Effects of blood processing techniques on sodium and potassium values: a comparison between Aldabra tortoises (Geochelone gigantea) and Burmese mountain tortoises (Manouria emys)

Background: Hematologic and plasma biochemical evaluations are routinely used in evaluating the chelonian patient, but appropriate processing techniques have been minimally defined.
Objectives: This study was designed to compare the effects of temperature, time, anticoagulant, and species on sodium and potassium values in the Aldabra tortoise ( Geochelone gigantea ) and the Burmese mountain tortoise ( Manouria emys ).
Methods: Blood samples from 7 Aldabra tortoises and 8 Burmese mountain tortoises were collected into tubes without anticoagulant and tubes containing lithium heparin. Sodium and potassium concentrations were measured by flame photometry in serum and plasma harvested immediately after collection and from aliquots of whole blood stored at 4°C and 25°C for 5 to 120 minutes.
Results: In Aldabra tortoises, storage time and temperature had no significant effect on potassium concentrations in heparinized blood and in blood without anticoagulant. However, sodium concentrations in serum and plasma decreased significantly in samples without anticoagulant stored at 4°C and 25°C and in heparinized samples stored at 4°C. In Burmese mountain tortoises, potassium concentrations in serum and plasma increased significantly with time in samples without anticoagulant and in heparinized samples stored at 4°C and 25°C, but the increases were less at 4°C. Sodium concentrations in serum and plasma decreased significantly in blood without anticoagulant and heparinized blood stored at 4°C and 25°C.
Conclusions: Storage of blood samples with and without anticoagulant at 4°C significantly improved the stability of potassium and sodium concentrations in both species of tortoises. Early separation of red cells from serum or plasma after blood collection is especially important to ensure the reliability of potassium measurements.