Techniques in extra corporeal circulation


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Techniques in extra corporeal circulation

  1. 1. Techniques inextracorporealcirculation
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  3. 3. Techniques inextracorporealcirculationFOURTH EDITION Edited by PHILIP H KAY MA DM FRCS Consultant Cardiothoracic Surgeon, Yorkshire Heart Centre, The General Infirmary, Leeds, UK and CHRISTOPHER M MUNSCH ChM FRCS (C/Th) Consultant Cardiothoracic Surgeon, Yorkshire Heart Centre, The General Infirmary, Leeds, UK A member of the Hodder Headline Group LONDON
  4. 4. First published in 1976 by Butterworth-Heinemann Ltd,Linacre House, Jordan Hill, Oxford, OX2 8DP.This edition published in Great Britain in 2004 byArnold, a member of the Hodder Headline Group,338 Euston Road, London NW1 3BHhttp://www.arnoldpublishers.comFirst published 1976Second edition 1981Reprinted 1982Third edition 1992Reprinted 1993Fourth edition 2004Distributed in the United States of America byOxford University Press Inc.,198 Madison Avenue, New York, NY10016Oxford is a registered trademark of Oxford University Press© 2004 ArnoldAll rights reserved. No part of this publication may be reproduced ortransmitted in any form or by any means, electronically or mechanically,including photocopying, recording or any information storage or retrievalsystem, without either prior permission in writing from the publisher or alicence permitting restricted copying. In the United Kingdom such licencesare issued by the Copyright Licensing Agency: 90 Tottenham Court Road,London W1T 4LP.Whilst the advice and information in this book are believed to be true andaccurate at the date of going to press, neither the author[s] nor the publishercan accept any legal responsibility or liability for any errors or omissionsthat may be made. In particular (but without limiting the generality of thepreceding disclaimer) every effort has been made to check drug dosages;however, it is still possible that errors have been missed. Furthermore, dosageschedules are constantly being revised and new side-effects recognized.For these reasons the reader is strongly urged to consult the drug companies’printed instructions before administering any of the drugs recommended inthis book.British Library Cataloguing in Publication DataA catalogue record for this book is available from the British LibraryLibrary of Congress Cataloging-in-Publication DataA catalog record for this book is available from the Library of CongressISBN 0 340 80723 71 2 3 4 5 6 7 8 9 10Commissioning Editor: Joanna KosterDevelopment Editor: Sarah BurrowsProject Editor: Zelah PengilleyProduction Controller: Deborah SmithCover Design: Lee-May LimIndexer: Laurence ErringtonTypeset in 10/12 pt Minion by Charon Tec Pvt Ltd, Chennai, IndiaPrinted and bound in Great Britain by Butler & Tanner Ltd What do you think about this book? Or any other Arnold title? Please send your comments to
  5. 5. Contents Contributors vii Foreword xi Preface to Fourth Edition – 50 years on xiii Preface to Third Edition xiv Preface to Second Edition xv Preface to First Edition xvi Acknowledgements xvii1 A brief history of bypass 1 Anil Kumar Mulpur and Christopher M Munsch2 Design and principles of the extracorporeal circuit 7 Medtronic, Inc., A Manufacturer of Technologies for Extracorporeal Circulation3 Physiology and pathophysiology of extracorporeal circulation 23 Jonathan AJ Hyde and Ralph E Delius4 Anaesthesia for cardiopulmonary bypass 57 Linda Nel and John WW Gothard5 Monitoring and safety in cardiopulmonary bypass 76 Jonathan M Johnson, Stephen Robins and Jonathan A J Hyde6 Priming fluids for cardiopulmonary bypass 99 Piet W Boonstra and Y John Gu7 Filters in cardiopulmonary bypass 108 Farah NK Bhatti and Timothy L Hooper8 The inflammatory response to cardiopulmonary bypass 117 Saeed Ashraf9 Pulsatile cardiopulmonary bypass 133 Terry Gourlay and Kenneth M Taylor10 Cardiopulmonary bypass and the brain 148 G Burkhard Mackensen, Hilary P Grocott and Mark F Newman
  6. 6. vi Contents11 Cardiopulmonary bypass in children with congenital heart disease 177 Carin van Doorn and Martin Elliott12 Intraoperative myocardial protection 184 John WC Entwistle III and Andrew S Wechsler13 Blood conservation 210 Mike Cross14 Mechanical circulatory support 236 Stephen Westaby and Satoshi Saito15 Extracorporeal membrane oxygenation 254 Scott K Alpard, Dai H Chung and Joseph B Zwischenberger16 The extended use of the extracorporeal circuit 292 Philip H Kay, Anil Kumar Mulpur, Dumbor Ngaage, Samir Shah, Kieran Horgan, John Pollitt and Stephen D Hansbro17 Cardiopulmonary bypass during Port-access™ and robotic surgery 298 Alan P Kypson and W Randolph Chitwood Jr18 Cardiac surgery without cardiopulmonary bypass 315 Joseph P McGoldrick19A The development of clinical perfusion education and standards in the UK and Ireland 332 Michael Whitehorne19B Standards, guidelines and education in clinical perfusion: the European perspective 337 Ludwig K Von Segesser19C Perfusion education in the USA at the turn of the twentieth century 341 Alfred H Stammers Index 345
  7. 7. ContributorsScott K Alpard MD Mike CrossSurgical Research Fellow, Consultant Anaesthetist,Division of Cardiothoracic Surgery, Yorkshire Heart Centre,University of Texas Medical Branch, The General Infirmary at Leeds,Galveston, TX, USA Leeds, UKSaeed Ashraf FRCS(CTh) MD Ralph E Delius MDConsultant Cardiothoracic Surgeon, Children’s Hospital of Michigan,Regional Cardiothoracic Centre, Detroit, MI, USThe Morriston Hospital, and Honorary Senior Lecturer,University of Swansea, Carin van DoornSwansea, UK Senior Lecturer in Cardiothoracic Surgery,Farah NK Bhatti University College London,Specialist Registrar in Cardiothoracic Surgery, and Honorary Consultant Cardiothoracic Surgeon,Wythenshawe Hospital, Cardiothoracic Unit,Manchester, UK Great Ormond Street Hospital for Children, London, UKPiet W BoonstraDepartment of Cardiothoracic Surgery, Martin ElliottUniversity Hospital, Consultant Cardiothoracic Surgeon,Groningen, The Netherlands Cardiothoracic Unit, Great Ormond Street Hospital for Children,Walt Carpenter London, UKDirector of Cardiopulmonary R&D,Medtronic Perfusion Systems, John WC Entwistle III MD PhDMinneapolis, MN, USA Assistant Professor of Cardiothoracic Surgery, Department of Cardiothoracic Surgery,W Randolph Chitwood Jr MD Drexel University College of Medicine,Senior Associate Vice Chancellor and Director, Philadelphia, PA, USANorth Carolina Cardiovascular Institute,Professor and Chairman,Professor of Surgery, John WW Gothard FRCAChief, Division of Cardiothoracic and Vascular Surgery, Consultant Anaesthetist,The Brody School of Medicine, Royal Brompton Hospital,East Carolina University, London, UKGreenville, NC, USA Terry Gourlay PhD BSc (Hons) CBiol MIBiol ILTHE FRSHDai H Chung MD British Heart Foundation Perfusion Specialist,Assistant Professor of Surgery, Department of Cardiothoracic Surgery,Chief, Section of Pediatric Surgery, NHLI,Department of Surgery, Imperial College Medical School,University of Texas Medical Branch, Hammersmith Hospital Campus,Galveston, TX, USA London, UK
