presentation for interpretation of blood gases

1. by dr M Osama Hussein

2. 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 Hussein

3. 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 started
the 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 Hussein

4. : According to the equation
B
=
pH
C
C = CO2 B= bicarbonate
by dr M Osama Hussein

5. 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 Hussein

6. Derangement
pH
B&C
Acute
Affected
Only one is affected
Minimally affected (near
normal)
Both are affected,
in the same
direction,
following each other.
Highly affected
Both are affected,
in opposite
directions,
not following each
other.
Chronic
Mixed
Derangement
pH Where is the error?
H+
Metabolic
Acidosis
Lower than normal range BicarbonateH(B)
Error in the Metabolite:
Higher ions
Respiratory
Alkalosis
Higher than the Respiratory gas: Lower H(C)
Error in normal range
PaCO2 ions
by dr M Osama Hussein

7. Acute
▼▼ B
ACUTE DERANGEMENTS= ▼▼ pH
Metabolic
--------------Acidosis
◄► C
Acute
Respiratory
Acidosis
Acute
Metabolic
Alkalosis
Acute
Respiratory
Alkalosis
◄► B
--------------▲▲ C
= ▼▼ pH
▲▲ B
--------------◄► C
pH=
◄► B
--------------▼▼ C
=
▲▲
▲▲ pH
pH is affected, Only B or C is affected
In metabolic derangement: B goes with pH
.In respiratory derangement: C goes the opposite direction
by dr M Osama Hussein

8. Compensated
ACUTE
CHRONIC (COMPENSATING) DERANGEMENTS
► RESULTANT
DERANGEMENT
by
CHRONIC DERANGEMENT
Chc. Met. Acidosis
▼▼▼B
----------- = ▼▼▼pH
◄►C
.
+
Ac. Resp.
Alkalosis
+
◄►B
----------- = ▲▲pH
▼▼C
►
+
Ac. Met. Alkalosis
►
◄►B
----------- = ▼▼▼pH
▲▲▲C
+
▲▲B
----------- = ▲▲pH
◄►C
►
Chc. Met. Alkalosis
+
Ac. Resp. Acidosis
►
▲▲▲B
----------- = ▲▲▲pH
◄►C
+
◄►B
----------- = ▼▼pH
▲▲C
►
Chc. Resp. Alkalosis
+
Ac. Met. Acidosis
►
+
▼▼B
pH▼▼----------- =
C ◄►
Chc. Resp. Acidosis
◄►B
pH▲▲▲----------- =
C▼▼▼
by dr M Osama Hussein
►
▼▼▼B
----------- = ▼pH
▼▼C
?
▲▲B
----------- = ▼pH
▲▲▲C
?
▲▲▲B
----------- = ▲pH
▲▲C
?
▼▼B
pH▲----------- =
C ▼▼▼

9. CHRONIC DERANGEMENT
Chc. Met. Acidosis
Compensated
by
ACUTE
DERANGEMENT
+
Ac. Resp.
Alkalosis
►
RESULTANT
►
▼▼▼B
----------- = ▼pH
▼▼C
▲▲B
----------- = ▼pH
▲▲▲C
▼▼▼B
----------- = ▼▼▼pH
◄►C
+
◄►B
----------- = ▲▲pH
▼▼C
Chc. Resp. Acidosis
+
Ac. Met. Alkalosis
+
▲▲B
----------- = ▲▲pH
◄►C
►
+
Ac. Resp. Acidosis
►
▲▲▲B
----------- = ▲▲▲pH
◄►C
+
◄►B
----------- = ▼▼pH
▲▲C
►
Chc. Resp. Alkalosis
+
Ac. Met. Acidosis
►
+
▼▼B
pH▼▼----------- =
C ◄►
◄►B
----------- = ▼▼▼pH
▲▲▲C
.
Chc. Met. Alkalosis
◄►B
pH▲▲▲----------- =
C▼▼▼
by dr M Osama Hussein
►
?
▲▲▲B
----------- = ▲pH
▲▲C
?
▼▼B
pH▲----------- =
C ▼▼▼

