Acid-Base balance revisited
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Acid-Base balance revisited. 2013, Wynyard Hall. Luciano Gattinoni, MD, FRCP Università di Milano Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico Milan, Italy. Sodium. Chlorine. Ionic Bond. Sodium Atom 11 p+ 11 e- Net charge = 0. Sodium Ion 11 p+ 10 e-

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Acid-Base balance revisited

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Acid base balance revisited

Acid-Base balance revisited

2013, Wynyard Hall

Luciano Gattinoni, MD, FRCP

Università di Milano

Fondazione IRCCS Ca’ Granda

Ospedale Maggiore Policlinico

Milan, Italy


Acid base balance revisited

Sodium


Acid base balance revisited

Chlorine


Acid base balance revisited

Ionic Bond

Sodium

Atom

11 p+

11 e-

Net charge = 0

Sodium

Ion

11 p+

10 e-

Net charge = +1

Chlorine

Atom

17 p+

17 e-

Net charge = 0

Chloride

Ion

17 p+

18 e-

Net charge = -1


Acid base balance revisited

Hydrogen

Oxygen


Acid base balance revisited

Na+ and Cl- ions become surrounded by spheres of H2O molecules

Cl-

Na+

Na+

Cl-

+

+

+

+

+

+

+

+

+

+

+

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

O

O

O

O

O

O

O

O

O

O

O

-

-

-

-

-

-

-

-

-

-

-


Acid base balance revisited

Lactic acid

Lactate

C3 H6 O3

CH3CH(OH)COO−


Acid base balance revisited

Pr

-

Pr

Pr

H

+H+

1 gr. of PROTEINS may bound 0.11 mEq [H+]


Acid base balance revisited

H

O

O-

O-

O

H

C

C

C

O

O

-O

+

O

C

H+ +

2H+ +

H

H

H

O

O

O

O

CO2

Carbon

Dioxide

H2CO3

Carbonic

Acid

HCO3-

Bicarbonate

CO32-

Carbonate

CO2 + H2O ßà HCO3- + H+      pKa = 6.10

HCO3-ßà CO3--+ H+       pKa = 8.92


Acid base balance revisited

Types of active transport

http://www.emc.maricopa.edu/faculty/farabee/biobk/biobooktransp.html


Acid base balance revisited

H+ number

1

Na+ number

1000000

:

H+ volume

1

:

Na+ volume

120


Acid base balance revisited

The players

Water

55000 mmol/L

Strong Ion+

150 mmol/L

Strong Ion-

110 mmol/L

Weak acid-

40 mmol/L

H+

0.0000004 mmol/L


Acid base balance revisited

The Stewart’s approach

The independent variables are:

The in

Strong Ion difference

PCO2

Amount of weak acid

(Proteins, Phosphate, Hemoglobin)


Acid base balance revisited

[Na+] 142

+

-

[K+] 4.1

[Ca2+] 4.6

[Mg2+] 1.6

[HCO3-] 24.5

[Alb-] 12.28

[Pi-] 1.82

[XA-] 8

[Cl-] 106

Plasma electroneutrality

150

BB= [HCO3-] +[A-]

i.e.

the negative charge

mEq/L

100

SID=[Na+]+[K+]+[Ca2+]+

[Mg2+]-[Cl-]-[XA-]

50

i.e.

BB=SID


Acid base balance revisited

Metabolic acidosis: generation

Na+

K+

mEq/L

Ca++

OH-

OH-

Cl-

160

Lactate-

A-

HCO3-

3

OH-

HCO3-

140

HCO3-

32

42

A-

120

A-

100

80

Positive

charges

Negative

charges

Negative

charges


Acid base balance revisited

Whatdoes Nature do torestore the pH?


Acid base balance revisited

Metabolic acidosis

Within the “BB”

Na+

K+

mEq/L

Ca++

OH-

OH-

Cl-

160

Lactate-

A-

HCO3-

HCO3-

3

OH-

HCO3-

140

32

32

A-

A-

120

Hypocapnia

100

80

Positive

charges

Negative

charges

Negative

charges


Acid base balance revisited

Metabolic acidosis

Within the “BB”

Na+

K+

mEq/L

Ca++

OH-

OH-

Cl-

160

Lactate-

A-

HCO3-

3

OH-

HCO3-

HCO3-

140

32

42

A-

120

A-

100

Chloride

excretion

80

Positive

charges

Negative

charges

Negative

charges


Acid base balance revisited

Measured and calculated values (mean +/- SD) at the different measuring points. Saline group = white dots; Ringer's group = black dots. Star = intragroup differences, P < 0.05; triangle = intergroup differences, P < 0.05.

