Are coagulation studies on blood sampled from arterial lines valid?

Area of Science:

• Clinical Pathology
• Intensive Care Medicine
• Laboratory Hematology

Background:

• Arterial blood sampling is common in intensive care units (ICUs).
• Concerns exist regarding the accuracy of coagulation tests performed on arterial samples due to potential dilution and heparin contamination.
• Validating arterial samples for coagulation testing is crucial for reliable patient management.

Purpose of the Study:

• To evaluate the validity of coagulation test results from arterial line samples compared to venous samples.
• To assess the impact of different discard volumes (4.5 ml vs. 16 ml) on arterial sample coagulation assays.
• To determine the clinical significance of observed differences between arterial and venous coagulation values.

Main Methods:

• Coagulation tests were performed on paired arterial and venous blood samples from 79 ICU patients.
• Two arterial samples were collected with different discard volumes (4.5 ml and 16 ml).
• Activated partial thromboplastin time (aPTT), thrombin time, prothrombin time, reptilase time, and fibrinogen were measured.

Main Results:

• Statistically significant differences were found for activated partial thromboplastin time (aPTT) and thrombin time between arterial and venous samples, and between the two arterial samples.
• These differences were small and clinically insignificant.
• No significant heparin contamination was detected in arterial samples.
• aPTT values from arterial samples were generally comparable to venous samples, with minimal deviation.

Conclusions:

• Arterial line samples are valid for activated partial thromboplastin time testing in ICUs.
• Both 4.5 ml and 16 ml discard volumes yield reliable aPTT results.
• Arterial sampling can be used interchangeably with venous sampling for aPTT monitoring in this setting.