[The endocrine stress reaction in anesthesia and surgery--origin and significance]

Abstract

Stress can be defined as a "reaction by living beings to any relevant impairment". The effect of anaesthesia on endocrine function is closely related to the actual stress concept based on the works by Cannon and Selye. Cannon described the role of catecholamines in stress and characterised the fight-flight reaction. Selye emphasised the role of the adrenocortical reaction defining the "general adaptation syndrome", which evolves in three stages ("alarm reaction", "stage of resistance", "stage of exhaustion"). Later, Henry postulated the dual stress concept. The sympathetic-adrenomedullary system is activated during the fight-flight reaction, thus representing an active role of the organism. The pituitary-adrenocortical system is activated during loss of control, submission and depression, especially in a social context. Main valid parameters of this endocrine stress response are adrenaline, noradrenaline, ADH, ACTH and cortisol. In the perioperative period, both pathways are "stressed". The most important factors are patient, operation, and anaesthesia. Anaesthesia can influence the stress response by afferent blockade (local anaesthesia), central modulation (general anaesthesia) or peripheral interactions with the endocrine system (etomidate). Up to now, a total peripheral blockade of the nociceptive system is impossible, due to surgical technique (destruction of nerve fibres) and release of mediator substances. With regard to reduction of endocrine stress response, inhalation anaesthesia with volatile anaesthetics and nitrous oxide may be less effective than neuroleptic, spinal or epidural anaesthesia. Immediately after extubation, rapid increases of endocrine parameters are observed. In addition to central modulation of pain and stress, both halothane and enflurane inhibit catecholamine release from the adrenal medulla. Neuroleptic anaesthesia and total intravenous anaesthesia are very potent and sufficient to control the increases in endocrine parameters even during major surgery, due to their central effects. Spinal and epidural anaesthesia alone as well as in combination with general anaesthesia can reduce the endocrine stress response more than necessary. This is due to the sympathetic blockade, combined with an afferent blockade of central cord fibers which modulate the pituitary-adrenocortical system. Only few data are available concerning the stress response during infiltration anaesthesia or nerve block, but additional sedation seems to be beneficial. Peripheral interactions with the endocrine system like blockade of the adrenal cortex by etomidate is dangerous and has caused a high mortality in intensive-care patients if the substance was admitted for a longer period. Assessment of endocrine stress response in anaesthesia and surgery is controversial.(ABSTRACT TRUNCATED AT 400 WORDS)