High viscosity plasma expanders: Volume restitution fluids for lowering the transfusion trigger

Area of Science:

• Hemorheology
• Physiology

Background:

• High plasma viscosity is detrimental, leading to hemodilution practices.
• Hemodilution aims to improve perfusion by lowering blood viscosity.
• The transfusion trigger (7-8 g/dl hemoglobin) limits hemodilution.

Purpose of the Study:

• To re-evaluate the role of blood and plasma viscosity in physiological conditions.
• To investigate the relationship between viscosity, capillary function, and organ perfusion.
• To determine if increasing plasma viscosity can extend the transfusion trigger.

Main Methods:

• Analysis of hemorheological principles and studies in hemorrhagic shock.
• Examination of functional capillary density (FCD) and tissue oxygenation.
• Correlation of hematocrit levels with blood and plasma viscosity.

Main Results:

• Reduced blood viscosity below the transfusion trigger decreases functional capillary density (FCD).
• Adequate FCD is critical for organ function and survival, more so than tissue oxygenation alone.
• Increasing plasma viscosity beyond the transfusion trigger maintains FCD and organ perfusion.

Conclusions:

• The transfusion trigger is also a 'viscosity trigger' indicating when viscosity is too low.
• Increasing plasma viscosity is beneficial when blood viscosity is reduced.
• Optimizing plasma viscosity can extend the transfusion trigger, potentially reducing blood transfusion needs.