Blood gases

Blood gas and pH
analysis
Ghollam-Reza Moshtaghi-Kashanian
Pathological Biochemist
Associated Professor
Biochemistry Department
Medical School
Kerman University of Medical sciences

Errors of pre-analytical
phase

NCCLS – National Committee for Clinical
Laboratory Standards
“Collection of a blood specimen, as well as its handling
and transport, are key factors in the accuracy of clinical
laboratory analysis and ultimately in delivering quality
patient care”
”Arterial blood is one of the most sensitive of the
specimens sent to the clinical laboratory for analysis”
”Blood gas and pH analysis has more immediacy on
patient care than any other laboratory determination”
”In blood gas and pH analysis an incorrect result can
often be worse for the patient than no result at all”

What is so special about blood
gases
• NOT like other blood samples
• STAT parameters
– Short Turn Around Time
– Must be analyzed within a short time
– pO 2 , pCO
2 , pH, LAC, GLU
• Valuable results right now
– Not in one hour
• Sample composition changes
• Patient status changes

The Patient Focus Circle
• The preanalytical phase
– Decision
– Order request
– Sample collection
– Transport and storage
• The analytical phase
– Analysis
– Verification of analyzer
performance
• The post-analytical phase
– Interpretation of data
– Data management
– Reporting
– Treatment of patient

“The weak link”
• Blood gas analyzers of today are
highly accurate
• Make sure that sample
represents patient status
• The pre-analytical phase is the
weak link in the Patient Focus
Circle
• Many potential errors
• Can be overcome by
–Training
–User guidelines
–Sampling products

Implications of errors
• Errors made in the
period prior to the
analysis of the
sample ...
• may influence
the quality of the
final measured
results ...
• and compromise
the diagnosis and
treatment of the
patient

Steps of the pre-analytical phase
Preparation prior to sampling
Sampling/handling
Storage/transport
Preparation prior to analysis

Potential pre-analytical errors
1: Preparation prior to sampling
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
– - dilution due to the use of liquid heparin
– - insufficient amount of heparin
– - binding of electrolytes to heparin
• Inadequate stabilization of the respiratory
condition of the patient
• Inadequate removal of flush solution in a-lines a
prior to blood collection

Potential pre-analytical errors
2: Sampling/handling
• Mixture of venous and arterial blood during
puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin

Potential pre-analytical errors
3: Storage/transport
• Incorrect storage
• Hemolysis of blood cells

Potential pre-analytical errors
4: Preparation prior to sample transfer
• Visually inspect the sample for clots
• Inadequate mixing of sample before
analysis
• Failure to identify the sample upon analysis

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Patient ID
• Essential that the sample is
labeled prior to sampling or
immediately after sampling
– Avoid mix-up of samples
– Avoid missing samples
– Avoid poor-data
– Avoid missing billing
opportunities

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Why is there no alternative to heparin
when measuring blood gases
Other anticoagulants, e.g. citrate and
EDTA are both slightly acidic.
There is a risk of pH being falsely lowered
by this effect.
Anticoagulation
• Modern blood gas syringes and
capillary tubes are coated with
heparin to prevent coagulation
in the sampler and inside the
blood gas analyzer
• The different types of heparin
are:
–Liquid non-balanced heparin
–Dry non-balanced heparin
–Dry electrolyte-balanced
heparin (Na + , K + , Ca 2+ )
–Dry Ca 2+ -balanced heparin

Liquid heparin - dilution
• Use of liquid
heparin as the
anticoagulant
causes a dilution of
the sample
• This may affect the
measured values
significantly

Dilution
• When liquid heparin is added
to a blood sample, it only
mixes with, i.e. dilutes, the
plasma and not the contents of
the blood cells
• Consequently
–Plasma components are
biased
–Oximetry
parameters given
as fractions are not biased

Dilution – whole-blood
parameters
• Parameters that are present
in the whole blood sample,
such as CO 2 will be diluted
as described below:
• 0.05 mL of liquid heparin is
mixed with a blood sample
of 1.0 mL (Hct
45 %)
• The sample is diluted from
1.0 to 1.05 mL, , i.e. 5 %

