Modifying the neuroendocrine stress response

Abstract

OF different techniques are availle to modify the neuroendocrine metabolic stress response. None has been as extensively studied as central neuraxial blockade, especially epidural anesthesia and analgesia. Nor has any other technique or agent been shown to be as effective in suppressing most components of the stress response. Therefore, after first summarizing the stress response to surgery, we will discuss in some detail suppression of the stress responses with neural blockade and its potential impact on improving surgical outcome. More briefly, we will touch on non-neural blockade interventions to suppress the stress response, specifically adrenergic blockade, s'ubstrate administration, reduction of heat loss, pain relief, and glucocorticoids. THE STRESS RESPONSE TO SURGERY The stress response is a normal physiologic reaction to trauma and surgery. It encompasses a wide range of endocrinologic, immunologic, and hematologic changes. Traditionally, the stress response to trauma or surgery is divided into 2 phases. The initial ebb phase is characterized by a hypodynamic state--a reduction in metabolic rate and most other physiologic activities. The ebb phase is usually transient or even absent, especially during modern surgery. The second phase, known as the flow phase, is a hyperdynamic state with elevated metabolic rate and increased cardiac output. Evolutionarily, the stress response is considered to play an important compensatory role and increase the victim's chance of survival. Circulating concentrations of norepinephrine and epinephrine are increased by augmented sympathetic nervous system activity, which leads to increases in heart