10. CHRONIC DERANGEMENT
Chc. Met. Acidosis
Compensated
by
ACUTE
DERANGEMENT
+
Ac. Resp.
Alkalosis
►
RESULTANT
►
▼▼▼B
----------- = ▼pH
▼▼C
►
▲▲B
----------- = ▼pH
▲▲▲C
▲▲▲B
----------- = ▲pH
▲▲C
▼▼▼B
----------- = ▼▼▼pH
◄►C
+
◄►B
----------- = ▲▲pH
▼▼C
Chc. Resp. Acidosis
+
Ac. Met. Alkalosis
◄►B
----------- = ▼▼▼pH
▲▲▲C
+
▲▲B
----------- = ▲▲pH
◄►C
Chc. Met. Alkalosis
+
Ac. Resp. Acidosis
▲▲▲B
----------- = ▲▲▲pH
◄►C
+
◄►B
----------- = ▼▼pH
▲▲C
►
.
+
Ac. Met. Acidosis
►
+
▼▼B
pH▼▼----------- =
C ◄►
Chc. Resp. Alkalosis
◄►B
pH▲▲▲----------- =
C▼▼▼
by dr M Osama Hussein
►
?
▼▼B
pH▲----------- =
C ▼▼▼

11. CHRONIC DERANGEMENT
Chc. Met. Acidosis
Compensated
by
ACUTE
DERANGEMENT
+
Ac. Resp.
Alkalosis
▼▼▼B
----------- = ▼▼▼pH
◄►C
+
◄►B
----------- = ▲▲pH
▼▼C
Chc. Resp. Acidosis
+
+
▲▲B
----------- = ▲▲pH
◄►C
Chc. Met. Alkalosis
+
+
◄►B
----------- = ▼▼pH
▲▲C
Chc. Resp. Alkalosis
+
+
►
▲▲B
----------- = ▼pH
▲▲▲C
►
▲▲▲B
----------- = ▲pH
▲▲C
►
▼▼B
pH▲----------- =
C ▼▼▼
Ac. Met. Acidosis
▼▼B
pH▼▼----------- =
C ◄►
►
▼▼▼B
----------- = ▼pH
▼▼C
Ac. Resp. Acidosis
▲▲▲B
----------- = ▲▲▲pH
◄►C
RESULTANT
Ac. Met. Alkalosis
◄►B
----------- = ▼▼▼pH
▲▲▲C
►
◄►B
pH▲▲▲----------- =
C▼▼▼
,pH is mildly affected
(Both B & C are affected inby dr M Osama Hussein (following each other
the same direction,

12. MIXED DERANGEMENTS
Metabolic
Derangement
plus
Respiratory
Derangement
►
Resultant
Metabolic Acidosis
+
Respiratory
Acidosis
►
Mixed Acidosis
▼▼B
----------- = ▼▼pH
◄►C
+
◄►B
----------▲▲C
Metabolic Alkalosis
+
Respiratory
Alkalosis
+
◄►B
----------▼▼C
▲▲B
----------- = ▲▲pH
◄►C
= ▼▼pH ►
►
= ▲▲pH ►
▼▼B
▼
----------- = ▼ ▼ pH
▲▲ C
▼
Mixed Alkalosis
▲▲B
▲
----------- = ▲▲ pH
▼▼C
▲
,pH is markedly affected
Both B & C are affected, but in 2 different directions (away
(from each other
by dr M Osama Hussein

13. CORRECTION OF METABOLIC ACIDOSIS
pH < 7.2 (7.25(
Bicarb. < 15 meq/L
BE > -10 meq/L
Contraindicated when there is Hypercarbia
CO2 wash can br induced by increasing RR either on ventilator, or
applying few breaths by the Ambu bag.
by dr M Osama Hussein

14. Capillary blood gas (CBG) samples may be used
in place of samples from arterial punctures or
indwelling arterial catheters to estimate acid-base
balance (pH) and adequacy of ventilation
(PaCO2).
by dr M Osama Hussein

15. Capillary PO2 measurements are of little value in
estimating arterial oxygenation.
A puncture or small incision is made with a lancet
or similar device into the cutaneous layer of the
skin at a highly vascularized area (heel, finger,
toe).
by dr M Osama Hussein

