Acute plasma expansion: left ventricular hemodynamics and endocrine function during exercise

Area of Science:

• Cardiovascular Physiology
• Exercise Physiology

Background:

• Understanding the effects of plasma expansion on cardiac function is crucial for managing various clinical conditions.
• Acute plasma expansion is a common intervention, but its impact on cardiac mechanics during exercise requires further elucidation.

Purpose of the Study:

• To investigate the effects of acute plasma expansion on left ventricular volumes and ejection dynamics at rest and during submaximal exercise.
• To assess the influence of plasma expansion on cardiac output, stroke volume, and filling pressures.

Main Methods:

• 11 healthy subjects underwent isotope cardiography to measure left ventricular end-diastolic volume (LVEDV) and end-systolic volume (LVESV).
• Measurements were taken at rest and during two submaximal one-legged exercise loads, before and after plasma expansion with a 6% dextran solution.
• Cardiac output, stroke volume, heart rate, central venous pressure (CVP), and systemic vascular resistance were also monitored.

Main Results:

• Plasma expansion significantly increased blood volume, cardiac output, and stroke volume at rest and during exercise.
• Left ventricular end-diastolic volume (LVEDV) increased post-plasma expansion, leading to a higher stroke volume without changes in left ventricular end-systolic volume (LVESV).
• Systemic vascular resistance and mean arterial pressure decreased, while left ventricular peak filling and ejection rates increased.

Conclusions:

• Acute plasma expansion effectively enhances cardiac output and stroke volume in healthy individuals.
• The improved cardiac performance is attributed to increased preload (LVEDV) rather than altered contractility (unchanged LVESV).
• Plasma expansion may be beneficial for augmenting cardiovascular function during exercise.