A therapy utilizing inhaled anesthetic agents (such as desflurane, sevoflurane, isoflurane, or xenon) for the sedation of patients outside of the immediate perioperative space such as in the medical intensive care unit (MICU) and the surgical intensive care unit (SICU). The therapy includes controlled delivery of volatile anesthetic agents to patients undergoing ventilatory support on an ICU ventilator over extended periods of time. A system which provides for the delivery of anesthetic agents includes an anesthetic agent vaporizer element, an anesthetic agent reflector, and a plug-in cassette which contains both a cartridge housing liquid phase volatile anesthetic agent and an anesthetic vapor scrubbing medium.