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Alterations in host defences during anaesthesia and surgery

Alterations occur in the systemic immune response overall during anaesthesia and surgery. Some parts of the immune response are activated and some parts are suppressed. Capacity of neutrophils to spontaneous migration and chemotaxis is decreased. Opsonization is slightly disturbed but neutrophil microbicidal capacity is well preserved. The phagocytic capacity of monocyte-macrophage system (MPS) is also slightly disturbed during an operation but increases postoperatively above the preoperative levels. Preliminary studies indicate that antigen processing and presentation by monocyte-macrophages is depressed, and there are alterations in the secretion of monokines. Complement is activated during major surgery. Cell-mediated immunity is depressed postoperatively and humoral immune responses are also depressed but to a minor degree (Table). The ex tent of surgical trauma determines the changes. Anaesthe sia has a minor role and psychic factors, blood transfusion, immobilization and starvation contribute in the alterations. The area of surgical trauma and the wound are biologically active. These can, therefore, be considered as a separate organ as proposed by Wilmore in the 1980's. Locally there is inflammatory reaction which initiates wound repair and removes microbes, debris and other foreign material from the area of surgical trauma. The inflammatory reaction is a multifaceted collection of reactions in which can be separated several partly successive and partly simultaneous phenomena. During the inflammatory reaction cascade systems such as complement, coagulation, fibrinolysis and kinin systems are activated locally. Thrombocytes in the area of trauma and inflammatory reaction are important in forming the primary haemostatic plug and release of mediators. The neutrophils are the first nucleated cells to arrive to the site of tissue injury and later on cells of the monocyte-macrophage series arrive. In rats anaesthesia and surgery has been shown to depress the inflammatory reaction after laparotomy and haemorrhagic shock. However, the effects of anaesthesia on the inflammatory response are not known in more details. The changes in the immune response are only a part of the general responses to anaesthesia and surgery and should be considered in relation with the other responses.