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 Strong Ion Difference Classification of Primary Acid Base Disturbances 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 ii 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 iv 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 vi 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 EASY WAY TO UNDERSTAND STEWART’S ACID-BASE STRONG ION DIFFERENCE IN KIDNEY THE KIDNEYS ARE THE MOST IMPORTANT REGULATOR OF [SID] FOR ACID-BASE PURPOSE TUBULAR FLUID INTERSTITIAL PLASMA CELL George, 2015 EFFECT OF DIURETICS IN URINE COMPOSITION Volume (ml/min) pH Sodium (mEq/l) Potassium (mEq/l) Chloride (mEq/l) SID (mEq/l) No drug 6.4 50 15 60 Thiazide diuretics 13 7.4 150 25 150 25 Loop diuretics 6.0 140 25 155 Osmotic diuretics 10 6.5 90 15 110 Potassium-sparing diurtics 7.2 130 10 120 15 Carbonic anhydrase inhibitors 8.2 70 60 15 120 Loop Diuretics (Furosemide) increase the excretion of Cl- via urine reducing urine [SID] and increasing the plasma [SID] alkalosis Tonnesen AS, Clincal pharmacology and use of diuretics In: Hershey SG, Bamforth BJ, Zauder H, eds, Review courses in anesthesiology Philadelphia: Lippincott, 1983; 217-226 20 COMPENSATION 21 EASY WAY TO UNDERSTAND STEWART’S ACID-BASE Renal Compensation for Chronic Respiratory Acidosis Hypochloremia increase Increase CO 2 increase the [H+] COPD [SID] decrease [H+] H+ HCO3 30 HCO3 Na 140 Cl 100 pH ↓ Na 140 CO2↑ [SID]↑ Cl ↓ 90 ↑NH4Cl urine Hypochloremia George 2015 RENAL & RESPIRATORY COMPENSATION FOR NON RENAL METABOLIC ACIDOSIS (UA) IN STEWART’S TERM Non Renal Met Acidosis (UA); Shock, MODS Hyperven la on decrease [H+] Plasma UA decrease the [SID] increase the [H+] H+ HCO3 - [SID] UA Na+ 140 Removal CO2 Early compensation pH ↓ Hours Days ↑NH4Cl urine 30 ↑NH Hypochloremia Kidney Removal Chlor- 22 [SID] Cl100 HCO3 - Liver George 2015 Na+ 140 Brain Stem NH3 Sintesis ↑ (Ammoniagenesis) Late compensation 22 UA hyperventilation Cl100 HCO3 - Na+ 140 [SID] UA Cl- ↓ 90 Hypochloremia will increase [SID] decrease [H+] Clinical Application EASY WAY TO UNDERSTAND BLOOD GAS ANALYSIS USING STEWART ‘S FORMULA THE PRACTICAL POINT; IF WE WANT TO CALCULATE THE pH, WE MUST KNOW THE CONCENTRATIONS OF THE STRONG IONS, AND PLUG THESE VALUE INTO EQUATIONS 23 EASY WAY TO UNDERSTAND STEWART’S ACID-BASE REUNIFICATION OF ACIDBASE: SID & BUFFER BASE BBe = Buffer Baseexpected = SID = HCO3- + A(expected if pH = 7.4 and pCO2 = 40) Mg++ Ca++ K+ HCO3 + A- HCO3 + A- BBe BBactual BECl (-) Hyperchloremia case Na+ 140 Cl102 Cl112 Base De cit due to increase Cl = BBa – BBe Any deviation in [Na+], [Cl-] or [Alb-] from normal values will produce either a positive or negative base excess A SIMPLIFIED FENCL-STEWART-STORY FORMULA BE from blood gas machine The [SID] e ect SBE = … Weak acid e ect Na–Cl e ect = [Na+]–[Cl–]–38 = Albumin e ect = 0.25 x [42–Alb(g/l)] =… Unmeasured anion UA = SBE – (Na–Cl)e ect – Albumin e ect =… Story, Morimatsu, Bellomo (2004), Bri sh Journal of Anaesthesia Vol 92, 24 CASE EXAMPLES Case 1; pH 7.25 / PaCO2 30 / BE -10 / HCO3 14 Na 140; Cl 112; Alb 4.0 SBE = … Base De cit – 10 (metabolic acidosis due to hyperchloremia) Na–Cl e ect = [Na+]–[Cl–]–38 = Albumin e ect = 0.25 x [42–Alb(g/l)] =… UA = SBE – (Na–Cl)e ect – Albumin e ect =… • SBE = -10 • Na–Cl effect = [Na+]–[Cl–]–38 = 140–112–38 = -10 • Albumin effect = 0.25 x [42–40(g/l)] = 0.5 • UA = -10 – (-10) – 0.5 = -0.5 No alkalinizing e ect of albumin No unmeasured anion was found The gamblegram 150 pH 7.25 / PCO2 30 / BE -10 / HCO3 14 140 HCO3Alb Base De cit due to ↑ Cl- -10 Alb 112 102 WD/: Metabolic acidosis due to hyperchloremia Etiology: Large saline administration, Acute Kidney Injury Th/: Saline restriction RRT Na+ Cl25 EASY WAY TO UNDERSTAND STEWART’S ACID-BASE Case 2: pH 7.48 / PaCO2 50 / BE + / HCO3 34 Na 140; Cl 93; Alb 4.2 SBE = … Na–Cl effect = [Na+]–[Cl–]–38 = Base Excess +9 (metabolic alkalosis due to hypochloremia) Albumin effect = 0.25 x [42–Alb(g/l)] =… UA = SBE – (Na–Cl)effect – Albumin effect =… • SBE = +9 • Na–Cl effect = [Na+]–[Cl–]–38 = 140–93–38 = • Albumin effect = 0.25 x [42–42(g/l)] = • UA = – – = No alkalinizing e ect of albumin No unmeasured anion was found The gamblegram pH 7.48 / PaCO2 45 / BE + / HCO3 34 140 HCO3- BE due to ↓ Cl- Alb +9 Alb WD/: Metabolic alkalosis due to hypochloremia ETIOLOGY: Loop