Human cardiovascular variability, baroreflex and hormonal adaptations to a blood donation

Abstract

1. We studied cardiovascular variability, baroreflex and blood volume regulating hormones to determine the relative roles of autonomic regulation and hormones during blood donation.2. The sympathetic response was studied by measuring the R-R interval and systolic blood pressure variability using coarse graining spectral analysis in eight blood donors. Beat-by-beat R-R intervals and blood pressure were recorded for 20 min before and 5 min after a whole-blood donation of 480+/-10 ml (about 7 ml/kg of blood volume, over 4 min). Plasma catecholamines, vasopressin, atrial natriuretic peptide, endothelin, active renin, osmolality, Na+, K+, haemoglobin and haematocrit were measured just before and after blood withdrawal.3. Blood donation led to increases in the plasma catecholamines (adrenaline, 21+/-2 versus 35+/-3 pg/ml; noradrenaline, 229+/-26 versus 323+/-37 pg/ml; dopamine, 34+/-3 versus 66+/-9 pg/ml) and in systolic blood pressure (130+/-6 versus 140+/-5 mmHg). These changes were independent of ionic or slow endocrine mechanisms. Heart rate, cardiovascular variability and the spontaneous baroreflex sensitivity did not change despite the increase in blood pressure and catecholamines. Thus the peripheral vascular control was probably involved.4. We conclude that the absence of any change in heart rate usually observed during non-hypotensive hypovolaemic stress is probably due to the sympathetic activation being counterbalanced by the high supine vagal tone at the heart and not to the heterogeneous nature of the sympathetic neural response or to changes in sympathetic and parasympathetic activity without any change in autonomic balance.

Stroke volume monitored by modeling flow from finger arterial pressure waves mirrors blood volume withdrawn by phlebotomy

“…However, a recent study showed fluid replacement occurs rapidly, within the time range of the present study i. e. 6-7 min [12]. Alltogether, these compensatory mechanisms explain why a 10 % blood volume reduction does not markedly affect BP [5,9,28,32].…”

“…However, the present protocol of phlebotomy did not significantly increase HR and the cardiac output was consequently reduced. Similarly, Fortrat et al [5] did not observe any HR Fig. 1 Example from one patient of the effects of phlebotomy on the hemodynamic indices.…”

Haematological rather than skeletal muscle adaptations contribute to the increase in peak oxygen uptake induced by moderate endurance training

“…Nonetheless, whilst speculative, it is possible that after phlebotomy an increase in sympathetic activation due to moderate hypovolaemia (Fortrat et al . ; Zollei et al . ) may have masked a possible decrease in vascular resistance at peak exercise which would contribute as a peripheral adaptation to the increase in and following ET (Klausen et al .…”

“…) related to the increase in sympathetic drive prompted by phlebotomy (Fortrat et al . ; Zollei et al . ).…”

The Effects of a One Unit Blood Donation on Auto-haemodilution and Coagulation

“…Blood donation per se is not a stressful event and moderate stress, as suggested by increased cortisol levels and heart rate at the first donation, is secondary to emotional rather than to physical stimuli 12 . In determining the relative roles of autonomic regulation and hormones during blood donation, Fortrat et al 13 found that blood donation led to increases in the plasma catecholamines and an increase in systolic blood pressure. Heart rate, cardiovascular variability and the spontaneous baroreflex sensitivity did not change.…”