  8. 8. viii ContributorsHilary P Grocott MD FRCPC G Burkhard Mackensen MDAssociate Professor, Assistant Professor,Department of Anesthesiology, Klinik für Anaesthesiologie,Duke Heart Center, Technische Universität München,Duke University Medical Center, Klinikum rechts der Isar,Durham, NC, USA München, Germany Joseph P McGoldrick MD FRCSY John Gu Consultant Cardiothoracic Surgeon,Department of Cardiothoracic Surgery, The Yorkshire Heart Centre,University Hospital, The General Infirmary at Leeds,Groningen, The Netherlands Leeds, UKStephen D Hansbro Anil Kumar Mulpur MS MCh FRCS (Edin)Department of Clinical Perfusion, FRCS (Glasgow) FRCS C/Th (Edin) FETCSLeeds General Infirmary, Consultant Cardiothoracic Surgeon,Leeds, UK Sri Sathya Sai Institute of Higher Medical Sciences, Whitefield, Bangalore, IndiaTimothy L Hooper Christopher M Munsch ChM FRCS (C/Th)Consultant Cardiac Surgeon, Consultant Cardiothoracic Surgeon,Wythenshawe Hospital, Department of Cardiothoracic Surgery,Manchester, UK The Yorkshire Heart Centre, The General Infirmary,Kieran Horgan Leeds, UKDepartment of General Surgery,Leeds General Infirmary, Linda Nel FRCALeeds, UK Consultant Anaesthetist, Southampton University Hospitals Trust,Jonathan AJ Hyde MD FRCS(CTh) Southampton, UKConsultant Cardiac Surgeon, Mark F Newman MDRoyal Sussex County Hospital, Professor and Chairman,Brighton, UK Department of Anesthesiology, Duke Heart Center,Jonathan M Johnson BSc ACP Duke University Medical Center,Chief Clinical Perfusionist, Durham, NC, USARoyal Sussex County Hospital,Brighton, UK Dumbor Ngaage Department of Cardiothoracic Surgery, Leeds General Infirmary,Bruce Jones Leeds, UKCardiopulmonary Product Manager,Medtronic Perfusion Systems, John PollittMinneapolis, MN, USA Department of General Surgery, Leeds General Infirmary,Philip H Kay MA DM FRCS Leeds, UKConsultant Cardiothoracic Surgeon, Stephen Robins PgDip AACPThe Yorkshire Heart Centre, Chief Clinical Perfusionist,The General Infirmary, New Cross Hospital,Leeds, UK Wolverhampton, UKAlan P Kypson MD Satoshi Saito MD PhDAssistant Professor of Surgery, Senior Clinical Research Fellow,Division of Cardiothoracic Surgery, Department of Cardiothoracic Surgery,Brody School of Medicine, Oxford Heart Centre,East Carolina University, John Radcliffe Hospital,Greenville, NC, USA Oxford, UK
  9. 9. Contributors ixLudwig K Von Segesser Andrew S Wechsler MDService de Chirurgie Cardio-Vasculaire, Professor and Chairman,Centre Hospitalier Universitaire Vaudois (CHUV), Department of Cardiothoracic Surgery,Lausanne, Switzerland Drexel University College of Medicine, Philadelphia, PA, USASamir ShahDepartment of Cardiothoracic Surgery, Stuart WellandLeeds General Infirmary, European Marketing Manager,Leeds, UK Medtronic Europe Sàrl, Tolochenaz, SwitzerlandAlfred H Stammers MSA CCPChief Perfusionist, Stephen Westaby PhD FETCS MSDepartment of Surgery, Consultant Cardiac Surgeon,Geisinger Medical Center, Department of Cardiothoracic Surgery,Danville, PA, USA Oxford Heart Centre, John Radcliffe Hospital,Editor, Journal of Extracorporeal Technology Oxford, UKJeanne Stanislawski Michael Whitehorne MSC ACP FCCPSCardiopulmonary Product Manager, Consultant Clinical Perfusion Scientist,Medtronic Perfusion Systems, Department of Cardiothoracic Surgery,Minneapolis, MN, USA King’s College Hospital,Wendy Svee London, UKCardiopulmonary Product Manager, Joseph B Zwischenberger MDMedtronic Perfusion Systems, Professor of Surgery, Medicine, and Radiology,Minneapolis, MN, USA Director, General Thoracic Surgery and ECMO Programs,Kenneth M Taylor Division of Cardiothoracic Surgery,Professor of Cardiac Surgery, University of Texas Medical Branch,Department of Cardiothoracic Surgery, Galveston, TX, USANHLI,Imperial College Medical School,Hammersmith Hospital Campus,London, UK
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  11. 11. ForewordI am most grateful to the editors for their invitation to preference for medical revascularisation (percutaneouswrite the foreword for this – the fourth edition of transluminal coronary angioplasty, stents, the expandingTechniques of Extracorporeal Circulation. My office book- range of percutaneous coronary interventions) at thecase currently contains the three previous editions, and expense of what we used to consider the unassailableif I am not considered presumptuous, I look forward to gold standard: conventional coronary artery bypass graftadding a copy of this fourth edition. surgery. John Gibbon received international acclaim for his For cardiopulmonary bypass and the perfusion pro-courage and determination on the 50th anniversary of fessionals, the challenge was different, but no less daunt-that historic open-heart operation in Philadelphia on ing: would off-pump coronary bypass render the use ofMay 5th 1953 when the heart–lung machine was used cardiopulmonary bypass in coronary surgery obsolete?successfully in a patient for the first time. Fifty years does One might reasonably assume that now is not the time tonot seem to me to be that long, although when I was invest in cardiopulmonary bypass – far too risky! I begyounger (i.e. not over 50) my opinions were different. It to differ, however. I would suggest that now is preciselyis always fascinating to hear graphic personal accounts of the time for investment in cardiopulmonary bypass.those early days of cardiopulmonary bypass where the It should, however, be specifically targeted investment,challenges seemed almost insuperable. a balanced investment portfolio. Things are very different 50 years on. The technology First, the further continual refinement of cardio-and the practice of cardiopulmonary bypass have been pulmonary bypass remains as great a challenge and anrefined to an exceptional degree. The benefits to the car- opportunity now as it was in the 1950s. Developments indiac surgical patients and the cardiac team of surgeons, medicine in general (particularly including molecularanaesthetists, perfusionists and nursing staff have been science and genetics/genomics) offer great potential toincalculable. I was asked a few years ago to give a talk on increase our understanding of the fundamental patho-the topic: ‘Can cardiopulmonary bypass become more physiological mechanisms of cardiopulmonary bypasspatient friendly?’ I observed at the start of the talk that and consequently introduce more effective preventativecardiopulmonary bypass had been a great friend to cardiac and therapeutic strategies.surgical patients and to cardiac surgeons and their col- Second, we need to broaden our horizons as far asleagues, and that John Gibbon would be turning over in extracorporeal circulation is concerned. Its potential roleshis grave at the very thought of the topic I had been given. in other forms of surgery (both in cardiac and non- I was exaggerating of course, and Gibbon and his fellow cardiac) in local circulations and in systemic circulatorypioneers would be the very last to encourage complacency and respiratory support present a wealth of opportunities.regarding cardiopulmonary bypass. As it so happened, the Third and finally, to quote the UK Prime Minister Tonyfollowing year I was asked to speak to another question: ‘Is Blair (who interestingly was born on May 5th 1953 –cardiopulmonary bypass in 2001 as good as it gets?’ I trust Gibbon’s historic day) ‘... education, education, education’.you will already have worked out that I was somewhat We need to apply ourselves, both individually and in thenegative in my response to that proposition! medical and perfusion schools of the future. New science They say that things come along in threes – and it fell brings with it new terminologies – we need to learn theto me to address another cardiopulmonary bypass languages. Then we can communicate with the basic sci-related question in 2002. ‘Would you invest in cardiopul- entists, with molecular experts, with geneticists and whomonary bypass in 2002?’ was the title. I found this exer- knows who else!cise particularly interesting. By then, cardiac surgery and It may be a daunting prospect for us, but spare acardiopulmonary bypass were each facing major chal- thought also for the basic scientists – when have they everlenges to their future importance. For cardiac surgery, before been visited by an enthusiastic perfusionist orthe challenge – indeed the threat – was the increasing cardiac surgical trainee?
