[Immune response in the surgical patient: effect of anesthesia and blood transfusion]

Anesthesiology has progressed spectacularly over the last two decades, largely parallel to developments in basic and clinically applied sciences such as immunology. The anesthesiologist's involvement now extends to all matters involved in perioperative care. Surgery, anesthetic procedures themselves, and other associated techniques such as blood transfusion all alter the patient's immune response and all fall within the range of procedures monitored by the anesthesiologist. The repercussions on the patient are important, given that alterations suppose increased risk of postoperative infection and increased recurrence of neoplastic disease. The present article reviews available knowledge on how and to what extent the patient's immune status is affected in the perioperative period. Generally, surgery and anesthesia induce immune system depression. It is possible to demonstrate a decrease in the number and activity of circulating immune cells and alterations of various types in interleukins and in protein synthesis during acute phase response. Research in this field is complex given that the individual effect of each factor involved is difficult to measure and experimental or clinical designs usually yield only biased views. Replacement of lost red blood cells is another factor leading to immunological changes. New anesthetic techniques, the optimization of methods already in use, and the development of modern, less immunodepressant drugs and of alternatives to homologous blood transfusion are all solutions that have been proposed. This is an exciting field of study in which today, perhaps more than ever, the anesthesiologist has a critical role to play.