Actively circulating blood volume in endotoxin shock measured by indicator dilution

Area of Science:

• Physiology
• Cardiovascular Research
• Hemodynamics

Background:

• Assessing active blood volume is crucial for understanding circulatory dynamics.
• Endotoxin shock significantly impacts physiological parameters, including blood volume distribution.

Purpose of the Study:

• To quantify the actively circulating blood volume in splenectomized dogs.
• To determine the effect of endotoxin infusion on red blood cell and albumin distribution volumes.

Main Methods:

• Utilized 51Cr-labeled erythrocytes and 125I-labeled albumin to monitor concentration changes.
• Applied a dual exponential equation to analyze data and determine distribution volumes.
• Measured mean arterial blood pressure during endotoxin shock.

Main Results:

• Active red blood cell and albumin volumes were initially high (89.8% and 92.0% of total).
• Endotoxin shock reduced active volumes significantly (to 60.0% for RBCs, 56.2% for albumin).
• Mixing time constants remained consistent, suggesting rapid equilibration within respective volumes.

Conclusions:

• An "active blood volume" can be differentiated from total distribution volume.
• Endotoxin shock causes a substantial decrease in actively circulating red blood cells and albumin.
• A significant portion of "extravascular plasma volume" measured by albumin dilution resides within the active circulation.