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

G ABOUT
FLUID
EASY WAY

STEWART
APPROAC
TO UNDERSTAND

STEWART’S
ACID-BASE

OUT FLUID IN

TEWART’S
PPROACH
FROM “SALINE” TO MORE
“PHYSIOLOGIC” FLUID
Yohanes WH George, MD


THINKING A


G ABOUT FLUID
EASY WAY TO UNDERSTAND
STEWART’S ACID-BASE

Yohanes WH George, MD


EASY WAY TO UNDERSTAND STEWART’S ACID-BASE

NOTICE
Medicine is an everchanging field. Because of new research and clinical experience
broaden our knowledge, changes in treatment and drug therapy may become necessary
or appropriate, Readers are advised to check the most current product information
provided by the manufacturer of each drug to be administered to verify the recommended
standard of administration. It is the responsibility of the licensed prescriber, relying on
experience and knowledge of the patient, to determine the best treatment of each
individual patient. Neither the publisher nor the author assume any liability for any injury
and/or damage to persons or property arising from this publication.

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
i


Contents
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

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EASY WAY TO UNDERSTAND STEWART’S ACID-BASE

iii


Dedication

To my great teacher and mentor;
In memoriam

DR. Iqbal Mustafa, MD. FCCM
The pioneer of the modern critical care medicine in Indonesia,
Head of Intensive Care Unit Harapan Kita Hospital (1992-2004),
Jakarta- Indonesia

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EASY WAY TO UNDERSTAND STEWART’S ACID-BASE

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

v


Foreword
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 Volta
Section of Anaesthesia and Intensive Care Medicine
University of Ferrara
S. Anna Hospital
Ferrara, Italy

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EASY WAY TO UNDERSTAND STEWART’S ACID-BASE

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, MD
Associate Professor, Faculty of Medicine
Department of Pathophysiology and Transplantation
Fondazione IRCCS Ca’ Granda – Ospedale Maggiore Policlinico
Milan, Italy

vii


Foreword
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 Center

Amsterdam, The Netherlands

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EASY WAY TO UNDERSTAND STEWART’S ACID-BASE

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 acidbase 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

ix


Preface

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 acidbase 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 Intensivist
Head of Emergency & Intensive Care Unit, Pondok Indah Hospital – Jakarta Indonesia
Lecturer, Department of Anesthesiology and Intensive Therapy – Faculty of Medicine,
University of Indonesia.
Email
Pages />x


EASY WAY TO UNDERSTAND STEWART’S ACID-BASE


INTRODUCTION

1


EASY WAY TO UNDERSTAND STEWART’S ACID-BASE

STEWART’S APPROACH IN BRIEF
•

GENERAL PRINCIPLES OF STEWART’S APPROACH
 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.

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
2


STRONG ION DIFFERENCE
•

DEFINITION:
 The strong ion difference is the charge imbalance of the strong
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
anion chloride (Cl -). BECAUSE STRONG IONS ARE ALWAYS
DISSOCIATED, THEY DO NOT PARTICIPATE IN CHEMICAL
REACTIONS (UNMETABOLIZABLE IONS). Their only role in
acid-base chemistry is through the ELECTRONEUTRALITY
relationship

THE GAMBLEGRAM

STRONG ION DIFFERENCE IN WATER
Water dissociation into [H+] and [OH-]
determined by change in [SID]

K+ 4

The [H+]

OH-

4.0x10-8

[SID]

Eq/L (very small)

Na+
140

CATION

Cl102

[Na+] + [K+] - [Cl-] = [SID]
140 + 4 – 102 = 34 mEq/L

ANION

Stewart Textbook of acid-base. Edited by; John Kellum, Paul Elbers. Copyright 2009 by AcidBase.org/
Paul Elbers, Amsterdam, The Netherlands
3


EASY WAY TO UNDERSTAND STEWART’S ACID-BASE

STRONG ION DIFFERENCE IN WATER
[H+]

[H+] ↑↑

[OH-] ↑↑

Alkalosis

Acidosis
OH-

Na Cl

(–)

OH-

Na

Cl

[SID]

OH-

Na
Cl

(+)

THE RELATIONSHIP BETWEEN [SID] AND pH/[H+]

4


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
ELECTRONEUTRALITY

H+

OH-

CO 32-

HCO3CHANGE IN pH OR [H+] AS A
CONSEQUENCE OF WATER
DISSOCIATION IN RESPONSE
TO CHANGE IN [SID], PCO2
AND WEAK ACID

Na+

Alb -

Posfat UA -

K+
Mg ++
Ca++

CATION

[SID]a
Weak acid
UA = UNMEASURED ANION

Mostly lactate and ketones

Cl -

ANION
George 2015

5


EASY WAY TO UNDERSTAND STEWART’S ACID-BASE

pH or [H+] DETERMINED BY

TWO VARIABLES
Determine
DEPENDENT
VARIABLE

INDEPENDENT
VARIABLE

Primary (cause)

Secondary (effect)

