Neonatology PREP Review

Neonatology PREP Review
June 6, 2008

Prep 2006: Question 8 You are called to the delivery room to evaluate an infant who has been delivered by spontaneous vaginal delivery. The term infant weighs 3.6 kg and has some grunting respirations. You decide to observe her in the newborn intensive care unit. One hour later, you are notified that the infant is experiencing pronounced respiratory distress and oxygen saturations in the 70% range in the right hand and in the 50% range in the right foot. There is poor perfusion. There are no murmurs, but there is a pronounced precordial lift and a loud second heart sound. Of the following, the MOST likely diagnosis for this infant is A. congenital diaphragmatic hernia B. congenital toxoplasmosis C. hypoplastic left heart syndrome D. persistence of the fetal circulation E. tetralogy of Fallot

Prep 2006: Question 8 Differential dx of cyanosis and hypoxemia in the neonate persistence of the fetal circulation (PPHN) meconium aspiration syndrome cyanotic congenital heart disease Problem = oxygen delivery Ductus arteriosus = fetal shunt, allowing right heart to deliver desaturated blood to placenta by shunting this blood away from high-resistance pulmonary arteries and to the descending aorta. Fetal pulmonary vascular resistance is slightly higher than systemic because the lungs are filled with fluid and the placenta is a low-resistance circuit. At birth, the lungs expand with air and the placenta is removed from the circulation, causing PVR to fall and SVR to rise. This leads to a reversal of flow across the ductus arteriosus (from the systemic into the pulmonary circuit). Over subsequent hours and days, the ductus arteriosus begins the process of spontaneous closure. In cases where PVR remains > SVR, right-to-left shunt across the ductus (now PDA) persists as long as the ductus arteriosus is patent, maintaining fetal circulation (“persistence of the fetal circulation," or perhaps better stated, "persistent pulmonary hypertension of the newborn”)

Review of Fetal Circulation

Prep 2006: Question 8 Causes of PVR? pneumonia, lung collapse, and pulmonary hypoplasia, MAS, surfactant deficiency/RDS Highly desaturated blood enters the descending aorta, often causing lower O2 sats in the LE than in the UE. Likely co-existent pulmonary pathology includes ventilation-perfusion (V-Q) returning relatively desaturated blood to the left heart, then to the aorta Signs of underlying pulmonary process: grunting (self-PEEP to keep alveoli and small airways open), tachypnea, and ultimately respiratory distress and failure PPHN will not improve with 100% O2 test because blood is bypassing the lungs Precordial lift caused by increased volume, pressure, and workload on the RV. Poor perfusion is caused by failure (diminished ventricular function) of the right ventricle and its impact on LV.

Prep 2006: Question 8 Neonates who have diaphragmatic hernia often present with respiratory distress and a shift of the precordium to the right chest because the gastrointestinal contents typically occupy the left thorax. Infants who have toxoplasmosis may have signs and symptoms of systemic infection, but they are unlikely to present solely with pulmonary pathology. Hypoplastic left heart syndrome also has R-to-L shunt at the ductus arteriosus (required to supply any systemic blood flow), but will have normal lungs and low PVR, with O2 sats typically in the % range. Tetralogy of Fallot usually presents with the murmur of pulmonary stenosis, and when the ductus arteriosus is present, blood flow is left to right because pulmonary vascular resistance and the lungs are normal.

Respiratory Distress: Matching
Term newborn becomes tachypneic in well baby nursery, desats to 89% but improves to 98% with blow-by O2 Post-term infant NSVD with rupture at time of crowning + meconium-stained fluid. On delivery, infant is limp with minimal respiratory effort. 30 WGA infant delivered by C/S second to PTL with fetal distress. Upon delivery infant is cyanotic with severe retractions, nasal frlaring and grunting.

