Biochemical Monitoring of the Fetus Molly S. Chatterjee Editor Biochemical Monitoring of the Fetus With 29 Figures Springer Science+Business Media, LLC МоНу S. Chatterjee, M.D. Dept. of Obstetrics & Gynecology University of New Мехјсо Albuquerque, NM 87131 USA Library of Congress Cata1oging-in-Publication Data Biochemical monitoring of the fetus / МоНу S. Chatterjee, editor. р. ст. Includes bibliographical references ISBN 978-0-387-97892-5 ISBN 978-1-4757-2259-8 (eBook) DOI 10.1007/978-1-4757-2259-8 1. Fetal blood-Analysis-Congresses. 2. Transcutaneous blood gas monitoring-Congresses. 3. Laser spectroscopy-Congresses. 4. Feta1 monitoring-Congresses. 1. Chatterjee, МоНу S., 1943- [DNLM: 1. Feta1 Monitoring-methods-congresses. 2. Feta1 Blood congresses. 3. Cardiotocography-congresses. WQ 209 В615 1993] RG628.3.B55B56 1993 618.3'2075б1-dс20 DNLM/DLC 93-1477 Printed оп acid-free paper. © 1993 Springer Science+B usiness Media New У ork Originally pubIished Ьу Springer-Verlag New York, Inc. јп 1993 АН rights reserved. This work mау по! he translated or copied јп whole or јп part without the written permission of the pubIisher,Springer Science+Business Media, LLC, ехсер! for brief excerpts јп connection with reviews or scholarly analysis. Use јп connection with апу form of information storage and retrieval, electronic adaptation, computer software, or Ьу similar or dissimilar methodology now known or hereafter developed is forbidden. ТЬе use of general descriptive names, trade names, trademarks, etc., јп this pubIication, еуеп if the former are по! especiaHy identified, is по! to Ье taken as а sign that such names, as understood Ьу the Trade Marks and Merchandise Marks Act, mау accordingly he used freely Ьу апуопе. While the advice and information јп this book are believed to Ье true and accurate at the date of going to press, neither the authors nor the editors nor the pubIisher сап accept апу legal responsibility for апу епогs or omissions that mау Ье made. The publisher makes по warranty, express or implied, with respect to the material contained herein. Production managed Ьу Natalie Johnson; manufacturing supervised Ьу Vincent Scelta. Camera-ready сору provided Ьу the editor. 987 6 543 2 1 ISBN 978-0-387-97892-5 Contents Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi Clinical Importance of Biochemical Monitoring of the Fetus During Labor with Demonstration of Typical Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 E. Saling and 1. Bartnicki Animal Study and Clinical Application of Laserspectroscopy in the Fetus 13 S. Schmidt, S. Gorrisen-Bosselmann, S. Spaniol, U. Wagner, K. Pringle, N. Helledie, P. Rolfe, and D. Krebs Computerized FHR Analysis and Biochemical Changes . . . . . . . . . . . . . . . . . 23 G.S. Dawes and Cw.G. Redman Laserspectroscopy: Technology and Theoretical Background. . . . . . . . . . . . . 30 S. Schmidt, U. Wagner, S. Spaniol, N. Helledie, P. Rolphe, and D. Krebs Continuous Base Excess Monitoring in the Human Fetus. . . . . . . . . . . . . . . . 35 Tom Weber and Carsten Nickelsen Importance of Pulsed Doppler and Color Flow Mapping in Diabetic Pregnancies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Molly S. Chatterjee A Certified Nurse-Midwife's Perspective on Intrapartum Biochemical Monitoring of the Fetus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Kay Sedler Cerebral Palsy and Fetal Hypoxia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Luis B. Curet The Effects of Anesthesia on Fetal Blood Gases . . . . . . . . . . . . . . . . . . . . . . . 55 Karen Knieriem Color Doppler and Fetal Echocardiography . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 U. Gembruch, R. Bald, and M. Hansmann UNM Experience with Color Doppler Flow Mapping in Fetal Echocardiography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Raymond R. Fripp Fetal Arrhythmia: Diagnosis, Significance, and Management. . . . . . . . . . . . . 76 Ulrich Gembruch, Rainer Bald, Dirk A. Redel. Matthias Manz, and Manfred Hansmann Magnetic Resonance Imaging: A Useful Adjunct in Evaluating the Abdominal Pregnancy ............................................ 83 Derek J. Ubng, David A. Turner. James A. Meserow, Bruce Silver and Howard T. Strassner Preface Biochemical monitoring of the fetus has been in the back of every perinatologist's mind. Technological advancements have been made in the last ten years but not to the expected level. A continued interest in the subject can only be maintained by symposiums of this nature where perinatologists from different countries can share their experience. Laserspectroscopy of the fetus is a valuable addition to this volume. The future of biochemical monitoring of the intrapartum fetus depends on the continued collection of scientific data and further technological advances. This successful symposium was held in October, 1990, in Albuquerque, New Mexico, USA. I would like to thank Hewlett Packard for their generous support without which this publication would not have been possible. My sincere thanks goes to my secretary, Nancy Whalen, who has done a tremendous job with the word processing, organization, and layout of the chapters. Molly S. Chatterjee, M.D. Associate Professor University of New Mexico Department of Obstetrics & Gynecology CLINICAL IMPORTANCE OF BIOCHEMICAL