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Essential Fluid, Electrolyte and Ph Homeostasis Essential Fluid, Electrolyte and Ph Homeostasis Cockerill Reed Essential Fluid, Electrolyte and pH Homeostasis Essential Fluid, Electrolyte and pH Gillian Cockerill, Reader in Vascular Biology, St George’s University of London, UK Stephen Reed, Principal Lecturer, School of Life Sciences, University of Westminster, UK The mechanisms of fluid, electrolyte and acid-base homeostasis are fundamental to normal cellular function. Students often struggle to understand these complex mechanisms and this book will prove Essential Fluid, invaluable in helping them get to grips with this difficult subject. The book has been carefully structured to present topics in ‘bite-sized’ chunks of information supported by numerous self assessment Electrolyte and exercises, clear diagrams and relevant case studies. This accessible, pocket-sized, self-directed learning guide details the chemical (mostly ionic) composition of body fluids, explains how abnormalities arise, pH Homeostasis what laboratory tests can be used to identify and analyse the cause of these disorders and shows how normality can be achieved to maintain health. As such it will be essential reading for biomedical, pharmacology, Gillian Cockerill | Stephen Reed medical and allied health students needing an understanding of how changes in fluid and key electrolytes affect the body in health and disease. O An accessible, pocket-sized introduction to fluid, electrolyte and acid-base homeostasis. Homeostasis O Carefully structured to present topics in ‘bite-sized’ chunks with clear, straightforward diagrams. O Includes numerous self-assessment questions and answers together with relevant case studies and clinical examples. www.wiley.com/go/cockerill/fluid P1: OTA/XYZ P2: ABC JWST065-fm JWST065-Cockerill July 8, 2011 13:43 Printer Name: Yet to Come P1: OTA/XYZ P2: ABC JWST065-fm JWST065-Cockerill August 26, 2011 12:32 Printer Name: Yet to Come Essential Fluid, Electrolyte and pH Homeostasis P1: OTA/XYZ P2: ABC JWST065-fm JWST065-Cockerill August 26, 2011 12:32 Printer Name: Yet to Come P1: OTA/XYZ P2: ABC JWST065-fm JWST065-Cockerill August 26, 2011 12:32 Printer Name: Yet to Come Essential Fluid, Electrolyte and pH Homeostasis Gillian Cockerill Reader, Vascular Biology, St George’s London Stephen Reed Principal Lecturer, School of Life Sciences, University of Westminster A John Wiley & Sons, Ltd., Publication P1: OTA/XYZ P2: ABC JWST065-fm JWST065-Cockerill August 26, 2011 12:32 Printer Name: Yet to Come This edition first published 2012 © 2012 by by John Wiley & Sons, Ltd. Wiley-Blackwell is an imprint of John Wiley & Sons, formed by the merger of Wiley’s global Scientific, Technical and Medical business with Blackwell Publishing. Registered Office John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK Editorial Offices 350 Main Street, Malden, MA 02148-5020, USA The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK 9600 Garsington Road, Oxford, OX4 2DQ, UK For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley-blackwell. The right of the author to be identified as the author of this work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988. All rights reserved. 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 or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Library of Congress Cataloging-in-Publication Data Cockerill, Gillian. Essential fluid, electrolyte, and pH homeostasis / Gillian Cockerill, Stephen Reed. p.; cm. Includes index. ISBN 978-0-470-68306-4 (pbk.) 1. Body fluids. 2. Acid-Base Equilibrium. 3. Water-electrolyte balance (Physiology) I. Reed, Stephen, 1954- II. Title. [DNLM: 1. Body Fluids–chemistry. 2. Acid-Base equilibrium–physiology. 3. Body Fluid Compartments–physiology. 4. Water-Electrolyte Balance–physiology. 