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OBJECTIVE Delta pulse pressure and delta down are used as dynamic preload indicators of fluid responsiveness during closed chest surgery. There are few data regarding their accuracy in open chest surgery. The present study aimed to evaluate the influence of sternotomy on the accuracy of both delta pulse pressure and delta down. DESIGN Prospective study. SETTING Single institution, nonacademic hospital. PARTICIPANTS The study comprised 127 adult patients scheduled for elective open chest cardiac surgery. INTERVENTIONS Delta pulse pressure and delta down were calculated for all patients before and 10 minutes after sternotomy. MEASUREMENTS AND MAIN RESULTS Statistical analyses were performed to assess the influence of sternotomy on the accuracy of delta down and delta pulse pressure. Mann-Whitney and Bland-Altman analyses demonstrated a significant influence of sternotomy on delta pulse pressure values but not on delta down values. Among patients who had a positive delta down and/or delta pulse pressure before sternotomy, sternotomy significantly modified the delta pulse pressure value (p = 0.02), but not the delta down value (p = 0.22). The kappa coefficient indicated a very good agreement between delta down before and after sternotomy (0.83) and a fair agreement between delta pulse pressure before and after sternotomy (0.4). The difference between kappa coefficients was highly significant (p < 0.001). CONCLUSIONS Within the study population, sternotomy significantly influenced delta pulse pressure but not delta down. In this preliminary study, delta down appeared to be more accurate to evaluate fluid responsiveness during open chest surgery than did delta pulse pressure. Before promoting delta down in current practice, confirmation is needed on a larger scale.