J Thorac Cardiovasc Surg 1994;107:646-0647
© 1994 Mosby, Inc.
Invited letter concerning: Nonpulsatile flow—A noncontroversy
Kazutomo Minami, MD
Department of Thoracic and Cardiovascular Surgery
Heart Center North Rhine-Westfalia
University of Bochum
Bad Oeynhausen, Germany
Reply to the Editor:
We read the preceding letter by Dr. Bartlett with great pleasure. In our opinion, it again adds to the complex matter of pulsatile and nonpulsatile perfusion, giving a compact and clear review on the current state of discussion. We agree that most studies indicate that the hypothetical advantage of pulsatile flow is difficult to extrapolate to clinical benefit, in particular in routine procedures with average pump runs.
Taylor and coworkers,
1 however, were able to discern clinical benefit of pulsatile perfusion. In 350 consecutive patients, they found lower mortality and morbidity from postoperative low cardiac output in the pulsatile group, as well as less need for mechanical or inotropic circulatory support. Their series consisted of patients encompassing the range of coronary artery and valvular disease, including elective and emergency cases.
To examine the clinical effects of pulsatile perfusion more closely, we designed two studies. The first dealt with postoperative morbidity and mortality among high-risk patients with extended perfusion times (>120 minutes of cardiopulmonary bypass time) 2 and the second concerned fluid retention after routine coronary artery bypass grafting (CABG). 3 The figures from our first study indicate a lower postoperative morbidity (Table I) for the pulsatile group, with an equal mortality in a total collected series of 175 patients undergoing combined elective surgical procedures (e.g., CABG and valve replacement or carotid artery thromboendarterectomy) and therefore long perfusion times. Whereas approximately 33% of patients in the pulsatile perfusion group had internal coronary artery thromboendarterectomy operations, this was true of only 17% in the nonpulsatile group. Thus the two groups are not totally comparable. However, because we assumed that operative risk of the first (high-risk) group was significantly increased, we consider the method and results applicable, implying an improved postoperative course in patients after pulsatile perfusion. Another result of this study was that an increased intraoperative volume supplement is considered necessary during nonpulsatile perfusion to maintain stable hemodynamics, contributing to volume overload. In the second study, we were able to show an approximately 950 ml higher total net fluid balance in patients receiving nonpulsatile perfusion 24 hours after initiation of cardio pulmonary bypass in two groups of 15 patients each, who were undergoing CABG with average perfusion times and routine surgical procedures. The difference in net fluid balance arose intraoperatively, with the postoperative balances during the first 24 hours at the intensive care unit being nearly identical.
The reliability of this study is limited by its small patient number, but we believe that both studies, together with the results of Taylor and associates, 1 are valuable evidence that clinical benefit in applying pulsatile perfusion is detectable. Furthermore, we believe that capillary leakage does occur, possibly as a result of venous throttling exceeding the effect of arteriolar vasoconstriction, caused by increased plasma catecholamines during nonpulsatile perfusion. 4
All our examinations were carried out with moderate flow, low-pressure perfusion. Thus our results would be located on the x-axis of the diagram presented by Dr. Bartlett where the two graphs diverge, achieving either flow pattern with a double roller pump system (therefore with no hemolytic effects). We conclude that at least patients at high risk undergoing a long pump run may benefit from pulsatile perfusion. We will focus our future attention on capillary leakage and studies with greater patient numbers to improve statistical validity.
References
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Taylor KM, Bain WH, Davidson KG, Turner MA. Comparative clinical study of pulsatile and non-pulsatile perfusion in 350 consecutive patients. Thorax 1982;37:324-30.[Abstract/Free Full Text]
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Minami K, Dramburg W, Notohamiprodjo G, Koerfer R. Effects of pulsatile perfusion on perioperative morbidity and mortality. In: Minami K, Koerfer R, Wada J, eds. Cardiothoracic surgery: what is new in current practice. Amsterdam: Elsevier Science Publishers, 1992:67-75.
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Thompson T, Minami K, Dramburg W, Koerfer R. Influence of pulsatile and non-pulsatile perfusion on fluid-retention after coronary artery bypass grafting. Perfusion 1992;7:201-11.[Abstract/Free Full Text]
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Minami K, Koerner MM, Vyska K, Kleesiek K, Knobl H, Koerfer R. Effects of pulsatile perfusion on plasma catecholamine levels and hemodynamics during and after cardiac operations with cardiopulmonary bypass. J THORAC CARDIOVASC SURG 1990;99:82-91.[Abstract]
