Controlled hypotension in theory and practice.

r has been said, with an element of truth, that progress in surgery is dependent upon advances in the field of anasthesia. The development of induced hypotension as an adjuvant to surgery is an excellent example of this interdependence. Fundamentally unrelated to anaesthesia, the techniques have been evolved almost exclusively by anaesthetists, who must be prepared to accept responsibility for the management of such cases. This, however, is but one example of the extension of the anaesthetist's duties in recent years. Today, he is expected to modify, disturb or odierwise alter basic physiological functions to meet the increasing demands of modern surgery. It behoves him therefore to be not only willing to accept these new responsibilities but also to be capable of undertaking them. Such capability presupposes a knowledge of basic physiological principles together with an understanding of the modifications produced by clinical intervention. This paper is an attempt to correlate these factors as applied to induced hypotension and to discuss, within a limited experience, their practical application. Under normal physiological conditions, the blood pressure is maintained by a finely adjusted balance between two