1234567 8910 help table of contents …downloads.aap.org/dosp/journalclub/respiaugust2005.pdf ·...

Education Module Learner

http://emb.aap.org/courseprodv2/Index.asp[4/5/2012 10:29:16 AM]

August 05 Questions Assessment Summary CME Credit Expired

2 3 4 5 6 7 8 9 10

Help | Table of Contents

A 4-hour-old term male infant has persistent drooling. The infant attempted to bottle-feed andimmediately choked and spit. The pregnancy was complicated by polyhydramnios. Atracheoesophageal abnormality is suspected.

Of the following, the MOST likely tracheoesophageal abnormality is:

esophageal atresia with a distal and a proximal tracheoesophageal fistula

esophageal atresia with a distal tracheoesophageal fistula

esophageal atresia with a proximal tracheoesophageal fistula

esophageal atresia without a tracheoesophageal fistula

tracheoesophageal fistula without esophageal atresia

You selected , the correct answer is .

Congenital esophageal atresia (EA) with or without a tracheoesophageal fistula (TEF) is acommon congenital anomaly with an incidence of 1 in 3,000 live births. Newborns with EA maypresent in the delivery room with either a sonorous "seal-bark" cry because of associatedtracheomalacia or within the first few hours after birth with excessive oral secretions. Feedingan infant with EA will cause spitting and choking, and aspiration pneumonia can occur. Refluxof gastric secretions through a distal TEF also can cause aspiration pneumonia. Diagnosis ofEA is suspected by failure to pass an orogastric tube beyond 10 cm to 11 cm from a terminfant's lips. Chest radiography confirms the position of the orogastric tube in the proximalesophageal pouch.

From 30% to 60% of infants with EA and TEF have associated anomalies, including cardiac(25%), genitourinary (15%), skeletal (14%), and intestinal atresias (13%). The VACTERLassociation (vertebral defects, anorectal abnormalities, cardiac defects, TEF, renalabnormalities, limb defects) occurs in approximately 10% to 25% of cases.

Embryologic development of the trachea and esophagus is a complex process. During weekfour of gestation, the embryo is C-shaped, and the primitive (primordial) gut is divided into theforegut, midgut, and hindgut. The trachea and esophagus are formed from the foregut. Thetrachea develops from the laryngotracheal tube, which buds off the ventral surface of theforegut. The tracheoesophageal septum separates the foregut into tracheal and esophagealtubes. The esophagus rapidly elongates with growth of the embryo. The lumen of theesophagus becomes obliterated by the proliferation of endodermal lining cells. During weekeight of gestation, endodermal cell death re-establishes the esophageal lumen. Failure of thetracheoesophageal septum to divide into the esophagus and trachea at week four of gestation,or failure of recanalization of the esophagus during week eight of gestation results in varioustypes of EA and TEF.

Polyhydramnios may develop because the fetus with EA cannot swallow amniotic fluid.Significant polyhydramnios may lead to premature delivery in approximately 30% of cases.Because the fetus may derive some nutritional benefit from swallowed amniotic fluid, newbornswith EA may be small for gestational age.

The most common tracheoesophageal abnormality (86%) is EA with a distal TEF (Fig. 1). Theproximal esophagus ends blindly in the superior mediastinum at the third or fourth thoracicvertebra. The distal esophagus usually enters the posterior wall of the trachea 1 cm to 2 cmabove the carina. The proximal esophageal pouch and the distal TEF may overlap or be

OverviewAssessment05

1 January 05

2 February 05

3 March 05

4 April 05

5 May 05

6 June 05

7 July 05

8 August 05

9 September05

10 October 05

11 November05

12 December05

NeoReviews BasicSelf Assessment

Go to theNeoReviews.org

homepage



separated widely. Because the distal TEF allows some amniotic fluid to flow from the trachea tothe gastrointestinal tract, polyhydramnios only occurs in approximately 33% of pregnancies withthis type of EA.

EA with distal and proximal TEF, also known as a double TEF, is a rare (<1%)tracheoesophageal abnormality (Fig. 2). This type of malformation may be misdiagnosed asthe more common EA with a distal TEF. If the small proximal TEF is unrecognized, thenrecurrent respiratory infections will occur. Preoperative endoscopy permits recognition of thedouble fistula and complete repair at the initial operation.