Prep 2006: Question 51 A mother brings in her 1-week-old female infant, who has been vomiting for the past 3 hours. In the past hour, the baby has vomited a combination of undigested food and green material. The infant has been fed with cow milk formula. Physical examination demonstrates an alert but fussy infant who is afebrile. Her abdomen is soft and mildly distended without any organomegaly. Of the following, the BEST next step is to A. begin therapy with oral ranitidine B. change the feeding to a protein hydrolysate formula C. obtain emergent abdominal ultrasonography D. obtain emergent barium enema E. obtain emergent upper gastrointestinal radiographic series

Prep 2006: Question 51 Any infant with sudden onset of bilious vomiting must be evaluated emergently for malrotation with or without volvulus because of risk of massive bowel necrosis if not operated on promptly. Approximately 20% of neonates who develop bilious vomiting have conditions that require surgical intervention. ~ 30% of cases of malrotation with volvulus present in the first postnatal week, 50% of cases present in the first postnatal month, but may occur at any age Assuming KUB does not show free air or high-grade obstruction, best test to evaluate for malrotation is an UGI (KUB may be normal)

Prep 2006: Question 51 Other conditions that may present BO and bilious vomiting in the neonatal period: duodenal atresia, annular pancreas, jejunal atresia, ileal atresia, colonic atresia, meconium ileus, and Hirschsprung disease BE may demonstrate malrotation, but not as reliable as UGI. BE more useful in evaluating distal bowel obstruction if suspecting Hirschsprung disease is high. Abdominal U/S useful for diagnosing pyloric stenosis, but not for malrotation. Pyloric stenosis typically presents with nonbilious vomiting between 3 wk - 3 mo. Until more serious surgical conditions have been excluded, empiric therapy with ranitidine (for reflux) or protein hydrolysate formula (for possible milk intolerance) is not indicated for an infant who vomits bile. The vomitus from infants who have gastroesophageal reflux or milk intolerance sometimes may contain small amounts of bile, but the clinician must exclude more serious pathology first.

Prep 2006: Question 68 A woman presents to her obstetrician at 36 weeks' gestation with a complaint of decreased fetal movement over the past 24 hours. Her doctor orders a nonstress test. Of the following, the nonstress test is MOST likely to help determine A. amniotic fluid volume B. fetal maturity C. fetal tolerance of labor D. integrity of the fetal autonomic nervous system E. uteroplacental insufficiency

Prep 2006: Question 68 NST is a measure of spontaneous fetal movement and fetal heart rate reactivity; thus, an indicator of fetal autonomic nervous system integrity, not fetal maturity. Decreased fetal movement requires investigation. NST should be the initial evaluation to look for a baseline fetal heart rate, short- and long-term fetal heart rate variability, and reactivity to any noted fetal movement. Results may be reactive (reassuring) or nonreactive (concerning), which requires further evaluation by ultrasonography. Then biophysical profile score is assigned, based on: amniotic fluid volume, fetal movement, and fetal breathing activity, together with the results of NST Contraction stress test measures fetal heart rate reactivity to uterine contraction and, therefore, can assess uteroplacental sufficiency and tolerance of labor.

Prep 2006: Question 100 A 30-week gestation 1,250-g infant is admitted to the neonatal intensive care unit. She exhibits no respiratory distress and has normal findings on physical examination. Of the following, the BEST type of intravenous fluid to administer to this infant is A. 0.45% sodium chloride B. 0.9% sodium chloride C. dextrose 5% in water D. dextrose 10% in water E. Ringer lactate solution

Prep 2006: Question 100 VLBW infants often are unable to consume adequate enteral nutrition on the first day after birth. Disease or distress increase energy requirements further. Glucose must be provided to maintain normal metabolism and avoid hypoglycemia, which is dangerous to the developing CNS. D10W is recommended to meet the VLBW infant's energy requirements (5 to 7 mg/kg/min of glucose) because D5W requires volumes of 150 to 200 mL/kg/d delivering excessive free water and possibly causing cardiopulmonary compromise. Saline-containing fluids, are unnecessary in the first hrs for most VLBW newborns because free water losses exceed solute losses and sodium balance is maintained. This period of volume contraction must occur before saline is provided intravenously.