Infused nearly 4.5-5 L

Dilution nearly 30%

Initial Vext nearly 15 L

Scheingraber: Anesthesiology, 90(5).May 1999.1265-1270


Acid base balance revisited

7.55

pH

dilution 20%

dilution 30%

7.50

dilution 40%

7.45

7.40

7.35

7.30

7.25

baseline

0

10

20

30

40

50

SID (mEq/L)

Effects of infusion SID

Sterofundin

Gelatin

RL

NS

HES

Carlesso E. et al. Intensive Care Med. 2011 Mar;37(3):461-8.


Acid base balance revisited

Effects of infusion SID

(in vitro experimental data

PCO2 = 35 mmHg )

18.3 ± 0.3

HCO3-Baseline

Carlesso E. et al. Intensive Care Med. 2011 Mar;37(3):461-8.


Acid base balance revisited

PCO2 and water

Consider a volume of water equilibrated at different PCO2 values…

[HCO3-]x[H+]

= Kc

[CO2 dissolved]

H-H equation

[HCO3-]

pH = pK + log10

Electroneutrality

[CO2 dissolved]

[HCO3-]=[H+]


Acid base balance revisited

PCO2, pH and water


Acid base balance revisited

PCO2,water and SID

Consider a volume of water equilibrated at different PCO2 values…with a strong ion difference higher than zero…

[HCO3-]x[H+]

= Kc

[CO2 dissolved]

H-H equation

[HCO3-]

pH = pK + log10

Electroneutrality

[CO2 dissolved]

[HCO3-]=[SID] + [H+]


Acid base balance revisited

PCO2 and water

SID

20

20 mEq/l

0.08

0.07

SID

15

15 mEq/l

0.06

0.05

SID

[HCO3-] (mmol/l)

10

0.04

10 mEq/l

0.03

SID

5

0.02

5 mEq/l

0.01

SID

0.00

0

0 mEq/l

0

20

40

60

80

100

120

140

160

180

200

PCO

(mmHg)

2


Acid base balance revisited

Effects of infinite dilution in open system (constant PCO2)

HCO3-

mEq/L

pH = pKc + log10

50

α PCO2

40

A-

SIDD = HCO3-I

30

HCO3-

SID

20

HCO3-

SID

10

HCO3-

SID

0

pH unmodified

pH increase

pH decrease

SID

A- prima


Acid base balance revisited

Effects of infusion SID

PCO2 = 40 mmHg

pH

7.55

SIDdiluent = 50

7.50

SIDdiluent = 40

7.45

SIDdiluent = 30

SIDdiluent = 24.42

7.40

SIDdiluent = 20

7.35

SIDdiluent = 10

7.30

SIDdiluent = 0

7.25

baseline

20

30

40

Dilution (%)

Carlesso E. et al. Intensive Care Med. 2011 Mar;37(3):461-8.


Acid base balance revisited

Effects of infusion SID

(in vitro experimental data)

PCO2 = 35 mmHg

SIDdiluent = 48

SIDdiluent = 36

SIDdiluent = 24

SIDdiluent = 18

SIDdiluent = 12

SIDdiluent = 0

Baseline

Carlesso E. et al. Intensive Care Med. 2011 Mar;37(3):461-8.


Acid base balance revisited

Effects of infusion

(12 pigs)

Langer T. et al. Intensive Care Med. 2012 Jan 25. [Epub ahead of print]


Acid base balance revisited

Effects of infusion

(12 pigs)

Langer T. et al. Intensive Care Med. 2012 Jan 25. [Epub ahead of print]


Acid base balance revisited

Effects of infusion

(12 pigs)

Langer T. et al. Intensive Care Med. 2012 Jan 25. [Epub ahead of print]


Acid base balance revisited

Differenttypesofcrystalloidsinfused

SID infused ~ 24 mEq/L

[n = 13]

(“balance” solution)

SID infused ~ 30 mEq/L

Study

population

[n = 20]

(RIII + SF + RL)

SID infused ~ 55 mEq/L

[n = 24]

(Rehydrating III – SID = 55)

Courtesyof Dr. P. Caironi


Acid base balance revisited

Variationof BE accordingto HCO3–baselinelevels

HCO3– ≤ 23.5 mmol/L

HCO3– > 23.5 mmol/L

P < 0.01

Delta

Base Excess

[mmol/L]

8

6

P < 0.01

4

2

0

-2

SID ~ 24

SID ~ 30

SID ~ 55

N = 13

N = 20

N = 24

Courtesyof Dr. P. Caironi


Acid base balance revisited

Variationof BE accordingtoinfused

SID – baseline HCO3–

7

Delta

Base Excess

[mmol/L]

6

5

4

3

2

1

P = 0.017

0

< –1

– 1 - 12

12 - 19

> 19

Quartile distribution of SID infused – baseline HCO3– [mEq/L]

Courtesyof Dr. P. Caironi


Acid base balance revisited

Improvement have been made on safety through more balanced crystalloid solutions

To maintain initial pH the infusion SID must be equal to HCO3-

The clinical benefit of balanced crystalloid solutions has to be determined.

Conclusions


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