Thromboembolic events are rare in childhood; however, neonates are disproportionately affected by thrombosis. The propensity for neonates to clot may be due to several contributing factors. First, neonates have an immature hemostatic system, which generally gives them physiologic thrombophilia. In addition, they are at high risk for sepsis, which leads to thrombosis due to inflammation or disseminated intravascular coagulopathy (DIC). The high use of central catheters, both arterial and venous, in neonates also increases their risk of thrombosis. Although often considered in neonatal thrombosis, the contributing role of inherited thrombophilias in both arterial and venous thrombotic events in this age group remains poorly defined.
Clinicians caring for neonates should be especially aware of clinical thrombotic events common in the neonate, including portal vein thrombosis, renal vein thrombosis, purpura fulminans, and neonatal stroke. The portal vein is a commonly affected anatomic vein, which is attributed to the use of central catheters. Renal vein thromboses have long been recognized as occurring spontaneously in neonates. Neonatal purpura fulminans is a rare condition of dermal microvascular thrombosis associated with DIC and perivascular hemorrhage. This is often associated with inherited thrombophilias, specifically protein C deficiency. Neonatal central nervous system thrombotic events, including cerebral sinovenous thrombosis and neonatal ischemic stroke, are important thrombotic events. These are discussed in detail in another chapter. In addition to familiarity with these sites of thromboses, it is crucial for clinicians to be aware of the different treatments that may be considered for the best long-term outcomes.
The majority of neonatal thrombi occur in the venous system, and most are associated with the placement of central venous catheters. Many of these cases are asymptomatic, though catheter-associated thrombi may present with catheter dysfunction. Symptomatic thrombi often present with swelling of the limbs and lower body in the case of inferior vena cava thrombosis versus swelling of the arm, head, and neck seen in superior vena cava thrombosis (otherwise known as SVC syndrome). Due to the frequent use of umbilical venous lines, neonates also may develop portal vein thrombosis, which can lead to hepatic lobar atrophy or portal hypertension. Intracardiac thrombosis may also develop. These thrombi are usually located in the right atrium and are often associated with central venous lines. The most frequent location for spontaneous venous thrombi in neonates is in the renal veins. Infants with renal vein thrombosis may present with macroscopic or microscopic hematuria, thrombocytopenia, or a palpable flank mass.
Neonatal arterial thrombi outside the central nervous system are almost exclusively due to iatrogenic causes. Rarely, a spontaneous thrombus may develop in the aorta. Femoral artery catheters used for cardiac catheterization and umbilical artery or peripheral arterial catheters used for blood pressure and blood gas monitoring are the main risk factors for arterial thrombi. These cases may be asymptomatic or present with signs of ischemia or organ dysfunction. Involved extremities ...