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
