Agreement Between Methods Assessing Changes in Plasma Volume During Fluid Therapy-A Post Hoc Analysis of a Randomized...

Area of Science:

• Critical Care Medicine
• Clinical Chemistry

Background:

• Accurate assessment of patient volume status is clinically challenging.
• Methods for measuring plasma volume are valuable for research and potentially guiding fluid therapy.
• Hematocrit and anthropometric formulas are simpler methods for estimating plasma volume.

Purpose of the Study:

• To evaluate hematocrit as a marker for plasma volume changes.
• To assess an anthropometric formula for estimating absolute plasma volume.
• To compare these methods against radiolabeled albumin as the reference standard.

Main Methods:

• Sixty-four postoperative patients received albumin (10 mL/kg).
• Plasma volumes were measured using radiolabeled albumin at baseline and post-infusion.
• Comparisons were made with plasma volumes derived from hematocrit changes (calibrated and anthropometric methods).

Main Results:

• The anthropometric formula showed low precision in predicting plasma volumes.
• Agreement between the anthropometric method and the reference method was poor.
• Changes in hematocrit during fluid therapy were too imprecise to replace the reference method for individual patient assessment.

Conclusions:

• The anthropometric formula is not precise enough for estimating plasma volume in postsurgical patients.
• Hematocrit changes are insufficient for accurately assessing plasma volume changes during fluid therapy.
• Simpler methods for plasma volume estimation have significant limitations compared to reference methods.