Ann Thorac Surg 1998;66:875-876
© 1998 The Society of Thoracic Surgeons
Original articles: cardiovascular
Invited commentary
Joanne Guay, FRCP(C)a,
Jean-Françoise Hardy, FRCP(C)b
a Department of Anesthesiology, University of Montreal, Hôpital Maisonneuve-Rosemont, 5415 Boul. L’Assomption, Montréal, PQ H1T 2M4, Canada
b Department of Anesthesiology, University of Montreal, Institut de Cardiologie de Montréa, 500 Est, rue Bélanger, Montréal, PQ H1T 1C8, Canada
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Invited commentary
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Pediatric cardiac operations are associated with high blood loss; in infants, the need for allogenic blood products is often higher than the patient’s estimated blood volume [1]. Surgical procedures performed in neonates are often complex, with a long duration of bypass, frequent use of deep hypothermic circulatory arrest, and multiple extracardiac suture lines often located on-high pressure vessels. Normal infants less than 6 months of age have decreased blood levels of factor II, V, VII, X, XI, XII, and XIII [2]. Fifty percent of neonates (<1 month) coming for a cardiac operation with the use of cardiopulmonary bypass have preoperative levels of coagulation factors significantly lower than normal values for age [3]. Also, infants with a body weight of less than 10 kg with cyanotic and acyanotic cardiac disease may present abnormal platelet function preoperatively [4, 5]. During cardiopulmonary bypass, neonates will suffer a more profound dilution of platelets and coagulation factors than older children and adults because of the proportionally high volume of the priming solution compared with their blood volume [3]. In addition, infants have a more severe inflammatory reaction during cardiopulmonary bypass as demonstrated by peak thromboxane levels inversely proportional to age [6]. Thus, hemodilution and activation of both the coagulation and fibrinolytic systems occur in children undergoing cardiopulmonary bypass, and the most severe coagulation defects are found in children with a body weight of less than 8 kg [7, 8].
In this issue of The Annals of Thoracic Surgery, Williams and associates present a large, well-designed, prospective study of cardiac operations in children aged from 0 to 18 years demonstrating that blood losses are inversely proportional to age. Further, the need for reexploration to control excessive bleeding after the operation is increased in neonates (<1 month). They also demonstrate that thromboelastographic evidence of fibrinolysis is found in 16% of children after cardiopulmonary bypass and that children with fibrinolysis are younger than those without fibrinolysis.
To date, studies determining the efficacy of various blood-sparing strategies in children have generally taken into account the complexity of the operation. Doing so, Manno and associates [1] demonstrated that the use of fresh whole blood of less than 48 hours decreases blood losses in children less than 2 years of age undergoing a complex operation. Yet, authors who have attempted to determine the efficacy of other strategies, aprotinin for example, to reduce blood loss in pediatric cardiac operations report conflicting results [9]. With the newly gained knowledge from this study by Williams and associates, such conflicting results may be explained, at least in part, by the wide range of ages of the children involved in some of those studies. Even the most recent studies on antifibrinolytics agents have included children with ages that ranged from 6 months to 12 years [10, 11]. There is no doubt that one specific strategy may not be the most effective one for children of all ages and that future studies on the efficacy of various blood-sparing strategies will have to define their subgroups of patients more precisely. The classification proposed by Williams and associates (<1 month, >1 month to 12 months, >1 year to 5 years, and >5 years) seems to be appropriate as they were able to demonstrate a significant difference between groups in the volume of whole blood, platelets, and total blood products transfused.
In conclusion, the time has come to abandon the use of nonspecific terms such as "children" or "pediatric patients." Physiologically, children are not a uniform cohort but, rather, involve different subgroups. These subgroups need to be studied independently to draw valid conclusions from the existing literature and to treat them appropriately. Although blood-sparing strategies in common use today in adults may be suitable for older age groups undergoing cardiac operations, neonates and infants (ie, children under the age of 12 months) will require an innovative approach, especially in view of the demonstration by Williams and associates that, in the absence of fresh whole blood, these age groups are exposed to a significant number of allogenic blood products of eight and six units per patient respectively.
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References
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- Manno C.S., Hedberg K.W., Kim H.C., et al. Comparison of the hemostatic effects of fresh whole blood, stored whole blood, and components after open heart surgery in children. Blood 1991;77:930-936.[Abstract/Free Full Text]
- Andrew M., Paes B., Milner R., et al. Development of the human coagulation system in the full-term infant. Blood 1987;70:165-172.[Abstract/Free Full Text]
- Kern F.H., Morana N.J., Sears J.J., Hickey P.R. Coagulation defects in neonates during cardiopulmonary bypass. Ann Thorac Surg 1992;54:541-546.[Abstract]
- Boldt J., Knothe C., Zickmann B., Wege N., Dapper F., Hempelmann G. Aprotinin in pediatric cardiac operations: platelet function, blood loss, and use of homologous blood. Ann Thorac Surg 1993;55:1460-1466.[Abstract]
- Maurer H.M., McCue C.M., Caul J., Still W.J.S. Impairment in platelet aggregation in congenital heart disease. Blood 1972;40:207-216.[Abstract/Free Full Text]
- Greeley W.J., Bushman G.A., Kong D.L., Oldham H.N., Peterson M.B. Effects of cardiopulmonary bypass on eicosanoid metabolism during pediatric cardiovascular surgery. J Thorac Cardiovasc Surg 1988;95:842-849.[Abstract]
- Chan A.K.C., Leaker M., Burrows F.A., et al. Coagulation and fibrinolytic profile of paediatric patients undergoing cardiopulmonary bypass. Thromb Haemost 1997;77:270-277.[Medline]
- Miller B.E., Mochizuki T., Levy J., et al. Predicting and treating coagulopathies after cardiopulmonary bypass in children. Anesth Analg 1997;85:1196-1202.[Abstract]
- Guay J., Rivard G.-E. Mediastinal bleeding after cardiopulmonary bypass in pediatric patients. Ann Thorac Surg 1996;6:1955-1960.
- D’Errico C.C., Shayevitz J.R., Martindale S.J., Mosca R.S., Bove E.L. The efficacy and cost of aprotinin in children undergoing reoperative open heart surgery. Anesth Analg 1996;83:1193-1199.[Abstract]
- Reid R.W., Zimmerman A.A., Laussen P.C., Mayer J.E., Gorlin J.B., Burrows F.A. The efficacy of tranexamic acid versus placebo in decreasing blood loss in pediatric patients undergoing repeat cardiac surgery. Anesth Analg 1997;84:990-996.[Abstract]
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Invited commentary
References