5. Water-Electrolyte Imbalance. QU 105] QP90.5.C55 2011 612.01522–dc23 2011015327 A catalogue record for this book is available from the British Library. This book is published in the following electronic formats: ePDF 9781119971894; ePub 9781119973669; Wiley Online Library 9780470683064; Mobi 9781119973676 Set in 9/11pt Sabon by Aptara Inc., New Delhi, India. First 2012 P1: OTA/XYZ P2: ABC JWST065-fm JWST065-Cockerill August 26, 2011 12:32 Printer Name: Yet to Come In loving memory of MW, EMS, IW and JFH P1: OTA/XYZ P2: ABC JWST065-fm JWST065-Cockerill August 26, 2011 12:32 Printer Name: Yet to Come P1: OTA/XYZ P2: ABC JWST065-fm JWST065-Cockerill August 19, 2011 11:36 Printer Name: Yet to Come Contents List of figures xiii List of tables xvii Preface xix Acknowledgements xxi Part 1: Background theory and basic concepts Section 1.i Introduction and overview 3 Section 1.ii Water 8 Section 1.iii Solutions: concentrations and colligative properties of solutes 12 Section 1.iv Self-assessment exercise 1.1 16 Section 1.v Acids and bases 18 Section 1.vi Buffers and the Henderson-Hasselbalch equation 23 Section 1.vii Self-assessment exercise 1.2 26 Section 1.viii Body fluids and their composition: overview 28 Section 1.ix Fluid balance: (a) between fluid compartments and (b) intake and loss 34 Section 1.x Ionic composition and electrical neutrality 39 Section 1.xi Water and ion distribution between compartments 1: Physical chemistry 43 P1: OTA/XYZ P2: ABC JWST065-fm JWST065-Cockerill August 19, 2011 11:36 Printer Name: Yet to Come viii Contents Section 1.xii Water and ion distribution between compartments 2: Physiology 50 Section 1.xiii Osmoregulation: solvent and solute balance 55 Section 1.xiv Self-assessment exercise 1.3 60 Section 1.xv Summary of Part 1 62 Answers to Part 1 self-assessment exercises 63 Part 2: Fluid and electrolyte homeostasis Normal physiology Section 2.i Fluid translocation: plasma to ISF and ISF to ICF 83 Section 2.ii Renal function: a brief overview 88 Section 2.iii Renal regulation of blood composition 93 Section 2.iv Self-assessment exercise 2.1 100 Section 2.v Minerals: key roles in physiology and metabolism 102 Section 2.vi Sodium and potassium 106 Section 2.vii Sodium and water homeostasis: renal regulation of blood pressure and blood volume 109 Section 2.viii Calcium and magnesium 115 Section 2.ix Iron 123 Section 2.x Selected trace elements: Mn, Co, Se and S 128 Section 2.xi Anions: bicarbonate, chloride, phosphate and proteins 130 Section 2.xii Self-assessment exercise 2.2 132 Section 2.xiii Laboratory measurements 1: Osmometry 134 P1: OTA/XYZ P2: ABC JWST065-fm JWST065-Cockerill August 19, 2011 11:36 Printer Name: Yet to Come Contents ix Section 2.xiv Laboratory measurements 2: Ion selective electrodes (ISEs) 138 Section 2.xv Laboratory measurements 3: Calcium, magnesium, vitamin D, phosphate and iron 147 Section 2.xvi Laboratory measurements 4: Miscellaneous methods for clinically useful analytes 150 Section 2.xvii Self-assessment exercise 2.3 154 Disorders of fluid and electrolyte balance Section 2.xviii Introduction 157 Section 2.xix Principles of data interpretation 160 Section 2.xx Sodium, protein and water 167 Section 2.xxi Hypernatraemia 173 Section 2.xxii Hyponatraemia 179 Section 2.xxiii Disturbances of potassium homeostasis 184 Section 2.xxiv Hyperkalaemia 186 Section 2.xxv Hypokalaemia 189 Section 2.xxvi Disturbances of calcium or magnesium balance 193 Section 2.xxvii Disorders of iron homeostasis 200 Section 2.xxviii Self-assessment exercise 2.4 202 Section 2.xxix Summary of Part 2 207 Answers to Part 2 self-assessment exercises 209 Part 3: Acid-base homeostasis Normal physiological processes Section 3.i Acidity, pH and buffers: recap of some basic chemistry 221 P1: OTA/XYZ P2: ABC JWST065-fm JWST065-Cockerill August 19, 2011 11:36 Printer Name: Yet to Come x Contents Section 3.ii Some worked example calculations 224 Section 3.iii Self-assessment exercise 3.1 227 Section 3.iv Homeostasis and the ‘daily acid challenge’ 228 Section 3.v Physiological buffering 232 Section 3.vi The role of the kidney in acid-base homeostasis 237 Section 3.vii Respiration: gas pressures and breathing 244 Section 3.viii The role of red cells: gas carriage by haemoglobin 248 Section 3.ix Self-assessment exercise 3.2 253 Section 3.x The liver and gastrointestinal tract in acid-base homeostasis 254 Section 3.xi The ‘traditional’ versus the ‘modern’ view of acid-base homeostasis 257 Section 3.xii Stewart’s three independent factors 262 Section 3.xiii Laboratory measurement of pH, PCO2 and bicarbonate 268 Acid-base disturbances Section 3.xiv Classification of primary changes based on pH and aetiology 273 Section 3.xv Overview of mechanisms 276 Section 3.xvi Physiological correction of primary disturbances 279 Section 3.xvii
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