A nurse is collecting a blood phenylketonuria (PKU) test for a newborn prior to discharge. The newborn's guardian asks the nurse what a positive PKU test would mean.
Which of the following statements should the nurse make?
A positive finding indicates the inability to metabolize galactose.
A positive finding indicates the infant will have a slow metabolism.
A positive finding indicates an inability to metabolize certain amino acids.
A positive finding indicates an increased risk for neurologic anomalies.
The Correct Answer is C
Choice A rationale
A positive phenylketonuria (PKU) test indicates an inability to metabolize the amino acid phenylalanine, not galactose. Galactosemia is a separate metabolic disorder characterized by the body's inability to break down galactose, a sugar found in milk. Both are inborn errors of metabolism, but their biochemical pathways and dietary interventions differ significantly.
Choice B rationale
A positive PKU test does not indicate a slow metabolism in general. Instead, it specifically points to a deficiency in the enzyme phenylalanine hydroxylase (PAH), which is necessary for converting phenylalanine into tyrosine. This enzymatic defect leads to an accumulation of phenylalanine in the blood and tissues, which can become neurotoxic if untreated.
Choice C rationale
A positive finding for phenylketonuria (PKU) signifies a genetic disorder where the body lacks or has insufficient amounts of the enzyme phenylalanine hydroxylase. This enzyme is crucial for metabolizing the essential amino acid phenylalanine into tyrosine. Without proper enzyme function, phenylalanine accumulates in the blood, leading to neurotoxic effects if a specialized diet is not initiated promptly.
Choice D rationale
A positive PKU finding, if left untreated, directly leads to severe intellectual disability and other neurological problems due to the accumulation of phenylalanine, which is toxic to the developing brain. Therefore, it indicates an increased risk for neurologic anomalies if the condition is not managed through a strict low-phenylalanine diet from early infancy. .
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A rationale
Magnesium sulfate toxicity causes central nervous system depression, including respiratory depression. A respiratory rate of 12 breaths/min indicates that the respiratory depression has resolved, suggesting the calcium gluconate, a magnesium antagonist, has effectively reversed the neuromuscular blockade caused by magnesium. A normal respiratory rate is 12-20 breaths/min.
Choice B rationale
Absent deep tendon reflexes (DTRs) are a sign of magnesium sulfate toxicity due to its depressant effect on neuromuscular transmission. If calcium gluconate were effective, DTRs would return to normal or become less diminished, indicating resolution of magnesium's inhibitory effects on the nervous system.
Choice C rationale
Slurred speech is a neurological symptom associated with magnesium sulfate toxicity, reflecting central nervous system depression. If calcium gluconate were effective in reversing the toxicity, slurred speech would improve or resolve as the central nervous system depression diminishes.
Choice D rationale
Urine output of 22 mL/hr indicates oliguria, which can be a sign of worsening preeclampsia or kidney dysfunction, and is not an indicator of effective calcium gluconate administration for magnesium toxicity. Adequate urine output (typically >30 mL/hr) is essential for magnesium excretion and overall renal function.
Correct Answer is B
Explanation
Choice A rationale
Variable decelerations are typically caused by umbilical cord compression, which can occur in various obstetric scenarios but are not a specific expected finding for placenta previa. In placenta previa, the primary issue is placental implantation over or near the cervical os, leading to distinct clinical manifestations.
Choice B rationale
Painless vaginal bleeding is the hallmark clinical finding of placenta previa. This occurs because the placenta is implanted in the lower uterine segment, potentially covering the internal cervical os. As the cervix effaces or dilates, the placenta separates from the uterine wall, leading to bleeding without the associated pain of uterine contractions.
Choice C rationale
A rigid abdomen is a classic sign of abruptio placentae, where the placenta prematurely detaches from the uterine wall. This causes internal bleeding and uterine spasm, leading to a board-like, tender abdomen, which is distinct from the typical presentation of placenta previa.
Choice D rationale
Uterine tachysystole, characterized by excessive uterine contractions, is a common finding in conditions like abruptio placentae or during labor induction. It is not typically associated with placenta previa, where the primary concern is the placental position and the risk of hemorrhage rather than abnormal contraction patterns.
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