  12. 12. xii Foreword So these are the challenges, and the opportunities. honourable tradition of risk-takers. As one of the NorthThis textbook will help considerably. Philip Kay and American insurance corporations proclaims in its adver-Chris Munsch have brought into this book the right tising: ‘the only risk is not to take one’.subjects and the right authors. This book contains a lot of John Gibbon would profoundly agree with that.information, which can be a launch pad for new ideasand new questions. Professor Kenneth M Taylor MD FRCS Are there risks? Of course there are! We must never FRCSE FESC FETCS FSAforget, however, that in cardiac surgery we come from an BHF Professor of Cardiac Surgery
  13. 13. Preface to Fourth Edition — 50 years onIn May 1953 Edmund Hilary and Sherpa Tensing became surgery make the clinical perfusionist obsolete? Whateverthe first men to stand on the summit of Mount Everest. happens there is no doubt that clinical perfusion will con-In that same month came John Gibbon’s moment of tri- tinue to evolve and develop. We believe that this fourthumph, with the first successful use of mechanical car- edition of Techniques in Extracorporeal Circulationdiopulmonary bypass in a human patient. deserves a place on the bookshelves of all healthcare pro- The seed had been sown and it subsequently fell to fessionals working in the cardiac surgical operating room.other pioneers to develop the science of extracorporeal We suspect, in an era of electronic communication, thatcirculation. the bookshelf may well be the first to become obsolete. Leeds was at the forefront of this exciting development Progress in surgery is often compared with moun-and, in 1957, Geoffrey Wooler used cardiopulmonary taineering and exploration (and contributors to thisbypass to repair a mitral valve. He then went on to edit the book have themselves used the analogy). A lot has hap-first edition of Techniques in Extracorporeal Circulation, pened in both spheres in the past 50 years. With that inpublished in 1976. The change in authorship and content mind, we would like to follow in John Hunt’s illustriousof the subsequent three editions reflects the evolution of footsteps and, as he did in The Ascent of Everest, dedicatethe speciality over a generation of cardiac surgery. this book … ‘To those who made it possible’. Who, reading the first edition, would have predictedthat the fourth edition, 27 years later, would contain chap- Philip Kay and Chris Munschters on robotic surgery and off-pump surgery? Will the Leedscombined threat of increasing angioplasty and off-pump 2003
  14. 14. Preface to Third EditionThe heart is a unique organ, simple in concept as a mus- The first edition of this book, edited by Mr M. Ionescucle pump, but complex in design and function. Heart and Mr G. Wooller 16 years ago, laid a solid foundation forfailure, from whatever cause, remains the commonest the student of extracorporeal circulation. It was followedcause of death in the western world. by a second edition five years later and, after a further 11 It is now almost 100 years since von Reyn contravened years, by this edition. Yet progress in this field is so fast thatthe dictates of Billroth, risked ‘loosing the esteme of many of the new developments in this book were not evenhis colleagues’ and successfully operated on the heart. contemplated in the final ‘future developments’ chapter ofHowever, cardiac surgery proceeded at a slow pace until the second edition, and so I am sure will be the case for thethe development of the extracorporeal circuit. Thereafter fourth edition. Similarly, much progress has been madethe understanding of the complex anatomy, biochem- during the three years it has taken to produce this book.istry, pharmacology and physiology of the heart has Nevertheless, this edition, like the original, provides a firmenabled us to take great strides in the complex repair basis for doctors, nurses, perfusionists and physicians’work that is now so common place in the operating assistants alike, all students of the extracorporeal circula-room. Concomitantly, advances in rheology and material tion and its ever increasing number of have provided a wider safety margin and there- I hope that it will stimulate its readers to continuingfore expanded the number of patients able to benefit the pioneering interface between the lone surgeon andfrom cardiac surgery. It is these advances that form the the increasingly complex machinery that surrounds him.basis of the third edition of Techniques in ExtracorporealCirculation. P.H. Kay
  15. 15. Preface to Second EditionThe preface to the first edition of this book was preceded theoretical aspects of extracorporeal circulation but doesby Michelangelo’s humble remark ‘ancora imparo’. Even not necessarily provide final answers.for the contents of this small book on techniques in In an effort to keep abreast of the many advancesextracorporeal circulation it proved its timeless veracity which have occurred, a number of additional topics haveas we ‘continue to learn’. been included in this present edition. Several new, out- The first edition, however, despite many short-com- standing contributors have participated, whilst the greatings, has fulfilled its role. majority of those chapters which appeared in the first During the past few years the energetic clinical and edition have been updated or augmented.research activities have led to many advances and have Despite the awareness of discontinuity and reitera-further broadened the concept of artificial circulation tion, this second edition of Techniques in Extracorporealand oxygenation so that an increasing number of sub- Circulation retains the structure of most modern booksspecialties are now attaining a certain contour. by being comprised of a series of individual chapters. In recent years, several areas of extracorporeal circula- I wish to express my enthusiasm for the privilege oftion have assumed increasing importance. The progress editing this text and gratefully acknowledge the out-made in the field of ischaemic heart disease and the standing contributions of the authors who have joined inmajor impact of myocardial protection through cardio- this endeavour.plegia are only two of the most obvious examples. I should like to thank Miss Wendy Lawrence for theRefinements in the construction and performance of complex and seemingly endless secretarial work.bubble oxygenators and the introduction of disposable My sincere appreciation is extended to Messrsmembrane oxygenating systems have changed the tech- Butterworths for their unfailing attention to detail andniques of heart–lung bypass and broadened its scope. for the maintenance of the high standards for which they Many pioneers in these fields have discovered and redis- are known.covered noteworthy features of great clinical significance. This second edition attempts to summarize the majortechnical problems and touches on some of the more Marian I. Ionescu
  16. 16. Preface to First Editionancora imparo single volume standard current techniques in extracorpor-Michelangelo Buonarotti eal circulation along with the more recent developments in this field. This is an attempt to answer some of theExtracorporeal circulation with an artificial heart-lung innumerable practical problems associated with the rou-machine has established itself as the routine adjunct to tine use of artificial circulation and oxygenation and tointracardiac and vascular surgery. Since its introduction present some models of standardized 1953, this method has been progressively improved by A major problem with such a book is to decide what todevelopment and simplification of the equipment and by include and what to omit. We are aware that omissionsbetter understanding of the body response to the alter- have been made, but we have aimed to keep the subjectations induced by the use of artificial perfusions. matter strictly circumscribed in the interest of text size and The method, established in the experimental labora- readability. The esoteric has been omitted on purpose andtory, has been perfected by clinical use. For many poorly emphasis is placed on the current practical methodology.understood aspects the method has continued to be Advances in modern surgical and perfusion techniquesinvestigated in the laboratory, where answers and solu- have been developed to such a degree that an entirely newtions have been found for innumerable bewildering and spectrum of problems evolves with each new develop-knotty clinical problems. ment. Such rapid changes and improvements will certainly A superficial look at today’s methods would give the call for another publication in the near future, and this isuninformed the general impression that no substantial another reason for limiting the size of this book.progress has been made in the past ten years. For example, Since this is a multi-authored book and the chaptersthe same principle of bubble oxygenation used at the begin- are designed to be read separately, some reiteration hasning of the open-heart surgery era is almost universally been inevitable, although an attempt was made to avoidemployed today. The same may be said for metallic pros- repetition.thetic valves with a ball or disc occluder mechanism. The Major attention has been focused on the cardio-vascularbest method for ‘myocardial preservation’ during open- system, the lung, the renal function and haematologicalheart surgery is yet to be established and the Montagues of changes. Clearly the brain, liver, gut, muscle masses andhypothermia still have to convince the Capulets of coronary reticuloendothelial system are of great importance in theperfusion of the veracity and superiority of their principle body response to extracorporeal circulation, but the meas-just as much as they had to ten years ago. urement of their function in the cardiovascular patient is On closer examination, one realizes that during the at the moment largely in the realm of the investigator.past ten years an enormous wealth of data and knowledge Although the principles and techniques described havehas been accumulated and the application of this know- become routine for practical purposes, they are by noledge has made clinical perfusions incomparably better means beyond challenge. As William Hazlitt put it ‘whenand safer. The results of cardiovascular surgery obtained a thing ceases to be a subject of controversy, it ceases to betoday, whether in the newborn or the elderly, for great a subject of interest’.arteries or coronary arteries, in routine cases or in emer- The Editors join the contributors in hoping that thisgencies, when compared with the results obtained only volume will be of interest to those active in the field often years ago, are the best proof of progress and continu- cardiovascular surgery.ous improvement in extracorporeal circulation. We take great pleasure in expressing our thanks to During the past few years many new and exciting prin- Dr Frank Gerbode for kindly writing the Foreword ofciples and techniques based on extracorporeal circulation this work. We are grateful to Miss Nancy Evans for herhave been brought into clinical use. Deep hypothermia for continuous and enthusiastic help.heart surgery in the newborn, prolonged extracorporeal Completion of this book within a few months wasoxygenation-perfusion for pulmonary insufficiency and promised, but it has taken almost two years and weintra-aortic balloon pumping for circulatory assistance are appreciate the forbearance and continuous help of oursome of the major achievements of the past decade. publishers, Butterworth and Co. Ltd. The paucity of books devoted exclusively to extracor-poreal circulation has prompted us to bring together in a M.I. Ionescu
  17. 17. AcknowledgementsPhilip H Kay and Christopher M Munsch would like to We are also indebted to everyone at Hodder Arnold whothank the individual chapter authors for their skilful and worked so hard to make it happen.patient contributions to this beautifully crafted book.