INDEPENDENT VARIABLES

CO2

pCO2
Controlled by the
respiratory system

STRONG ION
DIFFERENCE

SID

WEAK ACID

Atot

Weak Acid, The protein
concentration (controlled by
The electrolyte
the liver and metabolic
composition of the blood
state)
(controlled by the
kidney)

EVERY CHANGE OF THESE VARIABLE
WILL CHANGE THE pH
Stewart’s Textbook of acid-base. Edited by; John Kellum, Paul Elbers. Copyright © 2009 by AcidBase.
org/Paul Elbers, Amsterdam, The Netherlands
6


DEPENDENT VARIABLES

HCO3-

H+
OH-

AH
CO3=

A-

IF THESE VARIABLE CHANGE,
THE INDEPENDENT VARIABLES MUST HAVE
CHANGED
Stewart’s Textbook of acid-base. Edited by; John Kellum, Paul Elbers. Copyright © 2009 by AcidBase.
org/Paul Elbers, Amsterdam, The Netherlands

THE PRACTICAL POINT
INDEPENDENT VARIABLES

DEPENDENT VARIABLES

STRONG IONS
DIFFERENCE

pCO2

WATER
DISSOCIATION

H2O
OH-

PROTEIN
CONCENTRATION

Na+

Cl-

7


EASY WAY TO UNDERSTAND STEWART’S ACID-BASE

THE DIFFERENCE
Henderson-Hasselbalch

Stewart’s Approach

pH

pH

Respiratory

Metabolic

PCO2

Base Excess-HCO3

Respiratory

PCO2

[SID]

Cation;
Na+, K+,
Mg++,
Ca++

Determinants of plasma pH, as assessed
by the H-H. Base excess and standard
HCO3- determine the metabolic
component of plasma pH

Metabolic

[SID]
-

Cl ,
SO4-,
Lact,
Keto

A tot

[SID]
Atot
-

Cl ,
SO4-,
Lact,
Keto

Cation;
Na+, K+,
Mg++,
Ca++

Determinants of plasma pH, at 370C, as
assessed by the Strong Ion Difference [SID]
model of Stewart. [SID+] and [Atot] determine
the metabolic component of plasma pH
George 2015

•

The Stewart’s approach emphasizes mathematically independent
and dependent variables.

•

Actually, HCO3- and H+ ions represent the effects rather than the
causes of acid-base derangements.

8


CLASSIFICATION OF PRIMARY ACID BASE DISTURBANCE
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
RESPIRATORY

METABOLIC

pH

Abnormal
pCO2

Water

Abnormal Strong Anion

ALKALOSIS

Respiratory
alkalosis

Hypercarbia

ACIDOSIS

Excess
Hyponatremia/

Dilu onal acidosis

Respiratory
acidosis

LUNG

De cit
Hypernatremia/co
ntrac on alkalosis

BALANCE

Alb

Po4-

Unmeasured
Anion

Chloride

Hypocarbia

Abnormal Weak acid

Abnormal Strong Ion Di erence

Hypoalbuminemia
Hyposphatemia

Hypochloremia
a
Hypochloremic

Hypoalbuminemic/posphate
mic alkalosis

alkalosis

Hyperchloremia
Hyperchloremic
acidosis

Positive
Lac c / keto
acidosis

Hyperproteinemia
Hyperposphatemia
Hyperalbuminemic/pospha
temic acidosis

LIVER AND KIDNEY
Modified George 2015

9


EASY WAY TO UNDERSTAND STEWART’S ACID-BASE

simple analogy

WATER DEFICIT
Diuretic
Diabetes Insipidus
Evaporation

Plasma

Plasma

1
liter

Na+ = 140 mEq/L
Cl- = 102 mEq/L
[SID] = 38 mEq/L

[SID] : 38

140/1/2 = 280 mEq/L
102/1/2 = 204 mEq/L
[SID] = 76 mEq/L

½ liter

76 = alkalosis

CONTRACTION ALKALOSIS

WATER EXCESS
Plasma

1 Liter
water

Na+

= 140 mEq/L
= 102 mEq/L
Cl[SID] = 38 mEq/L

140/2 = 70 mEq/L
102/2 = 51 mEq/L
[SID] = 19 mEq/L

1 liter 2 liter
[SID] : 38

19 = Acidosis

DILUTIONAL ACIDOSIS
10


ABNORMAL IN SID AND WEAK ACID
K
Mg
Ca

Na
140

[SID]=34
Alb
PO4

Cl
102
Normal

[SID] ↓↓

[SID] ↓↓
Alb
PO4

[SID]↑↑

Alb
PO4

Cl ↑
115
Hyperchlor
acidosis

CL ↓
95

Laktat/keto

[SID] ↓↓

[SID]↑↑

Alb
PO4

Cl
102

Cl
102

Hypochlor Keto/lactate Hypoalb/
fosfat
alkalosis
acidosis
alkalosis

Alb/
PO4

Cl
102
Hyperalb/
fosfat
acidosis

George 2015

11