2015 handbook+of+stewart+acidbase+yohanes+george

THINKING ABOUT FLUID INSTEWART’S APPROACH THINKING ABOUT FLUID IN STEWART’S APPROACH Yohanes WH George, MD FROM “SALINE” TO MORE “PHYSIOLOGIC” FLUID TO UNDERSTAND STEWART’S EASY WAY ACI

THINKING ABOUT FLUID IN

STEWART’S APPROACH

THINKING ABOUT FLUID IN

STEWART’S APPROACH

Yohanes WH George, MD

FROM “SALINE” TO MORE

“PHYSIOLOGIC” FLUID

TO UNDERSTAND STEWART’S EASY WAY ACID-BASE

THINKING ABOUT FLUID IN

THINKING ABOUT FLUID IN EASY WAY TO UNDERSTAND

STEWART’S ACID-BASE

Yohanes WH George, MD

All right reserved No part of this publication may be reproduced or transmitted in any form or

by any means, electronic or mechanical; without permission in writing to the author or publisher

Copyright © 2015 Centra Communciations

Dedication iv

Foreword vi

Preface x

Stewart’s Approach in Brief 2

Strong Ion Difference 3

Classification of Primary Acid Base Disturbances 9

The Effect of Saline and Balanced Fluid from Stewart’s Perspective 12

Designing Balanced Crystalloids 15

Body pH Regulation: Interaction Between Membranes 17

Strong Ion Difference in Kidney 20

Compensation 21

Clinical application 23

Conclusions 31

References 32

iii

To my parents: Rijklof George and Yuliana Bororing, and

my brother and sister: Ivan and Rina,for teaching me through unforgettable life experiences

To my wife; Sari Mumpuni,for always being there for me, supporting me through ups and downs

To my team in Emergency and Intensive Care Unit Pondok Indah Hospital and to

my colleagues and fellows in Jakarta Critical Care Alumni,for providing me great suggestions and support to finish this handbook

To my great team, Staff Department of Anesthesiology and Intensive Therapy:

for giving me spirit and tremendous support

The title of this monograph tells us everything!

Sometimes physiology (better, physiopathology) is thought to be very difficult Sometimes Physicians prefer to treat patients without understanding what is going

on Sometimes Physicians realize that patientsneed fluids (which is good!) but the quality of fluids administered is felt not so relevant (which is bad!) Fluids must be regarded as a drug and, like every drug, can have positive or harmful effects Dr George wrote this book with the aim of making clear part of the human physiology that is considered difficult to understand – the Stewart’s approach to acid-base disorders; and what this approach teaches us in using the correct quality of fluids Iwill always remember the beautiful days spent in Indonesia with great friends talking about the clinical role played by the hypercloremic acidosis, one of the most relevant side effects of fluids therapy based on normal saline administration I hope that this fantastic book is born in one of the very hot evening (at least for me) when

we shared our ideas on the role played by fluids therapy I will never forget that time

of my life and the enthusiasm creates by those meeting Looking back to those days

I realize that this book isvery special for me

I hope that it will guide the future generations in the difficult field of fluids therapy

I always asked me if medicine is an art or science Probably medicine is both; but let me guess that books like this can help in making medicine an art based on science

Prof Carlo Alberto VoltaSection of Anaesthesia and Intensive Care Medicine

University of Ferrara

S Anna HospitalFerrara, Italy

Foreword

Although often strangely neglected, Acid-Base equilibrium constitutes most

of the background of organ physiology and cellular biology of human beings Nonetheless, it’s complex Many are the aspects we still need to elucidate and to unveil As such, in contrast to other parts of human physiology, we usually apply interpretational models to describe how Acid-Base equilibrium is preserved The

1912 Nobel Medicine Prize recipient Alexis Carrel, in his Reflections on Life (1952, London: Hamish Hamilton) states that “a few observations and much reasoning lead to error; many observations and a little reasoning to truth”, highlighting the primacy of “reality and facts” over our pre-defined interpretations I believe that such statement may well describe the interpretational model to Acid-Base that Peter Stewart has defined in the late ‘70s, starting from a quantitative chemical approach, and taking into account two aspects intrinsically related to this topic (although frequently omitted), i.e., electrolytes and plasma proteins The remarkable results

of his approach are before our eyes As very elegantly highlighted by Dr George

in his Handbook, one of the most relevant example for our daily-life of physicians, especially dealing with critically ill patients, is the understanding of the effects of fluid therapy on Acid-Base It is not a matter of “being right or wrong”, but rather of fully elucidating what we are facing every days with our patients

Dr George has the great merit of having brought at bedside, in our clinical daily practice, Stewart’s theories on Acid-Base equilibrium in a more comprehensible and easy way, so to open wide our mind to its real comprehension Let us hope to stick

on reality, rather than on our preconceptions

Pietro Caironi, MDAssociate Professor, Faculty of MedicineDepartment of Pathophysiology and TransplantationFondazione IRCCS Ca’ Granda – Ospedale Maggiore Policlinico

Milan, Italy

Stewart is easy! However, this continues to be challenged by many Especially

by those that have been trained according to the legacy approaches, including bicarbonate based and base excess methods In order to truly appreciate the potential of quantitative acid base analysis, one needs to temporarily forget the other approaches This requires courage

Therefore, I applaud the effort of dr Yohannes, who has produced an excellent introductory handbook to the Stewart approach This will be of great help to those wanting to explore the secrets of acid base medicine!