Prep 2006: Question 116 A 5-week-old infant who was born at 29 weeks' gestation and whose birthweight was 1,300 g is in the neonatal intensive care unit (NICU). She has experienced three cardiopulmonary arrests since birth, a grade III intraventricular hemorrhage, sepsis with associated shock, and necrotizing enterocolitis that did not require surgery. Physical examination today reveals normal neuromotor tone, normocephaly, a clear chest, and a soft abdomen. She is tolerating full enteral feedings by nasogastric tube. Her ophthalmologic examination to rule out retinopathy of prematurity is due next week. Of the following, the MOST accurate statement about this infant's prognosis is that A. hydrocephalus is an expected outcome B. long-term disability is related to morbidity in the NICU C. survival for very low-birthweight infants in modern NICUs is slightly more than 50% D. the most common disability for very low-birthweight infants is visual impairment E. this infant is unlikely to have any disability

Prep 2006: Question 116 Outcomes for infants in NICUs depends on multiple factors: GA (> 85% of VLBW infants survive; survival rates are correlated positively with GA) Perinatal brain injuries and their severity (particularly ICH and periventricular white matter disease) greatly influence long-term outcomes (affect approximately 35%, and their individual frequencies are inversely related to gestational age) Mild germinal matrix hemorrhage not intruding into the ventricle (Grade I) is not associated with significant disability; Grade II hemorrhage has a small but present risk of neurodevelopmental or neuromotor impairment; Grade III hemorrhage (associated with ventriculomegaly) has a 10% associated mortality risk and 30% likelihood of cognitive or motor impairments; Grade IV hemorrhage (intraparenchymal hemorrhage) has a nearly 80% mortality risk, with more than 90% of survivors having cognitive and motor impairments. Normal brain growth, normal findings on neurologic examination, and normal oromotor feeding skills at corrected gestational age are good prognosticators for a normal outcome ROP is not infrequent, affecting 20% to 40% of VLBW less than 1,250 g. Visual impairment occurs in about 10% of infants who have been in NICUs.

Prep 2006: Question 132 A seemingly healthy term infant is referred to your neonatal intensive care unit from a community hospital after he develops abdominal distention at 48 hours of age. He has been fed formula, and there has been no emesis. Physical examination findings are normal other than the abdominal distention; the anus is patent. An abdominal flat plate radiograph demonstrates large, dilated, stacked loops of bowel and an absence of air in the rectosigmoid area. Of the following, the BEST diagnostic imaging test to determine the cause of this infant's abdominal distention is a A. contrast enema B. fluoroscopic swallowing study C. Meckel scan D. ultrasonography of the gastric outlet E. upper gastrointestinal radiographic series

Prep 2006: Question 132 Abdominal distention is a hallmark of intestinal obstruction. < 24 h: UGI obstruction (duodenal atresia/stenosis, duodenal web, malrotation, volvulus); may be associated w/ bile-stained emesis. > 24 h: LGI obstruction; may be associated with absence of stool; emesis may not occur until more than h after birth. On KUB: SBO - enlarged gastric bubble of air, duodenal bubble of air, and absence of air in the remainder of the abdomen. LBO - air-filled loops of bowel are seen diffusely, but the bowel proximal to the obstruction frequently is markedly dilated, and the loops appear stacked on top of each other. May also have absence of air in rectosigmoid area (vignette)

Prep 2006: Question 132 Best diagnostic imaging approach for suspected LBO is BE Fluoroscopic swallowing study is used to evaluate swallowing dysfunction, laryngotracheal aspiration, or esophageal obstruction. UGI is for evaluating a suspected SBO, however, residual contrast material often precludes the assessment of the large bowel, and should follow, rather than precede, a contrast enema if uncertain of the location of the obstruction. Meckel scan is useful in evaluating SBO or intussusception; it seldom is used in the newborn period. Ultrasonography of the gastric outlet is useful in evaluating pyloric stenosis, an upper intestinal tract obstruction.

Prep 2006: Question 249 You are discussing neonatal hearing screening with medical students on rounds with you in the newborn nursery. Of the following, the statement that you are MOST likely to include in your discussion is that A. an infant should be tested while asleep B. intervention in children who have hearing impairment should begin at 12 months of age C. normal neonatal hearing screening results should be confirmed by repeat testing at 6 months of age D. otoacoustic emission is the definitive procedure for testing hearing in newborns E. visual reinforcement audiometry currently is used as a screening test in newborns

Prep 2006: Question 249 The prevalence of moderate-to-severe hearing loss in neonates is 1 to 3:1,000 infants. Early identification of hearing loss (ideally at younger than 3 months of age) and intervention for infants younger than 6 months of age is believed to improve speech and language development and cognitive outcomes. Universal newborn hearing screening (UNHS) can identify newborns who have hearing impairments, and early intervention may improve long-term outcomes. The three current screening technologies used are: automated auditory brainstem response (AABR), transient evoked otoacoustic emissions (TEOAE), and distortion product otoacoustic emissions (DPOAE). All three tests detect the response to sound and provide a "pass" or "fail" ("refer") outcome with an automatic analyzer. Accuracy is poor if the infant is not resting comfortably, preferably asleep, with either the ABR or OAE method of testing. Physical movement of the stimulus probe in the ear is the primary problem with OAE. Body movement may decrease sensitivity of the AABR. Specificity also is decreased if environmental noise levels are too high.

