Effects of systemic and epidural morphine on antidiuretic hormone levels in children.

Background: Although the use of opioids during general anaesthesia suppresses stress response to surgery and pain, the effects on antidiuretic hormone (ADH) are controversial. The aim of this study was to find the effects of morphine with either intravenous infusion or epidural route on ADH and other stress hormones.

Methods: Fifty children aging (1-15 years) undergoing major genito-urinary or abdominal operations were included in this study. The patients were allocated randomly to two groups receiving either a single dose of epidural morphine 0.1 mg.kg-1 (EP group, n = 25) postinduction or morphine infusion (INF group; n = 25) at 0.02 mg.kg-1.h-1 following 0.05 mg.kg-1 bolus. Blood samples were withdrawn for plasma ADH, osmolality, glucose, cortisol, insulin and morphine level analysis following induction and 1, 5, 12 and 24 h after initial morphine administration.

Results: The two groups were similar in demographic factors, pain scores, sedation scores, and incidence of nausea and vomiting. The amount of morphine received was different between groups and the changes in serum levels of morphine were statistically significant in EP group ( P < 0.05). The changes in cortisol, blood glucose and insulin levels were insignificant in both groups (P > 0.05). The changes of ADH levels were significant at time-points in both groups, reaching control levels at the 24th hour (P < 0.05).

Conclusion: Despite the effective pain therapy and suppression of cortisol and insulin response to surgical stimulus, the increase in ADH secretion is not effected by systemic or epidural morphine administration.