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Blood sampling for biochemical analysis from central venous catheters: minimizing the volume of discarded blood
1Department of Clinical Biochemistry, Roskilde University Hospital, Denmark. rslaod@ra.dk
Insights
Discarding only 3 ml of blood after saline flushing is sufficient for accurate central venous catheter blood sampling, minimizing blood loss. This optimized procedure reduces waste while maintaining sample integrity for various analyses.
Area of Science:
- Medical Laboratory Science
- Clinical Pathology
- Vascular Access Devices
Background:
- Routine blood sampling from central venous catheters often involves discarding a significant volume of blood (12 ml).
- Previous practices were based on older studies, potentially leading to unnecessary blood loss, especially in vulnerable patient populations.
- Optimizing blood sampling techniques is crucial for patient safety and efficient laboratory diagnostics.
Purpose of the Study:
- To establish a reliable and minimally invasive blood sampling procedure from central venous catheters.
- To determine the minimal discard volume required for accurate sample collection, reducing blood loss.
Main Methods:
- Investigated blood sampling from central venous catheters in patients undergoing hematological analyses (ethylenediaminetetraacetic acid plasma), coagulation tests (citrate plasma), and serum measurements.
- Compared sample integrity after discarding 3 ml of blood post-saline flush versus the traditional 12 ml discard volume.
- Assessed catheter dead-space to determine an adequate discard volume (at least six times the dead-space).
Main Results:
- A discard volume of 3 ml, following an initial 5 ml saline flush, was sufficient to clear the catheter of infusates.
- This 3 ml discard volume ensured accurate results for hematological, coagulation, and serum analyses.
- The established 3 ml discard volume represents at least six times the catheter's dead-space, ensuring sample purity.
Conclusions:
- A 3 ml discard volume is adequate for safe and reliable blood sampling from central venous catheters after saline flushing.
- This optimized procedure significantly reduces blood loss compared to traditional methods.
- The findings support the adoption of a reduced discard volume in clinical practice to improve patient care and conserve blood resources.
Abstract:
The purpose of the work was to establish a reliable procedure for blood sampling from central venous catheters with a minimal loss of blood. Based on previous studies of potassium measurements, the routine procedure had been to discard 12 ml of blood. In order to clear the catheter from substances from the infusion including potassium, the catheters were first flushed with 5 ml of saline. Repeated samples in fractions of 3 ml for hematological analyses (ethylenediaminetetraacetic acid plasma; seven patients), coagulation tests (citrate plasma; seven patients) and for serum measurements (eight patients) showed that a discarded volume of 3 ml corresponding to at least six times the dead-space of the catheters was sufficient after initial flushing with saline.