Effect of Time Delay and Syringe Surface Area on Partial Pressure of Oxygen and Oxygen Saturation of Arterial and Venous Blood Gas Samples. observational study

Background: Many medical disorders require blood gas analysis, especially in severely ill patients who undergo venous or arterial blood gas testing. However, resource constraints and blood gas analyzer shortages can delay sample analysis in some hospitals. Objective: This study aimed to evaluate the effects of time delay and syringe surface area on oxygen tension (PaO2), oxyhemoglobin saturation (SaO2), acidity (pH), and carbon dioxide tension (PaCO2) in arterial and venous blood gas samples Patients and methods: This observational research included 45 ICU and intraoperative patients. Both arterial and central venous samples were collected and divided into five parts: 1 ml in a heparinized syringe for immediate analysis and 1 ml in a 3 ml plastic and capillary insulin syringe for delayed analysis (after 30 minutes and 1 hour). To analyze arterial and venous samples simultaneously, all samples were held at ambient temperatures during the waiting period. Therefore, each patient had 10 samples tested for the final assessment. Results: There was a wide range of limits of agreement for oxygen saturation, PaO2, and PaCO2. The mean baseline PaO2 for arterial samples was 159.9 ± 113.6 mmHg. The mean bias (limits of agreement) for the 30-minute and 60-minute values from baseline in the 3 ml syringe were 21 (-99 to 142) and 38 (-112 to 188), respectively. The mean baseline PaCO2 for arterial samples was 36 ± 7.6 mmHg, with the mean bias (limits of agreement) for the 30-minute and 60-minute values from baseline being -0.4 (-4.8 to 4.1) and -3.8 (-11.8 to 4.1), respectively, in the 3 ml syringe. Conclusion: Delayed arterial and venous samples stored at room temperature yield different results compared to those analyzed immediately, with significant changes detectable as early as 30 minutes. In clinical practice, using plastic syringes is more convenient and safer.