Ann Thorac Surg 2005;80:243-244
© 2005 The Society of Thoracic Surgeons
Original article: Cardiovascular
Invited commentary
Mark Kurusz, CCP
Division of Cardiothoracic Surgery, University of Texas Medical Branch, 301 University Blvd, Galveston, TX 77555-0528
(Email: mkurusz{at}utmb.edu).
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Introduction
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Minimizing blood damage during cardiopulmonary bypass (CPB) and its sequelae, such as the systemic inflammatory response (SIR), has been an ongoing quest for decades. Recent efforts have focused on reducing the CPB blood surface area and concomitant hemodilution. In this article, a large number of patients undergoing first-time coronary artery bypass surgery had a modified, low-prime CPB circuit. To achieve reduced surface area, the circuit had no venous or cardiotomy reservoir, roller pump and heat exchanger/bubble trap for cardioplegia delivery, or arterial line filter. Venous drainage was achieved by direct aspiration using a centrifugal pump integral to the inlet of the oxygenator. During CPB, all cardiotomy-suctioned blood was processed by a cell salvage system. To address possible entrainment of room air at the venous cannulation site, the circuit included a novel evacuation system designed to automatically aspirate air (> 1 mL) volume before it entered the centrifugal pump. Patients perfused with this system were prospectively randomized and compared with a similar group perfused with a conventional CPB circuit with roller pumps, venous/cardiotomy reservoir, and arterial filter. Lung function, bleeding, and markers of SIR were assessed.
Patients in whom the modified circuit was used had reduced manifestations of SIR, yet increased blood loss and transfusion requirements when compared with those patients who had conventional CPB. Although the hematocrit at the end of CPB was modestly higher in those patients perfused with the modified circuit (25 ± 7 vs 21 ± 7%), this was most likely due the reduced priming volume (500 vs 1,750 mL). The authors attributed the increased blood loss and transfusion requirements to using a cell salvage system instead of direct reinfusion of cardiotomy-suctioned blood. Lung function was transiently impaired in both groups.
The authors conclude that the modified circuit is "safe and simple" and acknowledged no clear clinical benefit. Of note, the modified system is no longer commercially available. However, efforts to minimize CPB surface area and priming volume are being pursued by other manufacturers and may have a favorable impact in pediatric CPB where typical circuit-to-patient blood volume ratios are greater than in adults. Techniques such as retrograde autologous priming of the circuit before starting CPB and vacuum-assisted venous drainage may also permit reduced circuit priming volumes and lessen hemodilution.
Eliminating the venous reservoir compromises the removal of entrained venous air before blood is pumped into the oxygenator and places an extra burden on the surgeon to consistently provide a reliable airtight seal at the venous cannulation site. It also places an extra burden on the perfusionist to immediately decrease the systemic blood flow if any venous line air is detected until the source is identified and eliminated. For these reasons, use of such a modified CPB circuit necessitates inclusion of an air evacuation system, which in some circumstances may be ineffective, thus leading to the risk of systemic air embolism.
The message of the study is that a low-prime circuit can be used effectively for uncomplicated coronary artery bypass surgery with an experienced team. However, lack of flexibility inherent in conventional CPB and safety concerns when using this reservoir-less system appear to add risk without demonstrable clinical benefit.
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The Society of Thoracic Surgeons Policy Action Center
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The Society of Thoracic Surgeons (STS) is pleased to announce a new member benefit—the STS Policy Action Center, a website that allows STS members to participate in change in Washington, DC. This easy, interactive, hassle-free site allows members to:
- • Personally contact legislators with one’s input on key issues relevant to cardiothoracic surgery
- • Write and send an editorial opinion to one’s local media
- • E-mail senators and representatives about upcoming medical liability reform legislation
- • Track congressional campaigns in one’s district—and become involved
- • Research the proposed policies that help—or hurt— one’s practice
- • Take action on behalf of cardiothoracic surgery
This website is now available at www.sts.org/takeaction.
Related Article
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Initial Experience With a Minimized Extracorporeal Bypass System: Is There a Clinical Benefit?
- Ulf Abdel-Rahman, Feyzan Özaslan, Petar S. Risteski, Sven Martens, Anton Moritz, Abdallah Al Daraghmeh, Harald Keller, and Gerhard Wimmer-Greinecker
Ann. Thorac. Surg. 2005 80: 238-243.
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