Perfusion for Congenital Heart Surgery E-Book

Gregory S. Matte

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 434

Veröffentlichungsjahr: 2015

Beschreibung

A complete guide to the tools and techniques for modeling, simulating, and optimizing SSFE processes and phenomena

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Leseprobe

CONTENTS

Cover

Title page

Copyright page

Dedication page

Foreword

Preface

Acknowledgments

CHAPTER 1: Equipment for bypass

Oxygenators

Arterial line filters

Tubing packs

Cardioplegia systems

The heart–lung machine

The heater-cooler system

Cannulae

References

CHAPTER 2: Priming the bypass circuit

Prime constituents

Steps for priming

References

CHAPTER 3: The bypass plan

Communication agreement for case

Anticoagulation management

Blood gas management

Hematocrit management

Blood pressure management

Temperature management

Flow rates, regional perfusion, and hypothermic circulatory arrest

Methods of ultrafiltration

Standard and augmented venous return

The prebypass checklist

The surgical safety checklist for congenital heart surgery

References

CHAPTER 4: Typical phases of cardiopulmonary bypass

Commencement of bypass

Standard support phase of bypass

Termination of bypass

Post bypass

Reference

CHAPTER 5: Additional notes based on bypass tasks

Prebypass

On bypass

References

CHAPTER 6: Bypass considerations based on diagnosis

Anomalous coronary arteries

Aortic regurgitation/insufficiency

Aortic stenosis

Aortopulmonary collaterals

Aortopulmonary window

Atrial septal defect

Cardiomyopathy requiring orthotopic heart transplantation

Coarctation of the aorta

Common atrioventricular canal defect

Cor triatriatum

Corrected transposition of the great arteries (L-TGA, Levo-TGA, or C-TGA) or congenitally corrected TGA

Critical aortic stenosis

Double chambered right ventricle

Double inlet left ventricle

Double outlet left ventricle

Double outlet right ventricle

Ebstein’s anomaly

Hypoplastic left heart syndrome

Interrupted aortic arch

Left superior vena cava

Lung transplantation

Mitral regurgitation/insufficiency

Mitral stenosis

Patent ductus arteriosus

Pulmonary artery abnormalities

Pulmonary atresia

Pulmonary regurgitation/insufficiency

Pulmonary stenosis

Pulmonary vein stenosis or pulmonary venous obstruction

Tetralogy of Fallot

Total anomalous pulmonary venous return and partial anomalous pulmonary venous return

d-Transposition of the great arteries

Tricuspid atresia

Tricuspid regurgitation/insufficiency

Truncus arteriosus

Ventricular septal defect

References

CHAPTER 7: Notes on select issues during bypass

Blood pressure higher than expected

Blood pressure lower than expected

Bypass circuit pressure higher than expected

Bypass circuit pressure lower than expected

Central venous pressure elevated

Heat exchange issue (slow cooling or warming)

NIRS values lower than expected

PaCO

2

higher than expected

PaCO

2

lower than expected

PaO

2

lower than expected

Reservoir volume acutely low

References

CHAPTER 8: Notes on select emergency procedures during bypass

Arterial pump failure (roller head)

Failure to oxygenate

Massive air embolization

Acute aortic dissection at the initiation of bypass

Venous air lock

Inadvertent arterial decannulation

Inadvertent venous decannulation

References

CHAPTER 9: Brief overview of named procedures and terms

Alfieri stitch

Batista procedure

Bentall procedure

Bidirectional Glenn shunt

Blalock–Hanlon procedure

Blalock–Taussig shunt (BTS)

Brock procedure

Central shunt

Cone procedure

Cox maze procedure

Damus–Kaye–Stansel anastomosis

Double switch procedure

Fontan procedure

Gott shunt

Hemi–Fontan procedure

Holmes heart

Jatene operation

Kawasaki disease

Kawashima procedure

(Diverticulum of) Kommerell

Konno procedure

LeCompte maneuver

LeCompte procedure

Manougian procedure

Marfan’s syndrome

Maze procedure

Mustard procedure

Nicks procedure

Nikaidoh procedure

Noonan syndrome

Norwood operation

Pannus

Pentalogy of Cantrell

Potts shunt

Rashkind procedure

Rastelli operation

Ross procedure

Sano shunt

Scimitar syndrome

Senning operation

Shone’s complex

Takeuchi procedure

Taussig–Bing anomaly

Trusler repair

Van Praagh classification

Warden procedure

Waterston shunt

Williams syndrome

Yasui procedure

Reference

CHAPTER 10: Abbreviations for congenital heart surgery

CHAPTER 11: Recommended reference books

Cardiac anesthesia textbooks

Congenital cardiac intensive care textbook

Mechanical circulatory support textbook

Congenital cardiac surgery textbooks

Cardiopulmonary bypass textbooks

CHAPTER 12: Comprehensive experience-based equipment selection chart Select medications administered during bypass

Index

End User License Agreement

List of Tables

Chapter 01

Table 1.1 Oxygenators rated up to ~2 LPM.

Table 1.2 Oxygenators rated ~2 to ~5 LPM.

Table 1.3 Oxygenators rated up to 8 LPM (Part I of II).

Table 1.4 Oxygenators rated up to 8 LPM (Part II of II).

Table 1.5 External arterial line filters.

Table 1.6 Example of equipment selection based on anticipated maximum pump flow rate.

Table 1.7 Typical tubing sizes with flow maximums.

Table 1.8 Tubing prime volume.

Table 1.9 Venous cannulae for bicaval cannulation.

Table 1.10 Water chart flow rates for select venous cannulae.

Table 1.11 Water chart flow rates for select femoral venous cannulae.

Table 1.12 Arterial cannulae for central aortic cannulation.

Table 1.13 Arterial cannulae for femoral cannulation.

Chapter 02

Table 2.1 Crystalloid solution properties.

Table 2.2 Patient estimated blood volume.

Chapter 03

Table 3.1 Coagulation factors.

Table 3.2 Typical pH-stat blood gas values with equivalent alpha-stat values.

