Sepsis and septic shock are major global public health concerns. The main therapies for sepsis-related hypotension are fluid resuscitation and vasopressor therapy, though it can be challenging to determine the amount of fluid that should be given or the optimal timing to transition to vasopressor administration. To characterize patients' response to fluid bolus therapy (FBT) and analyze the sepsis progress using multiple vital signs, we mined a database containing 761 patients presenting to the Emergency Department (ED) with vital signs and laboratory values indicating high risk of septic shock. By clustering the patients' mean arterial pressure (MAP) time series during a time window around FBT, we found that clusters showing fluid responsiveness during the two hours after FBT only included about 25% of studied boluses. In addition, MAP responses tended to vary based on the initial MAP level. We also found that the trajectories of heart rate and MAP in a 2-D plane demonstrated general trends related to the hemodynamic progression of sepsis and previously described phases of septic shock. Potentially compensatory and decompensatory responses of the cardiovascular system to the insults of sepsis were reflected in the clusters representative of different phases.