Whole blood platelet deposition on extracellular matrix under flow conditions in preterm neonatal sepsis

Platelet function in preterm infants with sepsis was evaluated by measuring their adhesion and aggregation properties using the Cone and Plate(let) Analyser. This may lead to earlier detection of bleeding tendency in septic infants. Platelet function was investigated in 54 preterm infants, of whom 32 had proven neonatal sepsis and 22 were healthy matched controls. Citrated whole blood was subjected to shear stress (1300 s^-1) for 2 min on tissue culture plates precoated with subendothelial extracellular matrix (ECM). The percentage of ECM surface covered with platelets and the average size of the ECM-bound platelet particles were determined with an image analyser. Assays for von Willebrand factor (vWF) antigen, ristocetin co-factor, and vWF collagen binding activity (CBA) were performed on samples from an additional 47 preterm infants: 38 healthy and 9 septic. Platelets of the preterm infants with sepsis displayed lower adhesion than those of the healthy controls. Mean surface coverage was 16.9 ± 8.2% for the septic infants, 15.4 ± 7.9% for the septic infants after exclusion of those with coagulase-negative staphylococci sepsis, and 20.8 ± 9.6% for the healthy group (P < 0.05). Platelet aggregation, vWF antigen, ristocetin co-factor, and CBA levels were similar between the septic and healthy groups. The most significant factor influencing surface coverage was the presence of sepsis. Conclusion: platelet adhesion to extracellular matrix is significantly lower in septic preterm infants than in healthy preterm infants. Intrinsic platelet properties, rather than the concentration or activity of plasma von Willebrand factor, may be responsible for this difference. Surface coverage obtained by the collagen binding activity test under flow conditions, which represents platelet adhesion, may be an earlier, more sensitive indicator of bleeding tendency in neonatal sepsis than decreased platelet count.