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  19. 19. 1A brief history of bypassANIL KUMAR MULPUR AND CHRISTOPHER M MUNSCHIntroduction 1 Hypothermia 4The first heart–lung machine 1 Heparin 4Oxygenation 2 Summary 5Pumping the blood 4 Further reading 5Haemodilution 4 References 5INTRODUCTION THE FIRST HEART–LUNG MACHINEThe history of cardiopulmonary bypass is, in many ways, The concept of cardiopulmonary bypass is rightlya miniature representation of the history of all surgery. credited to Dr John Heysham Gibbon Jr (1903–1973).The discoveries and the experiments, the longed-for Dr Gibbon came from a family of doctors and was work-triumphs and the all too frequent disasters, the blood ing with Dr Churchill at Harvard Medical School. In(especially the blood), the sweat and the tears of years of October 1930 a female patient, who had undergonesurgical endeavour are all mirrored in the evolution of a cholecystectomy two weeks before, collapsed due tocardiac surgery. In 1880 Billroth stated that ‘any surgeon pulmonary thrombo-embolism. Dr Churchill did under-who wishes to preserve the respect of his colleagues, take a pulmonary embolectomy on her, but in that erawould never attempt to suture the heart’. What was once there were no survivors of this procedure in the USA.considered hazardous, outrageous or even sacrilegious Dr Gibbon looked after this patient in her last stages.has now become routine and commonplace. There is no This led to the genesis of an idea that Dr Gibbon outlineddoubt that the bravery and determination of the pion- (Gibbon, 1970):eers (both doctors and patients) has seen bypass developrapidly. Most cardiac surgeons these days prefer their During that long night, helplessly watching the patientheart surgery to be, if not boring, then at least not too struggle for life as her blood became darker and veinsexciting. more distended, the idea naturally occurred to me that if Much has been written about the history of cardio- it were possible to remove continuously some of the bluepulmonary bypass and the development of cardiac sur- blood from the patient’s swollen veins, put oxygen intogery. The interested reader, particularly one with an eye that blood and allow carbon dioxide to escape from it,for the flamboyant, is recommended to study Landmarks and then to inject continuously the now-red blood backin Cardiac Surgery (Westaby and Bosher, 1997). This into the patient’s arteries, we might have saved her life.chapter could never compete in such exalted company We would have bypassed the obstructing embolus andand, in fact, subsequent chapters in the current book performed part of the work of the patient’s heart andwill cover the historical background to specific areas of lungs outside the body.bypass in greater detail. Therefore, this introductorychapter will simply document some of the major mile- Dr Gibbon set out to devise a mechanical pump oxy-stones in the (relatively short) journey from impossible genator and, with his wife Mary Hopkinson, spent theto mundane. next 20 years in pursuit of his goal. The heart–lung
  20. 20. 2 A brief history of bypassmachine Model I was built by International Business carbon dioxide removal. It seemed that what was actuallyMachines (IBM) laboratories in 1949, by which time needed was in fact a lung, either natural or artificial.Gibbon was able to keep small dogs on bypass with only10 per cent mortality, and by 1951 a machine for clinicaluse was built. In 1953, using Model II, an atrial septal defect The lungswas closed successfully on cardiopulmonary bypass, forthe first time in history. In 1956, Campbell reported successful cardiac surgical However, this momentous occasion had much of procedures in humans on bypass, by use of dog lungsthe feel of a false dawn. Gibbon operated on four further (Campbell et al., 1956), and Mustard and co-workerspatients, all of whom died. He became disillusioned with reported the use of scrupulously washed monkey lungsthe technique and critical of his own surgical abilities, for oxygenation in human cardiac surgery in 1954. Theseand called a halt to the programme. experiments, although seemingly moderately successful, All was not lost though, and John Kirklin, using a were extremely complicated and soon abandonedmodified Model II, operated on eight patients with intra- (Mustard et al., 1954; Mustard and Thomson, 1957). Incardiac defects, with just four deaths, only one of which 1958 Drew used patients’ own lungs as the oxygenator,he attributed directly to complications of bypass. The with a combination of right and left heart bypass andimpetus had been regained and further progress in profound hypothermia (Drew and Anderson, 1959). Withmechanical cardiopulmonary bypass was stimulated. this technique, the time available for surgical repair was increased and more complex abnormalities could be addressed (Westaby and Bosher, 1997).OXYGENATIONThe historical development of oxygenators is summar- Cross-circulationized in Fig. 1.1. Many methods of oxygenating the bloodhave been investigated over the years. Early experiments Andreasen and Watson conducted some canine experi-involved actually injecting oxygen directly into the blood ments in Kent, England and published their resultsstream, whilst other equally inventive techniques of oxy- in 1952. If the superior vena caval entry into the heartgenation were attempted and soon abandoned. These was snared at the cavo-atrial junction, no dog survivedearly experiments focused purely on artificial oxygen- beyond 10 minutes. If the snare was distal to azygos vein,ation, without concerning themselves with the need for allowing azygos venous flow into the right atrium, there Oxygenators Natural Artificial oxygenators oxygenators Heterologous Homologous oxygenators oxygenators Dog Monkey lungs lungs Controlled cross-circulation Bubble Film Membrane Figure 1.1 Development of oxygenators for oxygenator oxygenator oxygenator cardiopulmonary bypass.
  21. 21. Oxygenation 3was adequate flow to prevent cerebral damage for up to sheet oxygenator, and improved the DeWall–Lillehei40 minutes. This finding challenged the existing notion bubble oxygenator further, which meant that the bub-that flows equivalent to normal cardiac output were nec- ble oxygenator became available as a sterile sealed unit.essary to prevent damage to vital centres, and suggested This development played a significant role in expandingthat in fact only eight to nine per cent of normal flow was cardiac surgery beyond Minnesota (Gott et al., 1957a,b).needed (Andreasen and Watson, 1952). Naef (1990) wrote: Lillehei, at the University of Minnesota, recognizedthe significance of these findings for cardiac surgery the home made helix reservoir bubble oxygenator of(Lillehei, 2000). After a series of careful experiments DeWall and Lillehei, first used clinically on May 13, 1955,(Cohen and Lillehei, 1954), he introduced the technique went to conquer the world and helped many teams toof ‘controlled cross-circulation’. As the name suggests, embark on the correction of malformations inside thethe technique used an adult whose circulation was con- heart in a precise and unhurried manner. The road to open-nected to a child patient, the adult subject acting as the heart surgery had been opened.oxygenator. In Lillehei’s own words, ‘controlled’ refers tothe use of a pump to precisely control the balance of the DeWall went on to develop the bubble oxygenator fur-volume of blood flowing into and out of the donor and ther and introduced the oxygenator and omnithermicthe patient. heat exchanger in a disposable and pre-sterilized poly- This was a daring and innovative idea. These oper- carbonate unit (DeWall et al., 1966). With the advent ofations carried a theoretical 200 per cent mortality. In fact, better technology, and safer operations under more con-there was no donor mortality in 45 operations. Of 45 trolled circumstances, surgeons were, for the first time,patients, 28 survived and were discharged from hospital, appreciating the intricacies of pathologic anatomy inmany surviving for as long as 30 years (Lillehei et al., congenital and acquired heart disease, and leading to the1986). Controlled cross-circulation, however, was limited development of surgical techniques in the present its use and could not fully support the circulation. Atthe same time, more conventional forms of extracorporealcirculation were being developed, and before long Lillihei Film oxygenatorshimself went on to develop a new pump oxygenator. Gibbon developed a film oxygenator with a rapidly revolving vertical cylinder. The film itself was a thin filmBubble oxygenators of blood on the metal plate, where the oxygenation took place. In the first model, there was no reservoir. Gas flowSimple measures to bubble oxygen into the blood met included a 95 per cent oxygen and five per cent carbonwith disastrous results because of air embolism. Clark and dioxide mixture at 5 L/min. The venous and arterial sidesco-workers had a breakthrough in 1950, when they started of the oxygenators had roller pumps and blood passedto use small glass beads or rods coated with DC Antifoam through tubing, which was immersed in a waterbathA, made by the Dow Corning Company in Michigan to maintain a constant temperature throughout the per-(Clark et al., 1950). This concept was further developed by fusion. Flows of up to 500 mL/min were generated withLillehei and DeWall, who used a spiral settling tube with a the initial model (Gibbon, 1937). Next, a wire mesh washelical system that largely eliminated bubbles. The initial introduced to produce a turbulent blood–gas interfacemodels were sterilized and re-used. Later on, disposable to improve oxygenation (Gibbon, 1954). This was fur-bubble oxygenators were developed. The first clinical use ther improvised at the Mayo Clinic, with 14 wire meshesof the DeWall–Lillehei bubble oxygenator was on 13 May enclosed in a lucite case. Blood flowed onto the screens1955, for a three-year-old child with a ventricular septal through a series of 0.6 micron slots. Gas flow was 10 L ofdefect and pulmonary hypertension. By use of normo- oxygen, and the carbon dioxide flow was varied depend-thermia, a Sigmamotor pump and flows of 25–30 mL/kg, ing on the pH of the blood (Kirklin et al., 1955). However,Lillehei reported the first success story with the bubble compared with the DeWall–Lillehei bubble oxygenator,oxygenator (Lillehei et al., 1956). the Mayo Clinic Gibbon film oxygenator, although impres- Bubble oxygenators were later refined to serve adult sive, was handcrafted and expensive, and difficult to usepatients. The Rygg–Kyvsgaard bag (Rygg and Kyvsgaard, and maintain.1956) combined the bubbling and settling chambers Kay and Cross developed a rotating disk film oxygena-with a reservoir, all in one plastic bag. Sponges made of tor in Cleveland, USA. Although this device did becomepolyethylene and coated with antifoam agent were used commercially available, it had serious drawbacks infor bubble removal. This model was manufactured in terms of ease of use, massive priming volumes, and diffi-Denmark. Up to 3 L/min flows were possible. Gott and culty in cleaning and sterilizing (Cross et al., 1956; Kayco-workers developed a self-contained unitized plastic et al., 1956).
