Relationship between body fluid volumes and arterial pressure

Area of Science:

• Cardiovascular Physiology
• Renal Physiology

Background:

• Blood volume is a critical determinant of arterial pressure.
• Understanding its influence is key, especially with reduced excretory capacity.

Purpose of the Study:

• To review the mechanisms linking blood volume to arterial pressure.
• To explore acute, transitional, and long-term phases of this relationship.

Main Methods:

• Review of existing literature on blood volume and arterial pressure regulation.
• Analysis of hydraulic, reflex, hormonal, and local autoregulatory responses.
• Examination of microcirculatory changes in transitional and long-term phases.

Main Results:

• Acute phase: hydraulic effects, reflex and hormonal responses.
• Transitional phase (1-2 days): increased O2 sensitivity, tone, vasomotion, and functional rarefaction at the local tissue level.
• Long-term phase: functional changes become structural (anatomical rarefaction), maintaining increased vascular O2 sensitivity and total peripheral resistance, leading to hypertension with normal blood volume and cardiac output.

Conclusions:

• Blood volume significantly influences arterial pressure through multifaceted mechanisms.
• Microcirculatory adaptations, both functional and structural, play a crucial role in sustained hypertension.
• These adaptations contribute to increased total peripheral resistance, even with normal blood volume and cardiac output.