Interpretation of blood Interpretation of blood gasesgases

Kidney fixes respiratory derangement, except if kidney malfunctioning

occur (e.g. sepsis, dehydration, prematurity or renal pathology)

Lung fixes metabolic derangement, except if lung malfunctioning occur

(e.g. infection, ARDS, or any lung pathology )

Renal mechanism is slow, that’s why respiratory derangement is

slowly fixed. While, respiratory mechanism is fast,

that’s why metabolic derangement is rapidly fixed.

Fixation ( compensation ) never brings acid-base balance to normal,

but near normal

Hassel Bach equation: pH = 6.2 + log ( Bicarbonate / PaCO2 )

For simplification: pH = B/C

by dr M Osama Husseinby dr M Osama Hussein

Compensation is an evidence of chronicity

During compensation, bicarbonates & PaCO2 follow each other,

so, both are changed & in the same direction.

The one with the bigger magnitude of change, is the one who startedthe derangement ( the chronic element which is to be compensated,

confirm with the resultant pH ).The one with the lesser magnitude of change, is the compensating

element.

Bicarbonates & PaCO2 serve the pH ( 2 servants & 1 lady ).

Bicarbonates & base deficit are nearly the same in both arterial &

venous samples.

by dr M Osama Husseinby dr M Osama Hussein

According to the equation:

B pH =

C

C = CO2 B= bicarbonate

by dr M Osama Husseinby dr M Osama Hussein

NORMAL VALUES

Arterialized Capillary& Arterial Samples

Venous Samples

PH 7.35 - 7.45 7.25 - 7.35

PO2 70 - 90 mmHg 60 - 80 mmHg

PCO2 35 - 45 mmHg 45 - 45 mmHG

Bicarbonates 18 - 25 meq/L

Don't complete reading & interpretation of the result of the blood gas

analysis when pH is within the normal range.

by dr M Osama Husseinby dr M Osama Hussein

Derangement pH B & C

Acute Affected Only one is affected

ChronicMinimally affected (near

normal)

Both are affected, in the same direction,

following each other.

Mixed Highly affected

Both are affected, in opposite directions,

not following each other.

Derangement Where is the error?

Metabolic Error in the Metabolite: Bicarbonate (B)

Respiratory Error in the Respiratory gas: PaCO2 (C)

Derangement pH H+

AcidosisAcidosis LowerLower than normal range than normal range HigherHigher H ions H ions

AlkalosisAlkalosis HigherHigher than normal range than normal range Lower Lower H ionsH ions

by dr M Osama Husseinby dr M Osama Hussein

Acute MetabolicAcidosis

▼▼ B---------------

◄► C= ▼▼ pH

AcuteRespiratory

Acidosis

◄► B---------------

▲▲ C= ▼▼ pH

Acute Metabolic

Alkalosis

▲▲ B---------------

◄► C= ▲▲ pH

Acute Respiratory Alkalosis

◄► B---------------

▼▼ C= ▲▲ pH

pH is affected, Only B or C is affected

In metabolic derangement: B goes with pHIn respiratory derangement: C goes the opposite direction.

ACUTE DERANGEMENTS

by dr M Osama Husseinby dr M Osama Hussein

CHRONIC (COMPENSATING) DERANGEMENTS CHRONIC DERANGEMENTCompensated

byACUTE

DERANGEMENT ► RESULTANT

Chc. Met. Acidosis + Ac. Resp. Alkalosis

▼▼▼B----------- = ▼▼▼pH ◄►C

+ ◄►B----------- = ▲▲pH ▼▼C

► ▼▼▼B----------- = ▼pH ▼▼C

Chc. Resp. Acidosis + Ac. Met. Alkalosis ► ? ◄►B----------- = ▼▼▼pH▲▲▲C

+ ▲▲B----------- = ▲▲pH ◄►C

► ▲▲B----------- = ▼pH▲▲▲C

Chc. Met. Alkalosis + Ac. Resp. Acidosis ► ?▲▲▲B----------- = ▲▲▲pH ◄►C

+ ◄►B----------- = ▼▼pH ▲▲C

► ▲▲▲B----------- = ▲pH ▲▲C

Chc. Resp. Alkalosis + Ac. Met. Acidosis ► ? ◄►B

----------- = ▲▲▲pH▼▼▼C

+ ▼▼B

----------- = ▼▼pH ◄►C

► ▼▼B

----------- = ▲pH ▼▼▼C

..