Table 3.3 Typical target blood pressure ranges during cardiopulmonary bypass.

Table 3.4 Temperature range classifications.

Table 3.5 Common index flows during cardiopulmonary bypass.

Chapter 12

Table 12.1 Comprehensive experience-based equipment selection chart.

Table 12.2 Select medications administered during bypass.

List of Illustrations

Chapter 01

Figure 1.1 Simplified schematic for basic cardiopulmonary bypass equipment (excludes cardioplegia system).

Figure 1.2 Terumo CAPIOX FX series of oxygenators

. Left to right: Terumo CAPIOX FX05, Terumo CAPIOX FX15-30, Terumo CAPIOX FX25. A—cardiotomy venous reservoir and B—oxygenator membrane with integrated arterial line filter and heat exchanger.

Figure 1.3 Typical components of an oxygenator system.

Figure 1.4 Primary types of oxygenators currently in use.

Figure 1.5 Simplified schematic of blood flow paths through an oxygenator.

Figure 1.6 Filters in the Terumo CAPIOX FX05 oxygenator.

A—cardiotomy filter in the CVR. B—venous filter in the CVR

.

Figure 1.7 Air removal in the CVR and oxygenator.

Figure 1.8 External arterial line filters.

(a)

Sorin Group D736

.

(b)

Sorin Group D733

.

(a)

and

(b)

Reproduced with permission from Sorin Group USA Inc., Arvada, CO. All rights reserved.

(c)

Terumo Capiox AF02

. Reproduced with permission from Terumo Cardiovascular Group, Ann Arbor, MI. All rights reserved.

(d)

Medtronic Affinity Pixie

.

Figure 1.9 Typical flow path through external arterial line filters. The top luer connector purges continuously via a line connected to the CVR.

Figure 1.10 Recirculating cardioplegia system table lines. Top: Recirculating delivery system with table line return limb clamped for cardioplegia delivery. Bottom: Recirculating delivery system with table line outlet limb clamped for recirculation.

Figure 1.11 Recirculating cardioplegia schematic. Note the table line outlet limb is clamped for recirculation.

Figure 1.12 Nonrecirculating cardioplegia schematic. The cardioplegia head draws a crystalloid component together with a blood component to be delivered through a cardioplegia heat exchanger to the patient.

Figure 1.13 Top and side views of a customized Stockert S5 heart–lung machine.

A—Arterial head and its controller A1, B—cardioplegia head and its controller B1, C—vent head and its controller C1, D—field sucker and its controller D1, E—field sucker and its controller E1, F—centrifugal head motor (for kinetic venous-assisted drainage) and its controller F1, G—electronic venous occluder and its controller G1, H—master display tower, I—sterile custom tubing pack, J—custom cardioplegia tubing set, K—oxygenator, L—hemoconcentrator, M—blood gas sampling manifold, and N—ice bucket for cardioplegia cooling coil.

Figure 1.14 Stockert heater-cooler system 3T (three-tank system).

A—Cold cardioplegia circuit. The first tank instantly provides 2–10°C water to the cardioplegia system. B—Warm cardioplegia circuit. The second tank instantly provides 15–41°C water to the cardioplegia system. It can also be fitted for a water-based patient surface cooling/heating blanket. C—Oxygenator circuit. The third tank provides 15–41°C water to the oxygenator heat exchanger. It has a second pump and circuit to provide water flow from the same tank to a water-based patient blanket if desired.

Figure 1.15 General cardiac anatomy. http://en.wikipedia.org/wiki/File:Relations_of_the_aorta,_trachea,_esophagus_and_other_heart_structures.png via Wikipedia.

Figure 1.16 Aortic arch anatomy. http://cnx.org/content/m46646/latest/2121_Aorta.jpg.

Figure 1.17 Central venous anatomy.

Figure 1.18 Select pediatric venous cannulae.

A—14 Fr. Terumo Tenderflow right angle PVC tip. B—14 Fr. Medtronic DLP right angle metal tip. C—12 Fr. Medtronic DLP right angle PVC tip. D—12 Fr. Edwards Lifesciences Thin-Flex right angle plastic tip. E—14 Fr. Medtronic Bio-Medicus straight with multiple side port holes. F—14 Fr. Medtronic DLP malleable straight PVC tip.

Figure 1.19 Select arterial cannulae for central cannulation.

A-6 Fr. Medtronic DLP One Piece. B-12 Fr. Medtronic Bio-Medicus. C-20 Fr. Medtronic EOPA. D-22 Fr. Medtronic EOPA CAP.

Figure 1.20 Luminal variation between types of arterial cannulae.

A-Standard round lumen for a 22 Fr. Medtronic arterial cannula. B-D-shaped lumen for a 22 Fr. Medtronic arterial cannula with central aortic pressure (CAP) monitoring capability. C-Left of

“

C” is the central aortic pressure monitoring port.

Chapter 03

Figure 3.1 Classical description of the blood coagulation pathways. VII-stabile factor, XII-Hageman factor, IX-Christmas factor, XI-plasma thromboplastin, XIII-fibrin stabilizing factor, Ca++ ionized calcium, PL-platelets, TF-tissue factor. http://commons.wikimedia.org/wiki/File:Classical_blood_coagulation_pathway.png.

Figure 3.2 Cell-based model of hemostasis

in vivo

. http://commons.wikimedia.org/wiki/File:Coagulation_in_vivo.png.

Figure 3.3 Heparin dose response curve for quantifying heparin and protamine doses. Graph of a heparin (and protamine) dosing algorithm. In the graph, the control activated clotting time (ACT) is shown as point A, and the ACT resulting from an initial heparin bolus of 200 units/kg is shown in point B. The line connecting A and B then is extrapolated and a desired ACT is selected. Point C represents the intersection between this line and a target ACT of 400 s, theoretically requiring an additional heparin dose represented by the difference between points C and B on the horizontal axis (arrow C). Similarly, to achieve an ACT of 480 s (higher horizontal dotted line intersecting the ACT versus heparin dose line at point D), one would administer the additional heparin dose represented by arrow D. To estimate heparin level and calculate protamine dose at the time of heparin neutralization, the most recently measured ACT value is plotted on the dose–response line (point E in the example). The heparin level present theoretically is represented by the difference between point E and point A on the horizontal axis (arrow E). The protamine dose required to neutralize the remaining heparin then may be calculated. Protamine 1.0 mg/kg is administered for every 100 units/kg of heparin present. From Hensley FA, Gravlee GP (2003). A Practical Approach to Cardiac Anesthesia.

