Meconium aspiration syndrome: Difference between revisions

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==Background==
==Background==
*May cause meconium aspiration syndrome (MAS) in a newborn infant that was born through meconium-stained amniotic fluid (MSAF)
*Presentation ranges from mild respiratory distress to life-threatening respiratory failure  
*Presentation ranges from mild respiratory distress to life-threatening respiratory failure  
*Incidence is 2-10% of infants born through MSAF
*Incidence is 2-10% of infants born through MSAF (meconium-stained amniotic fluid)
*Thought to be associated with fetal hypoxia and post-term delivery
*Thought to be associated with fetal hypoxia and post-term delivery
*Causes hypoxemia and acidosis via airway obstruction, chemical irritation/inflammation, infection, and surfactant inactivation
*Causes hypoxemia and acidosis via airway obstruction, chemical irritation/inflammation, infection, and surfactant inactivation
*Associated with persistent pulmonary hypertension of the newborn (PPHN)
*Associated with persistent pulmonary hypertension of the newborn (PPHN)
{{Newborn vital signs}}


==Clinical Features==
==Clinical Features==
*Tachypnea
*Usually develop symptoms within 15 minutes after birth
*[[Tachypnea]]
*Cyanosis
*Cyanosis
*Accessory muscle use (intercostal/subxiphoid retractions, paradoxical breathing, grunting, nasal flaring)
*[[Shortness of breath (peds)|Accessory muscle use]] (intercostal/subxiphoid retractions, paradoxical breathing, grunting, nasal flaring)
*Barrel-shaped chest
*Barrel-shaped chest
*Rales and rhonchi on lung auscultation
*Rales and rhonchi on lung auscultation
*Pneumothorax
*[[Pneumothorax]]
*Pneumomediastinum
*[[Pneumomediastinum]]
*Usually develop symptoms immediately after birth, but sometimes are born asymptomatic and develop symptoms as meconium moves into lower tracheobronchial tree


==Differential Diagnosis==
==Differential Diagnosis==
*[[Transient tachypnea of the newborn]] (TTN)
*[[Sepsis]]
*[[Sepsis]]
*[[Pneumonia]]
*[[Pneumonia]]
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*[[Pulmonary hypertension]]
*[[Pulmonary hypertension]]
*[[Congenital heart disease]]
*[[Congenital heart disease]]
*[[Respiratory distress syndrome]]
 
{{Newborn DDX}}


==Evaluation==
==Evaluation==
*Workup
===Workup===
**CXR
*[[CXR]]
**ABG
**Streaky, linear densities
**Echocardiogram
**Hyperinflated lungs and flattened diaphragm
**Blood and sputum cultures
**Diffuse patchy opacities (may appear similar to RDS if severe)
*[[ABG]]
*[[Echocardiography]]
*Blood and sputum cultures


===Diagnosis===
*Clinical diagnosis based on the following:
*Clinical diagnosis based on the following:
**Evidence of meconium on infant
**Evidence of meconium on infant
**Respiratory distress shortly after birth
**Respiratory distress shortly after birth
**Characteristic CXR findings
**Characteristic CXR findings
***Initially, streaky, linear densities
***Next, development of hyperinflated lungs and flattened diaphragm
***Finally, diffuse patchy opacities (may appear similar to ARDS if severe)
**If intubation required, meconium visualized in trachea
**If intubation required, meconium visualized in trachea
*Ways to differentiate between other causes of respiratory distress in a neonate:
*Ways to differentiate between other causes of respiratory distress in a neonate:
**TTN is more common in late preterm infants (34-37 weeks) and RDS in preterm infants, whereas MAS more common in postmature infants (>41 weeks)
**[[Transient tachypnea of the newborn]] is more common in late preterm infants (34-37 weeks) and RDS in preterm infants, whereas MAS more common in postmature infants (>41 weeks)
**Delayed transition from fetal circulation symptoms improve more quickly than those of MAS
**Delayed transition from fetal circulation symptoms improve more quickly than those of MAS
**Congenital cyanotic heart disease is differentiated by physical exam (murmurs, hepatomegaly), CXR (cardiac size/shape), and echocardiogram (cardiac anatomy and function)
**[[Congenital heart disease|Congenital cyanotic heart disease]] is differentiated by physical exam ([[murmur]]s, [[hepatomegaly]]), CXR (cardiac size/shape), and echocardiogram (cardiac anatomy and function)


==Management==
==Management==
*Empiric antibiotics while awaiting culture results (because of difficulty differentiating between pneumonia initially)
*Supportive care: see [[newborn resuscitation]]
 
