The immature-to-total neutrophil ratio (IT ratio) is a sensitive indicator of sepsis after paediatric cardiopulmonary bypass.

Cardiopulmonary bypass (CPB) causes a systemic inflammatory response syndrome (SIRS) with activation of neutrophils (increased immature-to-total neutrophil ratio, IT ratio). Does an additional inflammatory response induced by sepsis further increase the IT ratio, so that it can still be used as an indicator of sepsis? In 160 children we analysed retrospectively the IT ratios from the day before CPB to the 10th day after the operation (controls). The 95% confidence limits of the controls were plotted against postoperative day and compared with the IT ratio courses in all children of a 4-year period who developed sepsis during the first 10 days after CPB. All septic children (n = 9) had IT ratios above the upper 95% confidence limits of the controls on the day of positive culture or on the following day. The IT ratio remains a sensitive indicator of sepsis even after CPB.