Dilution - Plasma Electrolytes
• The ion-selective
electrodes of blood gas
analyzers measure plasma
electrolytes
• 0.05 mL heparin mixed
with 0.55 mL plasma
• The plasma phase is
diluted from 0.55 mL to
0.60 mL, , i.e. ~ 10 %

Dilution effect depends on
parameters
• Plasma electrolyte values will decrease
linearly with the dilution of the plasma
• pCO
2, cGlucose
and ctHb
values will decrease
linearly with the dilution of the entire sample

Dilution effect depends on
parameters
• pH and pO 2 values are relatively unaffected
by dilution
– pH: the ratio between CO 2 and bicarbonate is
relatively unaffected by dilution (both decrease
linearly with the dilution of the entire sample
– pO 2 : only 2 % of the O 2 is physically dissolved
in the plasma
• Oximetry parameters given in fractions (or
%) will be unaffected

Dilution errors - in theory
• If operators left exactly
the same amount of
liquid heparin and drew
exactly the same
sample volume every
time, dilution errors
would be systematic
errors that could be
corrected for

Dilution errors - in practice
• The dilution percentage in samples
varies
–Operators do not leave exactly the
same amount of heparin every time
–Operators do not draw exactly the
same sample volume every time

Dilution errors - in practice
• Consequently, dilution
errors are not systematic and
thus impossible to correct
• Under such circumstances it
may be clinically misleading
to compare sequential
samples from the same
patient

Amount of heparin
• Syringes for blood gas analysis can have a
wide range of heparin amounts
• The units are typically given as IU/mL
blood,
i.e. international units of heparin per mL
blood drawn into the syringe
• In order to obtain a sufficient final
concentration of heparin in the sample, you
must draw the blood volume recommended
by the syringe vendor

Amount of heparin, an example
75 IU/1 mL 75 IU/1.5 mL 75 IU/2 mL
YES Is because it a problem high to concentrations have a higher of nonbalanced
heparin concentration heparin can cause than falsely aimed low
electrolyte for results
• A syringe is stated to contain 50 IU/mL
when filled with 1.5 mL blood
• This means that the syringe contains a
total of 75 IU dry heparin. The vendor
recommends filling the syringe with a
sample volume of 1.5 mL
• If the user draws 2 mL, , the resulting
heparin concentration will be too low and
the sample may coagulate
• If the user draws only 1 mL, , the resulting
heparin concentration will be higher than
aimed for

Heparin-binding of electrolytes
• Heparin binds positive ions such
as Ca 2+ , K + and Na +
• Electrolytes bound to heparin
will not be measured by ion-
selective electrodes
• The final effect will be falsely
low measured values
• The binding effect and the
resulting inaccuracy of results are
especially significant for cCa
2+

Binding of Ca 2+ - an example
True value
1.15 mmol/L
Measured
value 1.08
mmol/L
• The sample in question has a
true cCa
2+ value of 1.15
mmol/L
• When using 50 I.U. of
uncompensated dry heparin per
mL plasma a value of 1.08
mmol/L is measured
• The decrease of 0.07 mmol/L
corresponds to 50 % of the
reference range for cCa
2+ (1.15
- 1.29 mmol/L)

Electrolyte-balanced heparin
• Electrolyte balanced heparin
significantly reduces the
binding effect and the
resulting inaccuracy

Electrolyte-balanced heparin
• Electrolytes are added to the heparin during
manufacturing, so that the activity of the
electrolytes in the heparin is the same as in normal
plasma
• No bias for values in the
normal ranges
– Samples with low or high concentrations will
be affected by a small positive or negative bias

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Stabilization of the respiratory
condition
• To get a true picture of
the patient’s s respiratory
condition the patient
should ideally be in a
steady state of ventilation

Stabilization of the respiratory
condition
– Patients should be at rest for 5 min
– Ventilator settings should be
unchanged for 20 min
• Pain and anxiety from arterial
puncture may influence the
steady state of respiration
and should thus be minimized

