Stability of pH, Blood Gas Partial Pressure, Hemoglobin Oxygen Saturation Fraction, and Lactate Concentration

The storage temperature and time of blood gas samples collected in syringes constitute preanalytical variables that could affect blood gas or lactate concentration measurement results. We analyzed the effect of storage temperature and time delay on arterial or venous blood gas stability related to pH, partial pressure of carbon dioxide (pCO2) and oxygen (pO2), hemoglobin oxygen saturation (sO2), and lactate concentration.

In total, 1,200 arterial and venous blood sample syringes were analyzed within 10 minutes of collection. The samples were divided into different groups to determine parameter stability at 25, 4-8, and 0-3.9°C and at different storage times, 60, 45, 30, and 15 minutes. Independent sample groups were used for each analysis. Percentage deviations were calculated and compared with acceptance stability limits (1.65× coefficient of variation). Additionally, sample group sub analysis was performed to determine whether stability was concentration-dependent for each parameter.

The pH was stable over all storage times at 4-8 and 0-3.9°C and up to 30 minutes at 25°C. pCO2 was stable at ≤60 minutes at all temperatures. pO2 was stable for 45 minutes at 0-3.9°C, and sO2 was stable for 15 minutes at 25°C and for ≤60 minutes at 0-3.9°C. Lactate concentration was stable for 45 minutes at 0-3.9°C. Subanalysis showed that stability was concentration-dependent.

The strictest storage temperature and time criteria (0-3.9°C, 45 minutes) should be adopted for measuring pH, pCO2, pO2, sO2, and lactate concentration in blood gas syringes.