression to renal failure. Twenty-six type 1 diabetic patients with proteinuria were studied with computerized monitoring of heart rate variation during timed ventilation, assumption of upright posture, and Valsalva maneuver and with 24-h ambulatory blood pressure monitoring at baseline. Renal function was evaluated over the ensuing 12 months of intensive insulin therapy. Blood pressure was treated so as to achieve consistent 24-h readings < 140/90 mm Hg. Angiotensin converting enzyme inhibitors were the preferred antihypertensive agents. Serial serum creatinine concentrations were compared using repeated measures analysis of variance. Over 12 months there were no significant serum creatinine changes for any autonomic test group with normal results at baseline. Groups with abnormal autonomic results at baseline demonstrated statistically significant increases in serum creatinine over 12 months compared to their baseline. Of the tests, Valsalva separated groups of patients with similar degrees of baseline renal impairment. Each of the sympathetic plus Valsalva combinations demonstrated a significant difference in progression of serum creatinine increase over 12 months. In each instance, if both sympathetic and Valsalva results were abnormal, there was a statistically significant increase in serum creatinine over 12 months when compared to groups in which one or both test results were normal. There is a relationship between autonomic function and the progression of renal dysfunction. The inability to vary the heart rate to a Valsalva maneuver identifies a degree of parasympathetic dysfunction that permits unopposed sympathetic tone, heralding more rapid renal destruction. A simple inexpensive bedside laboratory test discerned a relatively low-risk group of diabetic patients with proteinuria that demonstrated no deterioration in renal function over 12 months. When the Valsalva maneuver was markedly abnormal the presence of a mean arterial pressure > 100 mm Hg was associated with a greater likelihood of rapid renal deterioration. This group at higher risk of renal deterioration should undergo aggressive lowering of mean arterial blood pressure to < 95 mm Hg.