  22. 22. 4 A brief history of bypassMembrane oxygenators priming of the cardiopulmonary bypass circuits. DeWall and Lillehei subsequently confirmed the benefits ofBy 1944, Kolff had refined a cellophane membrane appar- haemodilution on cardiopulmonary bypass (DeWall andatus for dialysis as an artificial kidney. He later tried to Lillehei, 1962; DeWall et al., 1962; Lillehei, 1962). Despiteuse this as a membrane oxygenator, but found it to be abundant literature, the actual degree of acceptableinefficient (Kolff and Berk, 1944; Kolff and Balzer, 1955). haemodilution remains controversial even today.However, Clowes and Neville developed a teflon mem-brane oxygenator for human usage in 1957. The mem- HYPOTHERMIAbrane area was 25 m2, but the oxygenator was bulky withproblems of sterilization and assembly (Clowes andNeville, 1957). Once silicone became available as a mem- Historically, it is interesting to note that hypothermiabrane with satisfactory permeability to both oxygen and usage in cardiac surgery precedes the development ofcarbon dioxide, Bramson and colleagues (Bramson et al., cardiopulmonary bypass. Following his earlier work on1965) reported a new disposable membrane oxygenator the treatment of frostbite, William Bigelow had alreadywith integral heat exchanger. This model had 14 cells, done extensive experimental work on dogs on the physio-each having a silicone rubber membrane across which logical effects of hypothermia (Bigelow et al., 1950). Hediffusion took place. Bodell et al. (1963) proposed the predicted the possible use of hypothermia in cardiacuse of tubular capillary membranes instead of film, and surgery thus:this notion led to the hollow-fibre membrane oxygen- The use of hypothermia as a form of anesthetic couldators. Not to be outdone, Lillehei was also associated with conceivably extend the scope of surgery in many newthe availability of the first compact, disposable and directions. A state in which the body temperature is low-commercially manufactured membrane oxygenator for ered and the oxygen requirements of tissue are reduced toclinical use (Lande et al., 1967). a small fraction of normal would allow exclusion of organs from the circulation for prolonged periods. Such a technic might permit surgeons to operate upon the ‘bloodlessPUMPING THE BLOOD heart’ without recourse to extra corporal pumps, and perhaps allow transplantation of organs.A critical component of the heart bypass apparatus is These experiments soon led to the use of hypothermiasome form of efficient atraumatic mechanical pump. A alone, with inflow occlusion but without cardiopul-variety of pumping devices was developed before the dou- monary bypass, for the treatment of atrial septal defects.ble roller pump became widely used. Dale and Schuster On 2 September, 1952 Dr F. John Lewis and his team(1928) developed a diaphragm pump with valved inlet closed an ostium secundum atrial septal defect in a five-and outlet ports, but a single pump could not generate year-old girl on inflow occlusion and moderate totalsufficient flow, so Jongbloed used six pumps of this type in body hypothermia.parallel to conduct cardiopulmonary bypass (Jongbloed, Gollan should be given the credit of working on1949). In Minnesota, Lillehei’s group initially used a mul- the concept of combining hypothermia and cardiopul-ticam activated sigmamotor pump. monary bypass, before either actually became clinically However, as early as 1934, DeBakey had modified a applicable (Gollan et al., 1955). Sealy, of Duke University,previously available Porter–Bradley roller pump for rapid North Carolina, USA, subsequently employed a combin-blood transfusion (DeBakey, 1934). This pump was applied ation of cardiopulmonary bypass and hypothermia forto cardiopulmonary bypass, and rapidly became – and the first time in a clinical situation for closure of atrialremains – the most common type of pump in use for septal defect and this operation lasted for seven hoursclinical perfusion. and 15 minutes! By 1958, Sealy reported a series of 49 patients operated on by the combined technique (Sealy et al., 1958). As mentioned previously, Drew took theHAEMODILUTION temperature down to 12–15°C and pioneered the con- cept of circulatory arrest for cardiac surgery (Drew andTwo major problems were identified in patients after car- Anderson, 1959).diopulmonary bypass, namely ‘post-perfusion syndrome’and ‘homologous blood syndrome’. In the early daysthe oxygenators and the circuit were primed with donor HEPARINblood. Zuhdi et al. (1961a, 1961b), however, developedthe concept of haemodilution with five per cent dextrose It is almost impossible to imagine the conduct ofand thus began the usage of clear priming or crystalloid cardiopulmonary bypass without the use of heparin.
