Aim: Aim of this study is to investigate the impact of perfusion flow, haematocrit level, lactate level and DO2 (oxygen delivery) during extracorporeal circulation for paediatric patients post operative sepsis, liver and renal dysfunctions. Introduction: Organ dysfunction afterextracorporeal circulation (ECC) has been associated with oxygen delivery DO2. For conventional extracorporeal circuit required crystalloid priming solution of 350450 ml, resulting in hemodilution.The metabolic needs of paediatric patients during ECC is organ specific because of tissues oxygen consumption VO2. If the ratio of VO2/DO2 is increase during ECC in paediatric patients which give unreliable value of VO2/DO2.This unreliable values give an anaerobic metabolism and lactic acidosis. Due to hemodilution and low delivery of oxygen, postoperative morbidity and mortality will increase. Material and Methods: In this prospective study we enrolled total of 180 consecutive paediatric and small children. Who underwent for cardiac surgery with extracorporeal circulation system. Patients were divided into two groups, based on patients haematocrit level  8.5% and >8.5% haematocrit level, oxygen delivery (DO2) and extracorporeal circulation pump flow were recorded. For all paediatric operation with extracorporeal circulate system patients preoperative and postoperativetotal blood count, platelet count, blood urea, serum creatinine, electrolytes, SGPT, SGOT and total bilirubin(tb), serological viral test HepatitisB (HBsAg) and HIV test were performed. Result: In this prospective study we have investigated the lowest haematocrit, lowest oxygen delivery DO2, and low perfusion flow rates may increase postoperative sepsis, liver dysfunction, renal dysfunction and overall ventilation hours / ICCU stay. Conclusion: The present study explored the specific haematocrit level, oxygen delivery DO2 level, perfusion flow and lactate level during ECC in paediatric patients postoperative sepsis, liver dysfunction, renal dysfunction and overall ventilation hours / ICCU stay. The low haematocrit level and low perfusion flow during ECC in paediatric patients is a possible risk for post operative renal dysfunction. Adequate oxygen delivery and perfusionflow reduced risk of renal dysfunction and liver dysfunction.