Controlled hypotension (known alternatively as induced, permissive, and deliberate hypotension) is a technique used to improve surgical operating conditions by improving visualization in microsurgery (eg, middle ear, cerebral aneurysm clipping, and plastic surgery) or reduce the need for transfusion in orthopedic surgery or in patients with rare blood groups or religious objections to transfusion. While this technique was first described in the 1940s, there is a paucity of data to support or refute this hemodynamic technique as efficacious.