Transcript Blood gas analysis and acid

Blood gas analysis and
acid-basic disorder
Department of internal medicine
Chen Yu
Blood Gas Analysis
 Arterial
blood
 Sea level (101.3kPa, 760mmHg)
 Quiet
 Anti-coagulate blood
 Inspire air (Whether O2 supply)
Clinical Significance
 To
evaluate respiratory failure
type Ⅰ or type Ⅱ
 To
evaluate acid-basic disorder
How to evaluate respiratory failure?
PaO2:
Arterial blood oxygenic partial pressure.
Normal: 95-100mmHg (12.6-13.3kPa)
Estimate formula of age:
PaO2=100mmHg-(age×0.33) ±5mmHg
Hypoxia
 Mild:
80-60mmHg
 Mediate: 60-40mmHg
 Severe: <40mmHg
Respiratory Failure
PaO2<60mmHg
respiratory failure
Notice: sea level, quiet, inspire air
rule off other causes ( heart
disease)
Classification of Respiratory Failure
PaCO2: The carbon dioxide partial pressure
of arterial blood
Normal: 35-45mmHg (4.7-6.0kPa)
mean: 40mmHg
Classification of Respiratory Failure
PaO2 (mmHg)
PaCO2 (mmHg)
Type Ⅰ
<60
≤50
TypeⅡ
<60
>50
Other Parameters
SaO2: Saturation of arterial blood oxygen
Normal: 0.95-0.98
Significance: a parameter to evaluate
hypoxia, but not sensitive
ODC ( Dissociation curve of oxygenated
hemoglobin): “S” shape
SaO2%
PO2
Oxygen dissociation curve
PH
2,3DPG
temperature
CO2
ODC to right deviation
Oxygenated hemoglobin release oxygen
to tissue, prevent hypoxia of the tissue.
But absorbed oxygen of hemoglobin is
decreased from the alveoli.
Bohr effect: movement of ODC place is
induced by PH.
PA-aO2: Difference of alveoli-arterial blood
oxygenic partial pressure.
Normal: 15-20mmHg (<30mmHg in the old)
Significance: a sensitive parameter in gas
exchange
PvO2: Oxygenic partial pressure of mixed
venous blood.
Normal: 35-45mmHg
mean: 40mmHg
Significance: Pa-vO2 is to reflect the tissue
absorbing oxygen.
CaO2: The content of the oxygen of the
arterial blood.
Normal: 19-21mmol/L
Significance: a comprehensive parameter
to evaluate arterial oxygen.
Parameters in acid-basic disorder evaluation
PH: negative logarithm of Hydrogen
ion concentration.
Normal: 7.35-7.45
mean: 7.4
〔HCO3- 〕
PH=Pka+log
＝6.1+log
0.03PaCO2
20
1
HCO3- (bicarbonate):
SB (standard bicarbonate)
AB (actual bicarbonate)
SB: the contents of HCO3- of serum of arterial
blood in 38℃, PaCO2 40mmHg, SaO2 100%.
Normal: 22-27mmol/L
mean: 24mmol/L
AB: The contents of HCO3- in actual condition.
In normal person: AB=SB
 AB
and SB are parameters to reflect
metabolism, regulated by kidney.
 Difference of AB-SB can reflect the
respiratory affection on serum HCO3- .
Respiratory acidosis: AB>SB
Respiratory alkalosis: AB<SB
Metabolic acidosis: AB＝SB<Normal
Metabolic alkalosis: AB=SB>Normal
Buffer bases（BB)：
is the total of buffer negative ion of blood.
BB: HCO3hemoglobin
plasma proteins
HPO42- (phosphate)
Normal: 45-55mmol/L
mean: 50mmol/L
Significance: Metabolic acidosis: BB
Metabolic alkalosis: BB
Bases excess （BE):
the acid or bases used to regulate blood
PH 7.4 . ( in 38℃，PaCO2 40mmHg,
SaO2 100%)
Normal: 0±2.3 mmol/L
Significance:
add acid: BE(+), BB
add base: BE(-), BB
Total plasma CO2 (T-CO2)：
total content of the CO2 .
Normal: HCO3- >95%
Anion gap (AG):
the difference of undetermined anion
and undetermined cation in serum.
AG=Na+－(Cl-+ HCO3- )
Normal: 8-16mmol/L
Significance:
AG acidosis: ketoacidosis, kidney failure
AG normal acidosis: Cl
, diarrhea, fixed
acid decrease
to evaluate mix acid-basic disorder
Regulation of Acid-basic Balance
 Chemical
buffer
 Dielectric changes of incells and excells
H+---K+, HCO3- ---Cl Physiology regulation of the lung and
kidney
Classification of Acid-basic Disorder
 Complementary: PH
is normal
 Dis-complementary: PH is abnormal.
PaCO2, HCO3- are three important
parameters in acid-basic disorder
evaluation.
 PH,
Classification of Acid-basic Disorder
PH
Resp. acidosis
Resp. alkalosis
Meta. acidosis
Meta. alkalosis
PaCO2 HCO3-
Classification of Acid-basic Disorder
 Mixed
acid-basic disorder
 Complementary formula
example:
original disorder: chronic respiratory
acidosis
⊿ HCO3- =⊿PaCO2 ×0.35±5.58
complementary limit: 45mmol/L
Classification of Acid-basic Disorder
 Respiratory acidosis
with metabolic acidosis
 Respiratory acidosis with metabolic alkalosis
 Respiratory alkalosis with metabolic acidosis
 Respiratory alkalosis with metabolic alkalosis
Respiratory acidosis with
metabolic acidosis
PaCO2:
HCO3- : , normal, (slight)
AB, SB, BB: , normal, (slight)
PH:
BE: negative value
Respiratory acidosis with
metabolic alkalosis
PaCO2:
AB:
PH: , N,
Mixed by three types of disorder
 Respiratory acidosis
+ metabolic acidosis
+metabolic alkalosis
 Respiratory alkalosis
+ metabolic acidosis
+metabolic alkalosis