How would you handle these newborns?

June 1, 1999

General pediatricians do not always have access to a neonatologist when they need one. This case-based review will refresh and update your knowledge of how to approach neonatal problems ranging from the need for resuscitation to development of a rash.

How would you handle these newborns?

Jump to:Choose article section...ApneaRespiratory distressSeizuresHyperbilirubinemiaSkin lesionsOther common problemsA methodical approach

By Namasivayam Ambalavanan, MD, and Waldemar A. Carlo, MD

General pediatricians do not always have access to a neonatologistwhen they need one. This case-based review will refresh and update yourknowledge of how to approach neonatal problems ranging
from the need for resuscitation to development of a rash.

In addition to dealing with neonates routinely during well- baby check-upsand sick visits, general pediatricians sometimes must manage a neonate inthe delivery room or newborn nursery. Neonates not only have a much higherrisk of mortality and morbidity than older infants and children, but aremore challenging diagnostically. Since neonates have a limited spectrumof responses, a variety of illnesses may have similar presentations.

The following cases, modeled on real-life situations, cover a spectrumof neonatal disorders and touch on recent advances in newborn care. We havecast the cases in the form of a multiple-choice quiz; each scenario is followedby a list of possible answers and a discussion of why one is the best choice.A review of these 15 cases should help the general pediatrician handle neonatalproblems with confidence.

Apnea

CASE 1

Neonate requires resuscitation

After an uncomplicated pregnancy, a full-term baby boy is born by emergencycesarean section because of fetal bradycardia. The baby is placed underthe radiant warmer, dried, and suctioned. He is apneic despite tactile stimulationand is ventilated with bag and mask. After 20 seconds of ventilation, theheart rate is 90/min and increasing, but the infant continues to be apneic.The correct management plan is:

A.Discontinue bag and mask ventilation; start free-flow oxygen and performvigorous tactile stimulation

B. Continue bag and mask ventilation with 100% oxygen; re-evaluate in15 to 30 seconds

C. Continue bag and mask ventilation with 100% oxygen; start chest compressions;reevaluate in 15 to 30 seconds

D. Continue bag and mask ventilation with 100% oxygen; start chest compressions;administer epinephrine intravenously or by endotracheal tube; reevaluatein 15 to 30 seconds

The answer is B. Ventilation must be continued because the infant isapneic. The Neonatal Resuscitation Program of the American Academy of Pediatrics(AAP) recommends continuing ventilation if the heart rate, after the initial15 to 30 seconds of ventilation, is <100/min. Chest compressions (optionsC and D) are not required because the heart rate is >60 to 80/min. Epinephrineis very rarely required (option D); it is indicated only if the heart rateis <80/min after 30 seconds of ventilation and chest compression.

Few situations induce as much anxiety in pediatricians, or obstetricians,as delivery of a depressed neonate, and for a good reason--the extreme benefit/riskratio of suitable intervention. Rapid and appropriate resuscitation hasthe potential for significant improvement in outcome, while ineffectiveresuscitation may have serious consequences. Bradycardia in neonates ismost often caused by hypoxemia. An increasing heart rate is evidence ofadequate ventilation and oxygenation.

Suggested reading: Neonatal Resuscitation Program manual of the AAP

Respiratory distress

CASE 2

Grunting and tachypnea

An infant born at 35 weeks' gestation and an uncomplicated delivery hasApgar scores of 8 and 9 at one and five minutes, respectively. At firsthe seems fine, but at 4 hours of age he begins grunting and breathing rapidly(tachypnea). The most likely diagnosis is:

A. Respiratory distress syndrome

B. Hypocalcemia

C. Hyponatremia

D. Hypoglycemia

E. Sepsis

The answer is A. Even though the infant was asymptomatic soon after birth,respiratory distress syndrome is the most likely cause of breathing problemsthat develop so early in life. Sepsis and hypoglycemia should be considered.Hypocalcemia and hyponatremia are unlikely causes of respiratory distress.

