HEMATOLOGIC DISORDERS IN THE NEWBORN INFANT
Saturday, August 16, 2008
BLEEDING DISORDERS
Neonatal coagulation is discussed in Chapter 26. Bleeding in the newborn infant may result from inherited clotting deficiencies (eg, factor VIII deficiency) or acquired disorders—hemorrhagic disease of the newborn, disseminated intravascular coagulation (DIC), liver failure, and thrombocytopenia.
1. HEMORRHAGIC DISEASE IN THE NEWBORN INFANT
Hemorrhagic disease in the newborn infant is caused by the deficiency of the vitamin K–dependent clotting factors (II, VII, IX, and X). Bleeding occurs in 0.25–1.7% of newborns who do not receive vitamin K prophylaxis after birth, generally in the first 5 days to 6 weeks in an otherwise well infant. Sites of ecchymoses and surface bleeding include the gastrointestinal tract, umbilical cord, circumcision site, and nose, although devastating intracranial hemorrhage can occur. Bleeding from vitamin K deficiency is more likely to occur in infants of mothers taking hydantoin anticonvulsants or warfarin and in breastfed infants because of very low amounts of vitamin K in breast milk, with slower and more restricted intestinal colonization. Differential diagnosis includes DIC and hepatic failure, both occurring in ill infants .
Treatment consists of 1 mg of vitamin K subcutaneously or intravenously. Intramuscular injections should be avoided in infants who are bleeding.
2. THROMBOCYTOPENIA
Infants with thrombocytopenia have generalized petechiae (not just on the presenting part) and platelet counts under 150,000/µL (usually < 50,000/µL, may be < 10,000/µL). Neonatal thrombocytopenia can be isolated or may occur in association with a deficiency of clotting factors. The differential diagnosis for thrombocytopenia with distinguishing clinical features is presented in Table 1–25. Treatment of neonatal thrombocytopenia is transfusion of platelets (10 mL/kg of platelets increases the platelet count by approximately 70,000/µL). Indications for transfusion in the term infant are clinical bleeding or a total platelet count less than 10,000–20,000/µL. In the preterm infant at risk for intraventricular hemorrhage, transfusion is indicated for counts less than 40,000–50,000/µL.
Isoimmune thrombocytopenia (analogous to Rh isoimmunization, with a PLA-1-negative mother and PLA-1-positive fetus) requires transfusion of maternal platelets, because 98% of the random population will also be PLA-1-positive. The mother would be the most readily available known PLA-1-negative donor. Treatment with steroids has been disappointing. Treatment with IVIG infusion, 1 g/kg/d for 3 days or until the platelet count has doubled or is over 50,000/µL, is recommended. Antenatal therapy of the mother with IVIG with or without steroids is also beneficial, since 20–30% of infants with isoimmune thrombocytopenia will experience intracranial hemorrhage, half of them before birth.
Infants born to mothers with idiopathic thrombocytopenic purpura are at low risk for serious hemorrhage despite the thrombocytopenia, and treatment is usually unnecessary. If bleeding does occur, a 1- to 2-week course of prednisone, 2 mg/kg/d, is recommended. If severe hemorrhage is present, IVIG can also be used.
ANEMIA
The newborn infant with anemia from acute blood loss presents with signs of hypovolemia (tachycardia, poor perfusion, hypotension), with an initially normal hematocrit that falls after volume replacement. Anemia from chronic blood loss is evidenced by pallor without signs of hypovolemia, with an initially low hematocrit and reticulocytosis.
Anemia can be caused by hemorrhage, hemolysis, or failure to produce red blood cells. Anemia occurring in the first 24–48 hours of life is the result of hemorrhage or hemolysis. Hemorrhage can occur in utero (fetoplacental, fetomaternal, or twin-to-twin), perinatally (cord rupture, placenta previa, incision through placenta at cesarean section), or internally (intracranial hemorrhage, cephalohematoma, ruptured liver or spleen). Hemolysis is caused by blood group incompatibilities, enzyme or membrane abnormalities, infection, and DIC, and is accompanied by significant hyperbilirubinemia.
