A growing number of recent studies have observed an association between elevated hematocrit levels and thrombosis. However, the mechanism behind this pathway has remained elusive. A recent study induced an elevation of hematocrit levels in otherwise healthy mice to tease apart the etiology of the thrombosis formation under increased RBC levels. Compared with control mice, mice with elevated hematocrit had a shorter time to artery occlusion (13.2 vs 5.3 minutes, P<0.001) and reduced clotting time after tail transection. Elevated hematocrit levels increased the time that platelets are in close proximity to a thrombus, thereby increasing the probability that they will become activated and part of the clot. Whether venous thrombi form in a similar manner has yet to be determined, but this study highlights the importance of hematocrit levels on bleeding and thrombosis risk.
Walton BL, Lehmann M, Skorczewski T, Holle LA, Beckman JD, Cribb JA, Mooberry MJ, Wufsus AR, Cooley BC, Homeister JW, Pawlinski R, Falvo MR, Key NS, Fogelson AL, Neeves KB, Wolberg AS. Elevated hematocrit enhances platelet accumulation following vascular injury. Blood 2017;129: 2537-46.