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Base Excess and Critical Care in the past and in the future
Ivar Hejde Gøthgen M.D., D.M.Sc.
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Content
• Acid-base basic
• Scientist in the acid-base story
• Instruments in the acid-base story
• The future and Base excess
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Acid Base (concept of neutrality) _______________________________________________________________________
pN = [H+] = [OH-] (=neutrality)
pH = 6.80 [H+] = [OH-] = 160 nmol/l= neutrality at 37 oC
pH = 7.40[H+] = 40 nmol/l [OH-] = 640 nmol/l= Alkaline offset of 0.6 pH unit
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pH = 6.8Extracellularfluid pH = 7.40
Blood and extracellular fluid serve as sink for metabolic produced acids
H+
Acid Base (the simple model) _______________________________________________________________________
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Acid Base (the acid production) _______________________________________________________________________
Fixed Acids production [H+] : 60 mmol/24 hour => 700 nmol/sec
Volatile Acids production [H+] :13 mol/24 hour => 150000 nmol/sec> 200 times the fixed acids
Total extracellular free [H+] : 40 nmol/l * 15 l => 600 nmol
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Buffer Base 50 mmol/lBuffer base = H+ acceptors
_____________________________Red cell Hemoglobin 35%Red cell Bicarbonate 18%Plasma Bicarbonate 35%Plasma Proteins 7%Others (Phosphate ect.) 5%
Acid Base (the Metabolic component I ) _______________________________________________________________________
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BASE EXCESS and the Acid-Base nomogram
Base excess was introduced by Ole Siggaard Andersen for almost 50 years ago.
While pH and pCO2 are directly measured, the metabolic component, defined as Base excess, is calculated from pH and pCO2 using the Henderson-Hasselbalch equation and the Van Slyke equation.
By using base excess the acid base status is made simple and clinical useful.
Acid Base (the Metabolic component II) _______________________________________________________________________
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Can you go to a Pharmacyand buy a bottle of Base excess ?
Acid Base (the Metabolic component III) _______________________________________________________________________
BASE EXCESS
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The Van Slyke equation(= The equation for the CO2 equilibration curve of blood in vitro)
a-24.4 = -(2.3*b+7.7)*(c-7.40)+d/(1-0.023*b)
where:a = bicarbonate concentration in plasma (mmol/l)b = hemoglobin concentration in blood (mmol/l)c = pH of plasma at 37 oCd = base excess concentration in blood (mmol/l)
Acid Base (the Metabolic component IV) _______________________________________________________________________
(Scand J Clin lab Invest 1977:37,Suppl 146:15-20)
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pH: as a measure of the activity of free hydrogen ions.
pCO2: as a measure of the respiratory component, the activity of free CO2 in the blood.
Base Excess: as a measure of the metabolic component, (the concentration of titratable hydrogen ion in the extracellular fluid).
Acid Base (the acid-base status) _______________________________________________________________________
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Acid Base (the acid-base status)
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Respiratory changes alongThe bufferlines
Acid Base (the acid-base status)
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Metabolic changes acrossThe bufferlines
Acid Base (the acid-base status)
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concentration of freeH YD RO G EN IO N in p lasm anano m ol/L
20253035405060708090100120140
6.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7
pH in arteria l p lasm a
ACID EM IA N O R M AL ALKALEM IA
150
140
130
120
110
100
90
80
70
60
50
40
30
40
20
35
25
15
20.019.0
18.0
17.0
16.0
15.0
14.0
13.0
12.0
11.0
10.0
9.0
10.0
8.0
7.0
6.0
5.0
4.0
3.5
3.0
2.5
2.0
1.5
m m H g kPapC O in arteria l b lood2
HY
PE
RC
AP
NIA
NO
RM
AL
HY
PO
CA
PN
IA
concentration of titratab le H YDR O G EN IO N in extracellu lar flu id m m ol/L
H + D EFIC IT
IAN O R M A L
AR E A
6.8
S iggaard-Andersen Acid-Base C hart
Bicarbonate
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Content
• Acid-base basic
• Scientist in the acid-base story
• Instruments in the acid-base story
• The future and Base excess
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S.P.L. Sørensen 1868-1939
L.J. Henderson 1878-1942
K.A. Hasselbalch 1874-1962
Donald D van Slyke 1883-1971
Poul Astrup 1915-2000
John W. Severinghaus 1922-
Ole Siggaard-Andersen 1932-
Scientist in the acid-base story
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Søren P. L. Sørensen 1868-1939
Protein Chemist at the Carlsberg brewery.
