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Published on: June 4, 2015
The minimum discard volume: accurate analysis of peripheral hematocrit
1School of Nursing, University of Colorado Health Sciences Center, Denver, USA.
Summary
Discarding 1.5 ml of blood from peripheral intravenous catheters ensures accurate hematocrit readings. This volume, three times the catheter
Area of Science:
- Medical Laboratory Science
- Clinical Chemistry
Background:
- Accurate hematocrit (HCT) measurements are crucial for patient diagnosis and monitoring.
- Blood sampling from indwelling peripheral intravenous catheters (PIVCs) can be affected by flush solution dilution.
- Determining the optimal discard volume is essential to minimize sampling errors.
Purpose of the Study:
- To quantify the minimum discard volume from a PIVC required for accurate HCT determination.
- To establish a reliable method for assessing HCT accuracy after blood sampling from PIVCs.
Main Methods:
- Developed a mathematical model based on the Michaelis-Menten curve to describe blood-flush solution mixing.
- Conducted repeat blood sampling from nine subjects to validate the model.
- Calculated HCT values for various discard volumes and compared them to true HCT.
Main Results:
- The mathematical model accurately described the mixing dynamics within the PIVC.
- Discarding 1.5 ml of blood (three times the deadspace volume of 0.5 ml) resulted in a 95% confidence interval within 0.6% of the true HCT.
- This discard volume minimizes the impact of flush solution on HCT accuracy.
Conclusions:
- A discard volume of 1.5 ml is recommended for accurate HCT measurements from PIVCs.
- The developed mathematical model provides a robust method for estimating HCT accuracy in blood sampling.
- Adherence to this discard volume protocol enhances the reliability of clinical laboratory results.