16. The lancet may be used freehand or as part of a
device that limits puncture depth.
To accelerate blood flow and reduce the
difference between the arterial and venous gas
pressures, the area is warmed prior to the
puncture. As the blood flows freely from the
puncture site, the sample is collected in a
heparinized glass capillary tube.
by dr M Osama Hussein

17. ANION GAP
 The anion gap refers to the concentration
of unmeasured anions in blood. It
represents anions other than chloride and
bicarbonate that are required to electrically
balance cations, such as sodium.
Unmeasured anions include protein,
phosphate, sulfate, and organic acids.
by dr M Osama Hussein

18. ANION GAP
 Anion gap equation:
( [Na+]+[K+] ) - ( [Cl-]+[HCO3-] )
 The most commonly used formula to
measure the gap is
( [Na+] ) - ( [Cl-]+[HCO3-] )
by dr M Osama Hussein

19. ANION GAP

The anion gap is primarily used to classify metabolic
acidosis, which is caused by the retention of acid within
the body. Hydrogen ion reacts with bicarbonate to form
carbon dioxide, which is eliminated by the lungs. As
acidosis develops, bicarbonate levels decrease and are
replaced by the anionic component of the acid. In
inorganic acidosis, the anion is chloride and the anion
gap does not change. In organic acidosis, the anion gap
increases because bicarbonate decreases, chloride
remains constant, and the unmeasured anion (lactate,
ketone, phosphate) increases.
by dr M Osama Hussein

20. ANION GAP
 Metabolic acidosis can be divided into two
categories: normal anion gap and high
anion gap. High anion gap acidosis is
caused by acid retention, while normal
anion gap acidosis is usually due to loss of
bicarbonate.
by dr M Osama Hussein

21. ANION GAP

High Anion Gap
Ketoacidosis (diabetes, starvation, ethanol)
Lactic acidosis (circulatory or respiratory failure,
liver failure, tumors, oral hypoglycemics)
Renal failure (uremic acidosis)
Poisoning (salicylates, methanol, ethylene
glycol)
by dr M Osama Hussein

22. ANION GAP

Normal Anion Gap
Drugs (acetazolamide, carbonic
anhydrase inhibitor)
GI loss of bicarbonate (diarrhea)
Ureteroenterostomy (loss of bicarbonate from
chloride-bicarbonate exchange)
Renal tubular acidosis
Excess IV replacement with NaCl
by dr M Osama Hussein

23. pH
Bicarb.
PCO2
?B
----------?C
7.4
20
40
◄►B
----------C ◄►
pH?
Derangement
◄
NORMAL
pH
►
by dr M Osama Hussein
How you
Should feel?

24. pH
Bicarb.
PCO2
?B
----------?C
7.4
20
40
◄►B
7.25
▼ 10 ▼
◄
40 ►
----------C ◄►
▼▼B
----------C◄►
pH?
Derangement
◄
NORMAL
pH
►
PH
▼▼
by dr M Osama Hussein
Ac. Met. Acidosis
How you
Should feel?

25. pH
Bicarb.
PCO2
?B
----------?C
7.4
20
40
◄►B
7.25
▼ 10 ▼
◄
7.25
◄
20 ►
▲
----------C ◄►
40 ►
▼▼B
----------C◄►
60 ▲
◄►B
----------C▲▲
pH?
Derangement
◄
NORMAL
pH
►
PH
Ac. Met. Acidosis
PH
Ac. Resp. Acidosis
▼▼
▼▼
by dr M Osama Hussein
How you
Should feel?

26. pH
Bicarb.
PCO2
?B
----------?C
7.4
20
40
◄►B
7.25
▼ 10 ▼
◄
7.25
◄
20 ►
▲
7.55
▲
30 ▲
◄
----------C ◄►
40 ►
▼▼B
----------C◄►
60 ▲
◄►B
40 ►
pH?
Derangement
◄
NORMAL
pH
►
PH
Ac. Met. Acidosis
▼▼
----------C▲▲
▼▼
PH
Ac. Resp. Acidosis
▲▲B
----------C◄►
▲▲
Ac. Met. Alkalosis
pH
by dr M Osama Hussein
How you
Should feel?

