Effects Of Cardiopulmonary Bypass On Level Of Cytokines And Apoptosis Of Neutrophils In Paediatric Patients

Objective: Cardiac surgery with cardiopulmonary bypass (CPB) evokes a systemic inflammatory responses syndrome (SIRS). The following factors, such as, contact of peripheral blood with artificial surfaces, surgical trauma, ischemia-reperfusion injury, and transient endotoxemia have all been implicated in initiating or enhancing the proinflammatory response. Polymorphonuclear neutrophils (PMN) seems to have an important role in the systemic inflammatory response. Also, cytokines are believed to be important mediators in this systemic response to CPB. However, little is known about the influence of CPB on apoptosis of neutrophils in children. In contrast to adults, the cytokine response beyond 24 h postoperatively in infants and children seems to be less clear.There are few detailed descriptions of the balance between the proinflammatory and antiinflammatory response to cardiac surgery with CPB in children.The aim of our study was to describe the time course of proinflammatory cytokine (TNF-α, IL-8) and antiinflammatory cytokine (IL-10) responses and apoptosis of neutrophils in infants undergoing cardiac surgery with CPB. Furthermore, we aimed to investigate the relation between plasma cytokines concentration and apoptosis of neutrophils, and to give the experimental basis for preventing and treating SIRS.Methods: Thirty patients (aged from 1 to 4) undergoing elective surgery with CPB for ventricular septal defect were enrolled in the study. All patients received a similar anesthetic regime, including induction with ketamine, fentanyl, midazolam and maintenance with fentanyl and isoflurane. Neuromuscular blockade was achieved with vecuronium. Before aortic cannulation, 300 IU/kg heparin was administered. The extracorporeal circuit consisted of hollow fiber membrane oxygenators(MeDos, Germany) and nonpulsatile occlusive roller pumps(Sarns 8000). The bypass circuit was primed with crystalloid, colloid, mannitol (0.5 g/kg), packed red blood cells (150~300 ml). Full flow on bypass was calculated using a cardiac index of 2.2~3.0 L/min/m2. Systemic perfusion pressure was maintained at a mean of 35~65 mm Hg. Core temperature was controlled using a heat exchanger in the bypass circuit and monitored with a nasopharyngeal probe. Heparin was reversed at the end of the procedure with protamine (3 mg/kg).Blood samples were drawn into vacutainers containing heparin-lithium immediately after induction of anesthesia (T0), before rewarming(T1), after CPB(T2), 24h(T3) and 48 h(T4) postoperatively. TNF-α, IL-8, and IL-10 levels in the plasma were analyzed by a double sandwich enzyme-linked immunoassay (ELISA) technique using commercially available kits (R & D Systems, USA) according to the manufacturer's instructions. Rate of neutrophils apoptosis were measured on flow cytometer (BD Biosciences).All statistical analyses were performed using the SPSS 10.0 program package. Data were expressed as the mean±SD. Changes with time within individual group were analyzed by analysis of variances for repeated measurements (ANOVA), Correlation was performed by Pearson test. A P value of less than 0.05 was considered to be statistically significant.Results:1 All patients were similar with regard to demographic data. The average CPB times were 41~62(51.7±7.8)minutes. The outcome was good for all patients.2 Plasma concentrations of TNF-αincreased after CPB onset compared with baseline concentrations, peaking at CPB ending (T2) at 18.85±5.23 pg/ml (P<0.01), and thereafter decreased to the baseline at 24 h postoperatively (P>0.05).3 IL-8 concentrations increased markedly during CPB and reached its peak (41.18±22.39 pg/ml) at CPB ending (T2) (P < 0.01), returned to baseline values at 24 h postoperatively.4 IL-10 was also increased markedly after CPB compared with baseline, peak concentrations (194.47±82.81 pg/ml) occurred at CPB ending (T2), then decreased back toward baseline values at 48 h postoperatively.5 Rate of PMN apoptosis reduced significantly after CPB onset, and reached its lowest value (2.11±1.67%, P<0.01) at CPB ending (T2), then returned to the baseline after the 24th postoperative hour.6 The highest plasma level of TNF-αsignificantly correlated with the rate of PMN apoptosis(r=-0.578, P<0.05). Similarly, the highest plasma level of IL-8 significantly correlated with the rate of PMN apoptosis(r=-0.455, P<0.05), the highest plasma level of IL-10 markedly correlated with the rate of PMN apoptosis(r=0.374, P<0.05).Conclusions:1 The damages of systemic inflammatory response to CPB in paediatric patients were the result of both proinflammatory response and antiinflammatory response. The clinical prognosis following CPB may depend on the balance between proinflammatory and antiinflammatory cytokines.2 Pediatric cardiovascular surgery with CPB leads to depression of apoptosis of PMN, which may cause prolonged PMN survival and inflammatory response further delayed.3 Cytokines play a prominent role in the regulation of apoptosis.TNF-αand IL-8 possibly have an inhibitory action on apoptosis of PMN. In contrast, IL-10 acts as an apoptosis-inducing factor for PMN.4 A better understanding of the inflammatory response to CPB was gain by our observation. However, the complex interaction of cytokines, the interaction of cytokines and apoptosis of PMN, the significance of alterations in the time course of release, and their relation to the clinical prognosis remains to be fully elucidated. Further work is needed to the development of successful preventive and therapeutic strategies.