Acid Base Calculator

The Acid Base Calculator is a medical tool that helps interpret arterial blood gas (ABG) values and calculate the anion gap. It’s essential for assessing a patient’s acid-base balance and diagnosing various metabolic or respiratory disorders.

What is Acid-Base Balance?

Acid-base balance is a crucial physiological process where the body maintains blood pH within a narrow range (7.35-7.45). This balance is primarily maintained by:

• The lungs (respiratory system)
• The kidneys (metabolic system)

Understanding Blood Gas Values

Normal ranges for arterial blood gas components:

• pH: 7.35-7.45
• PaCO2 (Partial pressure of CO2): 35-45 mmHg
• HCO3- (Bicarbonate): 22-26 mEq/L
• Anion Gap: 8-16 mEq/L

Common Acid-Base Disorders

Acidosis (pH < 7.35)

1. Respiratory Acidosis

   • Caused by decreased ventilation
   • High PaCO2
   • Common in COPD, severe asthma

2. Metabolic Acidosis

   • Caused by bicarbonate loss or acid accumulation
   • Low HCO3-
   • Common in diabetic ketoacidosis, kidney failure

Alkalosis (pH > 7.45)

1. Respiratory Alkalosis

   • Caused by hyperventilation
   • Low PaCO2
   • Common in anxiety, high altitude

2. Metabolic Alkalosis

   • Caused by excess bicarbonate or acid loss
   • High HCO3-
   • Common in vomiting, diuretic use

Understanding Anion Gap

The anion gap is calculated as:

Anion Gap = Na+ - (Cl- + HCO3-)

Where:

• Na+ = Sodium
• Cl- = Chloride
• HCO3- = Bicarbonate

The anion gap should be corrected for albumin using:

Corrected AG = AG + 2.5 × (4.4 - albumin)

Clinical Applications

This calculator is useful for:

• Emergency medicine
• Critical care
• Internal medicine
• Pulmonology
• Nephrology

Limitations

Remember that:

• This calculator is for educational purposes
• Results should be interpreted by healthcare professionals
• Clinical context is essential for proper interpretation
• Multiple measurements may be needed for accurate assessment

References

1. Berend K, de Vries AP, Gans RO. Physiological approach to assessment of acid-base disturbances. N Engl J Med. 2014.
2. Kraut JA, Madias NE. Serum anion gap: its uses and limitations in clinical medicine. Clin J Am Soc Nephrol. 2007.