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Inadequate removal of flush solution
• Flush solutions used
in a-lines a
must be
removed completely
from the system to
avoid a dilution of the
blood sample

Inadequate removal of flush solution
• It is recommended
to withdraw a
volume equal to
three to six times
the “dead space”
of the catheter
system (NCCLS)

Inadequate removal of flush solutions
– an example
•Sample B and A are both a-line a
samples taken from the same
patient immediately after each other
•Before taking sample B only 1 mL of saline solution was
removed - the tubing, however, looked red
•Before taking sample A saline solution was removed as
recommended
Sample A
ctHb 6.2 mmol/L
cGlu 9.6 mmol/L
cK + 3.8 mmol/L
cNa + 130 mmol/L
cCa 2+ 1.00 mmol/L
cCl - 101 mmol/L
pH 7.271
pCO 2 50.5 mmHg / 6.7 kPa
pO 2 116.7 mmHg / 15.56 kPa
Sample B
ctHb 4.6 mmol/L
cGlu 6.9 mmol/L
cK + 2.5 mmol/L
cNa + 137 mmol/L
cCa 2+ 0.61 mmol/L
cCl - 113 mmol/L
pH 7.275
pCO 2 35.9 mmHg / 4.8 kPa
pO 2 129.3 mmHg / 17.2 kPa

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Mixture of venous and arterial blood
Artery
Vein
40 mmHg / 5.3 kPa
100 mmHg / 13.3 kPa
• When puncturing an artery it is
important not accidentally to
get the arterial blood mixed
with venous blood
• This may, for instance, occur, if
you hit a vein before locating
the artery
• Even an admixture of a small
amount of venous blood may
significantly bias the results
• This is especially true of pO 2
and sO 2 , but other parameters
may also be affected

Mixture of venous and arterial
blood
Vein:
Pressure rarely
> 10 mmHg
Artery:
Systolic blood
pressure normally
> 100 mmHg
• In arteries the blood pressure
is high enough to fill a self-
filling syringe
• If a self-filling filling syringe does
not fill it may be because a
vein has been hit
• In that case a new sample
should be taken

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Air bubbles
• Any air bubbles in the
sample must be expelled
as soon as possible after
the sample has been
drawn
–before
mixing the sample
with heparin
–before
any cooling of the
sample

Air bubbles
• Even small air bubbles
may seriously affect the
pO 2 value of the sample,
normally resulting in
increased values
• An air bubble whose
relative volume is 0.5 to
1.0 % of the blood in the
syringe is a potential
source of a significant
error

The effect of air bubbles depends on
Effect on pO 2
Surface area of air bubble
Increased
effect of air
• Size of bubble
• Number of bubbles
• Initial oxygen status
of sample
• Longer time
• Lower temperature
• Increased agitation

Effect of air bubbles - an
example
• Sample A and B were taken from the same patient
immediately after each other
• Sample A without air bubbles was analyzed immediately after
collection
• 100 µL L air was added to sample B (1 mL). It was stored cold
(0-4 °C) for 30 minutes and mixed for 3 minutes before
sample analysis
pO 2
Sample A
71.0 mmHg / 9.5 kPa
Sample B
pO 2
88.3 mmHg / 11.8 kPa
(air bubble pO 2
150 mmHg / 20 kPa)

Effect of air bubbles - an
example
• Sample A and B were taken from the same patient immediately
after each other
• Sample A without air bubbles was analyzed immediately after
collection
• 100 µL L air was added to sample B (1 mL). It was stored cold (0-4
°C) for 30 minutes and mixed for 3 minutes before sample
analysis
pO 2
Sample A
288.6 mmHg / 38.5 kPa
pO 2
Sample B
253.3 mmHg / 33.8 kPa

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Insufficient mixing with heparin
• Insufficient mixing can
cause coagulation of the
sample
• It is recommended to mix
the blood sample
thoroughly with heparin
• Invert the syringe 10 times
and roll it between your
palms

