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Human autonomic responses to blood donation
Eva Zöllei1, Dóra Paprika, Péter Makra
1University of Szeged, Faculty of Medicine, Cardiology Center, Medical Intensive Care Unit, Korányi fasor 7, Szeged 6720, Hungary. zollei@hotmail.com
Autonomic Neuroscience : Basic & Clinical
|March 30, 2004
Summary
Acute blood loss activates sympathetic nervous system responses, increasing blood pressure and altering heart rate variability oscillations. These changes, particularly in blood pressure variability, serve as sensitive indicators of minor volume depletion.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Regulation
- Human Physiology
Background:
- Understanding autonomic responses to acute volume loss is crucial for managing conditions like hypovolemia.
- Blood donation represents a controlled model for studying physiological responses to acute blood withdrawal.
Purpose of the Study:
- To characterize autonomic nervous system responses to acute volume loss induced by blood donation.
- To investigate changes in heart rate variability (HRV) and blood pressure (BP) variability following blood withdrawal.
- To assess baroreflex sensitivity and its role in mediating autonomic adjustments to reduced blood volume.
Main Methods:
- 48 healthy volunteers underwent supine electrocardiogram (ECG), blood pressure (BP), and uncalibrated breathing signal (UBS) recordings before and after blood donation (350-400 ml).
- Time and frequency domain analyses were applied to RR interval (RRI), BP, and UBS variability.
- Baroreflex gain was calculated using spontaneous sequence and cross-spectral analysis techniques.
Main Results:
- Following blood withdrawal, systolic, diastolic, and mean BP increased, indicating sympathetic activation.
- RR interval variability increased in the low-frequency (LF) band and tended to decrease in the high-frequency (HF) band.
- Blood pressure variability significantly increased in both LF and HF bands, particularly HF systolic BP variability.
- Baroreflex gain estimates, including up-sequence BRS and HF alpha index, decreased significantly.
- Phase angle analysis suggested baroreflex-mediated coupling in LF oscillations but not in HF oscillations between RRI and BP.
- Vagal withdrawal was evidenced by decreased RMSSD, decreased HF RRI power, and reduced up-sequence BRS.
Conclusions:
- Acute, minor volume depletion (blood donation) elicits sympathetic activation and increased BP, with BP oscillations serving as sensitive markers.
- Baroreflex mechanisms contribute to increased RRI oscillations in the LF band following volume loss.
- Changes in RRI and BP oscillations in the HF band suggest that baroreflex mechanisms do not fully explain these variations, implying other regulatory influences.
- Vagal withdrawal plays a significant role in the observed autonomic adjustments to acute volume depletion.