Normal Bicarbonate Range in Arterial Blood Gas
The normal range for bicarbonate (HCO3-) in arterial blood gas analysis is 22-26 mmol/L, which represents the standard reference range used for clinical decision-making in acid-base disorders. 1, 2
Standard Reference Values
- Bicarbonate levels between 22-26 mmol/L are considered normal for most patients and should be the target range for therapeutic interventions 1
- Values below 22 mmol/L indicate metabolic acidosis and warrant investigation and potential treatment 1, 2
- Values above 26 mmol/L suggest metabolic alkalosis or chronic respiratory acidosis with metabolic compensation 1
Clinical Thresholds for Specific Conditions
Screening Thresholds
- A serum bicarbonate >27 mmol/L serves as a critical screening threshold that should prompt arterial blood gas measurement to confirm hypercapnia, particularly in obese patients being evaluated for Obesity Hypoventilation Syndrome 3, 1
- A bicarbonate <27 mmol/L has a 99% negative predictive value for ruling out conditions like OHS, potentially eliminating the need for arterial blood sampling in low-risk patients 1
Chronic Kidney Disease Management
- Serum bicarbonate should be maintained at or above 22 mmol/L in patients with chronic kidney disease or on maintenance dialysis to prevent complications of metabolic acidosis 1, 2
- Monthly monitoring of bicarbonate levels is recommended for dialysis patients 2
Important Technical Considerations
Measurement Differences
- Serum bicarbonate on a Basic Metabolic Panel actually measures total CO2 content, which includes bicarbonate (approximately 96% of total), dissolved CO2, and other minor carbon dioxide components 1, 4
- ABG bicarbonate is calculated from pH and pCO2 values, not directly measured 5
- Strong correlation exists between serum and ABG bicarbonate values (correlation coefficient 0.842-0.857) 6, 7
Common Pitfalls to Avoid
- Sequential rather than simultaneous sampling can lead to significant discrepancies, especially in unstable patients—always verify timing of sample collection 1, 2
- Some ABG analyzers have a maximum display limit (typically 60 mmol/L), and values above this may not be displayed 5
- Extremely high bicarbonate values (>60 mmol/L) can occur in patients with chronic respiratory disease treated with furosemide or dexamethasone due to bicarbonate retention 5
Therapeutic Decision Points
- Bicarbonate therapy should be reserved for severe acidosis with arterial pH <7.1 and base deficit <-10, or special circumstances such as hyperkalemia or tricyclic antidepressant overdose 1, 2
- The best method of reversing acidosis in cardiac arrest is restoring spontaneous circulation rather than administering buffers 1
- Potential adverse effects of sodium bicarbonate administration include alkalemia, hyperosmolarity, and increased carbon dioxide production 1, 2