Effects of Syringe Material, Sample Storage Time, and Temperature on Blood Gases and Oxygen Saturation

BACKGROUND: The practice of on-ice storage of arterial-blood samples in plastic syringes for delayed analysis continues, and the effects of storage time and temperature on the measurement of blood-oxygen-saturation values (SaO2) have not been adequately described. OBJECTIVE: To de-termine the effects of syringe material, storage time, and storage temperature on normal arterial-ized blood gas and SaO2 values. METHODS: We used a temperature-controlled extracorporeal circuit to “arterialize ” 500 mL of fresh, whole human blood at 37°C, and we used certified cali-bration gases of 12 % O2 and 5 % CO2 to produce normal blood-gas values. From that arterialized blood we took 90 samples and randomly assigned them to 6 groups, until there were 15 samples in each group. The groups were (1) plastic syringe, analyzed immediately, (2) plastic syringe, stored 30 min at 0–4°C, (3) plastic syringe, stored 30 min at 22°C, (4) glass syringe, analyzed immediately, (5) glass syringe, stored 30 min at 0–4°C, and (6) glass syringe, stored 30 min at 22°C. RESULTS: Compared to the samples that were analyzed immediately, the PO2 of the samples stored in plastic syringes for 30 min at 22°C and at 0–4°C was significantly higher, with a clinically important magnitude of 11.9–13.7 mm Hg. The PCO2 of blood stored in glass for 30 min at 0–4°C was significantly lower, although the magnitude of the difference (1.5 mm Hg) was not clinically im-portant. There were no statistically significant differences in pH or oxygen saturation among the 6 groups. CONCLUSION: For accurate arterial-blood-gas results, samples drawn in plastic syringes should be analyzed immediately. If the analysis is going to be delayed, the samples should be drawn and stored in glass. Key words: blood gas analysis, syringes, temperature, time factors, specimen handling, glass, plastics, blood specimen collection. [Respir Care 2006;51(7):732–736. © 2006 Daeda-lus Enterprises