EA with a proximal TEF is another rare (2%) tracheoesophageal abnormality (Fig. 3). The TEFusually is located 1cm to2 cm above the distal end of the esophageal pouch. Polyhydramniosoccurs nearly 100% of the time because no distal fistula is present.

Isolated EA without a TEF (Fig. 4), occurs in 7% of tracheoesophageal abnormalities. Theproximal esophageal segment usually ends in the posterior mediastinum near the secondthoracic vertebra. Unlike EA with distal TEF, infants without a distal TEF have a flat, gaslessabdomen. A wide gap usually divides the upper and lower esophageal segments, makingprimary anastomosis difficult. Isolated EA without a TEF may be the result of failure ofrecanalization of the esophagus during week eight of gestation.

TEF without EA, also known as H-type TEF (Fig. 5), comprises 4% of tracheoesophagealabnormalities. Infants with H-type TEF may have intermittent choking episodes in the newbornperiod. More commonly, patients with H-type TEF present later in life, even into adulthood, withchronic cough, recurrent pneumonia, or reactive airway disease. This form of TEF is the mostdifficult to diagnose because the fistula may not be identified by routine contrast swallowstudies. Esophagoscopy or bronchoscopy may be necessary to visualize the TEF.

References:

Blair G, Konkin D. eMedicine: Esophageal atresia with or without tracheoesophageal fistulae.Available at: http://www.emedicine.com/ped/topic2950.htm. Accessed May 26, 2005

Driver CP, Shankar KR, Jones MO, et al. Phenotypic presentation and outcome of esophagealatresia in the era of Spitz classification. J Pediatr Surg. 2001;36:1419-1421

Goldman AS, Kaplan S. Embryology. In: Polin RA, Fox WW, eds. Fetal and Neonatal Physiology.2nd ed. Philadelphia, Pa: W.B. Saunders; 1998:31-33

Leibert PS. Color Atlas of Pediatric Surgery. 2nd ed. Philadelphia, Pa: W.B. Saunders; 1996:82-88.

Merei JM, Huston JM. Embryogenesis of tracheoesophageal anomalies: a review. Pediatr SurgInt. 2002;18:319-326

Nakayama DK. Congenital abnormalities of the esophagus. In: Oneill JA, Grosfeld JL,Fonkalsrud EW, Coran AG, Caldamone AA, eds. Principles of Pediatric Surgery. 2nd ed. St.Louis, Mo: Mosby; 2004:385-394

Moore KL, Persaud TV. The Developing Human. 6th ed. Philadelphia, Pa: W.B. Saunders;2000:261-262

Spitz L. Esophageal atresia and tracheoesophageal malformations. In: Ashcraft KW, Holcomb G,Murphy JP, eds. Pediatric Surgery. 4th ed. Philadelphia, Pa: W.B. Saunders; 2005:352-366

Content Specifications:

Know the morphogenesis of the gastrointestinal (GI) tract and factors that lead to congenitalmalformations

Know how to recognize and evaluate an infant with excessive gastric contents and hydramnios



Know how to diagnose polyhydramnios, its significance, and the management of pregnancywhen polyhydramnios is diagnosed

Plan appropriate management for an infant with airway obstruction, such as vascular rings,choanal atresia, and tracheal abnormalities

Recognize the clinical features of VATER association

NeoReviews Plus 2005

http://emb.aap.org/...prodv2/popup.asp?Nav=gotoMod&targetModule=p9328&Course=83&currentModule=p9304&popup=yes[4/5/2012 10:29:30 AM]



August 05 Questions Assessment Summary CME Credit Expired

Page 1 2 3 4 5 6 7 8 9 10

Help | Table of Contents

In the delivery room, you begin resuscitation of a term female infant who has apnea,bradycardia, and hypotonia. No meconium was present in the amniotic fluid. You havepositioned, dried, and suctioned the nose and mouth as well as provided tactile stimulation.However, her heart rate is 50 beats per minute. You begin positive pressure ventilation (PPV)with a bag and mask.

