Invited Commentary

Abstract

Bleeding after cardiopulmonary bypass (CPB) is a complicated issue, especially in pediatric patients. Multiple age-related, CPB-related, and surgery-related variables come together to influence the amount of coagulopathy any given child will experience after CPB. Fortunately, with the advent of viscoelastic tests, thromboelastography (TEG) or rotational thromboelastometry (ROTEM), a path to identify and correct the coagulation abnormalities that are likely responsible is clearer now more than ever. These tests, performed on whole blood, allow for rapid assessment of clotting time, thrombocytopenia, hypofibrinogenemia, and fibrinolysis. Furthermore, they offer insight into platelet–fibrin interactions, fibrin polymerization, and possibly even thrombin generation. Studies that incorporate TEG and ROTEM testing into transfusion algorithms are beginning to emerge and report success in reducing allogeneic blood product exposure without an increase in postoperative bleeding [1Romlin B.S. Wahlander H. Berggren H. et al.Intraoperative thromboelastometry is associated with reduced transfusion prevalence in pediatric cardiac surgery.Anesth Analg. 2011; 112: 30-36Crossref PubMed Scopus (102) Google Scholar, 2Nakayama Y. Nakajima Y. Tanaka K.A. et al.Thromboelastometry-guided intraoperative haemostatic management reduces bleeding and red cell transfusion after paediatric cardiac surgery.Br J Anaesth. 2015; 114: 91-102Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar, 3Kane L.C. Woodward C.S. Husain S.A. Frei-Jones M.J. Thromboelastography—does it impact blood component transfusion in pediatric heart surgery?.J Surg Res. 2016; 200: 21-27Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar]. In this issue of The Annals of Thoracic Surgery, Emani and colleagues report their experience along this path [4Emani S. Sleeper L.A. Faraoni D. et al.Thromboelastography is associated with surrogates for bleeding after pediatric cardiac operations.Ann Thorac Surg. 2018; 106: 799-806Abstract Full Text Full Text PDF PubMed Scopus (14) Google Scholar]. The authors perform a retrospective study in high-risk pediatric patients undergoing complex cardiac repairs to determine whether abnormal TEG parameters are associated with a surrogate endpoint for early postoperative bleeding. TEGs were obtained immediately after protamine administration (prior to the administration of post-CPB blood products) and upon arrival to the intensive care unit (ICU). To be clear, the TEGs were strictly observational and not clinically used to guide transfusion management. The authors define a composite endpoint for excessive bleeding, extended transfusion (ie, the need for blood products after the initial post-CPB transfusion of platelets), or the need for surgical reexploration. Of the 511 patients, 52% of patients with a maximum amplitude (MA) less than 45 mm reached the composite endpoint versus 31% with a MA greater than 45 mm (p < 0.001). In those patients who had an MA less than 45 mm, platelet transfusion intraoperatively was associated with a significant increase in median [IQR] MA (40.8 mm [37.5, 43] in the operating room versus 63.4 mm [56.2, 69.7] in the ICU; p < 0.001) and a lower incidence of the composite endpoint. Overall, MA less than 45 mm and neonatal age were independently associated with the composite endpoint. There are limitations to this study. The authors do not mention how it was decided to administer other products after the initial transfusion of platelets. Was there a defined process or was it subjectively decided by the anesthesia or surgery or ICU team? In addition, it is well known that neonates and small infants experience a significant dilutional hypofibrinogenemia after CPB, even when fresh frozen plasma is included in the circuit prime [5Hornykewycz S. Odegard K.C. Castro R.A. Zurakowski D. Pigula F. Dinardo J.A. Hemostatic consequences of a non-fresh or reconstituted whole blood small volume cardiopulmonary bypass prime in neonates and infants.Paediatr Anaesth. 2009; 19: 854-861Crossref PubMed Scopus (24) Google Scholar], and these patients often require fibrinogen repletion with cryoprecipitate. According to the authors’ defined composite endpoint, this would be considered “extended transfusion”. Thus, it is likely that the incidence they report for the composite endpoint is inflated. Nevertheless, studies similar to the one conducted by Emani and associates that explore the use of viscoelastic tests to guide transfusion algorithms are greatly needed. Such algorithms will likely vary according to institutions and their differing practices, and may even need to vary according to different target populations. In addition, the use of age-specific reference ranges and functional fibrinogen assays will further enhance our insight into the appropriate therapies. As reflected in the article by Emani and co-workers, we are beginning to make our way along this path. Thromboelastography Is Associated With Surrogates for Bleeding After Pediatric Cardiac OperationsThe Annals of Thoracic SurgeryVol. 106Issue 3PreviewPerioperative bleeding is a common complication in pediatric patients undergoing cardiac operation. Although thromboelastography (TEG) has been used in patients undergoing adult cardiac operation, limited data are available in pediatric patients. We hypothesize that TEG variables may be associated with surrogate end points for postoperative bleeding in pediatric patients undergoing complex cardiac operation. Full-Text PDF