ABGs (Arterial Blood Gases)

Definition

Arterial Blood Gases (ABGs) are a diagnostic laboratory test that measures oxygen (PaO2), carbon dioxide (PaCO2), bicarbonate (HCO3-), pH, and oxygen saturation (SaO2) in arterial blood. The test provides critical information about a patient's acid-base balance, ventilation, and oxygenation status.

Normal Values

• pH: 7.35 to 7.45
• PaCO2: 35 to 45 mmHg
• HCO3-: 22 to 26 mEq/L
• PaO2: 80 to 100 mmHg
• SaO2: 95 to 100%

Clinical Significance

ABGs are used to diagnose and monitor respiratory and metabolic disorders, including respiratory acidosis (COPD, hypoventilation), respiratory alkalosis (hyperventilation, anxiety), metabolic acidosis (DKA, renal failure, diarrhea), and metabolic alkalosis (vomiting, excessive antacids). Interpreting an ABG uses the ROME method: Respiratory Opposite, Metabolic Equal.

Nursing Considerations

After arterial puncture, apply firm pressure for at least 5 minutes (10 minutes if the patient is on anticoagulants) to prevent hematoma. Perform the Allen test prior to radial artery puncture to verify collateral circulation. Transport the sample on ice if not analyzed within 10 minutes.

NCLEX Relevance

ABG interpretation is a high-yield topic for physiological adaptation questions. Expect NGN case studies requiring identification of acid-base imbalances and prioritization of interventions such as oxygen therapy or bicarbonate administration.