Acid Base Calculator
Interpret arterial blood gas values and calculate anion gap for acid-base analysis
Acid-Base Analysis Calculator
FOR HEALTHCARE PROFESSIONALS ONLY
Acid-base disorders can be life-threatening. This tool aids interpretation but cannot replace clinical judgment and immediate medical intervention.
Arterial Blood Gas (ABG) Values
Normal: 7.35-7.45
Normal: 35-45 mmHg
Normal: 22-26 mEq/L
Anion Gap Calculation
Normal: 135-145 mEq/L
Normal: 95-105 mEq/L
Normal: 3.5-5.0 g/dL
Clinical Example
Case: COPD Patient with Shortness of Breath
Patient: 86-year-old male with severe COPD
Presentation: Fatigue and shortness of breath
ABG Results: pH 7.10, pCO₂ 56 mmHg, HCO₃⁻ 24 mEq/L
Electrolytes: Na⁺ 140, Cl⁻ 108, Albumin 3.3 g/dL
Interpretation
Primary Disorder: Severe respiratory acidosis
Compensation: No metabolic compensation (HCO₃⁻ normal)
Anion Gap: 8 mEq/L (normal)
Clinical Action: Improve ventilation, consider BiPAP or intubation
Normal ABG Values
Primary Disorders
Metabolic Acidosis
↓ HCO₃⁻, ↓ pH
DKA, lactic acidosis, uremia
Metabolic Alkalosis
↑ HCO₃⁻, ↑ pH
Vomiting, diuretics, hyperaldosteronism
Respiratory Acidosis
↑ pCO₂, ↓ pH
COPD, respiratory failure
Respiratory Alkalosis
↓ pCO₂, ↑ pH
Hyperventilation, anxiety
Compensation Rules
Winter's Formula
Expected pCO₂ = 1.5 × (HCO₃⁻) + 8 (±2)
Metabolic Alkalosis
Expected pCO₂ = 0.7 × (HCO₃⁻) + 21 (±2)
Respiratory Disorders
HCO₃⁻ changes 1-4 mEq/L per 10 mmHg pCO₂
Understanding Acid-Base Balance
Acid-Base Physiology
The body maintains acid-base balance through three systems: chemical buffers, respiratory system (controlling CO₂), and renal system (controlling HCO₃⁻). When one system fails, the others compensate to maintain pH homeostasis.
Henderson-Hasselbalch Equation
pH = 6.1 + log([HCO₃⁻] / (0.03 × pCO₂))
- •pH depends on the ratio of HCO₃⁻ to CO₂
- •Normal ratio is 20:1 (HCO₃⁻:CO₂)
Anion Gap Significance
The anion gap represents unmeasured anions in serum. An elevated anion gap suggests the presence of organic acids (ketoacids, lactate) or ingested toxins, helping differentiate causes of metabolic acidosis.
Clinical Applications
- •Rapid diagnosis of acid-base disorders
- •Assessment of respiratory/metabolic compensation
- •Detection of mixed acid-base disorders
- •Monitoring treatment effectiveness
Systematic ABG Interpretation
Step 1: pH
Determine if acidemia (<7.35), alkalemia (>7.45), or normal
Step 2: Primary
Identify if metabolic (HCO₃⁻) or respiratory (pCO₂) cause
Step 3: Compensation
Check if appropriate compensation is present
Step 4: Anion Gap
Calculate gap to determine cause of acidosis
⚠️ CRITICAL CLINICAL DISCLAIMER
FOR HEALTHCARE PROFESSIONALS ONLY. This acid-base calculator is designed for educational purposes and clinical decision support. It cannot replace comprehensive clinical assessment, laboratory correlation, and medical expertise.
EMERGENCY SITUATIONS: Severe acid-base disorders (pH <7.20 or >7.60) represent medical emergencies requiring immediate intervention. Always correlate with clinical presentation and repeat laboratory values.
Healthcare providers must independently verify all calculations and consider patient-specific factors, comorbidities, and clinical context. Complex mixed disorders may not be fully characterized by automated interpretation.
ALWAYS CONSULT with intensivist, pulmonologist, or nephrologist for complex cases or when clinical picture doesn't match calculated interpretation.