Outcome Goal:
Proper collection of arterial blood samples.
Arterial Blood Gas Test Definition
Blood is drawn anaerobically from a peripheral artery (Radial, Brachial, Ulnar, Femoral, Axillary, Posterior Tibial or Dorsalis Pedis) via a single percutaneous needle puncture, or from an indwelling arterial cannula or catheter for multiple sample.
Either method provides a blood specimen for direct measurement of:
• partial pressures of carbon dioxide (PaCO2);
• oxygen (PaO2);
• hydrogen ion activity (pH);
• total hemoglobin (Hbtotal);
• oxyhemoglobin saturation (HbO2);
• dyshemoglobins carboxyhemoglobin (COHb);
• methemoglobin (MetHb).
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.
• Respiratory Acidosis
• Anything which prevents the body from getting rid of excess CO2, increases acid which decreases pH
• Respiratory Alkalosis
• Anything which makes to body lose CO2, decreases acid, which increases pH
• Metabolic Alkalosis
• Anything which increases HCO3 increases base which increases pH
• Metabolic Acidosis
• Anything which decreases HCO3 decreases base which decreases pH
Apart from helping to establish a diagnosis, blood gases may also help to as certain the severity of a particular condition (e.g. metabolic acidosis in sepsis). This information can help to establish diagnosis, monitor severity, progression, and prognosis as well as guide therapy of:
• respiratory failure,
• cardiac failure,
• renal failure,
• hepatic failure,
• diabetic ketoacidosis,
• poisoning
• sepsis
Note:
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.
Basic Conditions Diagnosed by ABG's
• Respiratory Acidosis
• Anything which prevents the body from getting rid of excess CO2, increases acid which decreases pH
• Respiratory Alkalosis
• Anything which makes to body lose CO2, decreases acid, which increases pH
• Metabolic Alkalosis
• Anything which increases HCO3 increases base which increases pH
• Metabolic Acidosis
• Anything which decreases HCO3 decreases base which decreases pH
Apart from helping to establish a diagnosis, blood gases may also help to as certain the severity of a particular condition (e.g. metabolic acidosis in sepsis). This information can help to establish diagnosis, monitor severity, progression, and prognosis as well as guide therapy of:
• respiratory failure,
• cardiac failure,
• renal failure,
• hepatic failure,
• diabetic ketoacidosis,
• poisoning
• sepsis