Prep 2006: Question 249 Visual reinforcement audiometry is a behavioral screening method that can be used in children between 6 months and 2 years of age. In this test, a child's response to sound is rewarded by a stimulus, such as a toy or light, when the child looks up or toward the side of the auditory stimulus. It is not used in newborn screening. Normal neonatal hearing screening results do not always rule out a hearing deficit. Normal results on a neonatal screening test do not need to be confirmed by repeat testing at 6 months of age. However, any subsequent concerns for hearing deficits by either the clinician or parents should be addressed with a repeat hearing test. Hearing impairment that is due to either congenital (cytomegalovirus) or acquired (meningitis) infections will not be detected by newborn screening.

Prep 2007: Question 3 A term newborn is delivered by emergent cesarean section because of intrauterine growth restriction, oligohydramnios, and nonreassuring fetal heart rate monitoring in labor. Delivery room resuscitation includes endotracheal intubation and assisted ventilation with 100% oxygen, chest compressions, intravenous epinephrine, and volume expansion. Apgar scores are 1, 2, and 3 at 1, 5,and 10 minutes, respectively. An umbilical cord arterial blood gas measurement documents a pH of 6.9 and a base deficit of 20 mmol/L. At 12 hours of age, the infant demonstrates tonic-clonic convulsive activity of the arms and legs with a concomitant decrease in heart rate and bedside pulse oximetry saturation.Of the following, the MOST likely cause for this infant's seizure is A. Hypercalcemia B. Hypercarbia C. Hyperglycemia D. Hypomagnesemia E. Hypoxia

Prep 2007: Question 3 Seizures are the most frequent sign of CNS injury in the newborn. In a newborn who has depressed neuromotor tone, reflexes, and cardiopulmonary function at birth that requires assisted ventilation, perinatal asphyxia is likely. Apgar scores typically are depressed to < 3 at 5 or more min, and there is a severely acidotic umbilical cord arterial pH (<7.0), with evidence of metabolic acidemia. HIE is the most common cause of seizures in the first 24 h of postnatal life and accounts for up to 67% of early neonatal seizures. Other causes of neonatal seizure include intracranial hemorrhage, cerebrovascular accidents (stroke) or hemorrhagic infarction (10% to 15%); intracranial malformation (<10%); transient hypoglycemia or hypocalcemia (<10%); drug withdrawal (<5%); and inborn errors of metabolism (<5%).

Prep 2007: Question 3 When seizures occur > 24 hours after birth, especially in the absence of any history of fetal or neonatal asphyxia, evaluation should focus on potential causes other than HIE, like infection (meningitis, encephalitis). Asphyxia may result in hypocalcemia and hypoglycemia but hyperglycemia and hypercalcemia are not associated with HIE and do not typically cause seizures Hypomagnesemia may accompany hypocalcemia in the infant of a diabetic mother, but it is not common following asphyxia and is not associated with neonatal seizures. Hypercarbia may occur in the depressed newborn who has inadequate ventilation, but it is not associated with seizures unless there is corresponding hypoxia.

Prep 2007: Question 35 A term male infant is born to a woman who has known multiple drug abuse problems. Her urine drug screen was positive for barbiturates, benzodiazepines, and opioids upon admission to the labor and delivery unit. The infant is delivered vaginally without complications. Apgar scores are 8 and 9 at 1 and 5 minutes, respectively. His birthweight is 3,500 g. You are asked to evaluate the infant for early discharge at 23 hours of age. Findings on physical examination are normal, with the exception of jitteriness, and the infant is not breastfeeding well. Of the following, the BEST reason to keep this infant in the hospital is that A. a negative urine drug screen for the infant is required B. breastfeeding failure requires a lactation consultation C. foster care placement must be arranged D. jitteriness is most likely due to hypoglycemia that requires treatment E. neonatal abstinence syndrome may not be fully evident for 5 days or more

