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Arterial Blood Gas
Aka: Arterial Blood Gas, Blood Gas, ABG, PaCO2, PCO2
- See Also
- ABG Interpretation
- A-a Gradient
- Arterial Blood source
- Arterial Puncture
- Arterial Line
- Conditions invalidating or modifying ABG Results
- Delayed analysis
- Iced Sample maintains values for 1-2 hours
- Un-iced sample quickly becomes invalid
- PaCO2 rises 3-10 mmHg/hour
- PaO2 falls at a rate related to initial value
- pH falls modestly
- Excessive Heparin
- Dilutional effect on results
- Decreases bicarbonate and PaCO2
- Large Air bubbles not expelled from sample
- PaO2 rises 0-30 mmHg
- PaCO2 may fall slightly
- Fever or Hypothermia
- Machine temperature approaches 37 C
- Patient temperature shifts oxyhemoglobin curve
- Hyperventilation or breath holding (due to anxiety)
- May lead to erroneous lab results
- Primary and Secondary Acid Base Disorders
- Respiratory Acidosis (pCO2 increases)
- Compensated by Metabolic Alkalosis (HCO3 increases)
- Respiratory Alkalosis (pCO2 decreases)
- Compensated by Metabolic Acidosis (HCO3 decreases)
- Metabolic Acidosis (HCO3 decreases)
- Compensated by Respiratory Alkalosis (PCO2 decreases)
- Metabolic Alkalosis (HCO3 increases)
- Compensated by Respiratory Acidosis (PCO2 increases)
- Interpretation: pH
- Normal arterial pH = 7.36 to 7.44
- Metabolic Conditions are suggested if
- pH changes in the same direction as pCO2
- pH is abnormal but pCO2 remains unchanged
- Metabolic Conditions related changes in Bicarbonate
- Increase pH by 0.01 (with PaCO2 unchanged)
- Bicarbonate increases 0.67 meq/L
- Decrease pH by 0.01 (with paCO2 unchanged)
- Bicarbonate decreases 0.67 meq/L
- Interpretation pH
- See Calculated PaCO2
- References
- Arieff (1993) J Crit Illn 8(2): 224-46
- Narins (1982) Am J Med 72:496
- Narins (1980) Medicine 59:161-95
- Ghosh (2000) Fed Pract p. 23-33
- Rutecki (Dec 1997) Consultant, p. 3067-74
- Rutecki (Jan 1998) Consultant, p. 131-42