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Pediatrics: Cardiac Disease and Critical Care Medicine > Neonatology
Transient Tachypnea of the Newborn
Article Last Updated: Nov 21, 2006
AUTHOR AND EDITOR INFORMATION
Section 1 of 11  
Author: KN Siva Subramanian, MD, Professor of Pediatrics and Obstetrics/Gynecology, Chief of Neonatology, Director of Nurseries, Georgetown University Medical Center
KN Siva Subramanian is a member of the following medical societies: American Academy of Pediatrics, American Association for the Advancement of Science, American College of Nutrition, American Society for Parenteral and Enteral Nutrition, American Society of Law Medicine and Ethics, New York Academy of Sciences, and Southern Society for Pediatric Research
Coauthor(s):
Monisha Bahri, MBBS, MD, Fellow in Neonatal/Perinatal Medicine, Department of Neonatalogy, Georgetown University Hospital;
Stephen D Kicklighter, MD, Clinical Assistant Professor, Department of Pediatrics, Division of Neonatology, University of North Carolina at Raleigh and Wake Medical Center
Editors: Steven M Donn, MD, Professor of Pediatrics, Director, Neonatal-Perinatal Medicine, Department of Pediatrics, University of Michigan Health System; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Brian S Carter, MD, FAAP, Professor of Pediatrics, Department of Pediatrics, Division of Neonatology, Vanderbilt University School of Medicine; Co-director, Pediatric Advance Comfort Team, Vanderbilt Children's Hospital; Carol L Wagner, MD, Professor of Pediatrics, Medical University of South Carolina; Ted Rosenkrantz, MD, Head, Division of Neonatal-Perinatal Medicine, Professor, Departments of Pediatrics and Obstetrics/Gynecology, University of Connecticut School of Medicine
Author and Editor Disclosure
Synonyms and related keywords:
transient tachypnea of the newborn, TTN, transient tachypnea of newborn, respiratory distress syndrome type II, retained lung fluid syndrome, wet lung
Background
Transient tachypnea of the newborn (TTN) is a self-limited disease common in infants throughout the world and is encountered by all physicians who care for newborn infants. Infants with TTN present within the first few hours of life with tachypnea, increased oxygen requirement, and arterial blood gases that do not reflect carbon dioxide retention. When managing TTN, observing for signs of clinical deterioration that may suggest other diagnoses and for the development of respiratory fatigue is important.
Pathophysiology
Noninfectious acute respiratory disease develops in approximately 1% of all newborn infants and results in admission to a critical care unit. TTN is the result of a delay in clearance of fetal lung liquid. In the past, respiratory distress was thought to be a problem of relative surfactant deficiency, but it is now characterized by an airspace-fluid burden secondary to the inability to absorb fetal lung liquid.
In vivo experiments have demonstrated that lung epithelium secretes Cl- and fluid throughout gestation but develops the ability to actively reabsorb Na+ only during late gestation. At birth, the mature lung switches from active Cl- (fluid) secretion to active Na+ (fluid) absorption in response to circulating catecholamines. Changes in oxygen tension augment the Na+-transporting capacity of the epithelium and increase gene expression for the epithelial Na+ channel (ENaC). The inability of the immature fetal lung to switch from fluid secretion to fluid absorption results, in large part, from an immaturity in the expression of ENaC, which can be up-regulated by glucocorticoids.
Both pharmacologic blockade of the lung's EnaC channel and genetic knockout experiments using mice deficient in the ENaC pore-forming subunit have demonstrated the critical physiologic importance of lung Na+ transport at birth. When Na+ transport is ineffective, newborn animals develop respiratory distress; hypoxemia; fetal lung liquid retention; and, in the case of the ENaC knockout mice, death. Bioelectrical studies of human infants' nasal epithelia demonstrate that both TTN and respiratory distress syndrome (RDS) involve defective amiloride-sensitive Na+ transport. Mature newborns who have normal transitions from fetal to postnatal life have mature surfactant and epithelial systems. TTN occurs in mature newborns with mature surfactant pathways and poorly developed respiratory epithelial Na+ transport, while neonatal RDS occurs in infants with both premature surfactant pathways and immature Na+ transport.
