Platelet transfusion thresholds for vascular access: a reply

We thank Shah et al. for their comments [1] on the updated Association of Anaesthetists' safe vascular access guideline [2]. The lack of robust clinical evidence to support platelet transfusion thresholds has been acknowledged within the guidelines and supports the equipoise upon which the Thresholds for Platelets (T4P) trial is based. We await the future findings of this work, which will no doubt be invaluable in informing platelet thresholds in future guidelines. However, in the interim, the anaesthetic and critical care community requires guidance to support clinical decision-making, and our guidelines sought to advise the community based on knowledge and expertise that is currently available. The use of viscoelastic testing has been well documented in cardiac surgery, liver transplant surgery and trauma [3]. Although there is no robust evidence for its use in central venous catheter insertion, it remains theoretically valid that it can provide valuable information regarding clot formation and strength. For example, the critical care population is highly heterogeneous, and coagulation abnormalities are common and varied [4]. The functional assessment of coagulation provided by viscoelastic testing is likely to be informative as well as a step towards the personalised care that these patients require. We recognise the use of viscoelastic testing in central venous catheter insertion as an area for further research and strongly encourage studies in this area. There is also a need to develop standardised protocols to guide use and interpretation due to a lack of familiarity with the technology and its output together with cost and resource constraints [5]. We reiterate that the updated safe vascular access guidelines are based on current available evidence, and we welcome initiatives such as the T4P trial which aims to provide the community with a strong evidence base to inform future guidelines.