Effect of replacement fluids saline, gelofusine, and blood on biochemical and hematological parameters in rats subjected to repeated blood sampling.

Background: Multiple blood sampling in rat pharmacokinetic (PK) and toxicokinetic studies can result in a pathophysiological response and misleading data interpretation. This study investigated whether these drawbacks can be minimized by replacing withdrawn blood with saline, gelofusine, or donor blood.

Material/methods: Rats with cannulated jugular veins were subjected to 12 withdrawals of 250 and 500 microl of blood followed by replacement with the same amount of saline, gelofusine, or donor blood. Red blood cell, hematocrit, hemoglobin, total protein, albumin, glucose, Na, and Cl levels were determined in the drawn blood.

Results: Multiple blood sampling caused a time-dependent decrease in red blood cell counts and hematocrit, hemoglobin, total protein, and albumin levels in all the treatment groups, but these effects were significantly alleviated in the blood-treated group. Withdrawal of 500 microl of blood caused more pronounced changes than 250 microl blood withdrawal in the saline- and gelofusine-treatment groups, but not in the blood-treatment group. Plasma glucose and Na remained unchanged in all the treatment groups, while slight changes in Cl levels were observed in the saline- and gelofusine-treatment groups.

Conclusions: Blood sample volume had a crucial impact on the measured parameters, which were least affected in the donor blood-treated group. Regardless of the treatment, up to five 250 microl blood samples can be drawn without causing significant changes in a rat's normal condition. However, for a proper determination of PK profile, more than five blood samples are required and therefore drawn blood should be replaced, preferably with donor blood.