The effects of naloxone on circulating metabolites, glycoregulatory hormones and gut peptides during pelvic surgery

Summary. The role of endogenous opioid peptides in mediating the endocrine and metabolic response to pelvic surgery was investigated. Fourteen patients were studied; seven were infused with the specific opioid antagonist, naloxone, at a rate of 20 μg kg^‐1 (body weight) hr^‐1, while the remainder acted as a control group. Naloxone exacerbated the glycaemic response to surgery but had no statistically significant effect on changes in the glycoregulatory hormones, pancreatic glucagon, insulin, cortisol and growth hormone. However, there was a wide individual variation in the glucagon response to naloxone with marked stimulation in some patients. Naloxone infusion increased plasma pancreatic polypeptide secretion during the 1st hour of surgery and reversed the decline in plasma motilin concentrations, but had no effect on circulating somatostatin, vasoactive intestinal polypeptide, gastrin, enteroglucagon and neurotensin values. We conclude that endogenous opioid peptides have only a limited role in modulating the endocrine and metabolic response to surgery.