To save having to write that H+ = 0.000000040M, he devised the scale of acid in terms of pH, as the negative log of H+ ion activity. (1907)
Scientist in the acid-base story
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concentration of freeH YD RO G EN IO N in p lasm anano m ol/L
20253035405060708090100120140
6.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7
pH in arteria l p lasm a
ACID EM IA N O R M AL ALKALEM IA
150
140
130
120
110
100
90
80
70
60
50
40
30
40
20
35
25
15
20.019.0
18.0
17.0
16.0
15.0
14.0
13.0
12.0
11.0
10.0
9.0
10.0
8.0
7.0
6.0
5.0
4.0
3.5
3.0
2.5
2.0
1.5
m m H g kPapC O in arteria l b lood2
HY
PE
RC
AP
NIA
NO
RM
AL
HY
PO
CA
PN
IA
concentration of titratab le H YDR O G EN IO N in extracellu lar flu id m m ol/L
H + D EFIC IT
IA
N O R M A L
AR E A
6.8
S iggaard-Andersen Acid-Base C hart
Scientist in the acid-base story
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Lawrence J HendersonProf Biochemistry and Physiology.
Theory of buffering and of
bicarbonate-hydrogen ion-pCO2
relationship.
The Henderson equation
K = [H+][HCO3-]/[H2CO3]
K is the dissociation constant of carbonic
acid, about 10-3 M
A constant 0.1% of dissolved CO2 in water
is hydrated to carbonic acid.
Therefore it can be simplified to
H2CO3 = dissolved CO2
Where K’ is the apparent dissociation
constant K’ = 10-6.1
Scientist in the acid-base story
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concentration of freeH YD RO G EN IO N in p lasm anano m ol/L
20253035405060708090100120140
6.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7
pH in arteria l p lasm a
ACID EM IA N O R M AL ALKALEM IA
150
140
130
120
110
100
90
80
70
60
50
40
30
40
20
35
25
15
20.019.0
18.0
17.0
16.0
15.0
14.0
13.0
12.0
11.0
10.0
9.0
10.0
8.0
7.0
6.0
5.0
4.0
3.5
3.0
2.5
2.0
1.5
m m H g kPapC O in arteria l b lood2
HY
PE
RC
AP
NIA
NO
RM
AL
HY
PO
CA
PN
IA
concentration of titratab le H YDR O G EN IO N in extracellu lar flu id m m ol/L
H + D EFIC IT
IA
N O R M A L
AR E A
6.8
S iggaard-Andersen Acid-Base C hart
Scientist in the acid-base story
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Karl A Hasselbalch 1874-1962Agricultural chemist, Denmark.
Adapted Henderson’s equation to Sørensen’s logarithmic pH by replacing H2CO3 with S.pCO2 creating the
Henderson-Hasselbalch equation:
pH=pK’ + log[HCO3-/(S.pCO2)]
7.40 = 6.10 + log[24/{0.31.40}]Where S (solubility) = 0.031 mM/liter/mmHg at 37oC
Scientist in the acid-base story
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concentration of freeH YD RO G EN IO N in p lasm anano m ol/L
20253035405060708090100120140
6.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7
pH in arteria l p lasm a
ACID EM IA N O R M AL ALKALEM IA
150
140
130
120
110
100
90
80
70
60
50
40
30
40
20
35
25
15
20.019.0
18.0
17.0
16.0
15.0
14.0
13.0
12.0
11.0
10.0
9.0
10.0
8.0
7.0
6.0
5.0
4.0
3.5
3.0
2.5
2.0
1.5
m m H g kPapC O in arteria l b lood2
HY
PE
RC
AP
NIA
NO
RM
AL
HY
PO
CA
PN
IA
concentration of titratab le H YDR O G EN IO N in extracellu lar flu id m m ol/L
H + D EFIC IT
IA
N O R M A L
AR E A
6.8
S iggaard-Andersen Acid-Base C hart
Scientist in the acid-base story
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Donald D Van Slyke
1883-1971
Major developer of clinical chemistry in the 1910-50 period. His manometric blood gas apparatus (1924) was used to measure the content in blood of oxygen, carbon dioxide and many other variables.
