ACID%20

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ACID BASE DISORDERS

• Prof. M. Tatár
• Dept. of Pathophysiology JLF UK

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H affects structure and function of proteins
?
changes of cellular enzymes activity
?
cellular and organ functions changes
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acid substance containing (H) that can be
liberated in solution (proton donor)
base substance that can combine with (H)
from a solution (proton acceptor)
HCO3- ? H CO32-
HCO3- H ? H2 CO3
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Sources of H in organism
a) Volatile acid CO2 H2O ? H2CO3 ? H
HCO3-
b) fixed acids H2SO4, H3PO4
c) organic acids lactic acid, ketoacids
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Hydrogen ion
H 10 - 7,44 až 10 - 7,36
0,000000036 - 0,000000044 mol . l-1
36 - 44 nmol . l-1
pH - log H mol . l-1 pH 7,4 ? 0,04
1.6 µm3 activity of 40 H
mitochondria 2 - 5 active H
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H (nmol.l-1)
160
140
120
100
80
acidaemia
60
norm
40
basaemia
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pH
6,8
7,1
7,4
7,7
norm
acidaemia
basaemia
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acidemia - acidosis
alkalemia - alkalosis
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HENDERSON - HASSELBALCH equation
H . HCO3-
K ---------------------
H2CO3
H2CO3
H K . ----------------
HCO3-
1 1 HCO3-
log ----- log ----- log -------------
H K H2CO3
HCO3-
pH pK log ------------
H2CO3
24 mmol
( log 20 )
pH 6,1 log -----------
1,2 mmol
pH 6,1 1,3 7,4
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7,42
7,38
7,25
7,55
NL
Acidosis
Alkalosis
pH 6,80
7,8
7,36
7,44
Death
Death
One part of H2CO3 (1.2 mmol/l) PCO2 5.3 kPa
20 parts of HCO3- (24 mmol/l)
Blood pH
10
7,42
7,38
7,25
7,55
NL
Acidosis
Alkalosis
pH 6,80
7,8
7,36
7,44
Death
Death
1.5 part of H2CO3 (1.8 mmol/l) PCO28.0 kPa
20 parts of HCO3- (24 mmol/l)
Blood pH
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7,42
7,38
7,25
7,55
NL
Acidosis
Alkalosis
pH 6,80
7,8
7,36
7,44
Death
Death
24 parts of HCO3- (29 mmol/l)
One part of H2CO3 (1.2 mmol/l)
Blood pH
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Buffers 1
HCO3- 1. Bicarbonate system
------------
H2 CO3 HCl NaHCO3 ? H2 CO3
NaCl NaOH H2 CO3 ? NaHCO3 H2O
Hb 2. Hemoglobin system ---------
HbO2
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CO2 transport
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Buffers 2
proteinate- 3. Plasma proteins
--------------- H - protein
HPO42- 4. Phosphate system
----------
H2PO4-
HCO3-
- 53 (plasma 35, RBC- 18)
buffers Hb - HbO2 - 35 in blood
Phosphates - 5 Plasm. prot. -
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Proximal tubule
reabsorbed HCO3-
Na,K-ATPase
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Distal nephron
new HCO3-
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13,3
10,6
8,0
(kPa)
6,7
Pco2
5,3
4,0
2,7
7,0
7,2
7,4
7,6
pH
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Mechanisms of acid base disorders
metabolic
metabolic
4. alkalosis
1. acidosis
2. alkalosis
3. acidosis
HCO3-
pH
pK log ----------------------
PCO2
respiratory
5. acidosis
6. alkalosis
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Anion gap
Na - ( Cl- HCO3- ) 10 - 12
mmol.l-1 140 - ( 104 24 ) 12
mmol.l-1
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Causes of metabolic acidosis (MAC)
I. Normal anion gap MAC
bicarbonate loss ? hyperchloremic MAC
a) via the GIT diarrhea, small bowel fistula
b) kidneys renal tubular acidosis
II. High anion gap MAC
gains of noncarbonic acids
a) ? lactic acid hypoxia, liver insufficiency
b) ketoacidosis diabetes mellitus,
starvation, etanol
c) retention of fixed acids renal failure
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Compensatory response in MAC
1. ? ventilation M?
M? ----- ? -----
R R?
2. HCO3- retention in kidneys
Clinical features
- Kusmaul breathing - ? cardiac
contractility - lethargy - renal
osteodystrophy - hyperkalemia - vomiting
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Causes of metabolic alkalosis (MAL)
Cl- lost (hypochloremic alkalosis)
a) GIT prolonged vomiting
b) urine diuretics (furosemid)
Cl- and HCO3- have a reciprocal relationships to
maintaine electroneutrality
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Compensatory response in MAL
1. Alveolar hypoventilation
M?? M? ------ ?
------- R R?
2. Renal excretion of the excess HCO3-
Clinical features
- occasionally tetany - ? risk of cardiac
dysrhythmias - ? afinity of Hb to O2 -
hypokalemia
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Causes of respiratory acidosis (RAC)
Respiratory disorders ? CO2 accumulation -
alveolar hypoventilation
Compensatory response
HCO3- retention in kidneys
M? M? ------- ?
------- R ? R?
Clinical features
- CNS dysfunction confusion, somnolence
- cerebral vasodilation ? intracranial
pressure,
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Causes of respiratory alcalosis (RAL)
Alveolar hyperventilation as a result of
respiratory centre stimulation
a) the most common anxiety and emotional stress
b) hypermetabolic conditions fever, CNS lesions,
thyreotoxicosis
c) hypoxia pneumonia, pulmonary edema, high
alitude
Compensatory response
Clinical features
? renal excretion of HCO3- M?
M ? ------ ? -------
R ? R ?

• tetany
• - vomiting

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Mixed acid base disorders
- cardiopulmonary arrest
- sepsis
- pulmonary diseases and diabetes mellitus
- vomiting in renal failure