MONITORING OF THE FETUS DURING LABOR WITH DEMONSTRATION OF TYPICAL CASES E. SALING, J. BARTNICKI Institute of Perinatal Medicine, Free University of Berlin, Berlin, Germany The biochemical monitoring of the fetus during labor is historically the oldest part of prenatal medicine. The very first direct approach to the human fetus took place on June 21, 1960 when the first blood samples were taken from the fetal scalp in our labor room (3). In the meantime, this method has gone through a typical evolution of ups and downs. It started with enthusiasm because it was the first opportunity to examine fetal blood samples directly using more or less all clinically interesting analytic laboratory methods. Then when cardiotocography became available in 1968 for clinical routine, many clinicians converted to thinking that this was the philosopher's stone and they renounced on the additional use of fetal blood analysis and relied on cardiotocography alone. How essential this fault was has been demonstrated during the long lasting public discussions about all the adverse effects of one-sided intensive apparative supervision of the fetus during labor. Now, after several years, most obstetricians have returned to their objective senses and they know that the best compromise is combined supervision during labor, namely the biophysical and biochemical, in other words the use of cardiotocography combined - if necessary - with fetal blood analysis. The latter is now as before the most proved and most widespread biochemical method, which does not exclude that in the future other non-traumatic and maybe not invasive methods will also be applied in the daily routine. What are the specific benefits of both types of the methods used up to now? 1. Cardiotocography has the advantage that it allows a continuous electronic monitoring of the fetal heart rate. If the cardiotoco gram is normal an undisturbed condition of the fetus is reliably confirmed. This is an important fact. If on the other hand the cardiotocogram is abnormal, this is - in cases of real intrauterine 2 complications -a very early sign of threatened hypoxia. But often there is no hypoxia and therefore no dangerous condition. And so 2. A biochemical method - for widespread practical clinical use now as before fetal blood analysis - is necessary, which should only be employed as a complementary measure in cases with suspicious or pathological cardiotocogram. An additional biochemical method enables us: a. To clarify whether or not imminent fetal hypoxia and/or acidosis are really present; and if there is no evidence of hypoxia, unnecessary interventions can be avoided. If, on the contrary, early stages of real hypoxia are present, the best suitable time for termination of labor can be ascertained by using biochemical methods. b. To recognize whether in cases with imminent hypoxia conservative therapeutic measures are successful, such as use of tocolytics for inhibition of uterine contractions. As it has been shown in an evaluation from 1982 by U. Zitzelsberger (5) in our department in about 75 % of all cases with threatened acidosis a conservative treatment with tocolysis was successful in preventing a further fall of fetal pH values. If intrauterine hypoxia progresses in spite of conservative treatment, termination of labor by operation is indicated. In this way by using both cardiotocography and if necessary fetal blood analysis, it is possible to avoid unnecessary interventions and thus to achieve minimum of operative deliveries. All this can be done without reduction of fetal safety. The task of modem intensive slU)ervision during labor is certainly not only to avoid occasional severe late brain damage. Too many examiners, unfortunately rely on this one-sided aspect. The main aim of intensive supervision today is to reduce early morbidity to a minimum, particulary 3 in the period shortly after delivery. Severe stage of hypoxia, acidosis and clinical depression must always be taken seriously; they are known to be associated with a number of risks and disadvantages. Some of the important ones are: - intracranial hemorrhages occur more frequently - premature babies have respiratory distress syndrome more often - the intracellular metabolism is inhibited - the hematocrit is increased and consequently the blood flow properties are disturbed - the circulation of numerous organs is reduced - the breathing center can be depressed, and there can be a delay in the onset of respiration and lung function can be reduced - fall of cardiac output and a drop in blood pressure - disturbances of electrolyte balance between the intracellular and extracellular fluid occur - there is a reduction of the O binding capacity 2 - renal function is impaired - transfer of local anesthetic substances from the mother to the fetus is increased. Another benefit is that the consequent use of biochemical methods can prevent unnecessary risks to the mother. Risks of unnecessary operative interventions are too often underestimated or even ignored. In many places one has got so accustomed to the specific risks of operative measures, for example, cesarean sections are so frequent in some places - that laymen and even many obstetricians consider these risks as being practically non-existent. From the literature it is known that mortality after cesareans can be 5-10 times higher than after vaginal deliveries. Furthermore, it is known - which is in my opinion much more important - that morbidity after cesareans is also much higher than after vaginal deliveries. Frequency of morbidity up to 30% or more is published (1). So in any case, it is not justified to ignore such risks. As we calculated, the use of biochemical methods in addition to cardiotocography can reduce the absolute rate of cesareans by 1 %. If we pragmatically calculate how many unnecessary cesareans these are in a country as a whole, the results look quite serious. 