Impact of Thrombocytopenia and Platelet Transfusions on Neonatal Bleeding and Inflammation

This is a prospective observational study designed to contrast the potential positive effects of neonatal platelet transfusion on clinical bleeding vs. their potentially negative effects on NET formation, intravascular thrombosis and elevation of pro-inflammatory cytokines.

Importantly, patients will be consented when they have a platelet count \<100 x 109/L, but they will enter study only when the platelet count falls to \<50 x 109/L.

After obtaining signed Informed Consent, enrolled infants will undergo the following:

1\. Prospective collection of clinical and laboratory data, including:

1. Baseline demographic and clinical information from infants and mothers; 2. Clinical diagnoses at the time of enrollment (if NEC, then Bell's stage) and illness severity (SNAP scores) at the time of diagnosis; 3. All hemoglobins, hematocrits, PLT counts, IPF% and IPCs obtained during study. An IPF (the PLT equivalent of the reticulocyte count) is automatically run on every thrombocytopenic sample at all participating hospitals, and will provide information regarding mechanism of thrombocytopenia; 4. All blood culture results, and all markers of liver and renal function; 5. All PLT, RBC and plasma transfusions, including product characteristics, transfusion times, and volume; and 6. Neonatal outcomes including IVH (any grade), chronic lung disease (oxygen requirement at 36 wks post-conception), retinopathy of prematurity (any grade), and mortality.

Infants will be followed until resolution of the severe thrombocytopenia (PLT count \>50x109/L without PLT Tx x 72 hours), death or discharge, whichever comes first.

2\. Study-specific procedures. In addition to the data collected as above, enrolled infants will undergo the following study-specific measurements:

1. A bleeding score (Neo-BAT, see Appendix) will be obtained by the bedside nurse within 2 hours of every PLT count and IPF% checked. NeoBAT scores will include any bleeding since the last PLT count or over the prior 24 hours, whichever is shortest. This will serve to correlate bleeding scores with PLT counts, and to quantify changes following PLT Tx; 2. Two optional blood samples will be obtained within 2 hours prior to and 4±2 hours (see below) following the first clinically indicated PLT Tx after enrollment. These 2 study-specific blood samples (0.5-1.0 cc each) will be taken to the study laboratory for a CBC and plasma separation and storage for future measurements of dsDNA and MPO-DNA ELISA, markers of NET formation, TAT complexes (markers of intravascular coagulation), and for a panel of serum cytokines/vascular injury markers (IFNɣ, IL-6, IL-8, IL-10, IL-17, IL-18, TNFα/β, IP-10, MCP-1, ICAM, VCAM, and VEGF) by Luminex; 3. In addition, left-over plasma samples from clinical tests will be collected daily from the clinical laboratory, aliquoted, and frozen for future cytokine measurements, as we did to generate the preliminary data for this study.

• Measurement of changes in cytokine levels and markers of intravascular coagulation and NET formation following PLT Tx [Time frame: Approximately 3 years]