CASE 3

Defining risk

The neonate described in Case 2 is at increased risk of all but one ofthe following conditions:

A. Hypothermia

B. Hyperbilirubinemia

C. Sepsis

D. Poor feeding

E. Polycythemia

The answer is E. A borderline premature infant is at risk for hypothermia,hyperbilirubinemia, sepsis, and poor feeding. Premature infants are notat risk for polycythemia; indeed, the hematocrit tends to decrease withincreasing prematurity.

CASE 4

Low oxygen saturation

A full-term neonate is born after an elective repeat cesarean section.Thepregnancy was uncomplicated. Apgar scores are 8 and 9 at one and fiveminutes, respectively. At 6 hours of age, the baby is breathing at a rateof 70 to 80/min without grunting, flaring, or retractions. The oxygen saturationis 83% to 86% on room air. The correct plan is:

A. Observe the infant since these findings are consistent with normaltransition

B. Give chest physiotherapy and observe the infant

C.Do an arterial blood gas and if the arterial oxygen tension (PaO2)is low, administer 40% oxygen by hood

D. Administer 100% oxygen by hood and check oxygen saturation

E. Intubate the neonate and start mechanical ventilation

The answer is D. It is not uncommon for infants to be tachypneic soonafter birth. A respiratory rate of >60 to 70/min in a neonate is consideredtachypnea. A saturation of 83% to 86% at 6 hours of age is evidence of impairedoxygenation since normal neonates have an arterial PO2 of >60mm Hg and a saturation >94% by 2 hours of age. Cyanosis is usually clinicallyevident with a saturation below 85%.

The most likely diagnosis in this scenario is transient tachypnea ofthe newborn (TTN), though pneumonia and cardiac disease cannot be excludedby the available data. The neonate should be exposed to 100% oxygen fora hyperoxia test to differentiate pulmonary disease from cyanotic congenitalheart disease. With pulmonary disease, oxygenation usually improves dramatically;in cyanotic congenital heart disease, oxygenation improvement is often absentor minimal.

Chest physiotherapy (choice B) has not been proven to be of benefit andmay cause harm in the newly born. Although arterial blood gas analysis isthe gold standard for documenting the degree of hypoxemia (choice C), itis not required to "confirm" cyanosis. It may be useful to checkpH or arterial carbon dioxide tension (PaCO2) if indicated, orto document the response (or lack of it) in PaO2 during the hyperoxiatest. General indications for intubation and mechanical ventilation (choiceE) in neonates are apnea or respiratory compromise, which is signaled byrespiratory acidosis (pH <7.2, PaCO2>60 mm Hg) or hypoxemia(PaO2<50 mm Hg on >50% to 60% oxygen by hood). Most neonateswith TTN do not require mechanical ventilation.

Many pediatricians would also evaluate the neonate in this scenario forearly-onset neonatal sepsis and empirically administer antibiotics.

Seizures

CASE 5

A brief episode

A 4.5 kg neonate is delivered by cesarean section because of cephalopelvicdisproportion to a mother who had no prenatal care. Apgar scores are 8 and9. The baby has a brief episode of multifocal clonic seizures at 6 hoursof age. Of the following, the least likely cause of the seizures is:

A. Hypoglycemia

B. Hypocalcemia

C. Acute narcotic withdrawal

D. Inborn errors of metabolism

The answer is D. Inborn errors of metabolism can cause seizures but areless common than the other possibilities. In addition, seizures caused byinborn errors of metabolism usually do not occur in the first few hoursafter birth.

This neonate's seizures are more likely to be related to uncontrolledmaternal diabetes or uncontrolled hyperglycemia as a result of diabetesmellitus. In addition to being large for gestational age, infants of diabeticmothers are at high risk for hypoglycemia, hypocalcemia, polycythemia, jaundice,poor feeding, and--despite their gestational maturity--respiratory distresssyndrome. Hypoglycemia (blood glucose level <40 mg/dL), common in macrosomicinfants, usually becomes apparent in the first few hours after birth. Althoughmost infants with hypoglycemia are asymptomatic, some may be lethargic orjittery, or present with apnea, shock, seizures, or other signs.