An infant born by cesarean delivery is at risk of having excessive pulmonary fluid as a result of not having experienced all of the stages of labor and subsequent lack of appropriate catecholamine surge, which results in low release of counter-regulatory hormones at delivery. The end result is alveoli with retained fluid that inhibit gas exchange.
Frequency
United States
Approximately 1% of infants have some form of respiratory distress that is not associated with infection. Respiratory distress includes both RDS (ie, hyaline membrane disease) and TTN. Of this 1%, approximately 33-50% have TTN.
Mortality/Morbidity
TTN is generally a self-limited disorder without significant morbidity. TNN resolves over a 24- to 72-hour period.
Race
No racial predilection has been reported.
Sex
Risk is equal in both males and females.
Age
Clinically, TTN presents as respiratory distress in full-term or near-term infants.
History
The maternal history consists of caesarian delivery without labor or precipitous delivery. Signs of respiratory distress (eg, tachypnea, nasal flaring, grunting, retractions, cyanosis in extreme cases) become evident shortly after birth. The disorder is indeed transient, with resolution occurring usually within 72 hours after birth.
Physical
Physical findings include tachypnea with variable grunting, flaring, and retracting. The infant is often described as having "quiet" tachypnea. Extreme cases may exhibit cyanosis.
Causes
The disorder results from delayed absorption of fetal lung fluid following delivery. Transient tachypnea of the newborn (TTN) is commonly observed following birth by cesarean delivery.
- Cesarean delivery
- Studies using lung mechanic measurements were performed in infants born by either cesarean or vaginal delivery. Milner et al noted that the mean thoracic gas volume was 32.7 mL/kg in infants born vaginally and 19.7 mL/kg in infants born via cesarean delivery. Importantly, chest circumferences were the same. Milner et al noted that the infants born via cesarean delivery had higher volumes of interstitial and alveolar fluid compared with those born vaginally, even though the overall thoracic volumes were within the reference range.
- Epinephrine release during labor affects fetal lung fluid. In the face of elevated epinephrine levels, the chloride pump responsible for lung liquid secretion is inhibited, and the sodium channels that absorb liquid are stimulated. As a result, net movement of fluid from the lung into the interstitium occurs. Therefore, caesarian delivery without labor and the subsequent lack of this normal surge in counter-regulatory hormones limits the excursion of pulmonary fluid.
- Maternal asthma and smoking
- In a recent study, Demissie et al performed a historical cohort analysis on singleton live deliveries in New Jersey hospitals from 1989-1992. After controlling for confounding effects of important variables, infants of mothers with asthma were more likely to exhibit TTN than infants of mothers in the control group.
- Schatz et al studied a group of 294 pregnant women with asthma and a group of 294 pregnant women without asthma. Both groups had normal pulmonary function test results and were matched for age and smoking status. TTN was found in 11 infants (3.7%) of mothers with asthma and in 1 infant (0.3%) of a mother from the control group. No significant differences between asthmatic and matched control subjects in other TTN risk factors were observed.
- Other factors: Excessive maternal sedation, perinatal asphyxia, and elective cesarean delivery without preceding labor are frequently associated with TTN.
Congenital Pneumonia
Meconium Aspiration Syndrome
Neonatal Sepsis
Pneumomediastinum
Pneumothorax
Pulmonary Hypertension, Persistent-Newborn
Respiratory Distress Syndrome
Other Problems to be Considered
Congenital heart disease
Cerebral hyperventilation
Metabolic acidosis
Lab Studies
- Arterial blood gas
- An ABG assessment is important to ascertain the degree of gas exchange and acid-base balance.
- Consider an intraarterial catheter, such as an umbilical artery catheter, if the infant's inspired fraction of oxygen exceeds 40%.
- Hypoventilation is very uncommon, and partial carbon dioxide tensions are usually normal because of the tachypnea. However, a rising carbon dioxide tension in an infant with tachypnea may be a sign of fatigue and impending respiratory failure or a complication such as a pneumothorax.
