The Right Amount of Purge Useful for Blood Sampling on PiccLine

An increasing number of patients are receiving central lines, including PiccLine systems for the administration of therapeutics and nutrition.

Although these systems are not theoretically intended for blood collection, nurses prefer them as a puncture site when they are in place in their patients, saving them from further peripheral puncture in people who generally do not have optimal venous capital.

It is essential to purge the tubing in place in the patient and filled with infusion solution before drawing blood. Although the dead volume of the tubing used does not exceed 2mL, the volume of purging required before filling tubes for the laboratory appears to be much greater. Anecdotal evidence suggests a useful volume of 20ml but this has never been clearly demonstrated. In addition, the Biochemistry laboratory regularly sees blood samples diluted with perfusion solution, as evidenced by biochemical assays, leading to the cancellation of analyses received in the laboratory and a new sample being taken. This increases blood spoliation for these often already anaemic patients.

There is no consensus in the literature on recommendations for such sampling in PiccLine patients:

• The CLSI1 (Clinical and Laboratory Standart Institute), a non-governmental organisation, issued sampling recommendations in 2017 that were taken up by Becton Dickinson2, a supplier of blood collection tubes. These recommendations include:

• Rinse with 10 ml of 0.9% NaCl

• Then a purge of 3 to 11 ml (depending on the analysis sought)

• English-language articles3,4,5,6,7 show purge volumes ranging from 3 to 6 ml with significantly different sampling methods (rinsing or not).

The investigators therefore note a discrepancy between the sampling practices of the university hospital and the recommendations of the CLSI. In fact, the investigators noted a lack of rinsing prior to purging, which could explain the difference between 20 and 3 ml. This raises the issue of protocolisation of this type of sampling in order to standardise practices.

A consultation of other hospitals, carried out beforehand, enabled us to note that French practices are not in agreement with these recommendations. The management of the Rennes University Hospital as well as the Haute Autorité de Santé were contacted in order to confirm that no normative document had been published or was being drafted on this subject.

The fields of study are: sampling practices on PiccLine, the pre-analytical phase in medical biology.