Figure 3.4 Depiction of the operative field during aortic arch reconstruction with RLFP. Arterial inflow is through the cannulated shunt after the anastomosis to the innominate artery is performed. Exposure is maintained by the brachiocephalic snares, a clamp on the descending aorta, and the right atrial blood scavenger. The 3.5-mm polytetrafluoroethylene graft will admit an 8 F or 10 F arterial cannula (Medtronic Bio-Medicus, Eden Prairie, Minn). On completion of the neoaorta, deairing is accomplished by removing the aortic clamp.

Figure 3.5 Schematic depiction of three-region perfusion strategy during neoaortic arch reconstruction. Shaded bars depict the timeline of direct perfusion (shaded) or ischemia (white) to the cerebral (brain), splanchnic (kidney), and coronary (heart) circulations. Upper panel: three-region perfusion strategy described in this article, with drawings (a), (b), and (c) representing the corresponding stages of surgery. The cerebral and coronary circulations are perfused throughout the distal arch reconstruction (a). Distal arch complete, direct perfusion of the splanchnic circulation is resumed (b). Cardioplegia is administered and the coronary circulation is interrupted during only the proximal neoaortic arch completion (c). The direct perfusion of the cerebral circulation is uninterrupted throughout. Lower panel: perfusion and ischemia timeline of the standard approach, with continuous cerebral perfusion throughout, but cardioplegia and interruption of the coronary and splanchnic circulations during the entire neoaortic arch reconstruction (d). Typically, this results with corresponding cooling, rewarming, and overall cardiopulmonary bypass time longer than that of the three-region strategy.

Figure 3.6 Typical bypass circuit.

Figure 3.7 Typical AVMUF flow path through bypass circuit (GOSH method).

Figure 3.8 Typical SMUF flow path through bypass circuit.

Figure 3.9 Centrifugal head inserted into venous limb of bypass circuit to allow for kinetic-assisted venous drainage. The CVR remains vented to atmosphere.

Figure 3.10 Vacuum-assisted venous drainage with the single CVR vent port attached to the vacuum regulator and source with the vent-to-atmosphere limb clamped.

Figure 3.11 The Prebypass Checklist.

Figure 3.12 Prebypass worksheet example.

Figure 3.13 Surgical safety checklist example.

Chapter 06

Figure 6.1 Normal coronary artery connections.

Figure 6.2 Anomalous left coronary artery arising from the pulmonary artery.

Figure 6.3 Aortic regurgitation.

Figure 6.4 Valvar aortic stenosis.

Figure 6.5 Discrete membranous subaortic stenosis.

Figure 6.6 Hypertrophic subaortic stenosis.

Figure 6.7 Supravalvar aortic stenosis.

Figure 6.8 Major aortopulmonary collaterals from the descending aorta.

Figure 6.9 Aortopulmonary window.

Table 6.1 Endotracheal tube sizing for SVC.

Figure 6.10 Secundum atrial septal defect.

Figure 6.11 Primum ASD with cleft mitral valve.

Figure 6.12 Sinus venosus ASD with PAPVR (right pulmonary veins returning to the SVC/RA junction).

Figure 6.13 Example of persistent LSVC with unroofed coronary sinus.

Figure 6.14 Coarctation of the aorta.

Figure 6.15 Complete atrioventricular canal.

Figure 6.16 Cor triatriatum.

Figure 6.17 Congenitally corrected transposition of the great arteries with VSD.

Figure 6.18 Congenitally corrected transposition of the great arteries with IVS.

Figure 6.19 Critical aortic stenosis.

Figure 6.20 DORV, VSD, PS, Side by Side Great Arteries.

Figure 6.21 DORV, VSD, TGA.

Figure 6.22 Ebstein’s anomaly.

Figure 6.23 Ebstein’s anomaly with VSD.

Figure 6.24 Hypoplastic left heart syndrome.

Figure 6.25 Stage 1 repair of HLHS with arch reconstruction, anastomosis of the proximal aorta to the pulmonary artery (neoaortic root), and a tube graft placed between the right ventricle and pulmonary arteries (Sano shunt). The atrial septum is also excised (not shown).

Figure 6.26 Bidirectional Glenn Shunt.

Figure 6.27 Hemi-Fontan Procedure.

Figure 6.28 Lateral tunnel Fontan with baffle directing IVC blood flow to the lungs incorporating a prior Glenn Shunt. A fenestration in the baffle is also common (not shown).

Figure 6.29 The three types of interrupted aortic arches.

Figure 6.30 Left superior vena cava returning to the coronary sinus (without a bridging vein).

Figure 6.31 Left superior vena cava returning to the left atrium.

Figure 6.32 Mitral regurgitation.

Figure 6.33 Mitral stenosis.

Figure 6.34 Patent ductus arteriosus.

Figure 6.35 Branch PA stenosis.

Figure 6.36 PA sling with tracheal compression (LSVC to CS also shown).

Figure 6.37 Pulmonary atresia with intact ventricular septum.

Figure 6.38 PA/VSD, PDA, confluent PAs.

Figure 6.39 PA/VSD, PDA, abnormal PAs.

Figure 6.40 Pulmonary regurgitation.

Figure 6.41 Valvar pulmonary stenosis.