- Pulse oximetry
- Continuously monitor infants with pulse oximetry for assessment of oxygenation.
- Pulse oximetry allows the clinician to adjust the level of oxygen support needed to maintain appropriate saturation.
Imaging Studies
- Chest radiography
- Chest radiography is the diagnostic standard for transient tachypnea of the newborn (TTN).
- The characteristic findings include prominent perihilar streaking, which correlates with the engorgement of the lymphatic system with retained lung fluid, and fluid in the fissures. Small pleural effusions may be seen. Patchy infiltrates have also been described.
- Follow-up chest radiography may be necessary if the clinical history suggests meconium aspiration syndrome or neonatal pneumonia or if respiratory status worsens.
Medical Care
- Medical care is supportive. As the retained lung fluid is absorbed by the infant's lymphatic system, the pulmonary status improves.
- Supportive care includes intravenous fluids and gavage feedings until the respiratory rate has decreased enough to allow oral feedings. Supplemental oxygen to maintain adequate arterial oxygen saturation, maintenance of thermoneutrality, and an environment of minimal stimulation are the therapies necessary in these infants. ABG assessments should be periodically repeated, especially if the infant's condition worsens. Similarly, chest radiography should be repeated if clinical decompensation is observed.
- As transient tachypnea of the newborn (TTN) resolves, the infant's tachypnea improves, oxygen requirement decreases, and chest radiography shows resolution of the perihilar streaking.
- Infants with TTN may have signs that last from a few hours to several days. Rarely, an infant develops a worsening picture of respiratory distress after several days. This may require more aggressive support including the use of continuous positive airway pressure (CPAP) or mechanical ventilation.
Consultations
Infants with TTN occasionally may require consultation by a neonatologist. Consider this consultation if the fraction of inspired oxygen exceeds 40%, if metabolic or respiratory acidosis is present, if CPAP or mechanical ventilation is required, if the infant begins to display fatigue (periodic breathing or apnea), or if the infant fails to improve by age 48-72 hours.
Diet
Infants with TTN generally are supported by intravenous fluids or gavage feedings. Infants with significant distress have poor bowel motility and require intravenous therapy. Oral feedings are withheld until the respiration has improved.
The use of medications in transient tachypnea of the newborn (TTN) is minimal. Empiric antibiotics are often used for 48 hours after birth, until sepsis has been ruled out. Diuretics have not been shown to be beneficial.
Drug Category: Antibiotics
These agents are used when sepsis is clinically suggested. Antibiotics generally consist of a penicillin (usually ampicillin) and an aminoglycoside (usually gentamicin). Choices are based on local flora and antibiotic sensitivities. Dosage amounts and intervals are based on postmenstrual age (PMA), measured in weeks, and postnatal age, measured in days.
| Drug Name | Ampicillin (Omnipen-N) |
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| Description | A penicillin antibiotic with activity against gram-positive and some gram-negative bacteria. Ampicillin binds to penicillin-binding proteins (PBPs), inhibiting bacterial cell wall growth. |
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| Pediatric Dose | Dosage amount is 50 mg/kg/dose IV; dosage intervals are as follows:
PMA <29 wk and postnatal age 0-28 days: q12h
PMA <29 wk and postnatal age >28 days: q8h
PMA 30-36 wk and postnatal age 0-14 days: q12h
PMA 30-36 wk and postnatal age >14 days: q8h
PMA 37-44 wk and postnatal age 0-7 days: q12h
PMA 37-44 wk and postnatal age > 7 days: q8h
PMA > 45 wk and all postnatal ages: q6h |
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| Contraindications | Documented hypersensitivity |
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| Interactions | Probenecid increases the serum concentration of ampicillin |
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| Pregnancy | B - Usually safe but benefits must outweigh the risks.
