1 | Clinical Chemistry Prelim
CLINICAL CHEMISTRY PRELIMS • The order of preference as to the site of choice for
ABG determination in adults:
Chapter 3: Specimen Collection, Handling, 1. Radial artery
2. Brachial artery
and Processing
3. Femoral artery.
INTRODUCTION • In neonates:
- Scalp
• The most common sample analyzed in the clinical - Umbilical Artery Catheter
laboratory is serum (no anticoagulant) • Areas to avoid:
• It is processed from whole blood by allowing it to clot o irritated areas
for some time before centrifugation o edematous areas
• Other samples may be received such as arterial o areas near wounds
blood or plasma o areas with arterio-venous shunts or fistulas.
• In some instances, capillary blood may be the only
accessible sample from the patients particularly
• Allen Test
neonates.
• Test for collateral circulation.
• When using the radial artery, it is important to
SPECIMEN COLLECTION check for its collateral circulation first.
o This test consists of elevating the hand to
Arterial Puncture empty it of blood.
• Arterial blood is used for blood gas analysis (BGA) or
arterial blood gas (ABG) analysis because it has a
o The radial and ulnar arteries are then
more uniform composition than venous blood occluded.
• Venous blood is an inferior compared to arterial o The return of blood flow is observed with
blood because acid-base status taken from venous the ulnar artery as the hand is lowered.
samples reflects that of an extremity rather than that o It is important to do this to ensure that
of the body as a whole there is an available route for arterial
• However, venous blood may be adequate for pH blood in case the radial artery is occluded
determination but it gives incorrect values for arterial as a consequence of arterial puncture.
oxygen saturation and alveolar pCO2
• ABG ordinarily includes analysis of: • Arterial puncture is usually done by physicians.
o oxygen (pO2) and carbon dioxide (pCO2)
• Major complications of arterial puncture:
tension
o Thrombosis
o blood pH
o Hemorrhage
• ABG is critical in the assessment of oxygenation
o Possible infections
problems encountered in patients with
o Pneumonia
o Hematoma
o pulmonary embolism • Local anesthetic may be used but it is not
o chronic obstructive pulmonary disease. required.
• Do not use butterfly infusion set.
• It also benefits patients on prolonged oxygen
• Values obtained do not change whether one uses
therapy or mechanical ventilation and patients on
a 19-G or 26-G needle.
major surgery.
• For radial arterial puncture, 23 to 25-G needles
Procedure are preferred.
• In the collection of blood glass syringe is used. • For brachial arteries, use an 18 to 20-G needle.
• The anticoagulant of choice is heparin • The angle of the needle when hitting an artery is
• The preferred site is the radial artery. usually 45-60°.
• Use 90° when hitting the femoral artery.
• Blood fills the syringe by arterial pressure
Prepared by: Joshua S. Manong
, 2 | Clinical Chemistry Prelim
• Place blood in the water or 1-5 °C coolant to • The earlobe is either flicked with the index finger
minimize oxygen consumption by leukocytes. or is applied with Trafuril paste.
• After blood collection, compress the site with a • The arterialized blood is collected using
sterile gauze for a minimum of two minutes heparinized tubes.
(preferably 5 minutes). • Skin puncture is not acceptable for pCO2
determination in the first day of life due to poor
“Apply pressure immediately, don’t leave the vasoconstriction and poor perfusion of extremities.
patient while still bleeding” • The best method for blood gas collection in
newborns is still through the indwelling umbilical
Transcutaneous Monitoring artery catheter.
• Blood obtained by skin puncture is, in a strict
• For non-invasive and continuous measurement of sense, not a "capillary blood." It is a mixture of
blood from arterioles, venules and capillaries.
blood gases in newborn infants and adult intensive
Moreover, it contains interstitial and intracellular
care unit (ICU) patients.
fluids (tissue juices).
• Skin only • Arterialization of skin puncture:
o flicking the earlobes
Procedure: o application of Trafuril pastes
1. Skin is arterialized using electric heat. This o use of heat (e.g., use of paper towel
dilates the capillaries increasing capillary saturated with warm water, 39-40°C).
blood flow i.e., the blood becomes • Arterialized blood from the finger is only
arterialized. satisfactory for pH and pCO2 determinations. It is
2. The O2 and CO2 are allowed to diffuse not good for the measurement of pO2
through skin.
3. These blood gases are then measured
o Oxygen is measured by the Clark
electrode
Venipuncture
o Carbon dioxide is measured by the • Collection of venous blood may be done using:
Severinghaus electrode. o glass syringe (double movement technique)
o vacutainer lube (single movement technique).
Skin Puncture Order of Draw:
• Skin puncture in clinical chemistry is designed for
patients with
o Obesity
o Pediatrics
o Neonates/Infants
o Geriatrics
• Preferred sites in adults is the palmar surface of the
3rd or 4th finger
• Arterialized blood from these patients may also be
achieved using the earlobe.
o preferred site due to its vascularity
o low metabolic requirement
o ease of arterializations
• For Feraconates or infants, deep heel prick is used
• This is done at the distal edge of the calcaneal
protuberance.
Procedure
• First, pre-warm the site with warm water for 5 to
10 minutes.