Initial evaluation should include a review of the perinatal history, assessment of the infant’s volume status, and a complete physical examination. A Kleihaur-Betke test for fetal cells in the mother’s circulation should be done. A complete blood count, blood smear, reticulocyte count, and direct and indirect Coombs tests should be performed. This simple evaluation should suggest a diagnosis in most infants. It is important to remember that hemolysis related to blood group incompatibility will continue for weeks after birth. Serial hematocrits should be followed.
POLYCYTHEMIA
Polycythemia in the newborn is manifested by plethora, cyanosis, mild respiratory distress with tachypnea and oxygen need, hypoglycemia, poor feeding, emesis, and lethargy. The capillary hematocrit is > 68%, the venous hematocrit > 65%.
Elevated hematocrits occur in 2–5% of live births. Although 50% of polycythemic infants are AGA, the prevalence of polycythemia is greater in the SGA and LGA populations. Causes of increased hematocrit include (1) twin-twin transfusion, (2) maternal-fetal transfusion, (3) intrapartum transfusion from the placenta, and (4) chronic intrauterine hypoxia (SGA infants, LGA infants of diabetic mothers).
The consequence of polycythemia is hyperviscosity with decreased perfusion of the capillary beds. Clinical symptomatology can affect several organ systems (Table 1–26). Screening can be done by measuring a capillary (heel stick) hematocrit. If the value is greater than 68%, a peripheral venous hematocrit should be measured. Values greater than 65% should be considered consistent with hyperviscosity.
Treatment is recommended for symptomatic infants. Treatment for asymptomatic infants based strictly on hematocrit is controversial. Definitive treatment is accomplished by an isovolumic partial exchange transfusion with 5% albumin or normal saline, effectively decreasing the hematocrit. The amount to exchange (in milliliters) is calculated using the following formula:
where PVH = peripheral venous hematocrit, DH = desired hematocrit, BV = blood volume, and Wt = weight.
Blood is withdrawn at a steady rate from an umbilical venous line while the replacement solution is infused at the same rate through a peripheral intravenous line over 15–30 minutes. The desired hematocrit value is 50–55%; the assumed blood volume is 80 mL/kg.
Neonatal coagulation is discussed in Chapter 26. Bleeding in the newborn infant may result from inherited clotting deficiencies (eg, factor VIII deficiency) or acquired disorders—hemorrhagic disease of the newborn, disseminated intravascular coagulation (DIC), liver failure, and thrombocytopenia.
1. HEMORRHAGIC DISEASE IN THE NEWBORN INFANT
Hemorrhagic disease in the newborn infant is caused by the deficiency of the vitamin K–dependent clotting factors (II, VII, IX, and X). Bleeding occurs in 0.25–1.7% of newborns who do not receive vitamin K prophylaxis after birth, generally in the first 5 days to 6 weeks in an otherwise well infant. Sites of ecchymoses and surface bleeding include the gastrointestinal tract, umbilical cord, circumcision site, and nose, although devastating intracranial hemorrhage can occur. Bleeding from vitamin K deficiency is more likely to occur in infants of mothers taking hydantoin anticonvulsants or warfarin and in breastfed infants because of very low amounts of vitamin K in breast milk, with slower and more restricted intestinal colonization. Differential diagnosis includes DIC and hepatic failure, both occurring in ill infants .
Treatment consists of 1 mg of vitamin K subcutaneously or intravenously. Intramuscular injections should be avoided in infants who are bleeding.
2. THROMBOCYTOPENIA
Infants with thrombocytopenia have generalized petechiae (not just on the presenting part) and platelet counts under 150,000/µL (usually < 50,000/µL, may be < 10,000/µL). Neonatal thrombocytopenia can be isolated or may occur in association with a deficiency of clotting factors. The differential diagnosis for thrombocytopenia with distinguishing clinical features is presented in Table 1–25. Treatment of neonatal thrombocytopenia is transfusion of platelets (10 mL/kg of platelets increases the platelet count by approximately 70,000/µL). Indications for transfusion in the term infant are clinical bleeding or a total platelet count less than 10,000–20,000/µL. In the preterm infant at risk for intraventricular hemorrhage, transfusion is indicated for counts less than 40,000–50,000/µL.