Laboratories calculated pCO2 using the Henderson-Hasselbalch equation after measuring pH of blood and the total plasma CO2 by the Van Slyke apparatus until the polio epidemics resulted in two new methods: Astrup’s equilibration scheme and Severinghaus modification of the Stow CO2 electrode.
Scientist in the acid-base story
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concentration of freeH YD RO G EN IO N in p lasm anano m ol/L
20253035405060708090100120140
6.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7
pH in arteria l p lasm a
ACID EM IA N O R M AL ALKALEM IA
150
140
130
120
110
100
90
80
70
60
50
40
30
40
20
35
25
15
20.019.0
18.0
17.0
16.0
15.0
14.0
13.0
12.0
11.0
10.0
9.0
10.0
8.0
7.0
6.0
5.0
4.0
3.5
3.0
2.5
2.0
1.5
m m H g kPapC O in arteria l b lood2
HY
PE
RC
AP
NIA
NO
RM
AL
HY
PO
CA
PN
IA
concentration of titratab le H YDR O G EN IO N in extracellu lar flu id m m ol/L
H + D EFIC IT
IA
N O R M A L
AR E A
6.8
S iggaard-Andersen Acid-Base C hart
Scientist in the acid-base story
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Poul Astrup 1915-2000
Prof of Clinical Chemistry Univ. of Copenhagen
New method for pCO2
To avoid need for the VanSlyke and Henderson-Hasselbalch method, he devised a method for graphically calculating pCO2 by measuring pH before and again after equilibration of the blood to a known pCO2
Scientist in the acid-base story
IHG 05
concentration of freeH YD RO G EN IO N in p lasm anano m ol/L
20253035405060708090100120140
6.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7
pH in arteria l p lasm a
ACID EM IA N O R M AL ALKALEM IA
150
140
130
120
110
100
90
80
70
60
50
40
30
40
20
35
25
15
20.019.0
18.0
17.0
16.0
15.0
14.0
13.0
12.0
11.0
10.0
9.0
10.0
8.0
7.0
6.0
5.0
4.0
3.5
3.0
2.5
2.0
1.5
m m H g kPapC O in arteria l b lood2
HY
PE
RC
AP
NIA
NO
RM
AL
HY
PO
CA
PN
IA
concentration of titratab le H YDR O G EN IO N in extracellu lar flu id m m ol/L
H + D EFIC IT
IA
N O R M A L
AR E A
6.8
S iggaard-Andersen Acid-Base C hart
Scientist in the acid-base story
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John W Severinghaus
1922
Prof of Anestesia University of California San Francisco
Major developer of blood gas measurents since 1950. His modification (invention) of the CO2 electrode, the first blood gas apparatus (1958), the blood gas ruler, transcutaneous blood gas measurement and pulsoximetry, as well as important work in high altitude respiratory physiology
Scientist in the acid-base story
IHG 05
concentration of freeH YD RO G EN IO N in p lasm anano m ol/L
20253035405060708090100120140
6.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7
pH in arteria l p lasm a
ACID EM IA N O R M AL ALKALEM IA
150
140
130
120
110
100
90
80
70
60
50
40
30
40
20
35
25
15
20.019.0
18.0
17.0
16.0
15.0
14.0
13.0
12.0
11.0
10.0
9.0
10.0
8.0
7.0
6.0
5.0
4.0
3.5
3.0
2.5
2.0
1.5
m m H g kPapC O in arteria l b lood2
HY
PE
RC
AP
NIA
NO
RM
AL
HY
PO
CA
PN
IA
concentration of titratab le H YDR O G EN IO N in extracellu lar flu id m m ol/L
H + D EFIC IT
IA
N O R M A L
AR E A
6.8
S iggaard-Andersen Acid-Base C hart
Scientist in the acid-base story
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Ole Siggaard Andersen 1932
Prof of Clinical Chemistry Univ. of Copenhagen
A student of Astrup, he devised the micro-method and the concept of base excess and ECF base excess, now called SBE, for standard base excess.
His equation for SBE is now used in most blood gas apparatus.
