Effects of syringe type and storage conditions on results of equine blood gas and acid-base analysis

Objective-To determine effects of syringe type and storage conditions on blood gas and acid-base values for equine blood samples. Sample-Blood samples obtained from 8 healthy horses. Procedures-Heparinized jugular venous blood was equilibrated via a tonometer at 37°C with 12% O₂ and 5% CO₂. Aliquots (3 mL) of tonometer-equilibrated blood were collected in random order by use of a glass syringe (GS), general-purpose polypropylene syringe (GPPS), or polypropylene syringe designed for blood gas analysis (PSBGA) and stored in ice water (0°C) or at room temperature (22°C) for 0, 5, 15, 30, 60, or 120 minutes. Blood pH was measured, and blood gas analysis was performed; data were analyzed by use of multivariable regression analysis. Results-Blood Po₂ remained constant for the reference method (GS stored at 0°C) but decreased linearly at a rate of 7.3 mm Hg/h when stored in a GS at 22°C. In contrast, Po₂ increased when blood was stored at 0°C in a GPPS and PSBGA or at 22°C in a GPPS; however, Po₂ did not change when blood was stored at 22°C in a PSBGA. Calculated values for plasma concentration of HCO₃ and total CO₂ concentration remained constant in the 3 syringe types when blood was stored at 22°C for 2 hours but increased when blood was stored in a GS or GPPS at 0°C. Conclusions and Clinical Relevance-Blood samples for blood gas and acid-base analysis should be collected into a GS and stored at 0°C or collected into a PSBGA and stored at room temperature.