Titles in the series Problems in Anaesthesia: Analysis and Management S. Feldman, W. Harrop-Griffiths and N. Hirsch Life-Threatening Problems in the Emergency Room A. Sutcliffe Problems in Obstetric Anaesthesia: Analysis and Management A. Rubin and M. Wood Titles in preparation Problems in Intensive Care: Analysis and Management N. Soni and W. Harrop-Griffiths PROBLEMS IN OBSTETRIC ANAESTHESIA Analysis and Management Problems in Anaesthesia Anthony P. Rubin MB, BChir, MRCS, LRCP, FFARCS, DA Consultant Anaesthetist, Charing Cross Hospital, London, UK and Matthew L. B. Wood MB, ChB, MRCP, FFARCS Anaesthetic Senior Registrar, St George's Hospital, London, UK; Visiting Associate Professor, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA U T T E R W O R TH @ E I N E M A N N Butterworth-Heinemann Ltd Linacre House, Jordan Hill, Oxford 0X2 8DP ~isJ A member of the Reed Elsevier group OXFORD LONDON BOSTON MUNICH NEW DELHI SINGAPORE SYDNEY TOKYO TORONTO WELLINGTON First published 1993 © A. P. Rubin and M. L. B. Wood 1993 All rights reserved. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1P 9HE. Applications for the copyright holder's written permission to reproduce any part of this publication should be addressed to the publishers British Library Cataloguing in Publication Data Rubin, Anthony P. Problems in Obstetric Anaesthesia: Analysis and Management. - (Problems in Anaesthesia Series) I. Title II. Wood, Matthew L. B. III. Series 617.9 ISBN 0 7506 0710 6 Library of Congress Cataloguing in Publication Data Rubin, Anthony P. Problems in obstetric anaesthesia: analysis and management/ Anthony P. Rubin, Matthew L.B. Wood, p. cm. —(Problems in anaesthesia) ISBN 0 7506 0710 6 1. Anesthesia in obstetrics—Complications. I. Wood, Matthew L. B. II. Title. III. Series. [DNLM: 1. Anesthesia, Obstetrical. 2. Pregnancy Complications. WO 450 R896p 1993] RG732.R83 1993 617.9'682—<Ic20 DNLM/DLC for Library of Congress 92-48412 CIP Set 10 on 11 point Times by P&R Typesetters Ltd, Salisbury, Wilts Printed in Great Britain at the University Press, Cambridge Foreword Education in medicine and the long training of a specialist anaesthetist give a sound background of scientific and clinical information allowing assessment of the possible risks of any proposed treatment against the potential benefit to the patient. This risk-benefit analysis is fundamental to all doctors presented with a medical problem. Nowhere is this concept of greater importance than in the treatment of problems in obstetric anaesthesia where rapid decisions which may be a matter of life or death or result in a tragically damaged baby are essential. Because much obstetric care is provided by non-physician personnel many of the regimes of treatment are by protocol or mandated algorithms. Whilst this may be a framework to allow differing specialities to understand each other's role, they should not restrict the specialist anaesthetist's ability to select the most appropriate therapy for a patient in a particular set of circumstances. However, in order to decide upon the most suitable treatment it is necessary first to diagnose the condition accurately and to consider the problem it poses to the patient's physiology and the pharmacological implications it may have on any drugs administered. In the Problems in Anaesthesia series this approach has been used to explain the objectives of the treatment recom- mended. In this book, common obstetric problems are analysed and defined and the pathological and physiological consequences analysed. Any pharmacological implications of the process are presented. This leads to a rational presentation of therapeutic options. In this way the book points the way to logical decision making in obstetrics. A small book of this sort is not meant to be a definitive treatise on obstetric anaesthesia, but rather a companion to the anaesthetist in training, a revision source for those who have not recently been involved in anaesthetising women in vn Foreword labour and a source of information for those about to start obstetric anaesthesia. Professor S. Feldman vin Preface Providing anaesthetic cover for the labour ward is one of the responsibilities that falls to the trainee anaesthetist as they progress in a career in anaesthesia. The prospect of such responsibilities is understandably daunting and the first months working on the obstetric unit are often stressful for anaesthetists who are experienced in applying their skills to provide anaesthesia for elective and emergency general, urological and gynaecological surgery but whose exposure to the problems peculiar to obstetric anaesthesia are limited. The purpose of this book is to provide anaesthetists at such a stage in their training with an indication of the sorts of situations that they may reasonably expect to see in everyday obstetric practice and a guide to the management of such situations. It is hoped that the format of the book will allow it to be kept in a pocket and easily referred to at short notice when a situation is encountered for the first time and also as an aide memoir to those more experienced anaesthetists. We have attempted to present each subject in a consistent format: a definition of the problem; how to make the diagnosis; its possible causes where appropriate; the physio- logical significance of the condition to the mother and fetus; how to assess the state of the mother; and how to manage the problem in terms of providing analgesia during labour and anaesthesia for operative delivery. Some points that should be remembered when confronted by any situation in obstetric anaesthesia: 1. The pregnant woman comprises two people; the mother and the fetus. Changes seen in the mother such as hypotension will have adverse effects on the fetus if not treated promptly. 