Over 4 years, the Mayo clinic reviewed over 40,000 ICU patients, and sought to determine if prophylactic platelets for critically ill thrombocytopenics matter.
Of these 40,000 ICU patients, they excluded anyone who received RBCs within 24 hours prior to the PLT count that triggered transfusion “to minimize the risk of including those with active bleeding” … The primary outcome was essentially to determine if transfusing platelets led to more RBC transfusions, and, secondarily, all-cause mortality, ICU and hospital free days (among others). Seems backwards, but whatever.
So what falls out of this data?
For all comers, in a propensity matched cohort, one transfusion begets another – (46.3 % of those with platelet transfusions also had an RBC transfusion vs 10.4% of those without platelet transfusions who had an RBC transfusion). Interestingly, those transfused platelets had less ICU free days (22.7 vs 20.8), more hospital free days (15.8 vs 13). When you look specifically at the ~5000 patients with <50k platelet counts and compare those who were/were not transfused platelets, there was no change in ICU mortality, 30 day mortality, ICU-free days, or hospital free days. While this was underpowered to determine statistical significance for those with platelet counts <50k, it is not hard to imagine a larger study to suggest similar benefits of not transfusing these patients- particularly since this study saw fewer hospital free days and fewer ICU free stays (10.2 vs 7.8 days and 19.9 vs 18.3 days respectively) – favoring a more restrictive transfusion strategy (but again, not meeting statistical significance, perhaps due to so few patients with <50k PLT).
This is not the first study I have seen suggesting empiric transfusion or outright canceling of procedures based on platelet counts between 50k and 150k is essentially bunk, and that prophylactic platelet therapy is of little benefit, if not outright harmful. There is even a flicker of a signal that prophylactic platelet transfusions >20k may not be beneficial – but this has yet to be definitively shown true -yet.
I can not agree more with the last words to the authors, “Finally, it must be acknowledged that while clinical trajectories did not improve for the cohort as a whole after platelet transfusion, it is possible that certain subpopulations may indeed benefit from the intervention, though these subgroups have yet to be identified.”