Ann Lab Med.  2020 Nov;40(6):448-456. 10.3343/alm.2020.40.6.448.

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

• Arbiol-Roca A
• Imperiali CE
• Dot-Bach D
• Valero-Politi J
• Dastis-Arias M

• KMID: 2507790
• DOI: http://doi.org/10.3343/alm.2020.40.6.448

Abstract

Background
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.
Methods
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.
Results
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.
Conclusions
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.

Keyword

Stability; Blood gases; Storage; Temperature; Time; Preanalytical variables

Figure

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  Fig. 1 Study flow diagram. The stability study began with storing the samples for 60 minutes. If any parameter was not stable for ≤60 minutes, the study was started again with new samples for 45 minutes. If stability was still an issue, the experiment was carried out for 30 and 15 minutes, sequentially. Independent sample groups were used each time. Measurements were conducted using an ABL800 analyzer (Radiometer, Copenhagen, Denmark). Abbreviations: pCO2, partial pressure of carbon dioxide; pO2, partial pressure of oxygen; sO2, oxygen saturation.

• 

  Fig. 2 Mean bias from baseline for pH (A), pCO2 (B), pO2 (C), sO2 (D), and lactate concentration (E) at 25°C (solid black curve), 4–8°C (long dashed black curve), and 0–3.9°C (short dashed black curve). The two adjacent grey curves on either side represent the 95% confidence interval of the mean curve. The solid black lines correspond to stability (%) calculated as a CV percentage overall (within-run imprecision)×1.65. Data are displayed in Table 2. Independent sample groups were used for each time, even though there is a connection between lines. Abbreviations: pCO2, partial pressure of carbon dioxide; pO2, partial pressure of oxygen; sO2, oxygen saturation; CV, coefficient of variation.

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