by dr M Osama Husseinby dr M Osama Hussein

CHRONIC DERANGEMENTCompensated

byACUTE

DERANGEMENT ► RESULTANT

Chc. Met. Acidosis + Ac. Resp. Alkalosis

▼▼▼B----------- = ▼▼▼pH ◄►C

+ ◄►B----------- = ▲▲pH ▼▼C

► ▼▼▼B----------- = ▼pH ▼▼C

Chc. Resp. Acidosis + Ac. Met. Alkalosis

◄►B----------- = ▼▼▼pH▲▲▲C

+ ▲▲B----------- = ▲▲pH ◄►C

► ▲▲B----------- = ▼pH▲▲▲C

Chc. Met. Alkalosis + Ac. Resp. Acidosis ► ?▲▲▲B----------- = ▲▲▲pH ◄►C

+ ◄►B----------- = ▼▼pH ▲▲C

► ▲▲▲B----------- = ▲pH ▲▲C

Chc. Resp. Alkalosis + Ac. Met. Acidosis ► ? ◄►B

----------- = ▲▲▲pH▼▼▼C

+ ▼▼B

----------- = ▼▼pH ◄►C

► ▼▼B

----------- = ▲pH ▼▼▼C

..

by dr M Osama Husseinby dr M Osama Hussein

CHRONIC DERANGEMENTCompensated

byACUTE

DERANGEMENT ► RESULTANT

Chc. Met. Acidosis + Ac. Resp. Alkalosis

▼▼▼B----------- = ▼▼▼pH ◄►C

+ ◄►B----------- = ▲▲pH ▼▼C

► ▼▼▼B----------- = ▼pH ▼▼C

Chc. Resp. Acidosis + Ac. Met. Alkalosis

◄►B----------- = ▼▼▼pH▲▲▲C

+ ▲▲B----------- = ▲▲pH ◄►C

► ▲▲B----------- = ▼pH▲▲▲C

Chc. Met. Alkalosis + Ac. Resp. Acidosis

▲▲▲B----------- = ▲▲▲pH ◄►C

+ ◄►B----------- = ▼▼pH ▲▲C

► ▲▲▲B----------- = ▲pH ▲▲C

Chc. Resp. Alkalosis + Ac. Met. Acidosis ► ? ◄►B

----------- = ▲▲▲pH▼▼▼C

+ ▼▼B

----------- = ▼▼pH ◄►C

► ▼▼B

----------- = ▲pH ▼▼▼C

..

by dr M Osama Husseinby dr M Osama Hussein

pH is mildly affected,Both B & C are affected in the same direction, (following each other(

CHRONIC DERANGEMENTCompensated

byACUTE

DERANGEMENT ► RESULTANT

Chc. Met. Acidosis + Ac. Resp. Alkalosis

▼▼▼B----------- = ▼▼▼pH ◄►C

+ ◄►B----------- = ▲▲pH ▼▼C

► ▼▼▼B----------- = ▼pH ▼▼C

Chc. Resp. Acidosis + Ac. Met. Alkalosis

◄►B----------- = ▼▼▼pH▲▲▲C

+ ▲▲B----------- = ▲▲pH ◄►C

► ▲▲B----------- = ▼pH▲▲▲C

Chc. Met. Alkalosis + Ac. Resp. Acidosis

▲▲▲B----------- = ▲▲▲pH ◄►C

+ ◄►B----------- = ▼▼pH ▲▲C

► ▲▲▲B----------- = ▲pH ▲▲C

Chc. Resp. Alkalosis + Ac. Met. Acidosis

◄►B----------- = ▲▲▲pH

▼▼▼C+

▼▼B----------- = ▼▼pH

◄►C►

▼▼B----------- = ▲pH

▼▼▼C

by dr M Osama Husseinby dr M Osama Hussein

pH is markedly affected,Both B & C are affected, but in 2 different directions (away

