Abstract

Infectious complications of surgical procedures continue to be a major factor contributing to postoperative morbidity. Studies on host defense mechanisms and the possible modifying effect of anesthetic procedures may, therefore, have important clinical implications. This paper surveys clinical studies on the influence of anesthesia and elective surgical procedures on immunocompetence. It is concluded that anesthesia per se has little in vivo effect on various immunologic parameters compared to the surgically induced changes. Postoperative immunosuppression correlates to the magnitude of surgical trauma. No conclusive evidence exists showing major differences between the effects of various anesthetics on immunologic parameters. Combined general anesthesia and surgery lead to complement activation, a decrease in neutrophil chemotaxis, increased phagocytosis, and unaltered bactericidal activity of circulating neutrophils. However, in vivo mobilization of neutrophils is reduced and exudative neutrophils demonstrate reduced phagocytosis. This suggests that future studies of the influence of anesthesia and surgery on unspecific immunity should include in vivo assessment of host defense. Much evidence has accumulated that combined general anesthesia and surgery lead to lymphopenia involving both T-and B-lymphocytes and that the blastogenic response of circulating lymphocytes to both nonspecific and specific mitogens is impaired postoperatively. Similarly, surgery leads to a decreased response to recall antigens in vivo without correlation to in vitro blastogenic response of circulating lymphocytes. This again suggests a discrepancy between the functional capacity of intravascular and extravascular lymphocyte pools. In addition to the observed postoperative changes in cellular function, circulating substances with inhibitory activity on various immunologic parameters have been demonstrated. The basic mechanism(s) leading to postoperative immunosuppression is unknown. The influence of regional anesthesia on postoperative immunocompetence is unknown, but since neurogenic blockade has been demonstrated to minimize other aspects of the metabolic response to surgery, future studies should be done within this area. No conclusive data exist to demonstrate a correlation between the surgically induced changes in various parameters on immunocompetence and the occurrence of postoperative infectious complications. Despite the large number of studies on the influence of anesthesia and surgery on immunocompetence, no implications for anesthetic practice can be given at present.