[Anesthesia and perioperative immune function]

Innate and acquired immunity plays a pivotal role in the host defense response. Pain, stress, necrotic tissue and invading microorganisms are known modulators of the complex immune response of patients undergoing major surgery. Anaesthesia itself or perioperative interventions of the anaesthesiologist may substantially alter the immune function with potential impact on the postoperative course. For instance, transfusion of allogenic blood and administration of dopamine or metoclopramide may interfere with immunity. Stress and pain are associated with immune tolerance, increased susceptibility to infection and tumor spreading in animal models. Thus, anaesthesia may--through modulation of the neurohumoral stress response--indirectly affect immunity of the surgical patient. In particular epidural anaesthesia and/or administration of epidural or spinal opioids seem to attenuate the stress response with beneficial effects on cellular and humoral immunity. In addition, anaesthetics, such as etomidate, propofol, or thiopentone and opioid analgesics may directly affect function of immune competent cells. However, these actions may only be apparent with high or supraclinical concentrations and/or long-term exposure. Regarding the latter, evidence suggests that long-term sedation using thiopentone in neurosurgical patients is paralleled by infectious complications in a dose-dependent manner. At present, no data are available regarding the significance of the observed alterations associated with various anaesthetic procedures of the incidence of postoperative complications associated with impaired immunity, such as infection or metastatic spreading in oncological surgery.