Fetal or neonatal hypoxia, hypercapnia, poor cardiac output, and a metabolic acidosis can result from numerous conditions affecting the fetus, the placenta, or the mother. Whetherin utero or after birth, asphyxia-caused hypoxic-ischemic brain injury is the result of reduced gaseous exchange through the placenta or through the lungs. Asphyxia associated with severe bradycardia or cardiac insufficiency reduces or eliminates tissue blood flow, resulting in ischemia. The fetaland neonatal circulatory systems respond to reduced oxygenavailability by shunting the blood preferentially to the brain,heart, and adrenal glands and away from the intestine, kidneys, lungs, and skin.
Beta-ketothiolase deficiency (mitochondrial acetoacetyl CoA thiolase deficiency) BKT C5:1/C5OH
Cobalamin defects A, B CBL (A,B) C3
Long-chain hydroxyacyl-CoA dehydrogenase deficiency* LCHAD/D C16OH/C18:1OH
Trifunctional protein deficiency* TFP C16OH/C18:1OH
Very long chain acyl-CoA dehydrogenase deficiency VLCAD/D C14:1/C14
Galactosemia* GALT Total galactose, GALT activity
Congenital hypothyroidism CH T4, TSH HEMOGLOBIN DISORDERS
From Sahai I, Levy H: Newborn screening. In Gleason C, Devasker D editors: Avery’s diseases of the newborn, ed 9, Philadelphia, 2012, Saunders. *Can manifest acutely in the first week of life.
Metabolic acidosis during asphyxia is caused by the combined that interfere with uteroplacental perfusion (chronic hyper-effects of poor cardiac output secondary to hypoxic depression tension, preeclampsia, and diabetes mellitus) place the fetus of myocardial function, systemic hypoxia, and tissue anaerobic at risk for intrauterine asphyxia. Maternal epidural anesthesia metabolism. With severe or prolonged intrauterine or neonatal and the development of the vena caval compression syndrome asphyxia, multiple vital organs are affected (Table 58-6). may produce maternal hypotension, which decreases uterine
Many conditions that contribute to fetal or neonatal perfusion. Maternal medications given to relieve pain during asphyxia are the same medical or obstetric problems associ-labor may cross the placenta and depress the infant’s respiraated with high-risk pregnancy (Table 58-7). Maternal diseases tory center, resulting in apnea at the time of birth.
Table 58-5 Abnormal Newborn Screening Results: Possible Implications and Initial Action to Be Taken NEWBORN SCREENING FINDING DIFFERENTIAL DIAGNOSIS INITIAL ACTION ↑ Phenylalanine PKU, non-PKU hyperphenylalaninemia, pterin defect, galactosemia, transient hyperphenylalaninemia Repeat blood specimen
T4, ↑ TSH Congenital hypothyroidism, iodine exposure Repeat blood specimen or thyroid function testing, begin thyroxine treatment
T4, normal TSH Maternal hyperthyroidism, thyroxine-binding globulin Repeat blood specimen deficiency, secondary hypothyroidism, congenital hypothyroidism with delayed TSH elevation
Methionine Homocystinuria, isolated liver dysfunction, tyrosinemia Repeat blood and urine specimen type I, transient hypermethioninemia
Leucine Maple syrup urine disease, transient elevation Clinical evaluation including urine for ketones, acid-base status, amino acid studies, immediate neonatal ICU care if urine ketones positive
Tyrosine Tyrosinemia type I or type II, transient tyrosinemia, liver Repeat blood specimen disease