Comparison of whole blood and plasma colloid osmotic pressure in healthy dogs.

Objective: To determine the difference between colloid osmotic pressure (COP) values determined from plasma versus those determined from whole blood.

Design: Prospective observational study.

Settings: University veterinary teaching hospital.

Animals: Fifty-three healthy dogs.

Interventions: None.

Measurements And Main Results: Whole blood and plasma COP, CBC, plasma biochemistry. In all dogs, plasma COP values were significantly lower (P=0.02) than whole blood COP, with a mean of difference of 0.5 mm Hg. The mean and median whole blood COP was 21.75 and 21.4 mm Hg, respectively, with a range of 17.9-27.1 mm Hg. The mean and median plasma COP was 21.2 and 20.9 mm Hg with a range of 16.7-28.9 mm Hg.

Conclusions: While significant difference exists between plasma and whole blood COP, the individual values are within expected reference intervals for dogs (21-25 mm Hg). Using either sample appears to provide the same information in clinically healthy dog; however, it is recommended that clinicians utilize the same sample type for comparison in an individual patient.