Isoimmune thrombocytopenia (analogous to Rh isoimmunization, with a PLA-1-negative mother and PLA-1-positive fetus) requires transfusion of maternal platelets, because 98% of the random population will also be PLA-1-positive. The mother would be the most readily available known PLA-1-negative donor. Treatment with steroids has been disappointing. Treatment with IVIG infusion, 1 g/kg/d for 3 days or until the platelet count has doubled or is over 50,000/µL, is recommended. Antenatal therapy of the mother with IVIG with or without steroids is also beneficial, since 20–30% of infants with isoimmune thrombocytopenia will experience intracranial hemorrhage, half of them before birth.
Infants born to mothers with idiopathic thrombocytopenic purpura are at low risk for serious hemorrhage despite the thrombocytopenia, and treatment is usually unnecessary. If bleeding does occur, a 1- to 2-week course of prednisone, 2 mg/kg/d, is recommended. If severe hemorrhage is present, IVIG can also be used.
ANEMIA
The newborn infant with anemia from acute blood loss presents with signs of hypovolemia (tachycardia, poor perfusion, hypotension), with an initially normal hematocrit that falls after volume replacement. Anemia from chronic blood loss is evidenced by pallor without signs of hypovolemia, with an initially low hematocrit and reticulocytosis.
Anemia can be caused by hemorrhage, hemolysis, or failure to produce red blood cells. Anemia occurring in the first 24–48 hours of life is the result of hemorrhage or hemolysis. Hemorrhage can occur in utero (fetoplacental, fetomaternal, or twin-to-twin), perinatally (cord rupture, placenta previa, incision through placenta at cesarean section), or internally (intracranial hemorrhage, cephalohematoma, ruptured liver or spleen). Hemolysis is caused by blood group incompatibilities, enzyme or membrane abnormalities, infection, and DIC, and is accompanied by significant hyperbilirubinemia.
Initial evaluation should include a review of the perinatal history, assessment of the infant’s volume status, and a complete physical examination. A Kleihaur-Betke test for fetal cells in the mother’s circulation should be done. A complete blood count, blood smear, reticulocyte count, and direct and indirect Coombs tests should be performed. This simple evaluation should suggest a diagnosis in most infants. It is important to remember that hemolysis related to blood group incompatibility will continue for weeks after birth. Serial hematocrits should be followed.
POLYCYTHEMIA
Polycythemia in the newborn is manifested by plethora, cyanosis, mild respiratory distress with tachypnea and oxygen need, hypoglycemia, poor feeding, emesis, and lethargy. The capillary hematocrit is > 68%, the venous hematocrit > 65%.
Elevated hematocrits occur in 2–5% of live births. Although 50% of polycythemic infants are AGA, the prevalence of polycythemia is greater in the SGA and LGA populations. Causes of increased hematocrit include (1) twin-twin transfusion, (2) maternal-fetal transfusion, (3) intrapartum transfusion from the placenta, and (4) chronic intrauterine hypoxia (SGA infants, LGA infants of diabetic mothers).
The consequence of polycythemia is hyperviscosity with decreased perfusion of the capillary beds. Clinical symptomatology can affect several organ systems (Table 1–26). Screening can be done by measuring a capillary (heel stick) hematocrit. If the value is greater than 68%, a peripheral venous hematocrit should be measured. Values greater than 65% should be considered consistent with hyperviscosity.
Treatment is recommended for symptomatic infants. Treatment for asymptomatic infants based strictly on hematocrit is controversial. Definitive treatment is accomplished by an isovolumic partial exchange transfusion with 5% albumin or normal saline, effectively decreasing the hematocrit. The amount to exchange (in milliliters) is calculated using the following formula:
where PVH = peripheral venous hematocrit, DH = desired hematocrit, BV = blood volume, and Wt = weight.
Blood is withdrawn at a steady rate from an umbilical venous line while the replacement solution is infused at the same rate through a peripheral intravenous line over 15–30 minutes. The desired hematocrit value is 50–55%; the assumed blood volume is 80 mL/kg.
0 comments:
Post a Comment