Prep 2007: Question 35 In the US, 5% to 15% of all pregnancies may be complicated by perinatal drug exposure The most commonly used legal substances are tobacco and alcohol. Drug effects must be distinguished from withdrawal effects The direct effects of some drugs of abuse include sedation or somnolence, depression of respiratory drive, depressed neuromotor tone, bradycardia, thermoregulatory problems, and pinpoint pupils (methadone, morphine, heroin, codeine, oxycodone, alcohol, barbiturates, benzodiazepines) or increased sensory stimulation with agitation, tachycardia, hypertension, and dilated pupils (amphetamines, cocaine). Early discharge is not an option for any infant in whom perinatal drug exposure is a real concern, such as the infant described in the vignette, because the onset of symptoms of abstinence syndrome following delivery and postnatal cessation of drug exposure varies with the substance to which the fetus was exposed. It is also important to consider the timing of last known exposure (maternal use). No true withdrawal or abstinence syndrome for cocaine exists. Similarly, amphetamine effects dissipate after a few postnatal days, and no real abstinence syndrome exists for this class of substances. However, neither drug is considered safe or free of prenatal damage to the developing brain; both may have direct effects on neurotransmitters and affect brain circulation. Effects of cocaine and amphetamine on the maternal and uteroplacental circulation also may be related to the reduced fetal body and head growth described in some exposed fetuses.

Prep 2007: Question 35 Alcohol and barbiturate withdrawal syndromes share many common physical findings, including hyperactivity, irritability, crying, hyperphagia but poorly coordinated sucking and oral feeding, altered sleep-wake periods, tremors, diaphoresis, and seizures. Alcohol withdrawal also may present with hypoglycemia and excessive glucocorticoid release. In addition to a controlled, thermoneutral environment, with minimal stimulation, phenobarbital provides the best pharmacologic management. Such treatment should be used in conjunction with an objective scoring system for physical findings to titrate the dose to effect. A schedule for tapering phenobarbital over 4 to 6 weeks is recommended. An alternative, though less well substantiated, management approach is the use of a dilute tincture of opium and diazepam. Opioid withdrawal is best recognized by an abstinence syndrome that is characterized by numerous behavioral and physiologic stigmata, including hyperirritability, tremors, jitteriness, hypertonia, gastrointestinal distress (loose stools, emesis, and feeding problems), and vague autonomic symptoms such as yawning, lip-smacking, persistent sucking, mottling, and fever. Seizures may occur. Methadone or oral morphine must be used to manage the physical findings, which may not become manifest for 5 days (longer if the mother was treated with methadone). Again, the use of a neonatal abstinence scoring system is essential in managing affected newborns.

Prep 2007: Question 35 A urine drug screen for the infant described in the vignette may be obtained within 24 hours and would be most concerning if positive for any of the substances identified on his mother's urine drug screen. However, the more time that passes after birth and before collecting the newborn's urine, the less likely that the results will be positive because most drugs and their metabolites are cleared by 96 hours after birth. At fewer than 24 hours of postnatal age, the infant may be demonstrating simple breastfeeding problems or the problems may reflect oral-motor coordination issues related to drug exposure. Jitteriness suggests neurologic irritability associated with maternal drug use; hypoglycemia is a less likely cause in an appropriately grown term infant. Although social issues such as placement of an infant in a safe environment must be addressed, foster care placement may take a long time and is not the best reason for delaying discharge.

Image Recognition After a prolonged labor a boggy mass is palpable over vertex of skull in midline with visible overlying bruising. Diagnosis?

Image Recognition At the time of delivery a soft swelling palpable left of midline at vertex with palpable sagittal suture. Over the next several days the infant develops significant jaundice. The swelling resolves gradually over several weeks. Diagnosis? Cause for concern?

Image Recognition In the well baby nursery an infant is noticed to have an asymmetric lip upon crying. Diagnosis? Prognosis?

Image Recognition Based upon these images (drawing the elbow across the chin), which infant is more mature?

