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About This Panel

The Arterial Blood Gas (ABG) is a critical diagnostic test that provides immediate information about a patient's acid-base balance, oxygenation, and ventilation status. Obtained via arterial puncture (typically radial artery), the ABG is essential for evaluating respiratory failure, metabolic derangements, and tissue perfusion in critically ill patients.

ABG analysis is fundamental in emergency medicine and critical care, guiding immediate interventions such as mechanical ventilation adjustments, oxygen therapy, and correction of acid-base disorders.

Clinical Applications

  • Respiratory Failure: Hypoxemia, hypercapnia assessment
  • Acid-Base Disorders: Metabolic/respiratory acidosis & alkalosis
  • Mechanical Ventilation: Guiding ventilator settings
  • Shock States: Lactate and base deficit evaluation
  • DKA: Acidosis severity monitoring
  • COPD Exacerbation: Acute vs chronic changes
  • Pulmonary Embolism: Hypoxemia detection
  • Sepsis/Septic Shock: Lactate monitoring
  • Poisoning/Overdose: Anion gap, osmolar gap

Acid-Base Balance

pH

Normal: 7.35-7.45

Measures hydrogen ion concentration and overall acid-base status. Critical for determining acidemia vs alkalemia and guiding emergency interventions.

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PaCO2

Normal: 35-45 mmHg

Reflects ventilation status and respiratory component of acid-base balance. Elevated in hypoventilation, decreased in hyperventilation.

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HCO3⁻ (Bicarbonate)

Normal: 22-28 mEq/L

Metabolic component of acid-base balance. Decreased in metabolic acidosis, increased in metabolic alkalosis or chronic respiratory acidosis.

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Base Excess/Deficit

Normal: -2 to +2 mEq/L

Calculated measure of metabolic acid-base status independent of respiratory compensation. Negative values indicate metabolic acidosis.

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Oxygenation & Ventilation

PaO2

Normal: 80-100 mmHg (room air)

Measures oxygen dissolved in arterial blood. Reflects adequacy of gas exchange and alveolar oxygenation. Critical for hypoxemia diagnosis.

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SaO2

Normal: 95-100%

Percentage of hemoglobin saturated with oxygen. Directly measured from ABG (more accurate than pulse oximetry). Reflects oxygen-carrying capacity.

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Tissue Perfusion & Metabolism

Lactate

Normal: 0.5-2.0 mEq/L

Marker of tissue hypoperfusion and anaerobic metabolism. Elevated in shock, sepsis, and hypoxia. Critical prognostic indicator in critically ill patients.

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