Of the following, the MOST important clinical indicator of adequate ventilation is

chest rise

color

heart rate

muscle tone

skin perfusion

You selected , the correct answer is .

The most important step in resuscitation of the depressed, newly born infant (heart rate <100beats per minute, apnea or gasping respiration, hypotonia) is ventilation of the lungs. The mostimportant response to positive pressure ventilation (PPV) is an immediate rise in heart rate. Theinfant in the vignette is expected to have a rapid rise in heart rate after ventilation isestablished. Evidence for interventions during neonatal resuscitation often is limited tocomparative animal studies and consensus of opinion. Evidence that supports the heart rateresponse as the most important clinical indicator of response to PPV is based on animalexperiments performed during the early 1960s (Figure). In these cardiorespiratory studies,changes in heart rate, breathing, and blood pressure were recorded. A rapid heart rate increaseafter initiation of bag and mask ventilation is followed by a gradual blood pressure increase andsubsequent spontaneous respiration. Heart rate response as the most important clinicalindicator of adequate ventilation is different from the frequently taught concept that chest rise ismost important. Avoiding the risks associated with large tidal volume ventilation(pneumothorax and bronchopulmonary dysplasia) is an important goal that favors heart rateincrease as the preferred indicator of response to PPV.

Chest rise during PPV is an indication that ventilation of the lungs is occurring. Withinadvertent overventilation, the risks of volutrauma and barotrauma causing pneumothorax orinitiating bronchopulmonary dysplasia in very preterm infants has caused clinicians to reassessthe physiologic responses to, and technique of, ventilation with a resuscitation bag. Therefore,these risks of PPV and data from animal experiments indicate that a rapid heart rate increase,rather than chest rise, is a better indicator of adequate ventilation.

Mucus membrane color is an immediate clinical indicator of oxygenation. It follows that colorwill change from cyanotic to pink during the first minutes after birth in the healthy,spontaneously breathing newborn. Likewise, during PPV of an infant with bradycardia, apnea,and hypotonia, this transition to pink occurs only after ventilation of the lung with gas andestablishment of cardiac output to the pulmonary and systemic circulations, both primaryfactors in oxygen delivery to tissues. In the neonate, heart rate appears to be more importantthan stroke volume to increase cardiac output.

Improved muscle tone is a sign that oxygen delivery to the brain has improved. Improved skinperfusion, on the other hand, is a sign that oxygen delivery to other organ systems also hasimproved. Resolution of hypotonia and improved skin perfusion are expected to follow

OverviewAssessment05

1 January 05

2 February 05

3 March 05

4 April 05

5 May 05

6 June 05

7 July 05

8 August 05

9 September05

10 October 05

11 November05

12 December05

NeoReviews BasicSelf Assessment

Go to theNeoReviews.org

homepage



improvements in heart rate, establishment of lung volume and ventilation of the lung in theinfant in the vignette.

References:

Avery ME, Tooley WH, Keller JB, et al. Is chronic lung disease in low birth weight infantspreventable? Pediatrics. 1987;79:26-30

Boyle DW. Initial ventilation strategies during ventilation of the newborn in the delivery room[2005 International Consensus on CPR and ECC Science with Treatment Recommendations Website]. C2005 Evidence Evaluation Worksheets, Neonatal Life Support. Available athttp://www.americanheart.org/presenter.jhtml?identifier=3026625 Accessed Jan.25, 2005

Dawes GS. Birth asphyxia, resuscitation and brain damage. Chicago, IL: Year Book MedicalPublisher Inc. 1968:141-159

Kattwinkel J, ed. Textbook of Neonatal Resuscitation American Academy of Pediatrics andAmerican Heart Association. 4th ed. Elk Grove Village, Ill: American Academy of Pediatrics;2000:1.1-1.22

Van Marter LJ, Allred EN, Pagano M, et al. Do clinical markers of barotrauma and oxygentoxicity explain interhospital variation in rates of chronic lung disease. Pediatrics.2000;105:1194-1201

1234567 8910 help table of contents …downloads.aap.org/dosp/journalclub/respiaugust2005.pdf ·...

Documents