Figure 6.42 Repair of right PVO by using a “sutureless” free, pericardial patch. (a) PVO involves the right-sided PVs. (b) The obstructed PVs are widely incised. The incision is extended peripherally well beyond the obstructed segments. Proximally, it is carried across the PVs–LA junction. The dotted line indicates the line of suturing of the free pericardial patch. The suture line is kept away from the pulmonary venous endothelium. (c) The pulmonary venous pathway is reconstructed by using a free pericardial patch as shown. Care is taken to avoid injury of the right phrenic nerve and sinus node.

Figure 6.43 Tetralogy of Fallot.

Figure 6.44 TOF repair with VSD patch and transannular outflow patch.

Figure 6.45 Supracardiac total anomalous pulmonary venous return to the left vertical vein.

Figure 6.46 Cardiac total anomalous pulmonary venous return to the coronary sinus.

Figure 6.47 Infracardiac total anomalous pulmonary venous return to the ductus venosus.

Figure 6.48 Partial anomalous pulmonary venous return with right pulmonary veins returning to the junction of the superior vena cava and right atrium.

Figure 6.49 Partial anomalous pulmonary venous return with RUPVs returning to the superior vena cava and the right lower pulmonary vein returning to the right atrium.

Figure 6.50 d-TGA with IVS (before atrial septostomy).

Figure 6.51 d-TGA with VSD.

Figure 6.52 Arterial switch operation for d-TGA/IVS (coronaries are moved from the right-sided aortic root to the left-sided pulmonic/neo-aortic root).

Figure 6.53 Rastelli repair for d-TGA/VSD/PS (VSD is patched to the aorta and a conduit is placed from the RV to the PA).

Figure 6.54 Tricuspid atresia with BVF type ventricular septal defect and unrestrictive pulmonary artery.

Figure 6.55 Tricuspid regurgitation.

Figure 6.56 Truncus arteriosus Type I.

Figure 6.57 Truncus arteriosus Type II.

Figure 6.58 Truncus arteriosus Type III.

Figure 6.59 Truncus arteriosus Type 1 Repair. RV to PA conduit, ascending aorta repair and VSD patch.

Figure 6.60 Location of ventricular septal defects.

Figure 6.61 Location of ventricular septal defects.

Figure 6.62 Bulboventricular foramen in tricuspid atresia.

Guide

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Perfusion for Congenital Heart Surgery

Notes on Cardiopulmonary Bypass in a Complex Patient Population

Gregory S. Matte, CCP, LP, FPP

Co-Chief/Clinical Coordinator for Perfusion

Boston Children’s Hospital

Boston, MA, USA

Copyright © 2015 by John Wiley & Sons, Inc. All rights reserved

Published by John Wiley & Sons, Inc., Hoboken, New JerseyPublished simultaneously in Canada

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, [phone], fax [phone], or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ07030, [phone], fax [phone], or online at http://www.wiley.com/go/permissions.

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Library of Congress Cataloging-in-Publication Data

Matte, Gregory S., author.   Perfusion for congenital heart surgery : notes on cardiopulmonary bypass for a complex patient population / Gregory S. Matte.       p. ; cm.   Includes bibliographical references and index.

   ISBN 978-1-118-90079-6 (cloth)I. Title.[DNLM: 1. Heart Defects, Congenital–surgery. 2. Infant. 3. Cardiopulmonary Bypass–instrumentation. 4. Cardiopulmonary Bypass–methods. 5. Child. 6. Perfusion–methods. WS 290]   RD598.35.C67   617.4′12–dc23

2014046326

To Bridget, Nicholas, and Justin for their love, support, and regular reminders that we are all lifelong students.

Foreword

The art and science of providing perfusion for patients undergoing surgical correction of congenital heart lesions has advanced rapidly in the past decade. The complex equipment; the unique acid–base management strategies; the specialized perfusion and ultrafiltration techniques; the wide variation in patient’s age, size, and vulnerability to physiologic trespass; and the wide variety of surgical procedures performed set perfusion for congenital heart surgery apart from that provided for correction of acquired heart disease in adults. Consequently, provision of cardiopulmonary support for repair of congenital heart lesions has become a specialty unto itself.

There is no doubt that perfusionists caring for patients with congenital heart disease will find this manual invaluable. More importantly, from the perspective of a pediatric anesthesiologist and intensivist, this manual will be an essential resource for cardiac anesthesiologists and intensivists. The practical hands-on information contained herein is not currently readily available in any other publication. This manual will and should become part of the teaching curriculum for anesthesia and intensive care residents and fellows involved in the care of these complex patients.

James A. DiNardo, M.D., FAAPProfessor of AnaesthesiaHarvard Medical SchoolChief, Division of Cardiac Anesthesia

Francis X. McGowan, Jr., M.D.Chair in Cardiac AnesthesiaBoston Children’s Hospital

Preface

There are numerous excellent textbooks available today on congenital cardiac disease. Most congenital cardiac perfusion services have at their disposal updated texts regarding the disciplines of cardiology, cardiac surgery, anesthesia, nursing, and perfusion. The perfusion texts, of which I am most interested, can be found to have both vague and contradictory statements regarding how to actually “run the pump” for congenital cardiac cases. It is my hope that this book provides some direction. The aim of this book is not to provide a comprehensive textbook for congenital cardiac surgery or cardiopulmonary bypass. Nor is it to simply publish clinical practice protocols. Rather, the aim is to provide easily referenced information and reminders to the pediatric perfusionist and non-perfusionist alike, which can influence a bypass plan and perhaps become part of one’s practice. The pediatric perfusionist, with at least a general understanding of the other disciplines involved with cardiac surgery, should be able to reference this book with its provided notes, as I prefer to call them, to confidently devise a plan for a pump run.

The idea of creating this book stems from over 17 years of practicing perfusion for congenital heart surgery and nearly 25 years of working with critically ill children. The academic institutions where I have trained and worked regularly host visitors from around the country and world. They include fellows of anesthesia, cardiac surgery, and the intensive care unit, perfusion and nursing students, as well as current practitioners in those fields. The most common visitor question a department receives is, “Can I get a copy of your protocols?” My standard answer is always a qualified “yes.” It is quite simple to pass along perfusion protocols and customized tubing pack specifications. Those items are essential and useful. Though, in isolation, they fail to capture much of the thought and consideration put into every cardiopulmonary bypass plan for congenital cardiac cases. It is my hope that this book is a step toward filling this gap in currently available offerings.

