BETA‐ENDORPHIN INFUSION FAILS TO MODULATE THE HORMONAL AND METABOLIC RESPONSE TO SURGERY

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Abstract
The effects of an i.v. infusion of synthetic human .beta.-endorphin on the hormonal, metabolic and cardiovascular responses to surgery were investigated in female patients undergoing pelvic surgery. A .beta.-endorphin infusion (2 .mu.g/kg as a bolus at induction of anaesthesia + 10 .mu.g/h for the first hour of surgery) increased plasma .beta.-endorphin immunoreactivity to values at least 100-fold greater than those seen during surgery in a control group of patients. In spite of this massive increase the only significant findings were a transient augmentation of the expected hyperglycaemic response and increased plasma glucagon values. There were no significant changes in ACTH, GH, insulin and cortisol secretion, in blood concentrations of lactate or glycerol, or in cardiovascular variables. Complete dissociation between plasma and cerebrospinal fluid concentrations of .beta.-endorphin was found even when plasma values exceeded 10000 pmol/l in the presence of anaesthesia and surgery. These results show that the increases in circulating .beta.-endorphin immunoreactivity associated with clinical stress states are unlikely to modulate the associated hormonal, metabolic and cardiovascular changes.