The possibility that acute drug withdrawal has caused the seizures inthis case needs to be considered, especially since the mother did not receiveprenatal care.

Suggested reading: Cloherty JP, Start AR (eds): Manual of Neonatal Care,ed 4, chapters 2 and 19. Philadelphia, PA, Lippincott-Raven, 1998

CASE 6

Lab findings and lethargy

The neonate described in Case #5 had a blood glucose of 32 mg/dL anda serum calcium of 8.6 mg/dL. He was lethargic following the brief seizure,but the complete blood count and cerebrospinal fluid did not suggest sepsisor meningitis. The next appropriate step is to:

A. Administer 2 cc/kg of 10% dextrose intravenous (IV) as a rapid IVinfusion and recheck blood glucose in one hour, then once a shift. Administer200 mg/kg of 10% calcium gluconate as a slow IV infusion

B. Administer 2 mL/kg of 10% dextrose IV as a rapid IV infusion, thencontinue with 80 mL/kg/d of 10% dextrose. Recheck blood glucose in 15 to30 minutes, then hourly until stable at more than 40 mg/dL

C. Administer phenobarbital 20 mg/kg as an IV infusion. Repeat in onehour if seizures persist

D. Administer phenobarbital at 20 mg/kg as an IV infusion, and obtaina head ultrasound to rule out intracranial bleeds or malformations. If seizurespersist, administer lorazepam or phenytoin

The answer is B. A blood glucose level of <40mg/dL in neonates isusually defined as hypoglycemia, and a rapid postnatal fall in blood glucoseto this level may result in seizures. Fetal hyperglycemia due to maternaldiabetes often results in hyperactivity of the fetal pancreatic islet cellsand fetal hyperinsulinemia. When the neonate is delivered, glucose deliveryvia the placenta ceases, but pancreatic insulin secretion does not. Thishyperinsulinemia relative to glucose intake results in hypoglycemia.

A single bolus of IV dextrose is effective only transiently. To maintainblood glucose levels it must be followed by a slower continuous infusionof dextrose. If investigation does not reveal a correctable metabolic cause,for example hypoglycemia, hypocalcemia, or hyponatremia, and seizures recur,anticonvulsants such as phenobarbital or phenytoin are indicated.

Hyperbilirubinemia

CASE 7

Clinical jaundice at 3 days

A 3 kg breastfed Caucasian female infant is jaundiced at 36 hours ofage. The mother's blood is O positive and the neonate's A positive. Thedirect Coombs test is negative. The infant's physical examination is unremarkableexcept for the jaundice. The total serum bilirubin is 15 mg/dL (indirectfraction 14.6 mg/dL), the hematocrit is 60%, and the reticulocyte countis 5% at 38 hours of age. The next step is to:

A. Repeat serum bilirubin estimation in eight to 12 hours; start phototherapyif the level increases to >20 mg/dL

B. Start phototherapy; repeat bilirubin estimation in 24 to 36 hours

C. Start phototherapy; repeat bilirubin estimation in six to 12 hours;ensure adequate oral intake

D. Start phototherapy; start IV fluids; perform an exchange transfusionif bilirubin levels increase to >20 mg/dL

The answer is C. More than 60% of neonates are clinically jaundiced.Continuing uncertainty about the relationship of serum bilirubin levelsto neurologic morbidity contributes to marked variations in the managementof hyperbilirubinemia. To resolve some of the controversial issues, theAAP developed management guidelines for hyperbilirubinemia in the healthyterm neonate. When the bilirubin level of a neonate on phototherapy is increasing,they usually are checked every six to 12 hours.

Although some neonates who require phototherapy are dehydrated and needIV fluids (choice D), no evidence suggests that jaundiced but otherwisehealthy term neonates need intravenous fluids to maintain a normal fluidand electrolyte status, as long as they maintain adequate oral intake.

