Contact activation of coagulation in newly inserted central venous catheters (CAS-2): protocol for a randomised controlled study comparing four commercially available catheters.

introductionCentral venous catheters (CVCs) are essential in modern healthcare. Insertion of a CVC promotes a hypercoagulable environment, in part through activation of the intrinsic coagulation pathway. We have previously shown that blood obtained from newly inserted CVCs demonstrates immediate coagulation activation, with differences between samples collected directly after insertion and after flushing of the catheter. The aim of this randomised trial is to compare early coagulation activation between four commonly used CVCs and to assess whether the different CVCs demonstrate different degrees of coagulation activation. METHODS AND ANALYSIS: This is a single-centre, randomised, parallel-group trial where adult patients (≥18 years) with a clinical indication for a two-lumen CVC will be eligible for inclusion. Participants will be randomised in a 1:1:1:1 ratio to receive one of four commercially available CVCs. The calculated sample size is 88 participants. Two blood samples will be obtained from each newly inserted CVC, the first obtained from the initial backflow of blood within seconds after insertion and the second after flush and discard. Samples will be analysed using rotational thromboelastometry with the non-activated thromboelastometry (ROTEM NATEM) and plasma-based coagulation assays. The primary outcome is the between-group comparison of the change in ROTEM NATEM clotting time between the two samples. Secondary outcomes include within-group and overall cohort comparisons of changes in clotting time. Additional secondary outcomes are between-group, within-group and overall cohort comparisons of changes in other ROTEM NATEM parameters, including clot formation time, alpha angle and maximum clot firmness, and changes in plasma-based coagulation markers, including prothrombin time-international normalised ratio, activated partial thromboplastin time, Factor VII, Factor XII and thrombin-antithrombin complex concentration. The results may help identify catheter materials that are less prone to activate coagulation and support in the selection and development of CVCs. ETHICS AND DISSEMINATION: This study has been approved by the Swedish Ethical Review Authority (#2022-00265-0). Written informed consent will be obtained from all participants before inclusion. The results will be published in a peer-reviewed journal and presented at scientific meetings. TRIAL REGISTRATION NUMBER: NCT07014722.