Recruitment and case-matching process. Potential subjects were recruited throughout the study period. At the end of recruitment, and after excluding five cases due to aborted procedures or decision to proceed without an arterial line, there were thirty-five study cases in the closed-loop assisted group. During the same time period, 60 other patients who met the inclusion criteria received manual goal-directed fluid therapy (GDFT). All 35 study patients and 60 manual group patients were run in a propensity match process, after which each closed-loop assisted patient was matched to the closest possible manual patient, leaving 35 patients in each group. ASA, American Society of Anesthesiologists Physical Status patient classification; HR, Heart rate; MAP, Mean arterial pressure; SVI, Stroke Volume Index.