An arterial blood gas sample arrives 45 minutes after collection with an air bubble in the syringe. What should the technologist do?

An arterial blood gas sample arrives 45 minutes after collection with an air bubble in the syringe. What should the technologist do?

• A. Accept and analyze the sample
• B. Reject the sample because pCO2 would be falsely decreased
• C. Re-measure pO2 and proceed
• D. Dilute the sample and test

Answer: (B)

Gas exchange between the blood and air in the syringe is what makes this specimen unusable. An air bubble provides a pathway for gases to equilibrate with room air, so carbon dioxide diffuses out of the blood into the bubble (and oxygen diffuses in). That drives pCO2 lower than the true arterial value and can also raise pO2, so the reported gas tensions become unreliable. With the tube sitting for 45 minutes, metabolic changes during that time further skew the results. The only appropriate action is to reject the sample and obtain a fresh arterial blood gas drawn without air in the syringe and analyzed promptly to ensure accurate values.

Gas exchange between the blood and air in the syringe is what makes this specimen unusable. An air bubble provides a pathway for gases to equilibrate with room air, so carbon dioxide diffuses out of the blood into the bubble (and oxygen diffuses in). That drives pCO2 lower than the true arterial value and can also raise pO2, so the reported gas tensions become unreliable. With the tube sitting for 45 minutes, metabolic changes during that time further skew the results. The only appropriate action is to reject the sample and obtain a fresh arterial blood gas drawn without air in the syringe and analyzed promptly to ensure accurate values.