from each other(

MIXED DERANGEMENTS

MetabolicDerangement

plusRespiratoryDerangement

► Resultant

Metabolic Acidosis + Respiratory Acidosis

► Mixed Acidosis

▼▼B----------- = ▼▼pH ◄►C

+ ◄►B ----------- = ▼▼pH ▲▲C

► ▼▼B ▼----------- = ▼ ▼ pH ▲▲ C ▼

Metabolic Alkalosis +Respiratory Alkalosis

► Mixed Alkalosis

▲▲B----------- = ▲▲pH ◄►C

+ ◄►B ----------- = ▲▲pH ▼▼C

► ▲▲B ▲----------- = ▲▲ pH ▼▼C ▲

by dr M Osama Husseinby dr M Osama Hussein

CORRECTION OF METABOLIC ACIDOSISCORRECTION OF METABOLIC ACIDOSIS

pH < 7.2 (7.25( Bicarb. < 15 meq/L BE > -10 meq/L

Contraindicated when there is HypercarbiaCO2 wash can br induced by increasing RR either on ventilator, or

applying few breaths by the Ambu bag.

by dr M Osama Husseinby dr M Osama Hussein

pH Bicarb. PCO2

? B-----------

? CpH? Derangement How you

Should feel?

7.4 20 40 ◄►B-----------

◄► C

◄

pH ►

NORMAL

by dr M Osama Husseinby dr M Osama Hussein

pH Bicarb. PCO2

? B-----------

? CpH? Derangement How you

Should feel?

7.4 20 40 ◄►B-----------

◄► C

◄

pH ►

NORMAL

7.25 ▼ 10 ▼ ◄ 40 ► ▼▼B-----------

◄►C

PH▼▼

Ac. Met. Acidosis

by dr M Osama Husseinby dr M Osama Hussein

pH Bicarb. PCO2

? B-----------

? CpH? Derangement How you

Should feel?

7.4 20 40 ◄►B-----------

◄► C

◄

pH ►

NORMAL

7.25 ▼ 10 ▼ ◄ 40 ► ▼▼B-----------

◄►C

PH▼▼

Ac. Met. Acidosis

7.25 ◄ 20 ► ▲ 60 ▲ ◄►B-----------

▲▲C

PH▼▼

Ac. Resp. Acidosis

by dr M Osama Husseinby dr M Osama Hussein

pH Bicarb. PCO2

? B-----------

? CpH? Derangement How you

Should feel?

7.4 20 40 ◄►B-----------

◄► C

◄

pH ►

NORMAL

7.25 ▼ 10 ▼ ◄ 40 ► ▼▼B-----------

◄►C

PH▼▼

Ac. Met. Acidosis

7.25 ◄ 20 ► ▲ 60 ▲ ◄►B-----------

▲▲C

PH▼▼

Ac. Resp. Acidosis

7.55 ▲ 30 ▲ ◄ 40 ► ▲▲B-----------

◄►C

▲▲

pHAc. Met. Alkalosis

by dr M Osama Husseinby dr M Osama Hussein

pH Bicarb. PCO2

? B-----------

? CpH? Derangement How you

Should feel?

