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A 19-year-old primiparous woman develops toxemia in her last trimester of pregnancy and during the course of her labor is treated with magnesium sulfate. At 38 weeks™ gestation, she delivers a 2100-g infant with Apgar scores of 1 at 1 min and at 5 at 5 min. Laboratory studies at 18 h of age reveal a hematocrit of 79%, platelet count of 100,000/µL, glucose 38 mg/dL, magnesium 2.5 meq/L, and calcium 8.7 mg/dL. Soon after, this the infant has a generalized convulsion. The most likely cause of the infant™s seizure is ?
Options:
1. Polycythemia
2. Hypoglycemia
3. Hypocalcemia
4. Hypermagnesemia
5. Thrombocytopenia
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Correct Answer is: Polycythemia
Explanation:
An infant of 2100 g at 38 weeks would be considered small for gestational age (SGA), a not uncommon consequence of maternal toxemia. Pregnancy induced hypertension can produce a decrease in uteroplacental blood flow and areas of placental infarction. This can result in fetal nutritional deprivation and intermittent fetal hypoxemia, with a decrease in glycogen storage and a relative erythrocytosis, respectively. Hence, neonatal hypoglycemia and polycythemia are common clinical findings in these infants. A blood glucose level of 30 mg/dL in a full-term infant, however, is probably normal during the first postnatal day, and an infant is very unlikely to have a convulsion as a result of a level of 38 mg. Serum calcium levels usually decline during the first 2 to 3 postnatal days, but will only be considered abnormally low in a term infant when they fall below 7.5 to 8 mg/dL. Neonatal hypermagnesemia is common in an infant whose mother has received MgSO4 therapy, but is usually asymptomatic or produces decreased muscle tone or floppiness. A persistent venous hematocrit of greater than 65% in a neonate is regarded as polycythemia and will be accompanied by an increase in blood viscosity. Manifestations of the œhyperviscosity syndrome include tremulousness or jitteriness that can progress to seizure activity because of sludging of blood in the cerebral microcirculation or frank thrombus formation, renal vein thrombosis, necrotizing enterocolitis, and tachypnea. Therapy by partial exchange transfusion with albumin is probably more likely to be useful if performed prophylactically before significant symptoms have developed.