Prep 2007: Question 51 You are asked to see a term infant in the newborn nursery at 8 hours of age and consider her transfer to the neonatal intensive care unit. The problems and findings reported to you include: poor feeding, emesis, temperature instability (core temperature of 96｡F [35.5｡C]), hypoglycemia (whole blood glucose concentration of 25 mg/dL [1.4 mmol/L]), and polycythemia (hematocrit of 70% [0.70]).Of the following, the physical finding that is MOST likely to accompany these problems is A. a tuft of hair over the sacral region B. birthweight of 1,800 g C. cafe au lait macule on the left leg D. iris coloboma of the right eye E. isolated cleft of the hard palate

Prep 2007: Question 51 Infants who are small for gestational age (<2,500 g) at birth may be affected by maternal disease states (eg, advanced maternal diabetes mellitus, chronic hypertension, cardiovascular disease); pregnancy-related problems, including poor nutritional status with poor weight gain or pregnancy-induced hypertension (PIH); or fetal conditions such as congenital infection, chromosome abnormality, or birth defects. The infant's aberrant growth may be discerned prenatally (intrauterine growth restriction [IUGR]) or only noted at the time of birth. These infants have both increased morbidity and mortality compared with appropriately grown term infants (Item C51A). The fetus that experiences IUGR often has a poor tolerance for labor. Consequently, perinatal asphyxia is more common, and successful transition and adaptation to extrauterine life is fraught with complications. Such complications include temperature instability (hypothermia) related to a large head-to-body ratio, decreased subcutaneous fat, and small energy reserves, all of which require a thermoneutral environment and an avoidance of fasting. Hypoglycemia may be present and would be treated best with an intravenous dextrose infusion. Feeding problems that may preclude enteral feeding for a time or require the use of a nasogastric or orogastric feeding tube are not uncommon in the small-for-gestational age infant. Polycythemia may be present and reflects fetal adaptation to chronic hypoxia by increasing the erythrocyte mass to enhance oxygen-carrying capacity. Polycythemia also may be associated with impaired feeding, hypoglycemia, and jitteriness. When the hematocrit is greater than 70% (0.70) and there are clinical signs of altered neurologic function, a partial exchange transfusion with normal saline should be performed to reduce the hematocrit to 55% (0.55). The findings reported for the infant in the vignette most likely are associated with the infant being small for gestational age (<2,500 g birthweight). A tuft of hair over the sacral region may indicate occult spina bifida, but this finding would not be associated with growth impairment. Similarly, caf� au lait macules (often seen in neurofibromatosis), an iris coloboma (Item C51B) (seen in the CHARGE syndrome), and isolated clefting of the hard palate are not commonly associated with growth restriction.

Prep 2007: Question 67 An infant is delivered by cesarean section at 34 weeks' gestation because of preterm labor. There is no history of ruptured membranes, maternal fever, or abnormalities in fetal heart rate monitoring. The infant requires assisted ventilation with a bag-mask device and 100% oxygen in the delivery room. His Apgar scores are 5 and 7 at 1 and 5 minutes, respectively. An umbilical cord arterial pH is 7.23 and base deficit is 3 mmol/L. He is admitted to the newborn nursery, but transferred to the neonatal intensive care unit (NICU) within 1 hour for respiratory distress manifested by tachypnea and grunting. His arterial blood gas results (obtained on room air) upon admission to the NICU are: pH, 7.20; Pco2, 70 mm Hg; PO2, 50 mm Hg, and base deficit 10 mmol/L.Of the following, the MOST common cause for this infant's respiratory distress is A. aspiration of amniotic fluid B. Hemothorax C. Pneumopericardium D. Pneumoperitoneum E. pneumothorax

Prep 2007: Question 67 Grunting respirations, as described for the infant in the vignette, are indicative of an infant breathing against a partially closed glottis, allowing for a prolonged expiratory phase and an elevation of end-expiratory volume (described by some as self-induced positive end-expiratory pressure). This mechanism may be helpful to the newborn who has an effective loss of functional residual capacity (diffuse atelectasis or impaired pulmonary compliance), acidemia (metabolic or associated with sepsis) with associated hyperpnea as an attempt to accomplish compensatory respiratory alkalosis, and air-leak syndromes that result in grossly reduced functional residual capacity due to collapsed lung volume. Because the newborn in the vignette has received positive-pressure ventilation, the most likely cause of his grunting is a pneumothorax. Pneumopericardium and pneumoperitoneum are rare in newborns. Hemothorax is seen with trauma, coagulopathy, or chest surgery. Aspiration of amniotic fluid is unlikely in this scenario. The blood gas values reported for the infant are indicative of a mixed, but principally respiratory acidemia. The normal PCO2 is 35 to 45 mm Hg, and correcting the hypercarbia will restore the pH to greater than The base deficit of 10 mmol/L is mildly increased and likely reflects the mild hypoxemia (PO2 <60 mm Hg) associated with the respiratory distress, collapsed lung, and possible hemodynamic embarrassment.

