eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Neonatology
Polycythemia of the Newborn
Updated: Sep 4, 2007
Introduction
Background
Polycythemia, defined as a central venous hematocrit (Hct) of greater than 65%, is a relatively common disorder. The primary concern with polycythemia is related to hyperviscosity and its associated complications. Blood viscosity increases exponentially as the Hct rises above 42%. This associated hyperviscosity is thought to contribute to the symptom complex observed in approximately one half of infants with polycythemia. However, only 47% of infants with polycythemia have hyperviscosity, and only 24% of infants with hyperviscosity have a diagnosis of polycythemia.
Pathophysiology
As the central Hct increases, viscosity increases. The arterial oxygen content also increases. Changes in blood flow are observed in some organs; this is due to changes in viscosity or changes in arterial oxygen content. The change in blood flow may influence oxygenation and may influence the delivery of substances to organs that are dependent on plasma flow, such as glucose.
Many factors determine blood viscosity. The primary factor in the newborn is the Hct. As such, viscosity increases as Hct rises. Other factors that uniquely contribute to blood viscosity in the neonate include increased RBC volume and decreased deformability of the fetal erythrocyte. Plasma proteins, platelets, WBCs and endothelial factors also contribute to viscosity; however, they are not clinically significant in the newborn.
Frequency
United States
Polycythemia occurs in 0.4-12% of neonates. It is more common in infants who are small for their gestational age (SGA) and in infants who are large for their gestational age (LGA). However, most infants with polycythemia are of appropriate size or weight for their gestational age (AGA). Infants of mothers with diabetes have an incidence of more than 40%, and those born to mothers with gestational diabetes have an incidence of more than 30%. Polycythemia is also common in infants who have experienced delayed clamping of the umbilical cord. Hyperviscosity occurs in 6.7% of infants.
Mortality/Morbidity
- The central nervous, cardiopulmonary, gastrointestinal, and renal systems are at risk.
- Metabolic derangements are common.
- Coagulation also can be affected.
Age
- The Hct peaks 6-12 hours after birth and then declines until the infant is aged 24 hours, at which time it equals the Hct in cord blood.
- Fewer than 40% of infants with a Hct greater than 64% at 2 hours still have a high value at 12 hours or later.
Clinical
History
Neonates with polycythemia may have the following findings:
- Lethargy
- Irritability
- Jitteriness
- Tremors
- Seizures
- Cerebrovascular accidents
- Respiratory distress
- Cyanosis
- Apnea
Physical
- General
- The most obvious finding is plethora or ruddiness.
- Priapism may be observed in male patients.
- CNS
- CNS manifestations are the most common problems observed with polycythemia and hyperviscosity.
- Symptoms include lethargy, irritability, jitteriness, tremors, seizures, and cerebrovascular accidents.
- Cardiopulmonary: Manifestations include respiratory distress, tachypnea, cyanosis, apnea, and congestive heart failure. Increases in Hct are associated with a decrease in pulmonary blood flow in all newborns. In those with a Hct of 65% or more, the decrease in pulmonary blood flow may be associated with respiratory distress and cyanosis.
- Gastrointestinal
- Poor feeding is reported in more than one half of all infants with polycythemia and hyperviscosity.
- Necrotizing enterocolitis (NEC) is a rare but devastating complication of polycythemia or hyperviscosity. Historically, about 44% of term infants with NEC have polycythemia. More recent data suggest that polycythemia may not have a large role in the development of NEC in the term infant but may be related to partial exchange transfusion with colloid to reduce the Hct.
- Renal: Manifestations include decreased glomerular filtration rates, oliguria, hematuria, proteinuria, and renal vein thrombosis.
- Metabolic
- Hypoglycemia is the most common metabolic derangement and is observed in 12-40% of infants with polycythemia.
- Hypocalcemia is the next most common metabolic derangement and is found in 1-11% of neonates with polycythemia.
- Coagulation
- Coagulation can be affected.
- Thrombocytopenia
- Disseminated intravascular coagulation (DIC) is rare.
Causes
- Increased fetal erythropoiesis secondary to fetal hypoxia. Underlying causes include the following:
- Placental insufficiency can be secondary to preeclampsia, primary renovascular disease, chronic or recurrent abruptio placenta, maternal cyanotic congenital heart disease, postdate pregnancy, and maternal smoking. Most of these maternal conditions may also be associated with intrauterine growth restriction (IUGR).
- Endocrine abnormalities associated with increased fetal oxygen consumption resulting in fetal hypoxia include congenital thyrotoxicosis and Beckwith-Wiedemann syndrome or infants of a diabetic mother (IDM) with poor glycemic control.
- Genetics disorders (eg, trisomy 13, trisomy 18, trisomy 21) are also underlying causes.
- Hypertransfusion
- Delayed cord clamping allows for an increased blood volume to be delivered to the infant. When cord clamping is delayed more than 3 minutes after birth, blood volume increases 30%.
- Gravity also may be a factor because of the position of the delivered infant in relation to the maternal introitus before cord clamping.
- In the event of delayed cord clamping, blood flow to the infant is enhanced by oxytocin.
- Twin-to-twin transfusion syndrome due to a vascular communication occurs in approximately 10% of monozygotic twin pregnancies.
- In intrapartum asphyxia, blood volume is shifted from the placenta to the fetus.
More on Polycythemia of the Newborn |
 Overview: Polycythemia of the Newborn |
| Differential Diagnoses & Workup: Polycythemia of the Newborn |
| Treatment & Medication: Polycythemia of the Newborn |
| Follow-up: Polycythemia of the Newborn |
| References |
| Next Page » |
References
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Further Reading
Keywords
neonatal polycythemia, erythrocythemia, hematocrit, Hct, hyperviscosity, sludged blood, microthrombi, microthrombus
