Endogenous morphine is produced in response to cardiopulmonary bypass in neonatal pigs

Background: Cardiopulmonary bypass (CPB) is associated with a systemic infl ammatory response. Endogenous morphine production has previously been demon strated in humans after cardiac surgery with CPB. It has been hypothesized that morphine plays a role as an anti-inflammatory mediator in the systemic inflammatory response. The aim of this study was to investigate if the CPB procedure in itself elicits an endogenous morphine production in neonatal pigs. Methods: Endogenous morphine production was measured in arterial blood in p iglets exposed to sternotomy alone (sham group, n=10) or sternotomy and CPB (n=10). Blood samples were obtained immediately after the induction of ana esthesia, at the end of CPB and 4 h later. Morphine in arterial blood was d etected by radioimmunoassay and confirmed by gas chromatography mass spectr ometry. Results: Animals undergoing CPB showed detectable endogenous morphine conce ntrations immediately after CPB, with increased concentrations postoperativ ely. There was no measurable morphine production in the sham operated Figs. Conclusion: The CPB procedures elicits an endogenous morphine production in neonatal Figs. This morphine response is analogous to the previously demon strated response in patients subjected to cardiac surgery and CFB.