After blood sampling from an arterial catheter, the reinjection of the clearing fluid (a mixture of saline solution and blood) is proposed to limit blood loss. However, the status of coagulation in this clearing liquid remains poorly documented.

In the intensive care unit, blood sampling is mainly performed through an arterial catheter (radial or femoral artery). In addition to continuous arterial pressure monitoring, this provides an easy access to arterial blood without the need for venipuncture.

It is standard practice to first clear the arterial sampling line before drawing blood for biological tests, to prevent the blood sample from being diluted by the arterial catheter's perfusion solution. This clearing fluid (i.e., a mixture of saline solution and blood) is usually discarded. It has been reported that the clearing fluid volume alone represents 24 to 30% of the total blood volume required for blood sampling.

Devices for reinjecting this clearing fluid are already on the market. The advantages of these devices include blood saving, reduced risk of blood exposure, reduced biological waste and lower infection rates associated with catheter handling. The main drawback of these devices is their cost and the need for frequent replacement. Moreover, their impact on the decrease of blood transfusion remains unclear.

Furthermore, there are too few published data on the potential coagulation of clearing fluid reinjected into the patient nor the maximum time it can be safely reinjected.

The aim of this study is to assess the activation of coagulation over time in the clearing fluid during arterial catheter blood sampling

Inclusion Criteria:

• Patient older than 18 years old
• Admitted to the ICU
• With a radial or femoral arterial catheter
• Requiring blood sampling

Exclusion Criteria:

• Presence of a non-standard extension line: any tubing other than an arterial line intended for this purpose.
• Constitutional or acquired hemorrhagic disease,
• Major biological thrombophilia (anti-phospholipid syndrome, homozygous mutation of factor II or V, protein C, S or antithrombin deficiency),
• Thromboembolic event in progress or < 6 months,
• Bacteremia within the last 48 hours,
• Previous study participation,
• Pregnant or breast-feeding patient
• Moribund patient or patient with decision of withholding or withdrawing life-sustaining treatment
• Patient with no health insurance
• Patient under guardianship

adult patient with arterial catheter (radial or femoral).