Finally, we are all imperfect clinicians, and it has been said that no one can harm (or even kill) a patient faster than a perfusionist (or surgeon). With that being said, may your clinical errors be minor and preferably off cardiopulmonary bypass!

Gregory S. Matte, CCP, LP, FPP

Disclaimer

Perfusionists, by law, provide cardiopulmonary bypass under the supervision of a physician. This book contains information and recommendations that should be sanctioned by the supervising physician. Errors and omissions with the information provided are possible. Clinical practice is constantly evolving. Use of the information within this book is at your own discretion and risk.

Acknowledgments

A special thanks to Willis Gieser, former Chief of Perfusion at Boston Children’s Hospital, who accepted my unsolicited phone call, gave me an interview, and hired me many years ago.

I am also deeply indebted to the following individuals who provided feedback regarding the content of this book and/or reviewed chapters: James DiNardo, Frank Pigula, Kirsten Odegard, Chris Baird, Kevin Connor, Robert Howe, Mark Wesley, Robert Groom, Robert Wise, and Gerard Myers.

CHAPTER 1Equipment for bypass

The cardiopulmonary bypass plan starts with basics of patient height, weight, allergy history, original diagnosis, previous surgeries, and current indications for surgery. The perfusionist must select and assemble an array of equipment matched to the patient’s size, expected pump flow rates, and other factors related to diagnosis. The following is an overview of the major components of a bypass circuit. Please refer to Chapter 6 for equipment considerations in addition to patient size. Figure 1.1 is provided as a reference to basic equipment arranged for cardiopulmonary bypass.

Figure 1.1 Simplified schematic for basic cardiopulmonary bypass equipment (excludes cardioplegia system).

Oxygenators

The contemporary “oxygenator” is actually several integrated items that in addition to the oxygenating membrane may include the arterial line filter (ALF), venous reservoir and filter, cardiotomy filter, and heat exchanger. Figure 1.2 depicts the components of the Terumo CAPIOX FX series of “oxygenators.” Figure 1.3 depicts typical components of an oxygenator system.

Figure 1.2 Terumo CAPIOX FX series of oxygenators. Left to right: Terumo CAPIOX FX05, Terumo CAPIOX FX15-30, Terumo CAPIOX FX25. A—cardiotomy venous reservoir and B—oxygenator membrane with integrated arterial line filter and heat exchanger.

Figure 1.3 Typical components of an oxygenator system.

Reproduced with permission from Terumo Cardiovascular Group, Ann Arbor, MI. All rights reserved.

The oxygenator membrane

Membrane oxygenators allow for diffusion of gas, oxygen and carbon dioxide most importantly, across a material separating the blood path from the gas flow path (also called the blood and gas phases).

True membrane oxygenators allow for diffusion of gases through a membrane separating the blood and gas phases (see

Figure 1.4

). The type and thickness of the membrane, as well as blood and gas flow characteristics on opposing sides, determines overall diffusion rates.

Microporous membrane oxygenators allow for diffusion of gases through microscopic holes in the membrane material (see

Figure 1.4

). The gas transfers directly through these micropores and is therefore less impacted by the membrane material. However, blood and gas flow characteristics on opposing sides still impact diffusion capacity.

The vast majority of oxygenators for cardiopulmonary bypass are microporous membrane oxygenators. True membrane oxygenators have limited applications today including the use for ECMO at some institutions.

The membrane oxygenator size chosen for a particular patient should be the smallest which will allow for safe perfusion with some degree of functional reserve in case of decreasing efficiency during extended bypass runs or to account for markedly increased pump flows due to aortopulmonary connections (MAPCAs, surgical or other central shunts) or significant aortic regurgitation. Increased pump flow rates in these situations may be required to maintain adequate effective systemic perfusion.

Using an oxygenator above its manufacturer recommended maximum flow rate may increase arterial line GME transmission and is not recommended.

It is recommended to define the patient BSA and select an oxygenator based on the maximum expected pump flows. It is important to note that for neonates and infants in particular, their relatively higher metabolic requirement may require markedly increased pump flows during normothermic bypass (i.e., rewarming). Flows of 3.0–3.5 L/min/m

2

are not uncommon and should be considered for equipment selection.

Primary consideration is given to the manufacturer-recommended maximum flow rate that is based on gas exchange and other aspects of oxygenator, heat exchanger, and reservoir performance. The American Association of Medical Instrumentation (AAMI) standard reference values are usually not relied solely upon since they may not take into account additional factors that the manufacturer evaluates for overall performance.

Increased oxygenator bundle size does not linearly relate to performance since characteristics of the blood and gas flow paths vary among devices.

Oxygenators have either radial or axial blood flow paths that affect performance in competing ways in regards to oxygenating efficiency, pressure drop, microemboli removal, and heat exchanger performance (see

Figure 1.5

).

Microporous oxygenator bundles are important in the removal of air from the blood path. Some centers, particularly outside of the United States, deem the microporous oxygenator effective enough at air removal that they do not utilize a standalone ALF.

One oxygenator on the market, the Medtronic Affinity Fusion, has taken advantage of the air handling capabilities of microporous oxygenators, and unique bundle wrapping technology, to be FDA approved for use as an ALF as well as an oxygenator.

The perfusionist must be familiar with the

manufacturer

recommendations for treating an oxygenator suspected of “wetting out.” These values are listed in

Tables 1.1

to

1.4

.

Oxygenators are usually qualified for use by the manufacturer for up to 6 h. Use beyond this limit does occur and most often there is not a significant decrease in performance. However, safe use beyond this limit is not guaranteed. Consideration should be given to changing out an oxygenator after a long case in which an additional bypass run is a serious possibility. Elective change out while off bypass can be accomplished in a controlled manner and can eliminate several concerns of emergently resuming bypass with a product at the end of its rated performance limit.