  23. 23. References 5The discovery of heparin is an interesting story (Jaques, REFERENCES1978), and in the history of medicine is quoted as a classi-cal example of ‘serendipity’. Horace Well coined this term Andreasen, A.T., Watson, F. 1952: Experimental cardiovascularin 1754; ‘The Three Princes of Serendip’, was the title of a surgery. British Journal of Surgery 39, 548–51.fairy tale in which the heroes were always making fortu- Bigelow, W.G., Lindsay, W.K., Greenwood, W.F. 1950: Hypothermia:nate discoveries (Concise OED, 2002). McLean was a med- its possible role in cardiac surgery. An investigation of factorsical student working with W. H. Howell in 1916, on the governing survival in dogs at low body temperatures. Annals ofnature of ether soluble procoagulants, and by chance dis- Surgery 132, 849–66.covered a phospholipid anti-coagulant. Some years later Bodell, B.R., Head, J.M., Head, L.R. 1963: A capillary membranea water-soluble mucopolysaccharide was identified by oxygenator. Journal of Thoracic and Cardiovascular Surgery 46,Howell, and this proved to be heparin (McLean, 1959). 639–50.Even today, except in very rare circumstances, where it Bramson, M.L., Osborn, J.J., Main, F.B. et al. 1965: A newcannot be used, because of genuine hypersensitivity or disposable membrane oxygenator with integral heat exchanger. Journal of Thoracic and Cardiovascular Surgery 50,heparin-induced thrombocytopenias, heparin and car- 391–400.diopulmonary bypass are inseparable. Campbell, G.S., Crisp, N.W., Brown, E.B. Jr. 1956: Total cardiac bypass in humans utilising a pump and heterologous lung oxygenator (dog lung). Surgery 40, 364–71.SUMMARY Clark, L.C., Gollan, F., Gupta, V.B. 1950: The oxygenation of blood by gas dispersion. Science III, 85–7. Clowes, G.H.S., Neville, W.E. 1957: Further development of a bloodThe history of cardiopulmonary bypass is a truly fascinat- oxygenator dependent upon the diffusion of gases throughing story. Against many difficulties, with a combination plastic membranes. Transactions of the American Society forof perseverance, intellect and skill, the early pioneers Artificial Internal Organs 3, 53–8.developed the art of cardiopulmonary bypass as we see Cohen, M., Lillehei, C.W. 1954: A quantitative study of the ‘azygosit today. A large range of congenital and acquired heart factor’ during vena caval occlusion in the dog. Surgery,diseases can be treated surgically with the aid of cardiopul- Gynecology and Obstetrics 98, 225–32.monary bypass. With advancing technology, cardiopul- Concise Oxford English Dictionary (Tenth edition). 2002: Oxford:monary bypass continues to develop. Advances such as Oxford University Press.heparin-bonded circuits, methods minimizing systemic Cross, F.S., Berne, R.M., Hirose, Y. et al. 1956: Description andinflammatory response, percutaneous applications of evaluation of a rotating disc type reservoir oxygenator.bypass, port access surgery, continued improvement in Surgical Forum 7, 274–8. Dale, H.H., Schuster, E.A. 1928: A double perfusion pump. Journaloxygenators and ventricular assist devices; all these and of Physiology 64, 356–64.others will change the picture of cardiopulmonary bypass DeBakey, M.E. 1934: A simple continuous flow blood transfusionbeyond recognition, and the present day will then become instrument. New Orleans Med Surg J 87, 386–9.the history. DeWall, R., Lillehei, C.W. 1962: Simplified total body perfusion- reduced flows, moderate hypothermia and hemodilution.Key early events in the development of Journal of the American Medical Association 179, 430–4. DeWall, R., Lillehei, C.W., Sellers, R. 1962: Hemodilution perfusionextracorporeal circulation for open heart surgery. New England Journal of Medicine 266, 1078–84.• 1916: McLean; discovery of heparin. DeWall, R.A., Bentley, D.J., Hirose, M. et al. 1966: A temperature• 1930: Gibbon; initial idea of cardiopulmonary bypass. controlling (omnithermic) disposable bubble oxygenator for• 1934: DeBakey; concept of roller pump for total body perfusion. Diseases of the Chest 49, 207–11. extracorporeal circulation. Drew, C., Anderson, I.M. 1959: Profound hypothermia in cardiac• 1950: Bigelow; profound hypothermia for open- surgery. Lancet April 11: 748–50. heart surgery. Gibbon, J.H. Jr. 1937: Artificial maintenance of circulation during• 1953: Gibbon; first successful clinical use of experimental occlusion of pulmonary artery. Archives of Surgery 34, 1105–31. cardiopulmonary bypass. Gibbon, J.H. Jr. 1954: Application of mechanical heart and• 1954: Lillehei; use of controlled cross-circulation. lung apparatus to cardiac surgery. Minnesota Medicine 37, 171–80. Gibbon, J.H. Jr. 1970: The development of the heart–lungFURTHER READING apparatus. Rev Surg 27, 231–44. Gollan, F., Phillips, R., Grace, J.T. et al. 1955: Open left heart• General reading: Westaby, S., Bosher, C. 1997: Landmarks in surgery in dogs during hypothermic asystole with and without cardiac surgery. Oxford: ISIS Medical Media, 1997. A very extracorporeal circulation. Journal of Thoracic Surgery 30, well-written book on the history of cardiac surgery. 626–30.
  24. 24. 6 A brief history of bypassGott, V.L., DeWall, R.A., Paneth, M. et al. 1957a: A self contained, Lillehei, C.W., DeWall, R.A., Read, R.C. et al. 1956: Direct vision disposable oxygenator of plastic sheet for intracardiac surgery. intracardiac surgery in man using a simple, disposable artificial Thorax 12, 1–9. oxygenator. Diseases of the Chest 29, 1–8.Gott, V.L., Sellers, R.D., DeWall, R.A. et al. 1957b: A disposable Lillehei, C.W., Varco, R.L., Cohen, M. et al. 1986: The first open heart unitized plastic sheet oxygenator for open heart surgery. repairs of ventricular septal defect, atrioventricular communis, Diseases of the Chest 32, 615–25. and tetralogy of Fallot using extracorporeal circulation by crossJaques, L.B. 1978: Addendum: the discovery of heparin. Seminars in circulation: a 30 year follow up. Annals of Thoracic Surgery Thrombosis and Hemostasis 4, 350–3. 41, 4–21.Jongbloed, J. 1949: The mechanical heart/lung system. Surgery, McLean, J. 1959: The discovery of heparin. Circulation XIX, 75–78. Gynecology and Obstetrics 89, 684–91. Mustard, W.T., Thomson, J.A. 1957: Clinical experience with theKay, E.B., Zimmerman, H.A., Berne, R.M. et al. 1956: Certain clinical artificial heart–lung preparation. Journal of the Canadian aspects in the use of the pump oxygenator. Journal of the Medical Association 76, 265–9. American Medical Association 162, 639–41. Mustard, W.T., Chute, A.L., Keith, J.D. et al. 1954: A surgicalKirklin, J.W., Dushane, J.W., Patrick, R.T. et al. 1955: Intracardiac approach to transposition of the great vessels with surgery with the aid of a mechanical pump oxygenator system extracorporeal circuit. Surgery 36, 39–51. (Gibbon type): report of eight cases. Proceedings of Staff Naef, A.P. 1990: The story of thoracic surgery. Toronto: Hografe & Meetings of the Mayo Clinic 30, 201–7. Huber, 113–19.Kolff, W.J., Balzer, R. 1955: The artificial coil lung. Transactions Rygg, H., Kyvsgaard, E. 1956: A disposable polyethylene oxygenator of the American Society for Artificial Internal Organs 1, system applied in the heart/lung machine. Acta Chirurgica 39–42. Scandinavica 112, 433–7.Kolff, W.J., Berk, H.T.J. 1944: Artificial kidney: dialyser with a great Sealy, W.C., Brown, I.W., Young, W.G. 1958: A report on the use of area. Acta Medica Scandinavica 117, 121–34. both extracorporeal circulation and hypothermia for open-heartLande, A.J., Dos, S.J., Carlson, R.G. et al. 1967: A new membrane surgery. Annals of Surgery 147, 603–13. oxygenator–dialyser. Surgical Clinics of North America 47, Westaby, S., Bosher, C. 1997: Landmarks in cardiac surgery. Oxford: 1461–70. ISIS Medical Media.Lillehei, C.W. 1962: Hemodilution perfusion for open heart surgery. Zuhdi, N., McCollough, B., Carey, J. et al. 1961a: Hypothermic Use of low molecular weight dextran and five per cent dextrose. perfusion for open heart surgical procedures – report of the use Surgery 52, 30–31. of a heart–lung machine primed with five per cent dextrose inLillehei, C.W. 2000: Historical development of cardiopulmonary water inducing hemodilution. J Int Coll Surg 35, 319–26. bypass in Minnesota. In: G.P. Gravlee et al. (eds), Zuhdi, N., McCollough, B., Carey, J. et al. 1961b: Double helical Cardiopulmonary bypass: principles and practice reservoir heart–lung machine designed for hypothermic (second edition). Baltimore, MD: Lippincott Williams & perfusion primed with five per cent glucose in water inducing Wilkins, 3–21. hemodilution. Archives of Surgery 82, 320–5.
