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Plasma volume and hematocrit changes in recurrent fainters
Alfonso Lagi1, Antonio Rossi, Paolo Sorelli
1Internal Medicine Dept., Autonomic Unit Ospedale Santa Maria Nuova, Firenze, Italia. alfonso.lagi@asf.toscana.it
Summary
Recurrent fainting is linked to a significant reduction in plasma volume during orthostatic stress. This study quantifies plasma volume changes, identifying it as a key factor in vasovagal syncope.
Area of Science:
- Cardiology
- Physiology
Background:
- Reflex syncope, or fainting, involves blood pooling in limbs.
- Reduced plasma volume is a critical factor in fainting.
- Orthostatic stress causes plasma volume to shift to the lower body, decreasing circulating volume.
Purpose of the Study:
- To quantify plasma volume reduction during orthostasis in individuals prone to fainting.
- To compare plasma volume changes between recurrent fainters and healthy controls.
Main Methods:
- A comparative study involving 50 recurrent fainters and 37 controls.
- Blood samples were analyzed for hematocrit and hemoglobin in supine and orthostatic positions.
- Plasma volume variation was calculated based on hematocrit and hemoglobin changes.
Main Results:
- A significant difference in hematocrit and hemoglobin variation was observed between patients and controls.
- Plasma volume reduction was substantially greater in recurrent fainters (17.1%) compared to controls (8.6%).
Conclusions:
- Plasma volume reduction during orthostasis is a significant cofactor in the pathogenesis of reflex fainting.
- This study provides a simple method to assess the role of plasma volume reduction in vasovagal syncope.