Blood proteins coat a membrane oxygenator’s surface area, including the micropores through which gas exchange occurs.

Microporous membranes may experience increased protein coating and subsequent decrease in oxygen transfer during extended bypass runs. It is important to note that this protein coating may also decrease the air handling capabilities of the membrane.

The pressure drop across an oxygenator membrane is frequently listed as a specification. It may be measured in real time during bypass. A change in this value over time is important to consider during bypass as it can be an indicator of change in function.

Pressure drop is frequently equated with shear stress where a lower pressure drop is considered beneficial with lower shear stress. That is not always the case since shear is not only related to pressure. Additionally, pressure drop plays an important role in microembolic air removal in microporous systems [1]. Today’s FDA-approved oxygenators have shear values well within acceptable limits, and pressure drop across the device should not simply be minimized. Since pressure drop values may be misleading for initial consideration of a device, they are not listed in

Tables 1.1

to

1.4

.

Figure 1.4 Primary types of oxygenators currently in use.

Figure 1.5 Simplified schematic of blood flow paths through an oxygenator.

The integral ALF (select models only)

An ALF is a screen filter with a pore size generally in the 25–40 

μ

m range.

The ALF generally serves as the last safeguard in a cardiopulmonary bypass circuit to trap and/or remove particulate and air emboli from the blood before return to the patient.

An integrated ALF, if used, must meet or exceed the maximum oxygenator flow rate. One should not “push” an oxygenator with an integrated arterial filter beyond its recommended flow, even if gas exchange is acceptable, without manufacturer confirmation that the filter can safely handle a higher flow.

For additional information,

see section “Arterial Line Filters.

”

The venous reservoir

Most pediatric centers use open hard-shell reservoirs. The term “open” refers to the reservoir being open to atmosphere for use in a system using gravity siphon drainage. The reservoir must be properly vented to prevent pressurization and the risk of air embolization to the patient. Pressure in the reservoir can result from sucker, vent, and venous inflow if air is not allowed to escape through a vent port or vacuum system. (

See section

“Massive air embolism” in Chapter 8

and section

“Standard and augmented venous return” in Chapter 3

.

)

“Closed” bypass systems commonly incorporate a bag design for the venous reservoir, which significantly limits the blood:air interface. Closed systems have been shown to have a decreased inflammatory response and fewer hematologic disruptions. However, closed systems have less precise visual monitoring of venous return, require additional systems for purging venous bag air, and are not readily converted to vacuum-assisted venous drainage (which comes with its own set of additional concerns for safe use).

The venous reservoir contains the venous filter.

The venous reservoir generally collects venous blood and cardiotomy blood. Both venous blood and cardiotomy blood get filtered separately via different flow paths in the reservoir. The reservoir may therefore be referred to as the cardiotomy venous reservoir (CVR) (see

Figure 1.6

).

The reservoir capacity needs to handle the patient blood volume in cases of planned or unplanned low-flow or circulatory arrest.

The venous reservoir is an extremely important air removal device. The vast majority of air in the cardiotomy and venous blood flow paths is removed in their respective filtration systems (see

Figure 1.7

).

Venous reservoirs have inflows either near the top (top feeders) or bottom (bottom feeders). Both incorporate an extension tube (venous straw) which runs low in the reservoir to help maintain a continuous column of fluid for gravity siphon drainage.

Venous (and cardiotomy) filters are normally coated, at least in part, with a chemical compound to help prevent the formation of foam and to eliminate foam that has been introduced to the filter. Antifoam products containing silicone, simethicone, and methylcellulose are currently used for this application.

It is common for defoaming agents to coat only the upper levels of a filter system. This results in a system whereby it is not mandatory for the blood to pass through the defoamer. The blood/foam will only come in contact with the defoamer when it is more likely to be needed (i.e., foam rising above a certain reservoir level during periods of high sucker flow) and during periods when the reservoir level is high. If foam is seen in a CVR during bypass, the perfusionist should maintain a higher reservoir level to aid in the defoaming process. This aids in the removal of gaseous microemboli by allowing for an increased reservoir transit time.

Figure 1.6 Filters in the Terumo CAPIOX FX05 oxygenator. A—cardiotomy filter in the CVR. B—venous filter in the CVR.

Figure 1.7 Air removal in the CVR and oxygenator.

Reproduced with permission from Medtronic, Inc., Minneapolis, MN. All rights reserved.

The cardiotomy filter

The cardiotomy filter has its own flow rating that is generally less than the maximum oxygenator flow but well within the needs for field suction and left ventricular vent flow.

The cardiotomy filter generally provides more filtering capacity than the venous filter. Venous blood tends to be much “cleaner” with less air and particulate emboli, while cardiotomy blood generally has more.

An integrated cardiotomy filter is normally located higher than and behind the venous reservoir. This arrangement allows cardiotomy blood to passively flow into the venous reservoir after passing through the cardiotomy filter.

Consideration should be given to a secondary standalone cardiotomy reservoir if there is concern that the integrated CVR would overflow in cases of pump low-flow or circulatory arrest. The secondary reservoir can be used to temporarily store blood volume.

A secondary cardiotomy reservoir with filter should also be considered for cases with an expected high sucker flow (reoperations, patients with significant MAPCAs, very large patients with high pump flow, surgery in or around the liver). The additional filtration, or prefiltering, of shed blood provided by a secondary cardiotomy filter may increase the useful life of the primary CVR. When utilized, a secondary cardiotomy is usually set up to process vent and sucker return with drainage to the primary cardiotomy reservoir.

Cardiotomy (and venous) filters are normally coated, at least in part, with a chemical compound to help prevent the formation of foam and to eliminate foam that has been introduced to the filter. Antifoam products containing silicone, simethicone, and methylcellulose are currently used for this application.

