An implantable system for monitoring a hydration state of a patient and adjusting fluid removal from the patient includes a pressure sensor implantable within an inferior vena cava of the patient and a processor. The pressure sensor senses and generates an output representative of a baseline inferior vena caval pressure value of the patient and chronically senses and generates outputs representative of an inferior vena caval pressure value of the patient. The processor compares differences between the baseline inferior vena caval pressure value and subsequent inferior vena caval pressure values. The processor can reside in another implantable device or in an external device/system.