27. pH
Bicarb.
PCO2
?B
----------?C
7.4
20
40
◄►B
7.25
▼ 10 ▼
◄
7.25
◄
20 ►
▲
7.55
▲
30 ▲
◄
7.55
◄
20 ►
▼
----------C ◄►
40 ►
▼▼B
----------C◄►
60 ▲
◄►B
40 ►
20 ▼
pH?
Derangement
◄
NORMAL
pH
►
PH
Ac. Met. Acidosis
▼▼
----------C▲▲
▼▼
PH
Ac. Resp. Acidosis
▲▲B
----------C◄►
▲▲
Ac. Met. Alkalosis
B
----------C▼▼
▲▲
Ac. Resp. Alkalosis
pH
pH
by dr M Osama Hussein
How you
Should feel?

28. pH
Bicarb.
PCO2
?B
----------?C
7.4
20
40
◄►B
7.3
10▼▼
30▼
----------C ◄►
▼▼B
----------C▼
pH?
Derangement
◄
NORMAL
pH
►
pH▼
by dr M Osama Hussein
Chr. Met. Acidosis
& Ac. Resp. Alkalosis
How you
Should feel?

29. pH
Bicarb.
PCO2
?B
----------?C
7.4
20
40
◄►B
----------C ◄►
pH?
Derangement
◄
NORMAL
pH
►
7.3
10▼▼
30▼
▼▼B
----------C▼
pH▼
Chr. Met. Acidosis
7.3
▲26
▲60▲
▲B
pH▼
Chr. Res. Acidosis
----------▲▲C
by dr M Osama Hussein
& Ac. Resp. Alkalosis
& Ac. Met. Alkalosis
How you
Should feel?

30. pH
Bicarb.
PCO2
?B
----------?C
7.4
20
40
◄►B
----------C ◄►
pH?
Derangement
◄
NORMAL
pH
►
7.3
10▼▼
30▼
▼▼B
----------C▼
pH▼
Chr. Met. Acidosis
7.3
▲26
▲60▲
▲B
----------▲▲C
pH▼
Chr. Res. Acidosis
7.5
▲30▲
▲50
▲▲B
▲
Chr. Met.Alkalosis
----------C▲
pH
by dr M Osama Hussein
& Ac. Resp. Alkalosis
& Ac. Met. Alkalosis
& Ac. Resp. Acidosis
How you
Should feel?

31. pH
Bicarb.
PCO2
?B
----------?C
7.4
20
40
◄►B
----------C ◄►
pH?
Derangement
◄
NORMAL
pH
►
7.3
10▼▼
30▼
▼▼B
----------C▼
pH▼
Chr. Met. Acidosis
7.3
▲26
▲60▲
▲B
pH▼
Chr. Res. Acidosis
7.5
▲30▲
▲50
▲
Chr. Met.Alkalosis
7.5
13▼
▼20▼
----------▲▲C
▲▲B
----------C▲
pH
▼B
▲
----------▼▼C
pH
by dr M Osama Hussein
& Ac. Resp. Alkalosis
& Ac. Met. Alkalosis
& Ac. Resp. Acidosis
Chr. Res. Alkalosis
& Ac. Met. Acidosis
How you
Should feel?

32. pH
Bicarb.
PCO2
?B
----------?C
7.4
20
40
◄►B
7.1
▼10▼
▲60▲
----------C ◄►
pH?
Derangement
◄
NORMAL
pH
►
▼▼B
▼▼
--------C▲▲
▼▼
pH
by dr M Osama Hussein
Mixed Acidosis
How you
Should feel?

33. pH
Bicarb.
PCO2
?B
----------?C
7.4
20
40
◄►B
7.1
7.6
▼10▼
▲30▲
▲60▲
▼20▼
----------C ◄►
pH?
Derangement
◄
NORMAL
pH
►
▼▼B
▼▼
--------C▲▲
▼▼
▲▲B
▲▲
--------C▼▼
▲▲
pH
pH
by dr M Osama Hussein
Mixed Acidosis
Mixed Alkalosis
How you
Should feel?

34. by dr M Osama Hussein