2. The maintenance of adequate oxygenation and placental perfusion are the goals of treatment of the sick pregnant woman. IX Preface 3. All pregnant women after the fist trimester are at risk of aspiration of gastric contents during general anaesthesia and for this reason regional anaesthesia should be used wherever possible. 4. Aorto-caval compression must be anticipated and treated in all pregnant women by lateral displacement of the uterus either manually or by positioning the mother in the wedged or lateral position. 5. Always summon senior anaesthetic assistance when sig- nificant problems are anticipated, or if not anticipated then very soon after difficulties arise. x Cardiovascular disease Introduction Mothers may have a coexisting illness which may have implications for those involved in the care of the mother and fetus. The purpose of this section is to provide the trainee anaesthetist with a guide to the types of conditions that may present in a general obstetric unit; advice on how to assess their severity to allow meaningful communication between trainee and senior; and how to manage these conditions definitively or while awaiting the arrival of senior help. Cardiovascular disease The incidence of cardiac disease in pregnancy is low (0.4-2%) but it is a significant non-obstetric cause of maternal mortality. The relative incidence of congenital heart disease has increased because of more patients survive to childbearing age following corrective surgery. The types of problems encountered include: • Valvular lesions —aortic stenosis/insufficiency —mitral stenosis/insufficiency —mixed lesions • Prosthetic heart valves • Left-to-right shunts —ventricular septal defect (VSD) —atrial septal defect (ASD) —patent ductus arteriosus (PDA) • Right-to-left shunts —Tetralogy of Fallot —Eisenmenger's syndrome —pulmonary hypertension 3 Cardiovascular disease Introduction Mothers may have a coexisting illness which may have implications for those involved in the care of the mother and fetus. The purpose of this section is to provide the trainee anaesthetist with a guide to the types of conditions that may present in a general obstetric unit; advice on how to assess their severity to allow meaningful communication between trainee and senior; and how to manage these conditions definitively or while awaiting the arrival of senior help. Cardiovascular disease The incidence of cardiac disease in pregnancy is low (0.4-2%) but it is a significant non-obstetric cause of maternal mortality. The relative incidence of congenital heart disease has increased because of more patients survive to childbearing age following corrective surgery. The types of problems encountered include: • Valvular lesions —aortic stenosis/insufficiency —mitral stenosis/insufficiency —mixed lesions • Prosthetic heart valves • Left-to-right shunts —ventricular septal defect (VSD) —atrial septal defect (ASD) —patent ductus arteriosus (PDA) • Right-to-left shunts —Tetralogy of Fallot —Eisenmenger's syndrome —pulmonary hypertension 3 Problems in Obstetric Anaesthesia • Peripartum cardiomyopathy • Coronary artery disease • Arrhythmias Physiological significance. There is an increase in blood volume and cardiac output in pregnancy (Appendix I) which may cause decompensation of an already compromised cardiovascular system especially during the demanding peri- partum period. The risks of maternal morbidity, maternal mortality and perinatal mortality are determined by three factors: 1. The underlying lesion 2. The functional compromise due to the lesion 3. Associated pregnancy-related complications e.g. pre- eclampsia, haemorrhage and infection Assessment of the mother History. Symptoms of heart disease in the non-obstetric patient, dyspnoea, palpitations, tiredness, weight gain and oedema are common complaints in pregnancy, so a history of antenatal symptoms and any changes since the onset of pregnancy should be elicited. Syncope is unusual in normal pregnancy unless there is aortocaval compression and should be considered a significant symptom. On the basis of this history mothers can be graded according to the New York Heart Association (NYHA) functional impairment classifica- tion (see Table 1.1). Conditions in which pregnancy is well tolerated (less than 1% mortality) are: Septal defects Patent ductus arteriosus Corrected Tetralogy of Fallot Corrected coarctation of the aorta Pre-existing arrhythmias NYHA classes I and II 4