CASE 8

Clinical jaundice at 1 month

A breastfed 4 kg term neonate appears jaundiced at his 1-month visit.His parents observe that their son's stools are gray and pasty. The liveris palpable 2 cm below the right costal margin, and the tip of the spleentip can be felt as well. The baby is active, feeding well, and appears comfortable.A bilirubin estimation reveals a total bilirubin of 15.0 mg/dL of which12.5 mg/dL is conjugated. The next steps are to:

A. Obtain abdominal ultrasound; check urine for reducing sugars; checkblood and urine cultures; arrange urgent pediatric gastroenterology consultation

B. Ask mother to stop breastfeeding; recheck serum bilirubin in 48 hours

C. Obtain urine for cytomegalovirus (CMV) test and blood for TORCH (toxoplasmosis,other infections, rubella, cytomegalovirus infection, and herpes simplex)and hepatitis B titers. Obtain liver function tests and schedule pediatricgastroenterology consultation in two to three weeks

D. Start phototherapy. Recheck bilirubin in eight to 12 hours

The answer is A. The clinical presentation is cholestatic jaundice (conjugatedhyperbilirubinemia). The usual cause of cholestasis is a disorder of thebile ducts, such as biliary atresia (extrahepatic or intrahepatic), inspissatedbile syndrome, or neonatal hepatitis syndrome, which can have an infectious,metabolic, or toxic cause.

Most pediatricians and neonatologists would first obtain an abdominalultrasound to confirm the presence of the bile ducts and rule out a choledochalcyst. The urine should be tested for reducing substances to exclude galactosemia--althoughsevere liver disease may be associated with false positives. Blood and urinecultures are performed to exclude an otherwise silent sepsis or urinarytract infection, often due to gram-negative bacteria such as Escherichiacoli. Urgent pediatric gastroenterology consultation is warranted becauseliver biopsy or operative cholangiography is often required to distinguishbetween biliary atresia and neonatal hepatitis. In cases of biliary atresia,the Kasai operation (portoenterostomy), an accepted therapy, has good resultsonly if done in the first few weeks of life. Liver transplantation, theother accepted therapy, is often resorted to when the Kasai operation failsand increasingly is the first option.

Phototherapy (choice D) is not effective for hyperbilirubinemia thatis predominantly conjugated. Breastfeeding is not a contributing factor(choice B), though babies who are breastfed generally have higher levelsof unconjugated bilirubin than bottle-fed babies. Although TORCH screens,urine tests for CMV, and hepatitis B surface antigen (HBsAg) titers (choiceC) may help to determine that neonatal hepatitis is the cause of the hyperbilirubinemia,these tests are not often useful in the absence of additional signs. Perinataltransmission of hepatitis B usually leads to a chronic carrier state ininfancy rather than acute hepatitis. Rubella and toxoplasmosis only rarelycause neonatal hepatitis. Syphilis and herpes are more common causes; thesetwo conditions may have similar presentations, but other symptoms generallyare present.

Suggested reading: Balistreri WF: Cholestasis, in Behrman RE, KliegmanRM, Arvin AM (eds): Nelson Textbook of Pediatrics, ed 15, chapter 302. Philadelphia,PA, WB Saunders, 1996; and Dixit R, Gartner LM: The jaundiced newborn: Minimizingthe risks. Contemporary Pediatrics 1999;16(4):166.