Paul WG Elbers, MD, PhD

Intensivist

VU University Medical CenterAmsterdam, The Netherlands

Foreword

In critical care and anesthesia medicine, fluid administration is a key element

of resuscitation Currently, there are still controversies regarding fluid resuscitation strategies, both on ‘balanced fluid’ strategy, known as ‘goal-directed therapy’, and from ‘fluid option’ point of view, which is about fluid type selection In terms of

‘fluid option’, controversial debate about crystalloid and colloid has lasted for a long time and is no more a special concern Selection of resuscitation fluids based

on their effects on acid-base balance of the body is currently a particular concern Evidences suggest that saline use in fluid resuscitation causes hyperchloremic acidosis, therefore nonsaline-based fluid, also known as ‘balanced fluid’, is currently invented to avoid acidosis effect

The mechanism of acidosis following saline administration is based on base balance method by Stewart, that is also called quantitative method or physicochemical approach Unfortunately, this theory is not widely understood despite the fact that it has been known for quite some time (since 1978) and is being accepted slowly in critical care and anesthesia medicine, which is partly caused by its complexity and being not easily understood

The Department of Anesthesia of RSCM - FKUI finds that this handbook of

“EASY WAY TO UNDERSTAND STEWART’S ACID-BASE” is very useful and it will hopefully simplify the understanding of acid-base balance disturbance mechanism based on Stewart’s method for doctors, especially anesthesiologists and doctors who work in emergency departments and critical care units, which will eventually improve the safety and quality of resuscitation fluids selection We send our special thanks to dr Yohanes WH George who made this handbook schematic, practical and easy to understand

Aries Perdana, MD.Head of Department of Anesthesiology and Intensive Care Unit Cipto Mangunkusumo Hospital, Medical Faculty, University of Indonesia

Understanding the chemistry of water and hydrogen ions is an important part

of understanding the living system because hydrogen ions participate in so many reactions One interesting facet of human homeostasis is the tight control of hydrogen ion concentration, [H+] As metabolism creates about 300 liters of carbon dioxide each day, and as we also consume about several hundred mEq of strong acids and bases in the same period, it is remarkable that the biochemical and feedback mechanism can maintain [H+] between 30 and 150 nanoEq/liter

Appreciation of the physics and chemistry involved in the regulatory process is essential for all life scientists, especially physiologists Many physiology textbooks start the discussion of acid-base equilibrium by defining pH , which immediately followed by the Henderson-Hasselbalch equation

Attention has recently shifted to a quantitative physicochemical approach to base physiology Many of the generally accepted concepts of hydrogen ion behaviour are viewed differently This analysis, introduced by Peter Stewart in 1978, provides a chemical insight into the complex chemical equilibrium system known as acid-base balance

The impact of Stewart’s analysis has been slow, but there has been a recent resurgence in interest, particularly as this approach provides explanations for several areas which are otherwise difficult to understand (e.g dilutional acidosis, acid-base disorders related to changes in plasma albumin concentration)

Undoubtedly, the physicochemical approach will become more important in the future and this brief review provides an introduction to this method

Yohanes WH George, MD

Anesthesiology IntensivistHead of Emergency & Intensive Care Unit, Pondok Indah Hospital – Jakarta IndonesiaLecturer, Department of Anesthesiology and Intensive Therapy – Faculty of Medicine,

University of Indonesia.Email yohanesgeorge@yahoo.comPages https://www.facebook.com/critcaremedcom

INTRODUCTION

MATHEMATICAL ANALYSIS

The physicochemical acid-base approach (Stewart’s approach) is different from the conventional approach based on the Henderson-Hasselbalch equation, and requires a new way of approaching acid-base problems

In Stewart’s approach, the [H+] is determined by the composition of electrolytes and PCO2 of the solution

Mathematical analysis shows that it is not absolute concentrations of almost totally dissociated (“strong”) ions that influence hydrogen ion concentration, but the difference between the activities of these strong ions (this “strong ion difference” is commonly abbreviated ”[SID]”).

Stewart’s Textbook of acid-base Edited by; John Kellum, Paul Elbers Copyright © 2009 by AcidBase.org/Paul Elbers, Amsterdam, The Netherlands Info@acidbase.org

STEWART’S APPROACH IN BRIEF

 Electroneutrality In aqueous solutions in any compartment, the sum

of all the positively charged ions must equal to the sum of all the negatively charged ions.

 The dissociation equilibria of all incompletely dissociated substances,

as derived from the law of mass action, must be satisfied at all times.