Prep 2007: Question 67 A 30 weeks' gestation infant weighing 1,500 g experiences respiratory distress that requires assisted ventilation in the first 4 hours after birth. Some tachypnea with mild subcostal and intercostal retractions is evident on physical examination. Current ventilator parameters are: positive end-expiratory pressure of 4 cm H2O, peak inspiratory pressure of 22 cm H2O, synchronized ventilator rate of 40 breaths/min, and fraction of inspired oxygen of 0.8 to maintain a Pao2 of 60 mm Hg. A chest radiograph reveals low lung volumes, diffuse microatelectasis, and dense ground-glass opacities. You order surfactant for intratracheal administration.Of the following, the MOST expected event in the 4 hours following surfactant administration is A. decreased oxygen requirement B. decreased pulmonary compliance C. Hypotension D. increased inspiratory pressure E. pulmonary hemorrhage

Prep 2007: Question 67 Exogenous surfactant therapy for neonatal respiratory distress syndrome (RDS) is perhaps the greatest example of bench-to-bedside research that has benefited newborns. Since the late 1980s, when clinical trials demonstrated the efficacy and safety of intratracheally administered surfactant, it has become the standard therapy, in conjunction with assisted ventilation and judicious oxygen therapy, in treating millions of newborns who have RDS. Upon diagnosing RDS in a preterm infant by clinical, radiographic, and blood gas parameters, early administration of surfactant results in obvious improvement in each of these broad categories. Clinically, treated infants demonstrate less work of breathing, improved oxygenation and ventilation, a reduction in assisted ventilation (apparent by diminished FiO2), decreased mean airway pressure (most readily accomplished by a reduction in inspiratory pressure), and improved pulmonary compliance (reflected in improved changes in lung volume per unit of inspiratory pressure administered). Radiographically, the degree of lung aeration improves as microatelectasis is overcome, and lung volumes typically improve. Blood gas measurements indicate improved ventilation and oxygenation and resolution of acidemia. Hypotension is a complication of RDS in the critically ill newborn and may reflect impaired circulatory volume, venous return to the heart (preload), and cardiac output. With significant hypoxemia and acidemia, myocardial function may be impaired. Additionally, the ductus arteriosus may remain patent as a result of poor neonatal oxygenation. These conditions are not directly corrected by surfactant administration, but they are ameliorated as lung disease improves. Pulmonary hemorrhage is an infrequent adverse effect of surfactant therapy that is seen most commonly in the extremely low-birthweight infant (<1,000 g) and is associated with a patent ductus arteriosus.

Prep 2007: Question 99 A term infant is delivered vaginally following a pregnancy complicated by diabetes mellitus. His oral and nasal airways are suctioned and found to be patent and free of meconium. He has cyanosis and respiratory distress immediately following birth that requires intubation and assisted ventilation with 100% oxygen. Because no improvement is apparent in the next 5 minutes, he is admitted to the neonatal intensive care unit. His birthweight is 4,500 g. A chest radiograph reveals findings consistent with decreased pulmonary blood flow.Of the following, the MOST likely cause of respiratory distress in this infant is A. Anemia B. choanal atresia C. Hyperglycemia D. Hypermagnesemia E. persistent pulmonary hypertension