Skin lesions

CASE 9

Rash on extremities

A 4-week-old African-American girlis brought to the clinic with irritabilityand vesiculopustular lesions, some of which are crusted, over the palms,soles, and sides of her feet. According to the baby's mother, the lesionsfirst appeared two days ago, followed by a fresh crop the next day. A physicalexamination does not reveal any other abnormality. The most likely diagnosisis:

A. Erythema toxicum

B. Neonatal scabies

C. Infantile acropustulosis

E. Eosinophilic pustular folliculitis

The answer is C. Choices B and D are also possibilities but these diagnosesare less likely. Though infantile acropustulosis normally occurs at 2 to10 months of age, it is occasionally present at birth. Crops of intenselypruritic vesiculopustular lesions on the extremities are characteristic.Similar lesions also occur with scabies and eosinophilic pustular folliculitis,but the most common location in infants (not adults) is the scalp and face.Scabies often affects other members of the household. Erythema toxicum (choiceA) usuallyspares the palms and soles and classically occurs in the firstfew days of life. The differential diagnosis of these lesions in the neonateshould include staphylococcal pustulosis, transient neonatal pustular melanosis,cutaneous candidiasis, and congenital syphilis (which is more often vesicobullousthan vesiculopustular).

Suggested reading: Darmstadt GL, Lane A: Diseases of the neonate, inBehrman RE, Kliegman RM, Arvin AM (eds): Nelson Textbook of Pediatrics,ed 15. Philadelphia, PA, WB Saunders, 1996

CASE 10

Petechiae

A full-term infant is born with petechiae. A detailed physical examinationand laboratory evaluation reveal mild hepatosplenomegaly, a platelet countof 30,000/mL and direct hyperbilirubinemia. The most likely cause of thepetechiae is:

A. Congenital infection

B. Rh incompatibility

C. Biliary atresia

D. Galactosemia

E. Congestive heart failure

The answer is A. Congenital infections are the most likely cause of thethrombocytopenia, hepatomegaly, and direct hyperbilirubinemia. Rh incompatibilitywill cause indirect hyperbilirubinemia. Biliary atresia and galactosemiaare asymptomatic at birth. Cardiac failure causes these abnormalities onlyinfrequently.

Other common problems

CASE 11

Abdominal distension and vomiting

A 3-week-old girl who was previously feeding and stooling well on regularformula develops bilious vomiting. This is soon followed by passage of mucoidbloody stools. The infant is sleepy and has cool extremities but her axillarytemperature is normal. There is no abdominal distension. The next step shouldbe:

A. Obtain a detailed history of formula preparation and feeding technique;rule out possible contamination of formula and toxin exposure

B. Change to soy or lactose-free formula, and reassure parents

C. Start intravenous line, antibiotics, and orogastric drainage. Checkabdominal X-ray and get immediate pediatric surgical consultation

D. Do a rectal examination and obtain abdominal ultrasound to rule outintussusception

The answer is C. Although serious abdominal emergencies are rare in termneonates, vigilance is necessary to avoid missing a potentially fatal condition.Bilious vomiting is often a sign of intestinal obstruction below the openingof the common bile duct in the mid-duodenum. Proximal intestinal obstructiondoes not distend the abdomen. Mucoid bloody stools often indicate eitherinfection or ischemia of the colon. Although the axillary temperature isnormal, cold extremities mean that the infant may be in the early stagesof shock.

This presentation suggests intestinal malrotation with volvulus formation,which usually presents in the first month--often the first week--of life.Volvulus results in severe intestinal ischemia, bilious vomiting, rectalbleeding, and, occasionally, shock. This condition requires immediate surgicalintervention to prevent irreversible infarction of the bowel. Although milkcontamination (option A) may lead to vomiting (usually not bilious) or bloodydiarrhea, it is important first to exclude surgical diagnoses such as malrotation.

Primary lactose intolerance (choice B) is rare and not likely to startsuddenly at 3 weeks of age. Although the clinical symptoms are similar tothose of intestinal obstruction, intussusception (choice D), which is themost common cause of intestinal obstruction between 3 months and 6 yearsof age, is rare before 3 months of age.