It is common for defoaming agents to coat only the upper levels of a filter system. This results in a system whereby it is not mandatory for the blood to pass through the defoamer. The blood/foam will only come into contact with the defoamer when it is more likely to be needed (i.e., foam rising above a certain reservoir level during periods of high sucker flow) and during periods when the reservoir level is high. If foam is seen in a CVR during bypass, the perfusionist should maintain a higher reservoir level to aid in the defoaming process. Of course, this would also aid in the removal of gaseous microemboli by allowing for an increased reservoir transit time.

The heat exchanger

An oxygenator’s integrated heat exchanger must be water tested prior to the addition of crystalloid solutions for priming. Running water through the heat exchange system at a flow and pressure comparable to the operating room values and inspecting for leaks to the blood compartment are important steps in the process of setting up a heart–lung machine for bypass.

The water pathway through an oxygenator helps dissipate static electricity charges that may develop in the roller head pumps and be transmitted through the blood pathway. This feature is especially important in preventing static electricity discharge through the heart–lung machine circuitry that can cause damage.

Heat exchanger specifications are qualified by a “performance factor” defined as the difference of inlet (venous) and outlet (arterial) blood temps divided by the difference of inlet (venous) blood and inlet water temperatures.

The performance factor is frequently in the range of 0.4–0.7 at a device’s maximum rated flow.

The gradient between the venous blood and the water inlet temperature is usually limited to 10 °C (though some manufacturers allow for a gradient of up to 15°C). This is to prevent excessive gradients where there is potential for gas to come out of solution if warmed too rapidly (due to the decrease in gas solubility at higher temperatures). Limiting the temperature gradient also helps to evenly cool and warm a patient. A more homogenous warming may result from limiting the gradient during rewarm which can help prevent after-drop (whereby core patient temperature falls in the early post bypass period).

Some manufacturers may explicitly state that the gradient should be less than 10 °C (an 8°C maximum for example), which would be an important factor in evaluating a product for use in a congenital cardiac program that uses moderate-to-profound hypothermia. Lower gradients can increase the length of a bypass case since rewarming times will be longer. (

See section

“Temperature management” in Chapter 3

.

)

It is commonly accepted that limiting temperature gradients is important in preventing gas from coming out of solution. However, an animal study by Nollert

et al

. found no correlation between temperature gradient and emboli count [2]. Manufacturer-recommended gradient limits should not be exceeded.

The minimum acceptable heat exchanger performance factor is not defined by the manufacturer or AAMI. This leaves the practitioner to decide if heat exchange performance is acceptable at the intended bypass flow and/or up to the maximum recommended oxygenator flow. This assessment comes with clinical experience. To note, an oxygenator may provide acceptable gas exchange but unacceptable heat exchange for a planned deep hypothermic circulatory arrest case. This situation, for example, would encourage the perfusionist to upsize the oxygenator and therefore the integral heat exchanger.

It is important to note that there have been oxygenators manufactured with different oxygenator bundle sizes wrapped around the same-sized heat exchanger. Therefore, the perfusionist must be familiar with product line specifications.

The heat exchanger performance factor must be evaluated carefully. The value stated by the manufacturer is not standardized to a heat exchanger water flow rate. Furthermore, the value must be obtained from a chart that looks at the spectrum of performance factors over the entire rated flow range. Therefore, performance factors are ideally evaluated at the expected pump flow rate for a given case. To note, the values listed in

Tables 1.1

through

1.4

are performance factors at the maximum rated blood flow as stated by the manufacturer but are not always standardized to 10 LPM water flow since that information is not always available.

Heat exchanger performance will be least efficient at the upper flow rating for a device.

Increased heat exchanger surface area does not always equate to increased performance. The blood flow path through the oxygenator (axial vs. radial), the heat exchanger material, and characteristics of the water system will affect performance.

It is important to consider that the rates of cooling and warming on cardiopulmonary bypass are impacted by systemic vascular resistance management and pump flow.

Tables 1.1, 1.2, 1.3, and 1.4 list devices currently on the market. Adult-sized oxygenators are included since congenital cardiac perfusion programs must be able to accommodate patients of all sizes. Users are encouraged to trial oxygenators and evaluate all aspects of performance in their own operating room environment. Then, along with this thorough understanding of the oxygenators to be used, custom tubing packs can be created. Ultimately, a perfusion group should develop a chart identifying the components to be used for different expected pump flow ranges. (See section “Comprehensive experience-based equipment chart” in Chapter 12.)

Table 1.1 Oxygenators rated up to ~2 LPM.

Table 1.2 Oxygenators rated ~2 to ~5 LPM.

Table 1.3 Oxygenators rated up to 8 LPM (Part I of II).

Table 1.4 Oxygenators rated up to 8 LPM (Part II of II).

Arterial line filters

The cardiopulmonary bypass circuit contains filters in several systems: the cardiotomy reservoir, venous reservoir, oxygenator bundle, bypass arterial line, prebypass, gas line, crystalloid line, blood transfusion line, cardioplegia system, and others. The ALF tends to receive the most attention since it serves as the last system in a cardiopulmonary bypass circuit to trap and/or remove particulate and air emboli from the blood before return to the patient. It is important to note that one of the most important aspects of a bypass circuit is its ability to remove (and not create) particulate and air emboli. Several authors have conclusively shown that microair emboli are delivered to patients on bypass [3–8]. These emboli can result in microvasculature blockages with the downstream effects of hyoperfusion or ischemia. Air in particular is disruptive to the endothelial glycocalyx which has important implications for vascular permeability and the potential for edema throughout the body with cardiopulmonary bypass [9–11]. The cardiotomy reservoir, venous reservoir, and oxygenator bundle are all important air handling and removal devices in a cardiopulmonary bypass circuit. The ALF is the last removal device before blood reenters the body. Figure 1.8 depicts four commonly used external ALFs. The ALF must be properly deaired with a crystalloid priming solution before bypass. If a blood prime is used, blood should only be added after crystalloid priming and thorough ALF deairing.

ALFs are most commonly standalone add-ons to a perfusion circuit.

ALFs are screen filters with a pore size ranging from 25 to 40 

μ

m.

