IMPACT OF TRANSFUSION OF MEDIASTINAL SHED BLOOD ON SERUM LEVELS OF CARDIAC ENZYMES

Background. Infusion of shed mediastinal blood using an autotransfusio n system is a widely applied technique of blood conservation in cardia c surgery. Serial determinations of serum creatine kinase (CK), its MB isoenzyme (CK-MB), and lactate hydrogenase (LDH) levels have been use d to monitor perioperative myocardial injury. We investigated the impa ct of postoperative autotransfused blood infusion on serum levels of t hese enzymes. Methods. We performed a retrospective analysis of postop erative serum CK, CK-MB, and LDH levels of 300 patients who had electi ve uncomplicated aortocoronary bypass grafting. Shed mediastinal blood samples from 26 patients were analyzed for CK, CK-MB (enzymatic activ ity and mass), and LDH levels before infusion.Results. High postoperat ive serum levels of CK and LDH were observed after infusion of autotra nsfused blood. Shed mediastinal blood contained extremely high levels of these enzymes, particularly from patients who had internal mammary artery dissection. There was a strong correlation (r = 0.96) between m easured CK-MB enzyme activities and those calculated from the CK-MB ma ss units. Conclusions. Infusion of autotransfused blood containing hig h concentrations of CK and LDH results in elevated serum levels of the se enzymes. Hemolysis, frequently present in shed blood, does not inte rfere with the routine biochemical assays for CK and CK-MB enzyme acti vities. Caution should be taken when postoperative cardiac enzyme leve ls are used to determine myocardial injury after aortocoronary bypass grafting if autotransfusion is used as a method of blood conservation.