Suggested reading: Flake AW, Ryckman FC: Selected anomalies and intestinalobstruction. Part four of Chapter 44, in Fanaroff AA, Martin RJ (eds): Neonatal-PerinatalMedicine. Diseases of the Fetus and Infant, ed 6. St. Louis, MO, Mosby-YearBook, 1997

CASE 12

Maternal intrapartum antibiotic prophylaxis

A 2.7 kg neonate is born by spontaneous vaginal delivery at 36 weeksof gestation. Pregnancy was uncomplicated except for a positive vaginalgroup B streptococcal (GBS) culture at 35 weeks' gestation, until ruptureof membranes and onset of premature labor seven hours before delivery. Themother had received two prophylactic doses of intravenous ampicillin againstGBS infection. Apgar scores were 8 at both one and five minutes. The babyis asymptomatic with no respiratory distress and has good perfusion andactivity at 30 minutes of age. The recommended approach is:

A. No laboratory evaluation; no therapy; observe at least 48 hours inhospital

B. Limited evaluation--complete blood count, blood culture; full work-upand intravenous antibiotics if evaluation is abnormal; observe at least48 hours in hospital if evaluation is normal

C. Limited evaluation; empiric ceftriaxone 125 mg intramuscular singledose; observe 72 hours in hospital

D. Full sepsis work-up and empiric antibiotic therapy

The answer is A. Recently released recommendations for management ofthe neonate born to a mother colonized with GBS (see boxed figure) say thatan asymptomatic neonate born after at least 35 weeks of gestation does notneed further evaluation or therapy if the mother received two or more dosesof intrapartum antibiotic prophylaxis. The neonate should be observed inthe hospital for a minimum of 48 hours. When the baby is born before 35weeks' gestation or the mother received only one prophylactic dose, a limitedevaluation--CBC and differential and blood culture--is recommended, followedby a full evaluation and empiric therapy if sepsis is suspected. A fulldiagnostic evaluation--lumbar puncture at the discretion of the physician--andempiric therapy is also recommended for symptomatic neonates. Choice C,the empiric use of ceftriaxone, is popular for older children at risk forserious bacterial infection but is not recommended for neonates.

CASE 13

Watery eye (epiphora)

A 3-week-old afebrile neonate presents with excessive tears, particularlyfrom the right eye. Some photophobia and blepharospasm are present, andexamination of the eye is difficult. There is no obvious swelling, tenderness,or erythema. Which of the following conditions is not a possible diagnosis?

A. Corneal abrasion

B. Foreign body in eye

C. Congenital glaucoma

D. Acute dacryoadenitis

Acute dacryoadenitis (D) is not likely to be the cause of the neonate'sepiphora. Although blockage of the nasolacrimal ducts is the most commoncause of epiphora in neonates, the combination of epiphora, photophobia,and blepharospasm in a young infant points to congenital glaucoma, a cornealabrasion (often caused by fingernails), or a foreign body, such as an eyelash.Eversion of the upper eyelid may be required to detect a foreign body. Theneonate with congenital glaucoma may have a hazy, enlarged cornea (diameter>12 mm). Congenital glaucoma is not common but it warrants a high indexof suspicion because of the risk of serious permanent sequelae.

Dacryoadenitis, an inflammation of the lacrimal gland, is much less commonin neonates than dacryocystitis, a pooling of tears in the lacrimal sacwith associated inflammation. Dacryocystitis is often caused by an obstructionin lacrimal drainage.

Suggested reading: Hamming NA, Miller MT: Neonatal eye disease, in FanaroffAA, Martin RJ (eds): Neonatal-Perinatal Medicine. Diseases of the Fetusand Infant, ed 6. St. Louis, MO, Mosby-Year Book, 1997

CASE 14

"Growing" preterm infant

A baby boy born at 900 g after 27 weeks' gestation is discharged homeat 35 weeks postconceptional age with a weight of 1.9 kg. Neonatal problemsincluded respiratory distress syndrome requiring mechanical ventilationfor five days, followed by supplemental oxygen for 12 days. Cranial ultrasoundsin the first and fourth weeks revealed no intraventricular hemorrhage, periventricularleukomalacia, or ventriculomegaly. The neonate required intravenous antibioticsand hyperalimentation early in the hospital stay, but the remainder of thehospital course was uneventful. Appropriate management after discharge mightinclude all but which one of the following?

