Ann Thorac Surg 2005;80:2332
© 2005 The Society of Thoracic Surgeons
New technology
Invited commentary
Song Wan, MD, PhD,
Ahmed A. Arifi, MD
Division of Cardiothoracic Surgery, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, People's Republic of China
(Email: swan{at}cuhk.edu.hk).
For many cardiac surgeons who closely follow the latest clinical research on the inflammatory response to cardiopulmonary bypass (CPB), Nollert and colleagues' report [1] is thought-provoking. At first glance, this study appears not far from an apple and orange comparison, although the authors do clarify their intention to compare two completely different perfusion strategies rather than individual components of the CPB circuit. Their idea of studying a closed miniaturized CPB system is theoretically attractive, that is: (1) heparin-coated tubing and oxygenator has long been proposed to reduce contact activation and to enhance biocompatibility; (2) a centrifugal pump may help in decreasing hemolysis; (3) a cell saver device avoids direct intraoperative re-transfusion of pericardial blood that potentially carries pro-inflammatory mediators such as endotoxin or activated tissue factors; (4) removal of the venous reservoir reduces priming volume (less hemodilution) and eliminates blood-air interface; and (5) patients in the miniaturized CPB group received reduced doses of heparin and blood cardioplegia (instead of a significantly larger amount of crystalloid cardioplegia). Taken together, some beneficial effects in diminishing inflammatory reactions during CPB and improved clinical outcomes would be anticipated.
Surprisingly, such logical expectations were not shown by Nollert and colleagues' comprehensive data. Their negative findings, both biochemical and clinical, are likely related to inadequate sample size in a low-risk patient population with a relatively short pump run. However, the safety concerns raised by these authors are undeniably important, even though the two episodes of air leak described in the text were apparently both preventable.
The miniaturized CPB system was originally introduced as an assist device for beating heart procedures. Hence, removal of the venous reservoir and the vent for this application would not increase the risk of air emboli or ventricular distension. When the use of this miniaturized CPB system was extended to operations under cardioplegic arrest, however, absence of a venous reservoir and vent becomes a debatable issue. On one hand, the specific role of a venous reservoir in inducing inflammatory injury during CPB deserves further investigation. On the other hand, it is evident in the current study that the removal of the venous reservoir and venting device made surgeons and perfusionists uncomfortable. As Nollert and colleagues correctly point out, these particular modifications may ultimately narrow the patient safety margin.
This article once again reminds us as clinicians and researchers to carefully balance the risk and benefits before embarking on innovative adventures. Few would argue today that CPB is much safer when compared with half a century ago. Indeed, many achievements in the field of CPB would never occur without continued innovations and changes. Although we should always bear in mind Denton Cooley's advice to "simplify, modify, apply" we must also remember the words of Albert Einstein who said, "everything should be made as simple as possible, but not simpler."
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References
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- Nollert G, Schwabenland I, Maktav D, et al. Miniaturized cardiopulmonary bypass in coronary artery bypass surgerymarginal impact on inflammation and coagulation but loss of safety margins. Ann Thorac Surg 2005;80:2326-2332.[Abstract/Free Full Text]
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