Photo 1999 by JWS
Scientist in the acid-base story
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concentration of freeH YD RO G EN IO N in p lasm anano m ol/L
20253035405060708090100120140
6.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7
pH in arteria l p lasm a
ACID EM IA N O R M AL ALKALEM IA
150
140
130
120
110
100
90
80
70
60
50
40
30
40
20
35
25
15
20.019.0
18.0
17.0
16.0
15.0
14.0
13.0
12.0
11.0
10.0
9.0
10.0
8.0
7.0
6.0
5.0
4.0
3.5
3.0
2.5
2.0
1.5
m m H g kPapC O in arteria l b lood2
HY
PE
RC
AP
NIA
NO
RM
AL
HY
PO
CA
PN
IA
concentration of titratab le H YDR O G EN IO N in extracellu lar flu id m m ol/L
H + D EFIC IT
IA
N O R M A L
AR E A
6.8
S iggaard-Andersen Acid-Base C hart
Scientist in the acid-base story
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Content
• Acid-base basic
• Scientist in the acid-base story
• Instruments in the acid-base story
• The future and Base excess
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First Astrup pH apparatus for
equilibration of blood sample with known Pco2, then repeated pH measurement
1953
Instruments in the acid-base story
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Micro-Astrup pH and reference electrodes, 1957
Radiometer Co, Copenhagen, Denmark
The widely used Astrup equilibration method for estimating blood pCO2 by pH measurement before and after equilibration with gas of known pCO2. The glass pH capillary is “A”, filled by suction from “G”, and then connected to reference electrode “K” in saturated KCl “I”.
Instruments in the acid-base story
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First blood gas apparatus. Severinghaus and Bradley (1958)
O2 electrode consumed so much oxygen it needed stirring and calibration with equilibrated blood.
CO2 electrode
O2 electrodestirrer
tonometer
Instruments in the acid-base story
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Instruments in the acid-base story
ABL-1
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Instruments in the acid-base story
BMS-2 , OSM-3 and ABL-4 ( incl. Ole Siggaard-Andersen at work)
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Instruments in the acid-base story
ABL-700
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Polio victim in Copenhagen epidemic being ventilated manually by medical student through tracheostomy, 1952.
Critical care treatment and the acid-base story
Invasive ventilation
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Critical care treatment and the acid-base story
Non-invasive ventilation in Critical Care around 1955
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Critical care treatment and the acid-base story
To put a patient into a ventilator
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Critical care treatment and the acid-base story
Invasive ventilation in Critical Care in 2003
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Content
• Acid-base basic
• Scientist in the acid-base story
• Instruments in the acid-base story
• The future and Base excess
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Acid-Base status and Normal Saline versus Lactated Ringer’s solution ?
•The future and Base excess
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NaCl
LactateHC03
KCa
Normal Serum
lactated Ringer
NaCl 0,9%0
20
40
60
80
100
120
140
160
Normal Saline Versus Lactated Ringer's Solution
Normal Serum
lactated Ringer
NaCl 0,9%
•The future and Base excess
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•The future and Base excess
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•The future and Base excess
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How to interpret the difference in Acid Base Status afterInfusion of Normal Saline and Lactated Ringer’s Solution:
- Dilutional Acidosis versus HyperChloremic Acidosis
- Brønsted’s definition versus Arrhenius definition- Buffer Base (BB) versus Strong Ion Difference (SID)
When adding Lactate and Chloride measument, the interpretation of acid base status may be simple and illustrates that
- Buffer base equals SID as well as - Changes in Buffer Base equals Base Excess
•The future and Base excess
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Electrolyte balance of arterial plasma showing columns of cations and anions of equal height (law of electro-neutrality). The equality of the strong ion difference (SID) and buffer base (BB) is illustrated. The change in concentration of buffer base from normal (at pH = 7.40, pCO2 = 5.3 kPa, and T = 37 C) with opposite sign equals the concentration of titratable hydrogen ion.
•The future and Base excess
(O. Siggaard-Andersen in Encylopedia of Respiratory Medicine 2006)
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•The future and Base excess
Base Excess is a virtual parameter, making some very complex matter simple and clinical useful
Base Excess may continue to exist as the metabolic parameter in Acid-Base status
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Thanks to John W Severinghaus for his kind advice and help
Reykjavik june 2005
Thanks to Ole Siggaard-Andersen for his kind advice and help
Gilleleje 2003
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Advice from your brain and body: ”Use me or loose me”