Effects of collecting blood into plastic heparinised vacutainer tubes and storage conditions on blood gas analysis values in horses.

This research investigates the effects of using plastic heparinised vacutainer tubes, compared to glass syringes, on blood gas analysis values in horses, and how these values are affected by storage conditions and time. The findings suggest that this type of tube should not be used to collect samples for measuring blood PCO(2) and PO(2).

Research Methodology

• The study collected blood from six healthy horses and validated the blood at a controlled temperature (37 °C) with the presence of 12% Oxygen and 5% Carbon Dioxide (tonometered).
• The researchers then collected three milliliter aliquots of this tonometered blood using either a glass syringe or a plastic heparinised vacutainer tube.
• These samples were then stored either in iced water or at room temperature for time durations of 0, 5, 15, 30, 60 and 120 minutes.
• For the samples collected in the vacutainer tubes, they were further categorised by how they were collected – aerobically (tube opened for 5 seconds) or anaerobically (tube remained closed).
• Blood gas analysis was conducted using a Radiometer ABL5 and the resulting data was analysed using repeated measures analysis of variance.

Key Research Findings

• Blood samples collected in the plastic vacutainer tubes showed a significant, immediate and sustained increase in oxygen pressure values (PO2) and a transient yet significant decrease in carbon dioxide pressure values (PCO2). These changes were not observed in the samples collected using the glass syringes.
• When stored in iced water, the blood samples from the plastic vacutainer tubes displayed higher PO2 and PCO2 values, compared to those stored at room temperature.
• Measurements for blood pH, plasma bicarbonate concentration, total CO2 concentration and base excess in the extracellular fluid were consistently similar regardless of whether the blood was collected in plastic tubes or glass syringes. These values were also not affected by the storage temperature or time.

Research Conclusions

• The study concluded that plastic heparinised vacutainer tubes should not be utilized for collection of blood samples meant for measuring PCO2 and PO2.
• However, for measurements of plasma bicarbonate concentration, total CO2 concentration, and base excess, the vacutainer tubes proved to be accurate and reliable, unaffected by storage temperature or time.