4 In our country (West Germany), with about 600,000 deliveries per year, the number of unnecessary cesareans would be as much as 6000 avoidable operations, with all the accompanying morbidity and mortality; and in the United States the number concerned should be at least 20,000 avoidable interventions. I think such facts should not be ignored. From all that has been said, the logical conclusion is, that at all places where a biochemical method is not used in addition to cardiotocography, obstetrics is not performed in a progressive way. After monodiagnostic cardiotocographic indication, operative intervention would have been necessary in 73% of such high risk cases concerned, in order not to miss the 14% of fetuses who really were at high risk due to a fall in pH values. So here we have an over-diagnosis through cardiotocography of around 60%. We found such results in a previous evaluation in our unit together with K. Goeschen and T. Gruner (2). If the first stage and the second stage of labor are subdivided, the following picture emerges: in the first stage an operative delivery - mostly a cesarean due to suspicious or pathological cardiotocograms - would have indicated in 56% of the cases. After performing fetal blood analysis, however, the cesarean rate was only 10% - this means a saving of 46 %. Also in the second stage decisive advantages were found when combined monitoring was used. In a high risk group a considerably abnormal CTG score after Hammacher was recorded in 95 % of the cases. Instead of having to operate on all these 95 % high risk cases, through the results achieved by fetal blood analysis it was only really necessary to make an operative intervention in 54% of them. The remaining 41 % infants could be delivered spontaneously because of not too critical pH values. According to our experience fetal blood analysis is indicated in the early second stage, when the cervix is completely dilated but the presenting part is in the mid-pelvic plane or still higher. Operative interventions in the early second stage - that is mainly from the mid-pelvic plane, can by no means be regarded as harmless for the fetus. Often they require difficult manipulation and should therefore only be performed when there is a strong and real clinical indication. Operative interventions should not be performed when the heart rate patterns are suspicious or pathological but not due to hypoxia. In a prospective study 5 in our department performed together with M. Brand, we were able to show that intracranial hemorrhage - mostly of a slight degree - occurs twice as frequently in mature infants delivered operatively in the early second stage (10.5%) than in the late second stage (4.5%) and almost four times more frequently than in infants delivered spontaneously where the incidence was 2.6%. False interpretation of the reliability of intrapartum monitorine Let us see what happens when fetal hypoxia starts, from another viewpoint. A cardiotocogram is suspicious and fetal blood analyses are performed. The pH-values are still within the normal range but are sinking and cesarean is performed in good time. The pH -values measured immediately after delivery in the umbilical artery blood are still just within the normal range and the baby is clinically vigorous. In various publications such cases are erroneously classified as "false positive"; this is because the newborns are not born in pathological condition. The examiners concerned have apparrently forgotten an important fact, namely to ask themselves what is the task of modem method of supervision during labor at all? The task cannot only then be considered as having been achieved when - after suspicious findings immediately after delivery - pathological conditions are always present in the form of acidosis and/or a clinical depression of the baby. From the pathophysiological aspect it must be clear that a considerable number of infants still do not show signs of acidosis and are clinically vigorous. From clinical and scientific aspects it is not acceptable to classify the findings in those infants as "false positive". We have performed in our unit a study concerning these questions together with Sabine Brandt and P. van den Berg. Out of 110 fetuses who had abnormal cardiotocograms and simultaneously reduced scalp pH-values, 94% had, immediately after delivery an equal or lower pH-value in umbilical artery samples. Only 6% had higher pH-values. This means that fetal blood analyses have been misleading in only about 6% and the measured values would have been labelled as "false positive". So even with biochemical monitoring single unnecessary interventions are possible but rare.