Prepared by: Joshua S. Manong
CLINICAL CHEMISTRY PRELIMS • The order of preference as to the site of choice for
ABG determination in adults:
Chapter 3: Specimen Collection, Handling, 1. Radial artery
2. Brachial artery
and Processing
3. Femoral artery.
INTRODUCTION • In neonates:
- Scalp
• The most common sample analyzed in the clinical - Umbilical Artery Catheter
laboratory is serum (no anticoagulant) • Areas to avoid:
• It is processed from whole blood by allowing it to clot o irritated areas
for some time before centrifugation o edematous areas
• Other samples may be received such as arterial o areas near wounds
blood or plasma o areas with arterio-venous shunts or fistulas.
• In some instances, capillary blood may be the only
accessible sample from the patients particularly
• Allen Test
neonates.
• Test for collateral circulation.
• When using the radial artery, it is important to
SPECIMEN COLLECTION check for its collateral circulation first.
o This test consists of elevating the hand to
Arterial Puncture empty it of blood.
• Arterial blood is used for blood gas analysis (BGA) or
arterial blood gas (ABG) analysis because it has a
o The radial and ulnar arteries are then
more uniform composition than venous blood occluded.
• Venous blood is an inferior compared to arterial o The return of blood flow is observed with
blood because acid-base status taken from venous the ulnar artery as the hand is lowered.
samples reflects that of an extremity rather than that o It is important to do this to ensure that
of the body as a whole there is an available route for arterial
• However, venous blood may be adequate for pH blood in case the radial artery is occluded
determination but it gives incorrect values for arterial as a consequence of arterial puncture.
oxygen saturation and alveolar pCO2
• ABG ordinarily includes analysis of: • Arterial puncture is usually done by physicians.
o oxygen (pO2) and carbon dioxide (pCO2)
• Major complications of arterial puncture:
tension
o Thrombosis
o blood pH
o Hemorrhage
• ABG is critical in the assessment of oxygenation
o Possible infections
problems encountered in patients with
o Pneumonia
o Hematoma
o pulmonary embolism • Local anesthetic may be used but it is not
o chronic obstructive pulmonary disease. required.
• Do not use butterfly infusion set.
• It also benefits patients on prolonged oxygen
• Values obtained do not change whether one uses
therapy or mechanical ventilation and patients on
a 19-G or 26-G needle.
major surgery.
• For radial arterial puncture, 23 to 25-G needles
Procedure are preferred.
• In the collection of blood glass syringe is used. • For brachial arteries, use an 18 to 20-G needle.
• The anticoagulant of choice is heparin • The angle of the needle when hitting an artery is
• The preferred site is the radial artery. usually 45-60°.
• Use 90° when hitting the femoral artery.
• Blood fills the syringe by arterial pressure
Prepared by: Joshua S. Manong
, 2 | Clinical Chemistry Prelim
• Place blood in the water or 1-5 °C coolant to • The earlobe is either flicked with the index finger
minimize oxygen consumption by leukocytes. or is applied with Trafuril paste.
• After blood collection, compress the site with a • The arterialized blood is collected using
sterile gauze for a minimum of two minutes heparinized tubes.
(preferably 5 minutes). • Skin puncture is not acceptable for pCO2
determination in the first day of life due to poor
“Apply pressure immediately, don’t leave the vasoconstriction and poor perfusion of extremities.
patient while still bleeding” • The best method for blood gas collection in
newborns is still through the indwelling umbilical
Transcutaneous Monitoring artery catheter.
• Blood obtained by skin puncture is, in a strict
• For non-invasive and continuous measurement of sense, not a "capillary blood." It is a mixture of
blood from arterioles, venules and capillaries.
blood gases in newborn infants and adult intensive
Moreover, it contains interstitial and intracellular
care unit (ICU) patients.
fluids (tissue juices).
• Skin only • Arterialization of skin puncture:
o flicking the earlobes
Procedure: o application of Trafuril pastes
1. Skin is arterialized using electric heat. This o use of heat (e.g., use of paper towel
dilates the capillaries increasing capillary saturated with warm water, 39-40°C).
blood flow i.e., the blood becomes • Arterialized blood from the finger is only
arterialized. satisfactory for pH and pCO2 determinations. It is
2. The O2 and CO2 are allowed to diffuse not good for the measurement of pO2
through skin.
3. These blood gases are then measured
o Oxygen is measured by the Clark
electrode
Venipuncture
o Carbon dioxide is measured by the • Collection of venous blood may be done using:
Severinghaus electrode. o glass syringe (double movement technique)
o vacutainer lube (single movement technique).
Skin Puncture Order of Draw:
• Skin puncture in clinical chemistry is designed for
patients with
o Obesity
o Pediatrics
o Neonates/Infants
o Geriatrics
• Preferred sites in adults is the palmar surface of the
3rd or 4th finger
• Arterialized blood from these patients may also be
achieved using the earlobe.
o preferred site due to its vascularity
o low metabolic requirement
o ease of arterializations
• For Feraconates or infants, deep heel prick is used
• This is done at the distal edge of the calcaneal
protuberance.
Procedure
• First, pre-warm the site with warm water for 5 to
10 minutes.
Prepared by: Joshua S. Manong