Filter housings are preferably clear to visually facilitate deairing during crystalloid priming.

External ALFs most commonly have folded or wrapped filter medium that is not fully visible. The filter should be carbon dioxide flushed prior to crystalloid priming. Then, with fluid flowing through at the manufacturer’s recommended rate for priming, the filter should be adequately tapped to ensure no air is trapped (more precisely, any microbubbles present

should be

carbon dioxide).

Air emboli during bypass are generally purged from the filter by its flow characteristics and venting system with the flow velocity decreasing in the external ALF encouraging any bubbles to rise and exit via the top-mounted purge line.

The external ALF most often has a bleed line continuously returning a low flow back to the cardiotomy reservoir. Less commonly, hydrophobic material located at the top of the filter allows air to be directly vented to the atmosphere.

Figure 1.9

shows the typical blood flow path through two external ALFs with top-mounted purge lines.

Some oxygenators now have integrated screen filters wrapped around the oxygenator bundle. These integrated, or internal, ALFs additionally promote the removal of air in the blood by purging air directly through the microporous oxygenator fibers to be vented out the gas phase of the oxygenator. This is facilitated by the back pressure the internal filter provides and the proximity of the potential air to the oxygenator bundle’s micropores.

Oxygenator-integrated ALFs decrease circuit priming volume since the additional filtering medium and space usually adds less volume than a standalone external ALF to the overall prime.

Future oxygenators may employ microporous membrane wrapping technology to serve dual function as oxygenator and arterial filter. However, the use of oxygenator membranes serving the additional role of filter medium has not been adequately validated in the literature. The adult-sized Medtronic Affinity Fusion is currently the only oxygenator on the market FDA approved for this dual role.

The pressure drop across an ALF is an important factor to evaluate. However, filters today tend to have a generous surface area with rated flows well within acceptable values for sheer stress and turbulence.

Figure 1.8 External arterial line filters. (a)Sorin Group D736. (b)Sorin Group D733. (a) and (b) Reproduced with permission from Sorin Group USA Inc., Arvada, CO. All rights reserved. (c)Terumo Capiox AF02. Reproduced with permission from Terumo Cardiovascular Group, Ann Arbor, MI. All rights reserved. (d)Medtronic Affinity Pixie.

Reproduced with permission from Medtronic, Inc., Minneapolis, MN. All rights reserved.

Figure 1.9 Typical flow path through external arterial line filters. The top luer connector purges continuously via a line connected to the CVR.

Reproduced with permission from Sorin Group USA Inc., Arvada, CO. All rights reserved.

Table 1.5 lists commonly used external ALFs. The charts in Tables 1.1 to 1.4 can be used to compare the integrated ALFs some oxygenator models offer against the external model characteristics listed in Table 1.5.

Table 1.5 External arterial line filters.

Manufacturer

Model

Maximum flow (LPM)

Prime volume (mL)

Pore size (µm)

Sorin

KiDS D130

0.7

16

40

Sorin

KiDS D131

2.5

28

40

Terumo

Capiox AF02

2.5

40

32

Sorin

D736

2.5

47

40

Sorin

D735

2.5

47

27

Pall

AL3

3

28

40

Medtronic

Affinity Pixie

3.2

39

30

Sorin

D731

6

100

27

Sorin

D733

6

100

40

Terumo

Capiox AF125X

7

125

37

Maquet

QUART

7

180

40

Terumo

Capiox AF200X

7

200

37

Medtronic

Affinity

7

212

20

Medtronic

Affinity

7

212

38

Pall

AL6

8

100

40

Pall

AL8

8

170

40

Sorin

D732

8

195

27

Sorin

D734

8

195

40

Pall

AV6SV

8

220

40

Tubing packs

Custom tubing packs for cardiopulmonary bypass circuits are commonly created by the perfusion team to aid in quick and efficient setup of the heart–lung machine (HLM). A congenital cardiac program may have 3–5 different oxygenators as well as 3–5 tubing packs with overlap between oxygenators and tubing packs. This creates numerous options that come with several considerations when choosing equipment for bypass. Table 1.6 is an example of tubing pack specifications based on anticipated maximum pump flow rates. In addition to these items, an institutional comprehensive experience-based equipment chart is helpful in defining the options for nearly all common components for bypass. (See section “Comprehensive experience-based equipment chart” in Chapter 12.)

A cardiovascular team must define their maximum acceptable flows through the various sizes of available tubing: 3/16″, 1/4″, 3/8″, and 1/2″ (other sizes are available but are less commonly used).

Institutions vary in regards to standard bypass tubing length, table height, venous reservoir height, and typical venous cannulae style and size which all impact achievable flow rates.

Tubing used for venous return may be evaluated with gravity versus augmented drainage.

Boot (arterial pump raceway) tubing should be evaluated for flow based on head RPMs since spallation and the potential for failure are a function of the number of tubing compressions over time. Maximum RPMs used are commonly in the 160–170 RPM range even though roller heads may be capable of 250 RPMs.

Smaller raceway lengths (i.e., mini-heads) increase the compression rate for a given pump flow rate.

Table 1.7

outlines an

example

of the maximum flows used for various tubing sizes.

Each tubing size has a prime volume that can be calculated with a known length (

Table 1.8

).

The objective in defining custom tubing pack line sizes is to achieve the smallest prime volume while ensuring adequate and safe flow rates and pressures.

Consideration must be given to the range of operative table movement since rolling the bed away in an up position may require several inches of pump tubing to safely accommodate.

The venous line must have some slack in it to allow for “walking” air out if an air lock develops on bypass with gravity siphon drainage.

The total system prime volume will include the tubing pack, oxygenator, starting reservoir level, dynamic volume holdup (if significant), and hemoconcentrator (if primed before bypass).

The starting reservoir volume may be higher for surgeons who tend to give more pump volume during the cannulation process.

Tubing lengths will vary for each case based on how much of the arterial-venous loop is discarded before connection to the bypass cannulae. Excess tubing in the pack is important to accommodate varied pump positions, particularly variances for femoral bypass.