**Adequate oxygenation and ventilation
*Prevention
***Supplemental [[oxygen]] to keep saturation >99% and PaO2 55-90
**Fetal heart rate monitoring intrapartum to  reduce risk of fetal hypoxia
***Assisted ventilation with [[CPAP]] if FiO2 exceeds 0.4 to 0.5
**Induction of labor after 41 weeks gestation to reduce postmature delivery
***High frequency oscillatory ventilation or ECMO for those who fail conventional mechanical ventilation
**Amnioinfusion with isotonic fluid to dilute thick meconium is NOT routinely recommended
***Goal PaCO2 50-55 mmHg
 
**Maintain blood pressure and perfusion
***Umbilical lines to monitor blood gases and BP
**Correct metabolic abnormalities
*Empiric [[pediatric antibiotics|antibiotics]] while awaiting culture results (because of difficulty differentiating between pneumonia initially)
*Surfactant administration for severe disease requiring mechanical ventilation, FiO2>0.5, and mean airway pressure >10-12


==Disposition==
==Disposition==
*Admit to NICU


==Prevention==
*Fetal heart rate monitoring intrapartum to  reduce risk of fetal hypoxia
*Induction of labor after 41 weeks gestation to reduce postmature delivery
*Amnioinfusion with isotonic fluid to dilute thick meconium is NOT routinely recommended


==See Also==
==See Also==
 
*[[Newborn resuscitation]]


==External Links==
==External Links==
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==References==
==References==
<references/>
<references/>
[[Category:Pediatrics]]

Revision as of 16:56, 1 July 2020

Background

  • Presentation ranges from mild respiratory distress to life-threatening respiratory failure
  • Incidence is 2-10% of infants born through MSAF (meconium-stained amniotic fluid)
  • Thought to be associated with fetal hypoxia and post-term delivery
  • Causes hypoxemia and acidosis via airway obstruction, chemical irritation/inflammation, infection, and surfactant inactivation
  • Associated with persistent pulmonary hypertension of the newborn (PPHN)

Newborn Vital Signs[1]

Age Pulse^ Respiratory Rate Systolic BP
Preterm < 1 kg 120-160 30-60 36-58
Preterm 1 kg 120-160 30-60 42-66
Preterm 2 kg 120-160 30-60 50-72
Newborn 126-160 30-60 60-70
Min of life Target sat^^
1 min 60-65%
2 min 65-70%
3 min 70-75%
4 min 75-80%
5 min 80-85%
10 min 85-95%

^Fever directly causes an increase in heart rate of 10 beats per minute per degree centigrade[2] ^^Hyperoxia can be harmful

Clinical Features

Differential Diagnosis

Newborn Problems

Evaluation

Workup

  • CXR
    • Streaky, linear densities
    • Hyperinflated lungs and flattened diaphragm
    • Diffuse patchy opacities (may appear similar to RDS if severe)
  • ABG
  • Echocardiography
  • Blood and sputum cultures

Diagnosis

  • Clinical diagnosis based on the following:
    • Evidence of meconium on infant
    • Respiratory distress shortly after birth
    • Characteristic CXR findings
    • If intubation required, meconium visualized in trachea
  • Ways to differentiate between other causes of respiratory distress in a neonate:
    • Transient tachypnea of the newborn is more common in late preterm infants (34-37 weeks) and RDS in preterm infants, whereas MAS more common in postmature infants (>41 weeks)
    • Delayed transition from fetal circulation symptoms improve more quickly than those of MAS
    • Congenital cyanotic heart disease is differentiated by physical exam (murmurs, hepatomegaly), CXR (cardiac size/shape), and echocardiogram (cardiac anatomy and function)

Management

  • Supportive care: see newborn resuscitation
    • Adequate oxygenation and ventilation
      • Supplemental oxygen to keep saturation >99% and PaO2 55-90
      • Assisted ventilation with CPAP if FiO2 exceeds 0.4 to 0.5
      • High frequency oscillatory ventilation or ECMO for those who fail conventional mechanical ventilation
      • Goal PaCO2 50-55 mmHg
    • Maintain blood pressure and perfusion
      • Umbilical lines to monitor blood gases and BP
    • Correct metabolic abnormalities
  • Empiric antibiotics while awaiting culture results (because of difficulty differentiating between pneumonia initially)
  • Surfactant administration for severe disease requiring mechanical ventilation, FiO2>0.5, and mean airway pressure >10-12

Disposition

  • Admit to NICU

Prevention

  • Fetal heart rate monitoring intrapartum to reduce risk of fetal hypoxia
  • Induction of labor after 41 weeks gestation to reduce postmature delivery
  • Amnioinfusion with isotonic fluid to dilute thick meconium is NOT routinely recommended

See Also

External Links

References

  1. National-Model-EMS-Clinical-Guidelines-23Oct2014
  2. Davies P, Maconochie I. The relationship between body temperature, heart rate and respiratory rate in children. Emerg Med J. 2009 Sep;26(9):641-3. doi: 10.1136/emj.2008.061598.