Effect of temperature, duration of storage and sampling procedure on ammonia concentration in equine blood plasma.

The research study examines how storage duration, temperature, and sampling procedures can impact the ammonia concentration in horse blood plasma. It found that temperature and duration significantly affect the ammonia content while the method of blood sampling from the jugular vein results in only modest differences.

Effect of Storage Duration and Temperature

The team studied the influence of storage duration on plasma ammonia concentration in equine EDTA whole blood, EDTA plasma, and heparin plasma samples at various storage temperatures:

• EDTA whole blood stored at 4 degrees Celsius showed no significant increase in ammonia content after six hours. However, if the blood was kept at 20-22 degrees Celsius, the increase in ammonia content became significant three hours post-collection.
• EDTA plasma samples stored at different temperatures had varying ammonia formation rates. Samples stored at room temperature (20-22 degrees Celsius) showed an ammonia formation rate of 26.8 μmol/l per day. Samples stored at 4 degrees Celsius had a lower rate at 6.6 μmol/l per day. The rate dropped significantly for samples stored at -20 degrees Celsius, at only 0.03 μmol/l per day.

Comparison of EDTA and Heparin Plasma Samples

Next, the researchers compared the ammonia values of EDTA and heparin plasma samples:

• The ammonia values did not differ between these types of samples when measured immediately after sampling. There was also no significant difference after storing the samples at 4 degrees Celsius for three days, nor after storing them at -20 degrees Celsius for both three and ninety days.

Impact of Blood Sampling Procedure

The researchers also investigated if the compression of the jugular vein before and during blood sampling exhibited any effect on the plasma ammonia values:

• While there were significant differences in the mean plasma ammonia content between samples collected with and without compression of the jugular vein, the absolute differences were small. The content was 20.2 μmol/l (+/- 4.1) for blood sampled with compression, and 23.4 μmol/l (+/- 4.3) for sampling without compression.

In conclusion, the research emphasizes that the storage conditions, particularly temperature and duration, can greatly affect the ammonia concentration in equine blood samples. Besides, albeit of lesser impact, the method of blood sampling, especially the use of jugular vein compression, can also influence the ammonia content albeit to a smaller extent.