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| Precautions | Dose adjustments may be necessary in patients diagnosed with renal failure |
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| Drug Name | Gentamicin (Garamycin) |
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| Description | Provides gram-negative aerobic coverage. Gentamicin also provides synergistic activity with penicillins against gram-positive bacteria including group B Streptococcus and Enterococcus. Gentamicin inhibits protein synthesis by irreversibly binding to bacterial 30S and 50S ribosomes.
Given as IV infusion by syringe pump over 30 min. Administer as separate infusion from penicillin-containing compounds.
IM injection is associated with variable absorption, especially in VLBW infants. |
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| Pediatric Dose | PMA <29 wk and postnatal age 0-7 days*: 5 mg/kg IV q48h
PMA <29 wk and postnatal age 8-28 days*: 4 mg/kg IV q36h
PMA <29 wk and postnatal age >28 days*: 4 mg/kg IV q24h
PMA 30-34 wk and postnatal age 0-7 days: 4.5 mg/kg IV q36h
PMA 30-34 wk and postnatal age > 7 days: 4 mg/kg IV q24h
PMA >34 wk and all postnatal ages: 4 mg/kg IV q24h
*Use this dosage regimen in patients with significant asphyxia or PDA or who are receiving treatment with indomethacin |
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| Contraindications | Documented hypersensitivity |
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| Interactions | Amphotericin B, cyclosporine, cephalosporins, and furosemide may increase the risk of renal toxicity |
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| Pregnancy | D - Unsafe in pregnancy
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| Precautions | Nephrotoxicity and ototoxicity may be associated with prolonged elevated trough concentrations (monitor levels to minimize the risk of toxicity and to optimize therapy);obtain peak 30 min after end of infusion and trough just prior to next dose; therapeutic serum concentrations:
Peak: 5-12 mcg/mL
Trough: 0.5-1 mcg/mL |
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Further Inpatient Care
- After resolution of transient tachypnea of the newborn (TTN), focus further inpatient care on routine newborn management.
Transfer
- An appropriately trained support staff is needed to treat infants with TTN. Infants with TTN and pneumonia or meconium aspiration may have similar clinical presentations. Therefore, staff members must be competent in recognizing worsening respiratory distress or impending failure and must be able to appropriately resuscitate the infant.
- Transfer is generally indicated by the need for a higher level of observation and/or care.
Complications
- Few potential complications exist. Some infants may develop hypoxia, respiratory fatigue, and acidosis. Occasionally, air leaks (eg, a small pneumothorax or pneumomediastinum) may be seen in infants who have increased work of breathing. Hence, any infant who does not follow the typical course of TTN and who develops any concerning symptoms must be reevaluated.
Prognosis
Patient Education
- Inform parents that TTN is usually a self-limited disorder and is not life threatening.
- New data links TTN to the later development of childhood asthma. Birnkrant et al recently studied the association between childhood asthma and TTN in a nested cohort of 2137 term newborns who were subsequently diagnosed with asthma and a similar number of birthday-matched controls. After adjustment for confounding factors, TTN was significantly associated with the diagnosis of childhood asthma. The adjusted odds ratio was 1.5 (95% CI, 1.13-1.99; P = .005). The association of TTN and asthma was statistically strongest among nonwhite male infants whose mothers lived at an urban address and did not have asthma. Thus, parents should be made aware that their child has a small risk of subsequently developing childhood asthma, especially if the child is male.
Medical/Legal Pitfalls
- The major pitfall is assuming that respiratory distress is solely transient tachypnea of the newborn (TTN) and not a more serious disorder. (eg, sepsis, pneumonia, persistent pulmonary hypertension, cyanotic congenital heart disease). This assumption limits the evaluation of the infant, potentially resulting in misdiagnosis and inappropriate therapy for the true cause of the respiratory distress.
| Media file 1:
A supine anteroposterior chest radiograph of an infant with transient tachypnea of the newborn (TTN). Note the reticular appearance of the film with mild cardiomegaly and obvious interstitial fluid. |
 |  View Full Size Image | |
Media type: X-RAY
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Transient Tachypnea of the Newborn excerpt Article Last Updated: Nov 21, 2006
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