Trapped plasma vs. osmolality in canine microcapillary hematocrits.

Area of Science:

• Physiology
• Biochemistry
• Medical Diagnostics

Background:

• Accurate packed red cell volume determination is essential for clinical diagnostics.
• Understanding plasma trapping in hematocrit measurements is critical, especially under hypertonic conditions.
• Hypertonicity can alter blood properties, potentially affecting packed cell volume calculations.

Purpose of the Study:

• To quantify the volume of trapped plasma in hypertonic canine blood.
• To investigate the effect of different osmolality-increasing agents (sodium chloride and meglumine/sodium diatrizoate) on plasma trapping.
• To establish corrections for trapped plasma in microcapillary hematocrit analysis.

Main Methods:

• I-125 labelled albumin was used to measure trapped plasma in packed red cells.
• Canine blood osmolality was increased using sodium chloride or meglumine/sodium diatrizoate solutions.
• Hematocrit measurements were performed at various osmolality levels, noting hemolysis.

Main Results:

• Trapped plasma increased with osmolality for both sodium chloride and diatrizoate solutions.
• At osmolalities above 458 mOsm/kg, diatrizoate solutions resulted in significantly more trapped plasma than sodium chloride.
• Hemolysis at high osmolality (924 mOsm/kg with NaCl) led to a marked increase in trapped plasma.

Conclusions:

• Plasma trapping is osmolality-dependent and influenced by the type of solute used.
• Corrections for trapped plasma are necessary for accurate hematocrit values, particularly at higher osmolalities.
• The choice of osmolality-adjusting agent impacts the degree of plasma trapping.