diuretic, Vomiting, enterocutaneous stula Th/: Saline administration, limit the use of diuretic Na+ 26 Cl- Case 3: pH 7.30 / PaCO2 27 /BE -7 / HCO3 18 Na 128; Cl 100; Alb 3.0 SBE = … Base De cit – [metabolic acidosis due to the e ect of hyponatremia (-10)] with alkalinizing e ect of albumin (+3) Na–Cl effect = [Na+]–[Cl–]–38 = Albumin effect = 0.25 x [42–Alb(g/l)] =… UA = SBE – (Na–Cl)effect – Albumin effect =… • SBE = -7 • Na–Cl effect = [Na+]–[Cl–]–38 = 128–100–38 = -10 • Albumin effect = 0.25 x [42–30(g/l)] = • UA = -7 + 10 – = Slight alkalinizing e ect (+3) of hypoalbuminemia No unmeasured anion was found The gamblegram pH 7.30 / PaCO2 27 / BE -7 / HCO3 18 140 BE due to ↓ Na 128 BE due to ↓ alb -7 +3 Alb WD/: metabolic acidosis due to hyponatremia masking by slight alkalinizing e ect of hypoalbuminemia ETIOLOGY: Hemodilution, overload, early phase of shock TH/: Diuretic, inotrope, RRT Na+ Cl27 EASY WAY TO UNDERSTAND STEWART’S ACID-BASE Case : pH 7.42 / PaCO2 35 / PaO2 81 / BE -2 / HCO3 21 ; Na 140; Cl 102; Alb 1.8; lactate it’s a normal blood gas according to the traditional method SBE = … it’s a metabolic/lactic acidosis masking by hypoalbuminemia according to Stewart’s approach Na–Cl effect = [Na+]–[Cl–]–38 = Albumin effect = 0.25 x [42–Alb(g/l)] =… UA = SBE – (Na–Cl)effect – Albumin effect =… No SID e ect was found • SBE = -2 • Na–Cl effect = [Na+]–[Cl–]–38 = 140–102–38 = • Albumin effect = 0.25 x [42–18(g/l)] = • UA = -2 – – = -8 Unmeasured anion of lactate (-8) Alkalinizing e ect of hypoalbuminemia (+6) masking unmeasured anion The gamblegram pH 7.42 / PaCO2 35 / PaO2 100 / BE -2 / HCO3 21 140 BE = - + = - BE due to hypoalb + masking the UA - HCOHCO33 24 22 HCO330.7 UA = - Alb hipoalbumin Lac c Acidosis “masking” by hypoalbuminemia Na+ 28 Cl- SID normal BE due to UA 102 -8 EASY WAY TO INTERPRET BLOOD GAS ANALYSIS USING STEWART CALCULATOR 29 EASY WAY TO UNDERSTAND STEWART’S ACID-BASE Case 5; pH 7.32 /PaCO2 30 /PaO2 100 / BE -1 / HCO3 21 Na 134; K 4.2; Cl 97; Alb 2.8 INTERPRETATION INTERPRETATION UA Independent variables 30 Acidifying process Alkalinizing process CONCLUSION s There are three mathematically independent determinants of blood pH:  Strong ion Difference, the difference between the sum of the concentrations of strong cations and the sum of the concentrations of strong anions  Weak acid, the total weak acid “buffers” concentration (ATOT), which is mostly composed of albumin and phosphate  PCO2 s Stewart’s quantitative physical chemical approach enables us to understand the acid–base properties of intravenous fluids Lowering and raising plasma SID with constant ATOT cause metabolic acidosis and alkalosis, respectively Raising and lowering ATOT with constant SID can cause metabolic acidosis and alkalosis, respectively s Zero SID crystalloids such as saline cause a ‘dilutional’ acidosis by lowering extracellular SID s Plasma [SID] changes by plasma interaction with interstitial fluid through tissue capillary membranes Interstitial fluid in turn may interact with intracellular fluid through cell membranes s If we want to calculate the pH, we must: know the concentrations of the strong ions, and plug these value into equations 31 EASY WAY TO UNDERSTAND STEWART’S ACID-BASE REFERENCES s 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 s Kellum JA Determinants of blood pH in health and disease Crit Care 2000, 4:6–14 s 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 s Tonnesen AS, Clincal pharmacology and use of diuretics In: Hershey SG, Bamforth BJ, Zauder H, eds, Review courses in anesthesiology Philadelphia: Lippincott, 1983; 217-226 s Scheingraber S, Rehm M, Rapid Saline Infusion Produces Hyperchloremic Acidosis in Patients Undergoing Gynecologic Surgery Anesthesiology 1999; 90:1247–9 s Story, Morimatsu, Bellomo (2004), British Journal of Anaesthesia Vol 92 s Story DA, Anaesth Intensive Care 2000 32 EASY WAY TO UNDERSTAND STEWART’S ACID-BASE ... electronic or mechanical; without permission in writing to the author or publisher Copyright © 2015 Centra Communciations i Contents Dedication iv Foreword vi Preface ... Ca++ CATION [SID]a Weak acid UA = UNMEASURED ANION Mostly lactate and ketones Cl - ANION George 2015 EASY WAY TO UNDERSTAND STEWART’S ACID-BASE pH or [H+] DETERMINED BY TWO VARIABLES Determine... [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,