Platelet Aggregation Alterations in Patients with Severe Viral Infection Treated at the Intensive Care Unit: Implications for Mortality Risk.

Severe viral infections often result in abnormal platelet function, affecting various stages of hemostasis. Activated platelets are often considered prothrombotic and more susceptible to further stimulation. However, emerging evidence suggests that initial hyperactivation is followed by platelet exhaustion and hypo-responsiveness, affecting platelet degranulation, activation, and aggregation. We examined early alterations in platelet aggregation among patients (N = 28) with acute respiratory distress syndrome and SARS-CoV-2 infection who were receiving mechanical ventilation and venovenous extracorporeal membrane oxygenation support. Blood samples were stimulated with four different activators: arachidonic acid, adenosine diphosphate, thrombin receptor-activating protein 6, and ristocetin. Our observations revealed that platelet aggregation was reduced in most patients upon admission (ranging from 61 to 89%, depending on the agonist used), and this trend intensified during the 5-day observation period. Concurrently, other coagulation parameters remained within normal ranges, except for elevated d-dimer and fibrinogen levels. Importantly, we found a significant association between platelet aggregation and patient mortality. Impaired platelet aggregation was more severe in patients who ultimately died, and reduced aggregation was associated with a significantly lower probability of survival, as confirmed by Kaplan-Meier analysis (