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Obtaining blood samples for coagulation studies from a normal saline lock.
1Darnall Army Community Hospital, Fort Hood, Tex., USA.
Summary
Discarding 2 times the catheter dead space volume from saline locks ensures accurate activated partial thromboplastin time (aPTT) measurements in heparinized patients. This method minimizes patient discomfort and blood loss compared to repeated venipuncture.
Area of Science:
- Clinical Pathology
- Nursing Practice
- Laboratory Medicine
Background:
- Peripheral intravenous (IV) locks are commonly used for medication administration.
- Obtaining blood samples from IV locks can be convenient but may affect test accuracy.
- Activated partial thromboplastin time (aPTT) is a critical test for monitoring heparin therapy.
Purpose of the Study:
- To determine the optimal discard volume from a normal saline lock before collecting blood for aPTT.
- To evaluate the impact of discard volume on aPTT accuracy in patients on heparin therapy.
Main Methods:
- Prospective, quasi-experimental study with 32 patients.
- Compared aPTT from venipuncture (control) with samples from saline locks after discarding 0, 2, 4, and 6 times the catheter dead space (1.5 mL).
Main Results:
- A significant difference (P=.02) was observed in aPTT values.
- aPTT was 15% higher in samples from the saline lock with no discard volume compared to venipuncture samples.
Conclusions:
- Discarding a blood volume equal to 2 times the catheter dead space from saline locks allows for accurate aPTT measurements.
- This technique reduces patient discomfort and minimizes blood loss by avoiding repeated venipunctures.