Neuroendocrine and Immune Responses to Surgery

Surgery elicits profound changes in the neuroendocrine, metabolic, and immune systems, which collectively constitutes the “stress response”. These responses have been implicated in the development of a number of postoperative complications such as postoperative delirium, cognitive dysfunction, infection, and cancer recurrence. This review describes how ‘surgical stress’ and inflammatory responses affects the immune system as well as the patient's susceptibility to these untoward events. The immune system is composed of two major subdivisions, the innate or non-specific immune system and the adaptive or specific immune system. Each subdivision has humoral and cellular elements which allow the immune system to protect the body from foreign pathogens and cancer. The ‘Stress response’ results in the systemic release of cortisol, catecholamines, acute phase reactants, and cytokines which modulate the activity of both innate and adaptive components. There is a sensitive balance between proand anti-inflammatory cytokines after injury/surgery. Deficient responses may result in infections secondary to immunosuppression. On the other hand the excessive responses may lead to systemic inflammatory response syndrome (SIRS) and multi-organ failure (MOF). Additionally, we discuss how anesthesia and variable perioperative factors, such as blood transfusions, pain, and hyperglycemia can further disrupt immune performance. Understanding these postsurgical disruptions in immune homeostasis may aid the surgeon and anesthesiologist in choosing surgical and anesthetic techniques that preserve and/or enhance immune function.