For arterial blood gas samples, which steps ensure accuracy of gas measurements and pH?

For arterial blood gas samples, which steps ensure accuracy of gas measurements and pH?

• A. Use a plain glass syringe, mix vigorously, and expose to air.
• B. Use a heparinized syringe, avoid air bubbles, draw from a stable artery after an Allen test, seal promptly, and keep on ice.
• C. Use EDTA tube, shake vigorously, store at room temperature.
• D. Use a metal syringe, expose to light, transport at 37°C.

Answer: (B)

Preserving the sample’s gas tensions and pH from collection to analysis is what ensures accurate arterial blood gas measurements. Gas values change quickly if the sample is exposed to air or allowed to metabolize, so every step should minimize those changes. Using a heparinized syringe provides anticoagulation with minimal dilution of the blood, which keeps the gas content and electrolytes true to the patient’s state. Air bubbles must be avoided because even small bubbles exchange gases with the air, distorting oxygen and carbon dioxide levels and shifting pH. Drawing from a stable artery after confirming collateral circulation with an Allen test ensures the sample truly reflects arterial blood and protects distal perfusion during the procedure. Sealing the syringe promptly prevents air ingress and gas loss, and keeping the sample on ice slows metabolic activity, helping maintain the original gas tensions and pH until the analysis can be performed promptly. Other practices, like using non-heparinized containers, exposing the sample to air, or testing after delays or at room temperature, would allow gas exchange, clotting, or metabolic drift that misrepresent the patient’s true values.

Preserving the sample’s gas tensions and pH from collection to analysis is what ensures accurate arterial blood gas measurements. Gas values change quickly if the sample is exposed to air or allowed to metabolize, so every step should minimize those changes. Using a heparinized syringe provides anticoagulation with minimal dilution of the blood, which keeps the gas content and electrolytes true to the patient’s state. Air bubbles must be avoided because even small bubbles exchange gases with the air, distorting oxygen and carbon dioxide levels and shifting pH. Drawing from a stable artery after confirming collateral circulation with an Allen test ensures the sample truly reflects arterial blood and protects distal perfusion during the procedure. Sealing the syringe promptly prevents air ingress and gas loss, and keeping the sample on ice slows metabolic activity, helping maintain the original gas tensions and pH until the analysis can be performed promptly. Other practices, like using non-heparinized containers, exposing the sample to air, or testing after delays or at room temperature, would allow gas exchange, clotting, or metabolic drift that misrepresent the patient’s true values.