Circulating leptin levels after cardiopulmonary bypass in children

Objective: To characterize the dynamics of circulating leptin in children after cardiac surgery with cardiopulmonary bypass (CPB), which is known to induce a systemic inflammatory response. Design: Investigative study. Setting: University-affiliated tertiary care hospital. Participants: Eight children (age range, 3 months to 13 years) undergoing CPB to correct congenital heart disease. Interventions: The time courses of leptin and cortisol levels were determined. Serial blood samples were collected from the arterial catheter or from the CPB circuit preoperatively; on termination of CPB; and at 2, 4, 8, 12, 18, and 24 hours postoperatively. Plasma was recovered immediately, divided into aliquots, and frozen at -70°C until use. Leptin was measured by a human leptin radioimmunoassay kit. Measurements and Main Results: Leptin levels during CPB decreased to 50% of pre-CPB levels (p < 0.01). After termination of CPB, levels increased gradually and peaked at 12 hours postoperatively (10 P.M. to 1 A.M.). Cortisol levels were inversely correlated to leptin levels (p = 0.016). Conclusion: CPB is associated with acute changes in circulating leptin levels. These changes parallel those in cortisol, showing an inverse relationship between leptin and cortisol, suggesting a relationship between the neurobiology of these systems that could be important for the neuroendocrine response to CPB. A prognostic role of leptin and its relationship to cortisol after CPB warrant further study.