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  1. Problem. The hematocrit (Hct) is 68% in a newborn. The upper limit of a normal Hct for a newborn peripheral venous sample is 65%. Polycythemia occurs in 0.4–12% of newborn infants and is rare in premature infants <34 weeks' gestation.

  2. Immediate questions

      1. What is the central hematocrit (Hct)? In blood obtained by heelstick, the Hct may be falsely elevated by 5–15%. Treatment should never be initiated based on heelstick Hct values alone; a central (peripheral venous phlebotomy) Hct is needed. If the sample is from the umbilical vein or radial artery, the upper limit of normal is 63%.

      1. Does the infant have symptoms of polycythemia? Many infants with polycythemia are asymptomatic. One study found that feeding problems and lethargy were the most common symptoms. There are many symptoms and signs of polycythemia, which can include the following:

          1. Central nervous system. Lethargy, hypotonia, irritability, jitteriness, weak sucking reflex, vomiting, seizures, tremulousness, apnea, sleepiness, exaggerated startle, cerebrovascular accidents.

          1. Cardiovascular. Heart murmurs, congestive heart failure, cyanosis, plethora, tachycardia, cardiomegaly.

          1. Respiratory. Respiratory distress, tachypnea, cyanosis.

          1. Gastrointestinal. Poor feeding, poor suck, vomiting, necrotizing enterocolitis (NEC).

          1. Renal. Proteinuria, oliguria, hematuria, renal vein thrombosis.

          1. Hematologic. Thrombocytopenia, hepatosplenomegaly, thrombosis, disseminated intravascular coagulation (rare), elevated reticulocyte count.

          1. Metabolic. Hypoglycemia (12–40%), hypocalcemia (1–11%), increased jaundice (hyperbilirubinemia).

          1. Skin. Plethora or ruddiness.

          1. Miscellaneous. Testicular infarcts, priapism.

      1. Is the mother diabetic? Poor maternal control of diabetes during pregnancy leads to chronic fetal hypoxia, which may result in increased neonatal erythropoiesis. Infants of diabetic mothers have a 25–40% incidence of polycythemia. Infants of mothers with gestational diabetes also have an increased incidence (30%) of polycythemia.

      1. What is the infant's age? The Hct normally rises after birth and reaches a peak at 2 h of age and then slowly decreases. After 48 h of age, hemoconcentration as a result of dehydration may be present.

      1. Is the infant dehydrated? Dehydration may cause hemoconcentration, resulting in a high Hct. It usually occurs in infants >48 h old.

      1. Does the mother live at a high altitude? Infants born to mothers at high altitudes have a higher incidence of polycythemia.

      1. Is the infant small or large for gestational age? Polycythemia is more common in these infants.

  3. Differential diagnosis. See also Chapter 112.

      1. Falsely elevated Hct. This finding occurs most often when blood is obtained by heelstick.

      1. Dehydration. Weight loss and decreased urine output are sensitive indicators of dehydration. Hemoconcentration secondary to dehydration is suspected if >8–10% of the birthweight has been lost. It usually occurs on the second or third day of life.

      1. True polycythemia

          1. Placental transfusion (hypertransfusion) occurs with delayed cord clamping (defined as clamping the cord >3 min after delivery of the infant), twin-twin transfusion, maternal–fetal blood transfusion, stripping the cord, and holding the infant below the mother at delivery. Intrapartum asphyxia can cause blood volume to shift from the placenta to the fetus and cause polycythemia.

          1. Iatrogenic polycythemia is caused by overtransfusion.

          1. Intrauterine hypoxia may be caused by placental insufficiency. It may be seen in postmature, intrauterine growth restricted, or small for gestational age ...

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