Determination of single and repeated red cell volumes by the indicator dilution method using carbon monoxide as the...

Area of Science:

• Physiology
• Medical Imaging
• Clinical Chemistry

Background:

• Radioactive isotopes used for blood volume measurement present limitations for clinical applications, particularly in intensive care units (ICUs).
• Existing methods may involve lengthy procedures or undesirable background radiation levels.

Purpose of the Study:

• To evaluate a novel method for measuring red blood cell volume using carbon monoxide-labeled RBCs.
• To compare the efficacy and advantages of this new method against the established 51Cr method.

Main Methods:

• Red cell volumes were measured in six dogs and five human volunteers using carbon monoxide-labeled RBCs.
• Measurements were simultaneously compared with the 51Cr method in canine subjects.
• Data analysis involved calculating the ratio of carbon monoxide to 51Cr values and correlation coefficients.

Main Results:

• The ratio of carbon monoxide to 51Cr red cell volume measurements in dogs ranged from 0.86 to 1.17.
• A mean ratio of 1.0 +/- 0.1 (SD) with a correlation coefficient (r) of .93 was observed, indicating strong agreement.
• The carbon monoxide method demonstrated a short labeling time (approx. 1 minute).

Conclusions:

• The carbon monoxide-labeled RBC method is a viable alternative for blood volume measurement.
• Advantages include rapid labeling, quick clearance of background carbon monoxide levels with supplemental oxygen (FIO2 1.0), and repeatability over several hours.
• This method offers significant improvements over the 51Cr technique for clinical applications in critical care settings.