A. Palivizumab for respiratory syncytial virus (RSV) prophylaxis

B. Neurodevelopmental follow-up

C. A special formula for growing preterm infants (such as Similac Neosure)

D. Routine immunizations based on postnatal age

E. Follow-up head ultrasound at 6 months postnatal age

Appropriate management after discharge would not include E. A follow-uphead ultrasound is not usually required in an otherwise healthy ex-pretermneonate unless the 1-week or 4-week ultrasound examination shows an intraventricularhemorrhage, periventricular leukomalacia, or ventriculomegaly. Rapidly increasinghead size or presence of neurologic deficits also warrants a head ultrasound.

The AAP recommends RSV prophylaxis, with palivizumab or RSV-intravenousimmune globulin, for neonates of fewer than 32 weeks' gestation at birthwho are discharged during the RSV season. Neurodevelopmental follow-up isgenerally performed on all extremely low birth-weight neonates, those whohave undergone extracorporeal membrane oxygenation, and neonates with intraventricularhemorrhage, periventricular leukomalacia, or other neonatal problems associatedwith neurologic abnormalities. The use of human milk fortifier or pretermformulas, which supply more protein, calcium, phosphates, and other nutrientsthan regular formula, is not normally recommended because excess intakeof certain constituents, such as vitamin D, is possible. Routine immunizationsbased on postnatal age (not postconceptional age) are required for preterminfants, with the exception of hepatitis B vaccine. This vaccine usuallyis given at discharge, unless the mother's hepatitis B antigen status ispositive or cannot be determined, in which case the hepatitis B vaccineis given simultaneously with hepatitis B immune globulin soon after birth.

CASE 15

Shock

The parents of a 10-day-old boy report that he is lethargic and feedingpoorly and has occasional projectile vomiting. Physical examination revealssevere dehydration and hypotension. Serum electrolytes indicate sodium of122 mEq/L and potassium of 8.2 mEq/L. The arterial blood gas is pH 7.16,PaCO2 28 mm Hg, PaO2 89 mm Hg, and bicarbonate 6 mEq/L.The most likely diagnosis is:

A. Pyloric stenosis

B. Diabetes insipidus

C. Congenital adrenal hyperplasia (salt-losing type)

D. Feeds with overconcentrated formula

The answer is C. The low serum sodium and high potassium in the settingof dehydration suggest a lack of mineralocorticoid hormones, as seen inthe salt-losing form of congenital adrenal hyperplasia. Congenital adrenalhyperplasia may lead to virilization and ambiguous genitalia in female neonates,but the diagnosis is often delayed in males because phallic enlargementmay not be obvious. Immediate restitution of fluid and electrolyte balancewith saline and hydrocortisone is essential.

Pyloric stenosis is usually associated with a hypochloremic metabolicalkalosis due to loss of gastric secretions. Diabetes insipidus, which isuncommon, is characterized by excessive urine output and hemoconcentrationwith hypernatremia, not the hyperkalemia seen in this baby. Feeds with overconcentratedformula lead to hypernatremia, not the secondary hyponatremia that sometimesis caused by overdiluted formula. This secondary hyponatremia does not tendto be associated with hypotension or hyperkalemia.

A methodical approach

Although common problems in the neonate are somewhat different from thosein older infants and children, the keys to arriving at the correct diagnosisand management plan are the same: Begin with a good history and physicalexamination and take a logical approach to the differential diagnosis. Neonatalresearch is expanding rapidly; pediatricians can keep abreast of recentdevelopments through journal articles and practice parameters developedby organizations such as the AAP.

DR. AMBALAVANAN is Clinical Assistant Professor, Division of Neonatology,University of Alabama at Birmingham.

DR. CARLO isProfessor of Pediatrics and Director, Division of Neonatology,at the same institution.