Continuous wave Doppler ultrasound for evaluation of vasomotor tone of the radial artery

Abstract

Objective: At present, the sympathetic skin response (SSR) is the only routinely employed technique for evaluating the autonomic function of peripheral nerves. The present study was conducted in order to compare SSR to continuous wave Doppler (CWD) of the radial artery in both healthy control subjects and patients with lower brachial plexus lesions. Methods: Both methods were performed in 50 healthy volunteers (aged 23 to 70 years; mean age and standard deviation, 39.6±14.3 years) and six patients presenting with severe lesions of the lower brachial plexus (aged 22 to 60 years; mean age, 37.6±16.0 years). Results: In each control subject, a SSR could be evoked with a mean latency of 1.2±0.2 s and a mean amplitude of 2.9±1.5 mV. In 45 healthy subjects, CWD revealed both a reduction of systolic, diastolic, and mean peak blood flow velocity after electrical (ES) and acoustic (AS) stimulation as well as after inspiratory cough (IC). The mean latencies to the decrease in flow velocity decrease amounted to 1.8±0.7, 2.0±0.7, and 1.4±0.4 s, respectively. The resistance (Pourcelot) index increased significantly. CWD failed to show changes of blood flow velocity in five healthy subjects due to high sympathetic tone (no baseline diastolic blood flow) or instability of blood flow caused by respiration. In patients with lower brachial plexus lesions, SSR was diminished and changes in blood flow could not be observed on the affected side. Conclusion: CWD sonography allows easy quantitative assessment of arteriolar tone in healthy subjects and patients with autonomic nerve lesions of the limbs.