[Closed circuit anesthesia: a perspective in clinical practice].

"Care for the Earth" is a topic which everyone on this planet has to keep in mind, and anesthesiologist is no exception. More and more emphasis has been placed on minimization of air pollution. This inevitably influences our daily practice of anesthesia since many gaseous and volatile anesthetics are air pollutants. It is, therefore, high time to review closed circuit anesthesia (CCA), because CCA produces minimal (or, by definition, no) waste of anesthetics. Based on our extensive experience since 1977, we believe that CCA is not only safe to perform but also easy to learn once the differences and similarities between CCA and semi-closed circuit anesthesia (SCA) are clearly understood. This review focuses on fundamental principles of CCA with emphasis on some new concepts on how anesthesiologists control the depth of anesthesia during CCA and SCA. We hope these concepts help the readers overcome the traditional but unfounded impression that CCA is a highly specialized mode of anesthesia.