[Effect of blood withdrawal on changes in plasma volume and protein concentration during incremental cycling exercise...

The aim of this study was to evaluate the effect of blood withdrawal on the plasma volume and serum proteins concentration during incremental cycling exercise test performed 24 hours after blood donation (withdrawal of 450 ml of blood). Thirteen subjects (mean +/- SD), age 23 +/- 3 years; body mass 75 +/- 10 kg; BMI 23.4 +/- 2 kg.m-2; VO2max 2903 +/- 334 ml.min-1, performed an incremental cycling exercise test, starting at the power output of 20 W with an increase by 20 W every 3 minutes--until exhaustion. This test was performed twice: once in the control study (7-12 days before blood donation) and repeated 24 h after blood donation. The blood for this study was taken from the antecubital vein, in a sitting position at rest (6 minutes before the exercise test, at the end of the test (the stage of exhaustion) and 2 hours after the end of the test. The changes in plasma volume were evaluated on the basis of changes in hemoglobin and haematocrit concentrations. Significances of differences in the studied variables were tested using Wilcoxon test. At the end of the exercise test a significant (p < 0.05) decrease in plasma volume was found in both study. It amounted to -11.1 +/- 2.9% in the control study, and to -13.0 +/- 3.9% after blood donation. The difference in the changes in plasma volume in both tests was not significant. In the control study plasma volume return to the pre-exercise value within 2 hours after the end of the exercise test. In the study performed after blood donation the values of plasma volume exceeded the control value by 3.9 +/- 6.7% (p < 0.05) within 2 hours after finishing the exercise test. Taking into consideration the changes in plasma volume it was found that during incremental exercise there is a significant (p < 0.05) extra vascular escape of the serum proteins both in the control study, in case of total serum protein amounting to 4.05 +/- 2.97 g.l-1 as well as during exercise performed after blood donation, amounting to 5.49 +/- 3.98 g.l-1. Moreover, it was found that in the control study all the measured serum proteins concentrations (albumin, alpha 1-, alpha 2-, beta-, and gamma-globulins) return to the pre-exercise level within 2 hours after the end of exercise, but in the study performed after blood donation a continuous extra vascular escape of some serum proteins (alpha 1-, alpha 2- and gamma-globulins) was observed.