Prep 2007: Question 99 An infant of a diabetic mother (IDM), such as the infant described in the vignette, is predisposed to some increased risk of respiratory distress syndrome associated with an immature pulmonary surfactant profile. However, findings on this infant's radiograph are not consistent with this diagnosis, and the combination of cyanosis and respiratory distress that does not improve with intubation and assisted ventilation raises concerns for cyanotic heart disease and decreased pulmonary blood flow. Transposition of the great arteries is the most common cyanotic heart lesion in the IDM. The possibility of persistent pulmonary hypertension of the newborn (PPHN) must be evaluated. The findings on chest radiograph vary with the cause of PPHN. Diffuse ground-glass densities and low lung volumes are observed with congenital pneumonia. Patchy infiltrates and hyperinflation are seen in meconium aspiration syndrome. In idiopathic cases of PPHN, the lung fields are clear, with evidence for decreased pulmonary blood flow. Echocardiography is vital to discerning this infant's diagnosis. A hyperoxia test (assisted ventilation with 100% oxygen and blood gas analysis from preductal and postductal sites) to determine the presence of a fixed right-to-left extrapulmonary shunt is also an important evaluative tool. The IDM who has macrosomia is at risk for hypoglycemia, which also may present with cyanosis. Choanal atresia is characterized by cyanosis that resolves when an infant cries and an inability to pass a suction catheter through the nares. Anemia is associated with pallor, and in the IDM, polycythemia and plethora are more likely. Additionally, hypocalcemia and hypomagnesemia are common in the IDM.

Prep 2007: Question 115 You are making rounds in the neonatal intensive care unit and discussing the complications of necrotizing enterocolitis (NEC) with the residents.Of the following, the MOST likely long-term complication following NEC is A. Encopresis B. failure to thrive C. gastroesophageal reflux disease D. intestinal stricture E. pneumatosis intestinalis

Prep 2007: Question 115 The diagnosis of neonatal necrotizing enterocolitis (NEC) is based on clinical manifestations (poor feeding, vomiting, gastrointestinal tract bleeding, septic shock); laboratory data and physical findings (thrombocytopenia, abdominal distention); and radiologic evidence of an ileus (paucity of bowel gas), intramural air (intestinal pneumatosis) (Item C115A), portal venous air, or free air in the abdomen indicative of bowel perforation (pneumoperitoneum) (Item C115B). Early radiographic findings may be nonspecific and include dilated loops of intestine and bowel wall thickening consistent with edema. One third of cases lack radiographic findings, and in these, NEC is diagnosed only at surgery or autopsy. Very low-birthweight (<1,500 g) infants are affected most frequently by NEC, with an incidence of approximately 10% in this population in modern neonatal intensive care units (NICUs). The overall mortality for NEC ranges from 10% to 30%. It is a multifactorial disorder, the precise causes of which have not been completely elucidated. Risk factors include prematurity (most frequent), congenital heart disease, early and rapid feeding, hyperosmolar formulas, maternal cocaine use, respiratory distress syndrome, and perinatal asphyxia. The clinical staging of NEC is given in (Item C115C). Initial management of NEC includes making the infant nil per os, passing a nasogastric tube and applying low intermittent suction, providing intravenous fluids and nutrition, and administering appropriate antibiotic therapy. Additional monitoring of abdominal radiographic findings and laboratory parameters (complete blood count, platelet count, coagulation profile, and serum electrolyte concentrations) is essential. Surgical intervention may be necessary in up to 50% of infants and includes placing a peritoneal drain, performing an exploratory laparotomy, or bowel resection. Complications from NEC can be separated into acute or short-term problems encountered in the NICU or longer-term problems encountered after weeks or months. Among the short-term concerns are surgical site, anastomotic, or stoma problems; dehiscence or fistula development; infection; and recurrent NEC. Longer-term complications are either related to nutrition and growth (associated with degree of short bowel syndrome, ability to feed enterally, or dependance on parenteral nutrition) and late-occurring surgical complications such as strictures. Strictures (Item C115D) form at the site of either old medically managed NEC or at a surgical anastomotic site. More than 10% of infants who have had NEC develop intestinal strictures. Pneumatosis intestinalis is an acute finding with active NEC. Gastroesophageal reflux disease is no more common in infants who have NEC than in other preterm infants. The incidence of encopresis is not increased in children who have a history of NEC. Failure to thrive may occur in infants who have a history of NEC and short bowel syndrome. Although short bowel syndrome may occur in up to 25% of infants who have NEC, management with balanced enteral and parenteral nutrition largely avoids overt failure to thrive. Recent evidence attests to the negative impact that prematurity combined with NEC and associated lengthy hospitalization has on overall neurodevelopment in extremely low-birthweight infants (<1,000 g). Up to 50% of those who survive NEC experience some neurodevelopmental delay.

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