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Clinical Practice Guidelines/ABG sampling |
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Written by Ramaz Mitaishvili
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Wednesday, 09 May 2007 |
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Page 1 of 4  Alternative names: Arterial Blood Gas Analysis; ABG Sampling; Arterial Blood Gas Test Definition Blood is drawn anaerobically from a peripheral artery (radial, brachial, femoral, or dorsalis pedis) via a single percutaneous needle puncture, or from an indwelling arterial cannula or catheter for multiple samples. Either method provides a blood specimen for direct measurement of partial pressures of carbon dioxide (PaCO2) and oxygen (PaO2), hydrogen ion activity (pH), total hemoglobin (Hbtotal), oxyhemoglobin saturation (HbO2), and the dyshemoglobins carboxyhemoglobin (COHb) and methemoglobin (MetHb).
Outcome Goal Proper collection of arterial blood samples.
Purpose and indications
The purpose of arterial blood gas sampling is to assess patients
respiratory status as well as acid base balance or for laboratory
testing when venous blood is unavailable, and is frequently requested
for seriously ill patients. So, an arterial blood gas (ABG) will
help in the assessment of oxygenation, ventilation, and acid-base
homeostasis. It can also aid in the determination of
poisonings (carboxyhemaglobinemia or methemaoglobinemia)
and in the measurement of lactate concentration. Arterial puncture
is a relatively straight forward technique that is easily performed at
the bedside. Pulse oximetry will give a reasonable estimate of the
adequacy of oxygenation in many circumstances but does not assess
acid-base status or ventilation and should not be used alone in cases
where these measurements are important. Apart from helping to
establish a diagnosis, blood gases may also help to ascertain the
severity of a particular condition (e.g. metabolic acidosis in
sepsis). This information can help to establish diagnosis, monitor
severity, progression, prognosis as well as guide therapy of:
• respiratory failure,
• cardiac failure,
• renal failure,
• hepatic failure,
• diabetic ketoacidosis,
• poisoning
• sepsis
Normal Values in an ABG report
Values at sea level:
• Partial pressure of oxygen (PaO2) - 75 - 100 mm Hg
• Partial pressure of carbon dioxide (PaCO2) - 35 - 45 mm Hg
• A pH of 7.35 - 7.45
• Oxygen saturation (SaO2) - 94 - 100%
• Bicarbonate - (HCO3) - 22 - 26 mEq/liter
NOTE: mEq/liter = milliequivalents per liter; mm Hg = millimeters of mercury
At altitudes of 3,000 feet and above, the values for oxygen are lower. The
arterial pO2 reduces with age. A rough guideline is that above the age of 40
years, paO2 = 105-age in years/2.
Contraindications
Contraindications are absolute unless specified otherwise.
• Cellulitis or other infections over the radial artery
• Absence of palpable radial artery pulse
• Negative results of an Allen test (collateral circulation test),
indicating that only one artery supplies the hand and suggest to
select another extremity as the site for arterial puncture
• Coagulation defects (relative)
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Last Updated ( Thursday, 21 June 2007 )
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Alternative names: Arterial Blood Gas Analysis; ABG Sampling; Arterial Blood Gas Test Definition Blood is drawn anaerobically from a peripheral artery (radial, brachial, femoral, or dorsalis pedis) via a single percutaneous needle puncture, or from an indwelling arterial cannula or catheter for multiple samples. Either method provides a blood specimen for direct measurement of partial pressures of carbon dioxide (PaCO2) and oxygen (PaO2), hydrogen ion activity (pH), total hemoglobin (Hbtotal), oxyhemoglobin saturation (HbO2), and the dyshemoglobins carboxyhemoglobin (COHb) and methemoglobin (MetHb).
