Abstract
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 determine the effects of syringe material, storage time, and storage temperature on normal arterialized 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 calibration 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 important. 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.
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