Early detection of orthostatic hypotension by quantitative sudomotor axon reflex test (QSART) in type 2 diabetic patients

OBJECTIVE: Orthostatic hypotension is caused by autonomic nerve dysfunction, mainly by severe sympathetic nerve dysfunction in diabetic patients. Diabetes affects the peripheral nerves in a length-dependent manner. Quantitative sudomotor axon reflex test (QSART) is one of the sensitive tests for detecting sympathetic nerve function. We examined the relation between orthostatic hypotension and QSART at the foot and hand in type 2 diabetic patients. METHODS: Thirty-eight type 2 diabetic patients (age, 48.9 +/- 11.9 years; duration of diabetes, 13.4 +/- 8.6 years) and 13 age-matched non-diabetic controls were evaluated. All subjects aged under 65 years old were recruited. All subjects underwent Schellong tests and quantitative sudomotor axon reflex tests (QSART) at the back of the hand and dorsum of the foot. RESULTS: The sweating volume at the foot dorsum, but not the back of the hand, during the first 10 minutes of QSART was significantly related to the orthostatic hypotension on the Schellong test. In patients with normal, borderline and abnormal blood pressure response to standing, 6 out of 17 (35.3%), 9 out of 12 (75.0%) and 9 out of 9 (100%) had decreased sweating volume of the foot dorsum, respectively. CONCLUSIONS: Our results suggest that orthostatic hypotension may be detected early by QSART at the dorsum of the foot in type 2 diabetic patients.