Authors' contribution Wkład autorów:A. Study design/planning zaplanowanie badań B. Data collection/entry zebranie danych C. Data analysis/statistics dane -analiza i statystyki D. Data interpretation interpretacja danych E. Preparation of manuscript przygotowanie artykułu F. Literature analysis/search wyszukiwanie i analiza literatury G. Funds collection zebranie funduszy Summary Background. Infusion therapy is the primary stage of resuscitation in patients with septic shock. But excess fluids may cause adverse outcomes, so which indicators should doctors monitor to predict whether the infusion volume is sufficient? Material and methods. The prospective clinical study included 68 consecutive intensive care unit (ICU) adult patients with septic shock, who had an active surgical infection. Minimally invasive methods were used to continuously record cardiac output (CO). In this study, we compare the passive leg raise (PLR) test and initial central venous oxygen saturation (ScvO 2 ) levels in terms of correlation with, and predictive accuracy for, infusion response. Results. The predictive accuracy of PLR testing and initial ScvO 2 levels for infusion response was 55.9% vs. 67.6% in septic shock patients with abdominal infection. Results from the PLR test and reaction to infusion therapy revealed a slight positive correlation (R=0.239, P=0.018), initial ScvO 2 and reaction to infusion therapy revealed a moderate negative correlation (R=-0.305, P=0.009). Conclusions. In intra-abdominal septic shock patients, the PLR test is not a reliable predictor of response to infusion, but low initial ScvO 2 levels can be used for the prediction of response to infusion. Administering a fluid challenge with dynamic indicators (such as CO) is the most accurate method for clinicians to determine the need for further infusion therapy.