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Ann Thorac Surg 2000;70:749-750
© 2000 The Society of Thoracic Surgeons

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Invited commentary

Invited Commentary

^a Department of Cardiac Surgery, Children’s Hospital, 300 Longwood Ave, Bader 279, Boston, MA, 02115 USA,

e-mail: delnido{at}cardio.tch.harvard.edu

Invited commentary

Operative results in children undergoing repair of congenital heart defects has steadily improved over the last two decades. These advances have been due in large part, to improved methods of diagnosis, optimizing timing of surgery, improved myocardial protection and cardiopulmonary bypass, as well as increased experience by the surgical teams. With the improvement in outcome, indications for mechanical circulatory assistance in children have changed. Inability to wean off bypass following repair has become less frequent. However, more centers have recognized the potential benefit of having a rapid response system available for establishing mechanical circulatory assistance in patients who deteriorate early after surgery, sometimes unexpectedly, and also for patients with cardiomyopathy who may deteriorate due to arrhythmias. Whereas traditionally the type of extracorporeal membrane oxygenator circuit that was developed for neonatal respiratory failure has also been utilized for patients with primary cardiac failure, most centers have recognized that important limitations of these types of circuits are the large priming volume and long set up time.

Since true ventricular assist devices designed for chronic support of children are currently not available in the United States, conventional pumps such as the roller head or centrifugal pumps continue to be the only devices available for pediatric use. The need for a mechanism to prevent cavitation from an occluding roller pump has resulted in continued use of gravity dependent drainage, pressure sensitive bladder box as a regulator of electrical power to the roller pump. The limitations of gravity dependent drainage is overcome by an active suction system provided by the centrifugal pump at the expense of durability and a higher potential for cavitation. In the report by Jacobs and colleagues, they describe a system that utilizes a centrifugal pump combined with a hollow fiber oxygenator, which dramatically decreases set up time and minimizes priming volume. This type of system addresses two of the major drawbacks of conventional extracorporeal membrane oxygenator circuits that utilize Teflon membrane oxygenators and roller pumps. The larger priming volume required by this circuit results in increased hemodilution if blood is not available for priming. The long set up time significantly delays initiation of support if a system is not set up and ready to go as is currently done in many cardiac intensive care units. This miniaturized system represents a clear advantage for the rapid institution of mechanical support. It’s long term use however is still limited in that durability of the centrifugal pump head as well as efficiency of the hollow fiber oxygenator necessitate conversion to a conventional oxygenator and/or frequent replacement of the circuit if support is required for several days. Use of anticoagulation is still generally recommended even when heparin coated circuits are used since we and others have seen thrombus formation within 24 to 48 hours after initiation of support when heparin levels are kept very low. Alternative strategies for managing postoperative bleeding in cases where mechanical circulatory support is initiated early after surgery are platelet transfusions, administration of cryoprecipitate and fresh frozen plasma to maintain fibrinogen levels, and judicious use of anti-fibrinolytics. In our experience, this approach has resulted in adequate control of operative site bleeding while still administering heparin and minimizing the risk of thromboemboli.

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Pedro J. del Nido Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by del Nido, P. J. Search for Related Content PubMed Articles by del Nido, P. J.