  25. 25. 2Design and principles of the extracorporeal circuitMEDTRONIC, INC., A MANUFACTURER OF TECHNOLOGIES FOR EXTRACORPOREAL CIRCULATIONHistory of cardiopulmonary bypass 7 Heat exchangers 14Bubble oxygenators 8 Tubing 15Membrane oxygenators 8 Myocardial protection 15Components of the extracorporeal circuit 9 Biocompatibility 16Pumps 9 Adequacy of perfusion 21Venous reservoir 12 Acknowledgements 21Cardiotomy reservoirs 13 References 21 the extracorporeal circuit are adequately perfused KEY POINTS with oxygenated blood by continual monitoring of blood flow rate, perfusion pressure, acid/base state, oxygen consumption, coagulation and renal • The essential components of the clinical function. extracorporeal circuit are a pump (artificial heart), an oxygenator (artificial lung), a reservoir and the tubing to connect these devices, although systems are now emerging without traditional reservoirs. HISTORY OF CARDIOPULMONARY BYPASS • Additional components include a heat exchanger, a system for myocardial protection, and gas and emboli filters. Secondary suction circuits may be The first proposal for artificial circulation was put for- added for salvaging shed blood, and venting the ward by Le Gallois in 1812 when he perfused rabbit heart. brains through carotid arteries. Between 1848 and 1853 • The current generation of membrane oxygenators Brown Sequard showed that dark venous blood, when incorporating reservoirs and heat exchangers exposed to air and shaken, turned bright red. He further provide safety, efficacy and ease of use. demonstrated the feasability of perfusing isolated brain • Centrifugal pumps are compact, durable, easy to specimens with this ‘arterialized’ blood. The first bubble set up and cause minimal haemolysis compared oxygenator, utilizing the same principle of mixing venous with roller pumps. While their cost is certainly blood with air, was assembled by Shroder in 1882. And higher than a simple length of roller pump tubing, then, two years later, von Frey and Gruber created the first it may be more than offset by savings in ventilatory membrane oxygenator, in which the direct blood–air and ICU time, as well as overall hospital stay. interface of the bubbler design was avoided. • A body of published evidence, as well as extensive In 1900, Howell and colleagues discovered the anti- clinical experience by surgeons and perfusionists, coagulant properties of heparin. Without the risk of cata- supports the value of heparin-based biosurfaces strophic clotting within the bypass circuit, it was now for thrombo-resistance and biocompatibility possible to expose the blood to extended periods of during extracorporeal circulation. extracorporeal circulation. • It is the responsibility of the perfusionist to The first clinical application of extracorporeal circula- ensure that the organs of the body supported by tion was performed by Dr John Gibbon, Massachusetts
  26. 26. 8 Design and principles of the extracorporeal circuit Table 2.1 Developmental history of oxygenators Non-membrane oxygenators 1937 Gibbon Blood filter – pulmonary embolus 1951 Dennis/Bjork Rotating screen and cardiopulmonary bypass rotating disk 1955 Lillehei/DeWall First bubble oxygenator with helix reservoir 1956 Kay/Cross Refind disk oxygenator for up to 4000 mL of venous blood 1956 Rygg/Kyvsgaard First disposable plastic bag oxygenator, Polystan (Rygg Bag) 1962 Cooley/Beall Proposed use of commercially available disposable bubble oxygenators (Travenol Bag) 1966 DeWall/Najafe/Roden First disposable hard shell oxygenator (polycarbonate) with built-in heat exchanger (Bentley Labs) Membrane oxygenators 1955 Kolff/Balzfer Oxygenated blood through polyethylene membrane (animals) 1956 Kolff First coiled polyethylene tube oxygenator 1958 Clowes First to test Teflon as membrane plate oxygenator 1968 Lande Methyl silicone folded plate membrane oxygenator (Lande/Edwards) 1969 Pierce Co-polymer of dimethyl siloxan and polycarbonate 1969 Pierce Pierce-GE 1971 Kolobow Silicone rubber reinforced by nylon mesh rolled or coiled (SciMed–Kolobow) 1972 Eiseman/Spencer Expanded (Teflon) membrane sheets (Travenol/TMO) 1975 Travenol Labs Polypropylene (expanded) plate or sheets (TMO) 1985 J& J Cardiopulmonary First hollowfibre polypropylene oxygenator (Maxima)General Hospital who, in 1953, successfully repaired an into the bubble chamber. The early Bentley model hasatrial septal defect in a young female. Despite subsequent the heat exchanger located within the arterial reservoir.setbacks, Dr C Walton Lillehei of the University of Bubble oxygenators are efficient and easy to use. Unfor-Minnesota and several others persevered in further tunately, the nature of the foaming/defoaming processdeveloping the techniques and equipment, with Lillehei causes significant haemolysis, which becomes clinicallyusing the first bubble oxygenator in 1955. significant after only a few hours. Bubble oxygenators also The bubble oxygenator, first developed by Rygg, was present a higher risk of micro- and macro-air embolism:produced commercially by 1956. The years since have seen the defoaming process is imperfect, and inadvertentmyriad refinements and improvements in oxygenator and emptying of the arterial reservoir can lead to massiveother component designs, which unlike the early systems amounts of air being pumped directly to the patient, atare now completely disposable. A brief history of the least when roller pumps are used. Further, because of thedevelopment of oxygenators is summarized in Table 2.1. bubbling process, it is not considered safe to blend oxy- gen with air (since nitrogen bubbles would be so much less soluble) making independent control of pO2 andBUBBLE OXYGENATORS pCO2 impossible. This would also necessitate the mixing of small amounts of carbon dioxide with the oxygen toBubble oxygenators were the first design to be commer- prevent the pCO2 from falling too far. For these reasons,cially available in completely disposable form, and were bubblers are rarely used today. Several safe, efficientin wide use throughout the world for more than 46 years. membrane oxygenators currently dominate the market.A ‘bubbler’ usually consists of an integrated design, incorp-orating the oxygenator, heat exchanger, arterial reservoir MEMBRANE OXYGENATORSand cardiotomy filter in one unit. The unit functions bypassing incoming venous blood over a perforated orporous sparger plate, through which oxygen is passed, Membrane oxygenators of various designs have beenturning the venous blood into a foam of variously sized used sporadically since the mid-1950s, but it was notbubbles. As oxygen diffuses across the bubble surfaces until 19 years ago that relatively low-prime volume, easy-into the blood, and conversely, as excess carbon dioxide to-use units became commercially available. In the mem-diffuses from the blood into the bubbles, the blood is brane oxygenator, the ventilating gas is separated from thearterialized. The blood is then passed through a silicone- blood by a semi-permeable membrane fabricated frombased defoaming medium, collects in an arterial reser- polypropylene, or in one case, silicone rubber. Unlike bub-voir section and is returned to the patient. The heat ble oxygenators, there is no direct contact between theexchanger in most bubble oxygenators was incorporated blood and ventilating gas. Gas exchange is accomplished
  27. 27. Pumps 9 For routine use, the micro-porous polypropylene membrane, with its lower blood volume, is considered to be more versatile and easier to prime and use. In this design, the material is manufactured with tiny holes, too small for blood to pass through but large enough to allow gas transfer. The material can be fabricated in sheet form or more commonly, in tubular or ‘microfibre’ form. In most cases, the micro-fibres are arranged – much like the relationship between blood and gas in the alveoli – to allow blood to flow around the outside of the tubes while the ventilating gas passes through the lumen of the tubes. Although the arrangement has been reversed in some units, this configuration is by far the most common and considered by most practitioners to be more physiological and less damaging to the formed elements of the blood. Modern membrane oxygenators often incorporate an integral heat exchanger where blood can be cooled or warmed before being ventilated. The Medtronic AFFINITY® oxygenator is an example of the latest in membrane/heat exchanger design and can be used with or without the integral cardiotomy/venous reservoir (Fig. 2.2). COMPONENTS OF THE EXTRACORPOREAL CIRCUIT The extracorporeal system consists of interconnected devices for the oxygenation and circulation of the blood, temporarily replacing the function of the heart and lungs. The main components of the circuit (Fig. 2.3) are a pump (artificial heart), an oxygenator (artificial lung), venousFigure 2.1 Kolobow/SciMed/Medtronic paediatric membrane and cardiotomy reservoirs (sometimes integrated), a heatoxygenators. Photo © copyright Medtronic, Inc. exchanger (usually integrated with the oxygenator), a sys- tem for myocardial protection (cardioplegia), gas andby diffusion across the membrane, driven by the partial emboli filters, and the tubing to connect these devices.pressure gradients of dissolved gases between the blood Typical secondary circuits include suction, provided byside of the membrane and the gas side. This same mech- roller pumps or a vacuum source, for salvaging shed blood,anism drives respiration in the natural lung, making the and venting to prevent distension of the left ventricle.membrane oxygenator a much more physiologic substi-tute than the bubbler for artificial ventilation. Since thereis no foaming/defoaming process, it is safe to blend air PUMPSwith the oxygen, making independent control of pO2 andpCO2 possible. While the oxygenator performs the ventilatory task of Most commercially available membrane oxygenators the lungs on cardiopulmonary bypass, the arterial pumpuse silicone rubber or micro-porous polypropylene. The takes over for the heart. Its sole function is to provide anbest-known example of a silicone device is the Medtronic/ adequate flow of oxygenated blood to the patient’s arter-Kolobow design, in which a long narrow sheet of silicone ial circulation. The main technical requirements of anrubber is wound spirally along with spacer/support arterial pump are as follows:material to form two independent pathways for bloodand gas. These devices are available in various sizes to 1 Wide flow range (up to 7ϩ L/min).accommodate different patients, from small neonates to 2 Low haemolytic effect.large adults (Fig. 2.1). They are biocompatible, minimize 3 Minimum turbulence and blood stagnation.damage to the blood and are the membrane of choice for 4 Simplicity and safety of use.long-term ventilatory assistance. 5 Cost-effectiveness.