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Storage recommendations
General storage recommendation
Do not cool the sample
Analyze within 30 minutes
For samples with high pO 2
Analyze within 5 minutes
For special studies, e.g. shunt
Analyze within 5 minutes
For samples with high leukocyte or platelet count
Analyze within 5 minutes
Expected delayed analysis
When analysis is expected to be delayed for more than 30
minutes, the use of glass syringes and storage in ice slurry is
recommended

Storage recommendations
• Storage and transport time should be kept at a
minimum
–Volatile nature of gases
–Continued metabolism in blood
• For parameter panels including GLU/LAC, be
aware that 30 minutes storage might lead to biased
results
• It is recommended by the NCCLS to avoid cooling
of samples when kept in plastic

Continued cellular metabolism in
sample
pO 2 since oxygen will still be
consumed
pCO
2 since carbon dioxide
will still be produced
pH
primarily due to the change
in pCO
2 and glycolysis

Continued cellular metabolism in
sample
cCa
2+ since the change in pH
will influence the binding of Ca 2+
to protein
cGlu
since glucose will be
metabolized
cLac
due to glycolysis

Slowing down the metabolism
pO 2
Time
0-4º C
25º C
• Blood gas samples in glass
samplers can be cooled
• Storing the sample at a lower
temperature (0-4 °C) will slow
down the metabolism by at
least a factor of 10 [NCCLS]
• Cool samples in an ice
slurry or other suitable coolant
• Never store the samples
directly on ice as this causes
hemolysis of the blood cells

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Hemolysis of blood cells
• The blood cells are
relatively fragile,
and therefore
hemolysis may
easily occur during
blood sampling

Hemolysis of blood cells
• Hemolysis may, for instance, occur due to
– high filling pressure through a narrow entrance (e.g.
during
too vigorous sample aspiration, sample transfer to the
analyzer,
etc.)
– vigorous rubbing or squeezing of the skin during
capillary
sampling
– too vigorous mixing of the sample
– cooling down the sample below 0 °C

Hemolysis
cCa 2+ (c)= 1 µmol/L
cK + (c) = 150 mmol/L
cCa 2+ (P) = 1.2 mmol/L
cK + (P) = 4 mmol/L
• Hemolysis may lead to
significantly increased
plasma cK + values due to
the large difference in the
K + concentration inside
and outside the blood
• Extensive hemolysis may
also result in a significant
fall in cCa
2+

Hemolysis - an example
• Sample A and B were taken from the same patient immediately
after each other
• Sample A was analyzed immediately after collection
• Sample B was stored on ice for 25 minutes and mixed
for 5 minutes before sample analysis
Sample A
cK + 3.3 mmol/L
cCa 2+ 1.08 mmol/L
Sample B
cK + 43.6 mmol/L
cCa 2+ 0.33 mmol/L
• Extensive hemolysis as the above will often be detected
• A smaller degree of hemolysis and the resulting inaccuracy
may often not be detected

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Visually inspect the sample
• Before analyzing the
sample, make a visual
check of the blood
• Inspect for air bubbles
• You may expel a few
drops of blood from
the syringe to inspect
for clots

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Inadequate mixing of sample
before analysis
• How fast does a
whole-blood sample
sediment
– Within 30 minutes
– Within 10 minutes

Inadequate mixing of sample before
analysis
• There is no universal
answer
• Sedimentation time is
individual and depends on
age and immunological
condition
• A fully sedimented sample
is easy to detect, but can
you spot a sample that is
only 5 % sedimented

Inadequate mixing of sample
before analysis
• If the sample is visibly
sedimented, , it needs
mixing for several
minutes. Follow the
mixing procedures of
your unit.