7.4 20 40 ◄►B-----------

◄► C

◄

pH ►

NORMAL

7.25 ▼ 10 ▼ ◄ 40 ► ▼▼B-----------

◄►C

PH▼▼

Ac. Met. Acidosis

7.25 ◄ 20 ► ▲ 60 ▲ ◄►B-----------

▲▲C

PH▼▼

Ac. Resp. Acidosis

7.55 ▲ 30 ▲ ◄ 40 ► ▲▲B-----------

◄►C

▲▲

pHAc. Met. Alkalosis

7.55 ◄ 20 ► ▼ 20 ▼

B-----------

▼▼C

▲▲

pHAc. Resp. Alkalosis

by dr M Osama Husseinby dr M Osama Hussein

pH Bicarb. PCO2

? B-----------

? CpH? Derangement How you

Should feel?

7.4 20 40 ◄►B-----------

◄► C

◄

pH ►

NORMAL

7.3 10▼▼ 30▼ ▼▼B-----------

▼C

pH▼ Chr. Met. Acidosis& Ac. Resp. Alkalosis

by dr M Osama Husseinby dr M Osama Hussein

pH Bicarb. PCO2

? B-----------

? CpH? Derangement How you

Should feel?

7.4 20 40 ◄►B-----------

◄► C

◄

pH ►

NORMAL

7.3 10▼▼ 30▼ ▼▼B-----------

▼C

pH▼ Chr. Met. Acidosis& Ac. Resp. Alkalosis

7.3 ▲26 ▲60▲ ▲B-----------

▲▲C

pH▼ Chr. Res. Acidosis& Ac. Met. Alkalosis

by dr M Osama Husseinby dr M Osama Hussein

pH Bicarb. PCO2

? B-----------

? CpH? Derangement How you

Should feel?

7.4 20 40 ◄►B-----------

◄► C

◄

pH ►

NORMAL

7.3 10▼▼ 30▼ ▼▼B-----------

▼C

pH▼ Chr. Met. Acidosis& Ac. Resp. Alkalosis

7.3 ▲26 ▲60▲ ▲B-----------

▲▲C

pH▼ Chr. Res. Acidosis& Ac. Met. Alkalosis

7.5 ▲30▲ ▲50 ▲▲B-----------

▲C

▲

pHChr. Met.Alkalosis& Ac. Resp. Acidosis

by dr M Osama Husseinby dr M Osama Hussein

pH Bicarb. PCO2

? B-----------

? CpH? Derangement How you

Should feel?

7.4 20 40 ◄►B-----------

◄► C

◄

pH ►

NORMAL

7.3 10▼▼ 30▼ ▼▼B-----------

▼C

pH▼ Chr. Met. Acidosis& Ac. Resp. Alkalosis

7.3 ▲26 ▲60▲ ▲B-----------

▲▲C

pH▼ Chr. Res. Acidosis& Ac. Met. Alkalosis

7.5 ▲30▲ ▲50 ▲▲B-----------

▲C

▲

pHChr. Met.Alkalosis& Ac. Resp. Acidosis

7.5 13▼ ▼20▼ ▼B-----------

▼▼C

▲

pHChr. Res. Alkalosis

& Ac. Met. Acidosis

by dr M Osama Husseinby dr M Osama Hussein

pH Bicarb. PCO2

? B-----------

? CpH? Derangement How you

Should feel?

7.4 20 40 ◄►B-----------

◄► C

◄

pH ►

NORMAL

7.1 ▼10▼ ▲60▲ ▼▼B---------

▲▲C

▼▼

pH▼▼

Mixed Acidosis

by dr M Osama Husseinby dr M Osama Hussein

pH Bicarb. PCO2

? B-----------

? CpH? Derangement How you

Should feel?

7.4 20 40 ◄►B-----------

◄► C

◄

pH ►

NORMAL

7.1 ▼10▼ ▲60▲ ▼▼B---------

▲▲C

▼▼

pH▼▼

Mixed Acidosis

7.6 ▲30▲ ▼20▼ ▲▲B---------

▼▼C

▲▲

pH▲▲

Mixed Alkalosis

by dr M Osama Husseinby dr M Osama Hussein

by dr M Osama Husseinby dr M Osama Hussein