Platelet Transfusions in the Neonatal Intensive Care Unit

Thrombocytopenia, generally defined as a platelet count less than 150 × 109/L, is (after anemia) the second most common hematologic disorder of infants admitted to neonatal intensive care units (NICUs). It affects 18–35% of all patients admitted to NICUs and approximately 70% of extremely low birth weight (ELBW) infants with a birth weight less than 1,000 grams.1–4 The incidence of thrombocytopenia is inversely proportional to the gestational age, and it represents a risk factor for poor neonatal outcomes.5 Recently, Wiedmeier and collaborators published the largest study on neonatal platelet counts conducted to date, which included approximately 47,000 infants delivered between 22 and 42 weeks gestation.6 This study showed that platelet counts at birth increased with advancing gestational age (Figure 1). Linear regression analysis showed that, for each week increase in gestational age, there was a corresponding increase in mean platelet count of approximately 2 × 109/L. Importantly, while the mean platelet count was ≥ 200 × 109/L even in the most preterm infants, the 5th percentile in this large epidemiological study was 104 × 109/L for those ≤ 32 weeks gestation and 123 × 109/L for late-preterm and term neonates (Figure 1A).6 These findings indicated that different definitions of thrombocytopenia should be applied to preterm infants. Figure 1 First recorded platelet counts, obtained in the first three days after birth, in neonates born at 22 to 42 weeks gestation. Mean values are indicated by the red line, and the 5th and 95th percentiles are shown in the blue and green lines, respectively. ... The etiologies of thrombocytopenia are highly diverse, as is the natural history. Clinically, a distinction is frequently made between “early onset’ (≤3 days of life) and “late onset” (≥4 days of life) neonatal thrombocytopenia. Intra-uterine growth restriction, pregnancy induced hypertension or diabetes, perinatal infection, and transplacental passage of maternal allo- or autoantibodies are frequently associated with early onset thrombocytopenia. Late onset neonatal thrombocytopenia is most commonly due to bacterial infection or necrotizing enterocolitis.