Inadequate mixing of sample before
analysis
• The cell stacks are
most effectively
disturbed when the
syringe is rotated
through two axes,
i.e.
– Rolling it between
the hands AND
– Inverting it
vertically

Inadequate mixing - an example
• Sample A and B were taken from the same patient immediately
after each other and stored cold for 10 minutes
• Sample A was mixed in a rotator (14 revolutions/min) for 3
minutes
• Sample B was mixed in a rotator (14 revolutions/min) for 1
minute
Sample A
ctHb 6.2 mmol/L
ctHb
Sample B
4.5 mmol/L

Potential pre-analytical errors
Preparation
prior
to sampling
Sampling/handling
Storage/transport
Preparation prior to
sample transfer
• Missing or wrong patient/sample identification
• Use of the wrong type or amount of anticoagulant
- dilution due to the use of liquid heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the respiratory condition of
the patient
• Inadequate removal of flush solution in a-lines prior to
blood collection
• Mixture of venous and arterial blood during puncturing
• Air bubbles in the sample
• Insufficient mixing with heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample for clots
• Inadequate mixing of sample before analysis
• Failure to identify the sample upon analysis

Failure to identify sample before
analysis
• Essential that the sample is labeled with ID
• For documentation purposes, the ID must be
entered during sample analysis
– Avoid mix-up of samples
– Avoid missing samples
– Avoid poor-data
– Avoid missing billing opportunities

Some points to keep in mind
Preparation prior
to sampling
• Label the sampler with patient ID
• Use dry electrolyte balanced heparin
• Endeavor to keep the patient’s respiratory condition
stable for a certain period prior to sampling
Sampling/handling
• Be careful not accidentally to get the arterial blood
mixed with venous blood during puncturing
• Expel any air bubbles immediately after sampling
• Mix the sample thoroughly with heparin immediately
after sampling
Storage/transport
• Analyze the sample immediately
• If storage is unavoidable, store the sample at room
temperature for max. 30 min. Samples with expected
high pO 2
values should be analyzed immediately.
Preparation prior to
sample transfer
• Before transferring the sample into the analyzer mix
thoroughly
• Visually inspect the sample for clots and air bubbles
• Enter patient ID in analyzer logs

Some points to keep in mind
- sampling from A-linesA
Preparation prior
to sampling
• Label the sampler with patient ID
• Use dry electrolyte balanced heparin
• Endeavor to keep the patient’s respiratory condition
stable for a certain period prior to sampling
• Make sure that the a-line has been adequately
cleared of flush solution
Sampling/handling
• Aspirate the sample slowly to prevent degassing and
Hemolysis
• Expel any air bubbles immediately after sampling
• Mix the sample thoroughly with heparin after sampling
Storage/transport
• Analyze sample immediately
• If storage is unavoidable, store the sample at room
temperature for max. 30 min. Samples with expected
high pO 2
values should be analyzed within 5 min.
Preparation prior to
sample transfer
• Before transferring the sample into the analyzer mix
thoroughly
• Visually inspect the sample for clots and air bubbles
• Enter patient ID in analyzer logs

Death
Death
6.8 6.9 7.0 7.1 7.2
7.3 7.4 7.5 7.6 7.7 7.8
Acidic pH Normal pH Alkali pH
Bicarbonate
Bicarbonate
Bicarbonate
2
pCO
2 pCO 2
2
pCO 2
pCO 2
pCO 2
pCO 2
Low Normal High Low Normal High Low Normal High
pCO pCO pCO
2
L
L N H
L
L H
H
N
L N H H L H
Metabolic alkalosis with sign of compensation
Mixed metabolic and respiratory alkalosis
Metabolic alkalosis without sign of compensation
Respiratory alkalosis without renal compensation
Error of analyzer, wrong report
Respiratory alkalosis with renal compensation
Primary respiratory acidosis with chronic compensation
Primary metabolic alkalosis with chronic compensation
Acidosis or alkalosis that have been fully compensated
Normal acid base (no acid base disorder)
Primary respiratory alkalosis with chronic compensation
Primary metabolic acidosis with chronic compensation
Acidosis or alkalosis that have been fully compensated
Respiratory acidosis with renal compensation
Error of analyzer, wrong report
Respiratory acidosis without sign of compensation
Mixed metabolic and respiratory acidosis
Metabolic acidosis without respiratory compensation
Metabolic acidosis with respiratory compensation