Stability of blood gases when refrigerated

Ferreira, J.; Silva, S.; Rodrigues, P.; Abreu, M.; Maia, J.; Carvalho, D.; Carvalho, L.

http://hdl.handle.net/10400.16/1274

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Background: Blood gas analysis is a widely used procedure. In clinical practice, the physicians may not always have a blood gas analyzer in their proximity. Not infrequently, blood gas samples are stored in a fridge or on ice and read retrospectively. Continued anaerobic and aerobic metabolism in the blood may alter blood gases in the interval between drawing arterial blood and its analysis, which may cause a fall in the PaO2 and pH and a rise in the PaCO2. Methods: Two sets of arterial blood samples were obtained from hospitalized patients. After the initial analysis, one sample from each patient was put in raw ice within a specimen bag (0 to +1 oC) and the other in the fridge (+4 to +8 oC). These samples were submitted to serial analysis at 30 minutes, 1 hour and 2 hours after the initial analysis. Results: Two hundred arterial blood gas results from 25 patients were analysed. The mean values of PaO2, PaCO2, HCO3-, Na+, K+, Ca2+ and lactate at 0 minutes, 30 minutes, 1 hour and 2 hours were not signifi cantly different between the two alternatives of storage. However, within each group, signifi cant changes were found over time for PaO2, K+, Na+, Ca2+ and lactate. Conclusions: When using plastic syringes, arterial blood gas analysis should be processed shortly after collecting the sample. Despite the fact that low temperatures can slow down the metabolism, neither the ice nor the fridge preserved all the sample parameters.