Immune system and surgical site infection.

It is well known that altered host defenses in general can play a significant role in the development of infection in any patient but their role becomes even more important in surgical patients where infections are the result of individual risk factors associated with the patient and other specific factors associated with the surgery itself. Thus all possible factors that can help modify the immune response should be taken into account in order to intervene, whenever possible, with therapies based on defined abnormalities to reduce the rate of post-surgical infections. Many factors associated with the patient have been clearly identified as responsible for a decreased immune response: old age, concomitant diseases (diabetes, renal and liver failure, solid and hematologic neoplasias, malnutrition, autoimmune diseases, AIDS) and concomitant therapies (corticosteroid, cytotoxic agents). Old age can affect both humoral and cell-mediated immune responses. Chronic diseases can be responsible for a reduced primary response or depression of delayed hypersensitivity reactions (renal failure, neoplasias) or changes in leukocyte function (diabetes, leukemia, lymphomas). Malnutrition frequently accompanies diseases such as cancer, chronic and acute pancreatitis, inflammatory bowel diseases. Deficiencies in important vitamins and minerals (B6, A, folate, biotin, riboflavin...) can alter significantly the leukocyte function and immune response. Finally, there appears to be innate immune-suppression following any form of injury which is correlated with its magnitude and can affect any aspect of immunity. This has been well studied both in burn and surgical trauma. Alteration of phagocytosis, opsonization and chemotaxis are typically affected in burns, whereas surgical stress can include some reduction of cell mediated immunity. The best approach today to minimizing post-surgical infections is probably, besides use of antibiotic prophylaxis, to reduce the surgical trauma which consequently reduces the stress response and immune-suppression and to optimize the immune response by maintaining homeostasis through nutritional support.