Adaptations to an intra-thoracic fluid-status-trend indication and/or alert algorithm are disclosed. Some embodiments monitor fluid levels in heart failure patients and others suffering from pulmonary edema and the like. Some embodiments reset a cumulative fluid index when a short-term intra-thoracic impedance value exceeds a baseline impedance value minus a predetermined positive hysteresis value. Many device, system, and method embodiments hereof serve to reduce the number of false positive alerts while retaining the desired sensitivity.