  28. 28. 10 Design and principles of the extracorporeal circuit Figure 2.2 AFFINITY® adult hollow fibre oxygenator with integrated CVR. Photo © copyright Medtronic, Inc.Of the myriad arterial pump designs that were applied to order to minimize the inevitable resultant haemolysis,extracorporeal circulation in the early years, only two are the rollers are adjusted axially so that the pump is slightlyin widespread use today. Worldwide, just over half of car- underocclusive. (This is defined as allowing a 1 cm/mindiopulmonary bypass procedures are performed with drop along a 1 m high saline column in 3/8-inch tubing.)roller pumps, the remainder use centrifugal pumps. Flow rate in a roller pump is a derived value, calculated from the stroke volume multiplied by the revolutions per minute (RPM).Roller pumps The roller pump is a simple, inexpensive, easy-to-use mechanism. One must keep in mind, however, that it is aThe roller pump (Fig. 2.4) consists of a semi-circular sta- positive-displacement pump. A line restriction upstreamtor, within which is mounted a rotor with twin rollers will create an excessive vacuum, leading to degassing ofplaced at 180° to each other. The blood tubing is the blood and generation of a ‘bubble train’ inside thecompressed between the stator and the rotor. Since one tubing. Conversely, a line restriction downstream willroller is engaged with the stator just before the other lead to immediate pressure build-up, with possible direroller leaves the semi-circle, flow is unidirectional. In consequences depending on the source of the obstruction.
  29. 29. Pumps 11 Arterial cannula Vent catheter Cardictomy Cardioplegia cannula Bio Trend Sucker Arterial Venous Venous SAT SAT/HCT return catheter MYOtherm XP Autolog Affinity CVR Affinity Cardiotomy/Venous arterial reservoir filter Cardioplegia solution Sequestra 1000 Affinity Bio- oxygenator probe Heater/cooler HMS Bio-pumpFigure 2.3 Components of the extracorporeal circuit. Schematic © copyright Medtronic, Inc. Figure 2.4 Roller pump head. Photo © copyright Medtronic, Inc.A roller pump displaces air as effectively as blood, so that Centrifugal pumpsit is possible, for instance in the event of inadvertentemptying of a hard shell venous reservoir, to pass massive The centrifugal pump is essentially a vortex generator.amounts of air downstream towards the patient. Several By spinning an impeller (which may consist of vanes or, intechniques and systems are utilized to mitigate against the case of the Medtronic Bio-Pump® Centrifugal Bloodsuch a disaster, such as reservoir level sensors, in-line air Pump, nested cones) within a housing at high speed, andetectors, membrane oxygenators and arterial filters. area of low pressure is created in the centre, and higher
  30. 30. 12 Design and principles of the extracorporeal circuit imparted to the blood by the hydrofoil configuration of the vanes. This is efficient, but can create turbulence on the trailing edges of these vanes. In the Medtronic Bio-Pump® design (Fig. 2.5 (a) and (b)) energy is imparted strictly by viscous drag inherent in the blood itself, minimizing tur- bulence. An inherent safety feature of centrifugal pumps is their inability to pump very large amounts of air. When air fills the pump chamber, the pump is not able to develop sufficient pressure to expel it against the backpressure of the extracorporeal circuit. Whatever the impeller design, centrifugal pumps are all classified as non-positive displacement pumps – they will respond to changes in both pre-load and after-load with changes in flow rate, much as the native heart does. Centrifugal pumps require in-line monitoring of the flow rate that is accomplished in the Medtronic system, for example, by electromagnetic induction. Other sys- tems use an ultrasonic probe to detect flow. The in-line flow measurement allows accurate adjustment of the pump speed when necessary to regulate flow in the case of changes in pre-load and after-load. Centrifugal pumps are very practical. They are com- pact, durable, easy to set up, and cause minimal haemolysis compared with roller pumps. While their cost is certainly higher than a simple length of roller pump(a) tubing, it may be more than offset by savings in ven- tilatory and ICU time, as well as overall hospital stays that have been demonstrated in numerous clinical studies (Morgan et al., 1998). VENOUS RESERVOIR The general functions of the venous reservoir are to accumulate blood from the patient’s venous system and to remove both air and microaggregates present in venous blood. Venous reservoirs may be either rigid (hard shell) or soft (bag). Rigid reservoir A rigid reservoir consists of a clear plastic shell, vented to the atmosphere either by basic design or integral(b) valve, with a provision for defoaming and gross-filtering (100– 200 ␮) of incoming venous blood. Typical reservoirFigure 2.5 (a) The nested cones design within the Medtronic capacity may range from 1 L to 4.5 L (Fig. 2.6).Bio-Pump®; (b) BPX-80 adult Bio-Pump®. Photos © copyrightMedtronic, Inc. Soft reservoirpressure is generated along the outside circumference.Blood is drawn axially into the centre by the vortex and The soft or ‘bag’ reservoir is constructed of soft PVC withexpelled under pressure through a port oriented tangen- a 100–200 ␮ filtering screen. Typical reservoir capacitytial to the axis of rotation. With the vane design, energy is ranges between 200 mL and 3.0 L (Fig. 2.7).
  31. 31. Cardiotomy reservoirs 13Figure 2.6 Hard shell reservoir. Photo © copyrightMedtronic, Inc. Hard shell reservoirs are easy to use and offer theadvantage of integration with the cardiotomy function,simplifying the circuit. They can handle incoming venousair with ease. With simple modifications, hard shell reser-voirs can be used for vacuum-assisted venous drainage.Their principal disadvantage is that it is very possible toempty the reservoir and pass air to the arterial pump, Figure 2.7 Soft reservoir bag. Photo © copyright Medtronic, Inc.which, if it is a roller pump, will pass the air downstream.This risk can be mitigated somewhat with the use of reser-voir level sensors and in-line air detectors, which may ormay not shut the arterial pump off automatically. CARDIOTOMY RESERVOIRS Bag reservoirs can be slightly more cumbersome touse since incoming venous air does not vent automat- Blood from the cardiotomy suckers and vents is mostically and must be actively aspirated from the bag. Also, often delivered to the cardiotomy reservoir. This serves asthey require a separate hard shell cardiotomy reservoir to a storage area and also filters the large number of solidhandle returning cardiotomy suction blood and left ven- and gaseous micro-emboli. The rigid reservoir is made oftricle vent return. Many practitioners consider them polycarbonate, with ports that direct incoming bloodsafer than hard shell reservoirs since, when maintained through both defoaming layers and micro-aggregateproperly air-free, bag reservoirs will not allow massive air filters of between 20 ␮ and 40 ␮ (Fig. 2.8).embolism, because the soft bag simply collapses upon Another option with growing acceptance is toemptying, presenting nothing for the arterial pump to deliver suction blood to a cell-saving device (Fig. 2.9).pass. The soft shell system also may be preferable because Here, the red cells can be separated from the activatedof the elimination of the air–blood interface found in platelets, white cells and plasma before returning themopen, hard shell systems. to the patient. It is common practice today to integrate
  32. 32. 14 Design and principles of the extracorporeal circuit Figure 2.8 Cardiotomy reservoirs. Photo © copyright Medtronic, Inc.these cardiotomy functions with a hard shell venous which have their strengths and weaknesses. Aluminumreservoir. has by far the best heat exchange performance, but is not biocompatible unless coated, which degrades its per- formance somewhat. Plastic is inexpensive, but has rela- tively poor heat transfer properties and requires largeHEAT EXCHANGERS surface areas. Stainless steel seems to be the most popular because of its combination of good heat exchange coeffi-During cardiopulmonary bypass the temperature of the cient, ease of fabrication in either pleated or tubularperfusate may be adjusted to improve myocardial protec- form, and biocompatibility.tion and optimize the operating conditions for the To adjust the temperature of the perfusate, water ofpatient. This is accomplished within the extracorporeal variable temperatures is circulated through the heatcircuit by one or more heat exchangers that are com- exchanger, cooling or warming the perfusate as the clin-posed of two pathways, one for the perfusate and one for ical situation dictates. To further enhance efficiency, thewater. These pathways are separated by material that water flows in the opposite direction relative to the per-allows efficient thermal exchange between the fluids. The fusate, maximizing the temperature differential through-material may be plastic, aluminum or stainless steel, all of out the transit.