PERIPHERAL VASOCONSTRICTOR RESPONSES TO SYMPATHETIC ACTIVATION IN DIABETIC-PATIENTS - RELATIONSHIP WITH RHEOLOGICAL DISORDERS

The sympathetic nervous system regulates peripheral blood flow. This s tudy investigated sympathetic vascular control in diabetic patients by measuring cutaneous blood flow (CBF) with a laser Doppler device at r est and during three sympathetic activation tests: deep-breathing, cha nging positions from sitting to standing, and using the Valsalva maneu ver. The influence of various factors, particularly rheological change s, was also assessed. Forty-two type II diabetes mellitus (non-insulin -dependent [NIDDM]) patients and 14 control subjects were studied. The mean value and standard deviation (SD) of basal CBF at rest were not significantly different in the two groups. In 12 NIDDM patients, the S D was less than the lowest limit found in the controls. During the thr ee tests, the reduction in CBF and its downward slope were lower in NI DDM patients than in controls, with the greatest difference occurring during the deep-breathing test. During this test, the downward slope o f CBF was less than the lowest control level in 14 NIDDM patients. The log SD of basal CBF correlated with the decrease in CBF during the si tting-to-standing and Valsalva tests in control subjects and during al l three tests in NIDDM patients. In NIDDM patients, log mean basal CBF correlated negatively with the log erythrocyte filtration index ([FI] an index of rigidity) and positively with hemoglobin A(1)c (HbA(1)c). The log downward slope of CBF during the deep-breathing test correlat ed negatively with log erythrocyte Fl. The log downward slope of CBF d uring the sitting-to-standing and Valsalva tests correlated positively with total cholesterol and triglycerides, respectively. Basal CBF and the CBF response to these tests did not correlate with retinopathy, n ephropathy, peripheral neuropathy, or heart rate variations during the se tests. This study suggests that CBF assessment by laser Doppler flo wmetry affords an attractive noninvasive way to investigate sympatheti c nervous function in diabetic patients. The amplitude of changes in b asal CBF and the decrease in CBF during the deep-breathing test show t hat this is a simple and sensitive procedure for detecting sympathetic nerve dysfunction. Moreover, rheological blood properties and metabol ic factors seem to strongly influence resting CBF and vasomotor reflex es. Copyright (C) 1997 by W.B. Saunders Company.