Illustrative example of Doppler evaluation of brachial artery peak velocity variation in a responder patient and nonresponder patient. In the responder patient (left), volume expansion (VE) induced a decrease of brachial artery peak velocity variation (ΔVpeakbrach) by 15% (from 23% at baseline to 8% after VE) and an increase of stroke volume index and cardiac index by 27% and 12%, respectively. Radial pulse pressure variation (ΔPPrad) and stroke volume variation (ΔSVVigileo) also significantly decreased in the same patient (from 23% to 4%, and from 24% to 11%, respectively). In nonresponder patients (right), VE did not induce any significant change in ΔVpeakbrach (from 9% to 9% after VE), ΔPPrad (from 10% to 8%) or ΔSVVigileo (from 13% to 12%). Neither cardiac index nor stroke volume index increased significantly after VE (6% and 8%, respectively). SVi = stroke volume index.