 Conservation of mass, the amount of a substance remains constant unless it is added, removed, generated or destroyed The relevance is that the total concentration of an incompletely dissociated substance

is the sum of concentrations of its dissociated and undissociated forms.

2

STRONG ION DIFFERENCE

• DEFINITION:

ions In detail, the strong ion difference is the sum of the concentration of the strong base cations, less the sum of the concentrations of the strong acid anions

 Strong electrolytes are those which are fully dissociated in aqueous solution, such as the cation sodium (Na+), or the

DISSOCIATED, THEY DO NOT PARTICIPATE IN CHEMICAL REACTIONS (UNMETABOLIZABLE IONS) Their only role in acid-base chemistry is through the ELECTRONEUTRALITY

K + 4

Cl102

[SID]

STRONG ION DIFFERENCE IN WATER

Water dissociation into [H +] and [OH - ] determined by change in [SID]

STRONG ION DIFFERENCE IN WATER

STRONG ION DIFFERENCE IN PLASMA

BIOCHEMISTRY OF AQUEOUS SOLUTIONS

1 Virtually all solutions in human biology contain water and aqueous solutions provide a virtually inexhaustible source of [H+]

2 In these solutions, [H+] concentration is determined by the dissociation of water into H+ and OH- ions

3 Changes in [H+] concentration or pH occur NOT as a result of how much [H+] is added or removed BUT as a consequence of water

dissociation in response to change in [SID], PCO2 and weak acid

STRONG ION DIFFERENCE IN PLASMA

TO CHANGE IN [SID], PCO2

AND WEAK ACID

Weak acid

UA = UNMEASURED ANION Mostly lactate and ketones

George 2015

TWO VARIABLES

pH or [H+] DETERMINED BY

DEPENDENT VARIABLE

EVERY CHANGE OF THESE VARIABLE

WILL CHANGE THE pH

Controlled by the

respiratory system The electrolyte

composition of the blood (controlled by the kidney)

Weak Acid, The protein concentration (controlled by the liver and metabolic

state)

Stewart’s Textbook of acid-base Edited by; John Kellum, Paul Elbers Copyright © 2009 by AcidBase.org/Paul Elbers, Amsterdam, The Netherlands Info@acidbase.org

6

IF THESE VARIABLE CHANGE, THE INDEPENDENT VARIABLES MUST HAVE

CHANGED

STRONG IONS

DIFFERENCE

WATER DISSOCIATION

Atot [SID]

pH Respiratory

pH Metabolic Respiratory Metabolic

P CO2 Base Excess-HCO 3 P CO2 [SID] A tot

Cation;

THE DIFFERENCE

[SID]

Determinants of plasma pH, as assessed

by the H-H Base excess and standard

HCO3- determine the metabolic

component of plasma pH

Determinants of plasma pH, at 37 0 C, as assessed by the Strong Ion Difference [SID] model of Stewart [SID + ] and [A tot ] determine the metabolic component of plasma pH

Cl - ,

SO 4 - , Lact, Keto

and dependent variables.

• Actually, HCO3- and H+ ions represent the effects rather than the

causes of acid-base derangements

8

Hypoalbuminemic/posphate mic alkalosis

Respiratory

acidosis Dilu onal acidosisHyponatremia/ Hyperchloremic acidosis Hyperalbuminemic/pospha

temic acidosis Lac c / keto

acidosis

Modified George 2015

Fencl V, Jabor A, Kazda A, Figge J Diagnosis of metabolic acid-base disturbances in critically ill patients Am J

Respir Crit Care Med 2000 Dec;162(6):2246-51

CLASSIFICATION OF PRIMARY ACID BASE DISTURBANCE

Na+ = 140 mEq/L

Cl- = 102 mEq/L

[SID] = 38 mEq/L

140/2 = 70 mEq/L102/2 = 51 mEq/L[SID] = 19 mEq/L

1 liter 2 liter

WATER EXCESS

1 Liter water

simple analogy

10

PO 4

Alb

[SID]=34

Cl ↑ 115

Alb

PO 4 [SID] ↓↓

Cl

102

Laktat/keto

CL ↓ 95

Cl 102

acidosis

Hypochlor alkalosis

fosfat alkalosis

Hyperalb/ fosfat acidosis

[SID] ↓↓

[SID] = 34 mEq/L

Lactate (organic strong anion) undergo rapid metabolism a er infusion

Cation + = 137 mEq/L

Cl - = 109 mEq/L Lactate - = 28 mEq/L [SID]= 0 mEq/L

[SID] : 34 plasma pH become more alkalosis than plasma pH a er Saline infusion

Lactate Ringer infusion will not cause acidosis because it replaces

28 mEq/L of Cl- with lactate which can undergo rapid metabolism

THE EFFECT OF SALINE AND BALANCED FLUID FROM THE STEWART’S PERSPECTIVE

Stewart’s approach not only explains fluid induced acid–base phenomena but also provides a framework for the design of fluids for specific acid–base effects