Meconium Aspiration

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Meconium Aspiration

MAS can happen before, during, or after labour and delivery when a newborn inhales (or
aspirates) a mixture of meconium and amniotic fluid (the fluid in which the baby floats inside
the amniotic sac).

Meconium is the baby's first feces, or poop, which is sticky, thick, and dark green and is
typically passed in the womb during early pregnancy and again in the first few days after
birth.

The inhaled meconium can partially or completely block the baby's airways. The meconium
irritates the baby's airways and makes it difficult to breathe.

MAS can affect the baby's breathing in a number of ways, including chemical irritation to the
lung tissue, airway obstruction by a meconium plug, infection, and the inactivation of
surfactant by the meconium (surfactant is a natural substance that helps the lungs expand
properly).
The severity of MAS depends on the amount of meconium the baby inhales as well as underlying
conditions, such as infections within the uterus or postmaturity (when a baby is overdue, or more than
40 weeks' gestational age). Generally, the more meconium a baby inhales, the more serious the
condition.
Causes
MAS is often related to fetal stress. Fetal stress can be caused by problems in the womb, such as
infections, or by difficulties during the labor process. A distressed baby may experience hypoxia
(decreased oxygen), which may make the baby's intestinal activity increase and may cause relaxation
of the anal sphincter (the muscular valve that controls the passage of feces out of the anus). This
relaxation then moves meconium into the amniotic fluid that envelops the baby.
Additional risk factors for MAS include:

a difficult delivery

advanced gestational age (or postmaturity)

a mother who smokes cigarettes heavily or who has diabetes, hypertension (high blood
pressure), or chronic respiratory or cardiovascular disease

umbilical cord complications

poor intrauterine growth (poor growth of the baby while in the uterus)
Prematurity is not a risk factor. In fact, MAS is rare in babies born before 34 weeks.
Signs and Symptoms
At birth, the doctor will likely notice one or more symptoms of MAS, including:

meconium or dark green streaks or stains in the amniotic fluid

discoloration of the baby's skin — either blue (cyanosis) or green (from being stained by the
meconium)

problems with breathing — including rapid breathing (tachypnea), labored (difficulty)
breathing, or suspension of breathing (apnea)

low heart rate in the baby before birth

low Apgar score (the Apgar test is given to newborns just after birth to quickly evaluate color,
heartbeat, reflexes, muscle tone, and breathing)

limpness in the baby

postmaturity (signs that a baby is overdue such as long nails)
Diagnosis
If a baby is thought to have inhaled meconium, treatment will begin during delivery.
laryngoscope into the baby’s trachea to remove any meconium that might be present. The doctor will
also probably listen to the baby's chest with a stethoscope for sounds in the lungs that are common in
infants with MAS.
The doctor may also order tests — a blood test (called a blood gas analysis) that helps determine if
the baby is getting enough oxygen and a chest X-ray that can show patches or streaks on the lungs
that are found in babies with MAS.
Treatment
Current recommendations say that if an infant has inhaled meconium but looks active, appears well,
and has a strong heartbeat (>100 bpm), the delivery team can watch the baby for MAS symptoms,
which typically appear within the first 24 hours. So the baby is observed for such signs as increased
respiratory rate, grunting, or cyanosis.
For an infant that has inhaled meconium and shows signs of poor activity level, has a lower heart rate
(<100 bpm), is limp, and has poor muscle tone, the goal is to clear the airway as much as possible to
decrease the amount of meconium that's aspirated.
This is done by putting in an endotracheal tube (a plastic tube that's placed into the baby's windpipe
through the mouth or nose) and applying suction as the tube is slowly removed. This allows the infant
to receive suctioning of both the upper and lower airways. The doctor will continue trying to clear the
airway until there's no meconium in the suctioned fluids.
Most babies with MAS improve within a few days or weeks.
Babies with MAS may be sent to a special care nursery or a neonatal intensive care unit (NICU) to be
closely monitored for the next few days. Treatments may include:

oxygen therapy by oxygen hood or ventilation

antibiotics

use of surfactant

nitric oxide

obtaining blood routinely to determine if the baby is receiving enough oxygen
Babies who have severe aspiration and require mechanical ventilation are at increased risk for
bronchopulmonary dysplasia, a lung condition that can be treated with medication or oxygen. Another
complication associated with MAS is a collapsed lung. Also known as pneumothorax, a collapsed lung
is treated by reinflating the lung (inserting a tube between the ribs, allowing the lung to gradually reexpand).
Although rare, a small percentage of babies with severe MAS develop aspiration pneumonia. If this
occurs, the doctor may recommend advanced lung rescue therapy.
Three therapies are currently used to treat aspiration pneumonia and severe forms of MAS:

Surfactant therapy — An artificial surfactant is instilled into the baby's lungs, which helps to
keep the air sacs open.

High-frequency oscillation — This special ventilator vibrates air enriched with extra oxygen
into the baby's lungs.

Rescue therapy — Nitric oxide is added to the oxygen in the ventilator. It dilates the blood
vessels and allows more blood flow and oxygen to reach the baby's lungs.
If one of these therapies (or a combination of them) doesn't work, there is another alternative. Extra
corporeal membrane oxygenation (ECMO) is a form of cardiopulmonary bypass, meaning that an
artificial heart and lung will temporarily take over to supply bloodflow to the baby's body. ECMO
reduces the fatality rate for these severely distressed infants from 80% to 10%. Not all hospitals are
ECMO centers, so babies that require ECMO may need to be moved to another hospital.
Babies with severe cases of MAS may come home from the hospital on oxygen. They may be more
likely to have wheezing and lung infections during their first year, but lungs can regenerate new air
sacs, so the long-term prognosis for their lungs is excellent.
Severely affected babies are at risk for developing chronic lung disease and may also have
developmental abnormalities and hearing loss. Babies diagnosed with MAS will be screened at the
hospital for hearing problems or neurological damage. Although very rare, severe cases of MAS may
be fatal. Studies have indicated that deaths from MAS have decreased significantly through
interventions such as suctioning and reducing the number of post-term births.
Prevention
It's important for a pregnant woman to tell her doctor immediately if meconium is present in the
amniotic fluid when her water breaks, or if the fluid has dark green stains or streaks. Doctors also use
a fetal monitor during labor to observe the baby's heart rate for any signs of fetal distress. In some
cases doctors may recommend amnioinfusion, the dilution of the amniotic fluid with saline, to wash
meconium out of the amniotic sac before the baby has a chance to inhale it at birth.
Although MAS is a frightening complication for parents to face during the birth of their child, the
majority of cases are not severe. Most infants are monitored for fetal distress during labor, and
doctors pay careful attention to any signs that would indicate meconium aspiration. If it does occur,
treatment will begin immediately.
For most infants who have inhaled meconium, early treatment can prevent further complications and
help to reassure anxious new parents.
http://kidshealth.org/parent/medical/lungs/meconium.html
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