Amniotic fluid and meconium aspiration syndrome
Introduction
Introduction of amniotic fluid and meconium aspiration syndrome Amniotic fluid and meconium aspiration syndrome (aspirationofamnioticfluidandmeconiumsyndrome) account for 0.3% to 2.0% of live births, more common in term infants and expired children. The main reason is that the fetus inhales amniotic fluid with meconium during birth, causing a series of symptoms such as suffocation and difficulty in breathing. Severe cases develop into respiratory failure or death. There are often fetal distress in the medical history, prolonged labor, placental insufficiency, dystocia, etc. Amniotic fluid stained meconium is often expressed as fetal hypoxia, but full-term or expired children can have a small amount of physiological meconium discharged into amniotic fluid. basic knowledge The proportion of illness: 1.2% to 2.2% Susceptible population: full-term children and expired children Mode of infection: non-infectious Complications: pneumonia, atelectasis, emphysema, mediastinal emphysema, pneumothorax, intracranial hemorrhage
Cause
The cause of amniotic fluid and meconium aspiration syndrome
Fetal hypoxia (15%):
Fetal hypoxia can cause group reflex, discharge meconium, and spontaneous breathing, inhalation of meconium and amniotic fluid keratinocytes, thick meconium inhalation can cause complete tracheal obstruction, atelectasis, acute asphyxia, hypoxia, thin Meconium amniotic fluid or inhaled amount can cause partial obstruction, causing sub-segmental atelectasis, obstructive emphysema, if alveolar rupture can cause interstitial emphysema or pneumothorax, when gas along the vessel wall and lymph Diffusion of the tube into the mediastinum can cause mediastinal emphysema.
Meconium contamination (25%):
At the time of birth, meconium is contaminated throughout the body. If the fetus is immersed in meconium and amniotic fluid for 4 to 6 hours, the nail can be dyed yellow-green. The umbilical cord of 10 to 12 hours, fetal fat, and placental amnion can be stained with meconium. Breathing is severely inhibited, bradycardia, hypotonia and shock, spontaneous breathing can be seen, breathing difficulties, gradual difficulty in breathing, intercostal depression and expiratory sputum, skin color cyanosis, such as cyanosis, oxygen-free, no improvement It should be considered to combine the continuous pulmonary hypertension of the newborn. The lung signs are related to the amount and thickness of the inhaled meconium. If there is a pneumothorax, the breathing sounds on both sides can be asymmetrical.
Meconium amniotic fluid stimulation (10%):
Meconium-stained amniotic fluid stimulates the respiratory mucosa or secondary infection can cause pneumonia. After entering the recovery period, the inhaled matter is absorbed or swallowed, and severe cases form fibrosis, and emphysema and other diseases appear.
Asphyxia and hypoxia (10%):
Severe asphyxia caused by cardiovascular adaptation disorder, right to left shunt, giant heart with peripheral circulatory congestion, occasionally convulsions, blood gas analysis showed that PO2 decreased, Pco2 increased and pH decreased, severe cases in the few minutes after birth After several hours of death, the survivor's course is prolonged. The general case is obviously improved within 2 days. After 10 days or more, the patient recovers completely. The light case can be difficult to breathe after a few hours after birth. The lungs are thickened by X-ray examination. Mild emphysema, mild decrease of diaphragm, more inhalation of meconium, both lungs may have dense patchy or nodular infiltration, excessive lung expansion, occasional small effusion of the chest, interstitial emphysema , squatting gas or pneumothorax.
Prevention
Amniotic fluid and meconium aspiration syndrome prevention
Proper treatment of fetal distress during prenatal delivery, try to avoid and reduce inhalation, fetal head delivery is not squeezed before the first breath or use a disposable pipette to remove oropharynx, nasal mucus is extremely important, is also the key to reduce the incidence It is necessary for the perinatal doctors and the nursing staff to pass the suffocation resuscitation treatment and pass the training.
Complication
Amniotic fluid and complications of meconium aspiration syndrome Complications pneumonitis atelectasis emphysema mediastinal emphysema pneumothorax intracranial hemorrhage
Simple amniocentesis is easy to absorb, and secondary pneumonia is also less. Inhalation of meconium and amniotic fluid can be accompanied by different degrees of obstruction and atelectasis, emphysema, mediastinal emphysema and pneumothorax, severe hypoxic acidosis can cause intracranial hemorrhage And pulmonary hemorrhage, patients with prolonged disease often have interstitial pneumonia and pulmonary fibrosis.
Symptom
Amniotic fluid and meconium aspiration syndrome symptoms Common symptoms Amniotic fluid fecal amniotic fluid meconium meconium contamination respiratory shortness three concave sign nose flap fan dyspnea hypoxemia purpura barrel chest
Clinical manifestation
The clinical manifestations of children with MAS vary according to the severity of hypoxic damage and the amount and viscosity of meconium-stained amniotic fluid.
1. If the child is exposed to meconium-contaminated amniotic fluid in the uterus for >4-6 hours, the whole body skin, nails and umbilical cord are dyed yellow-green or dark green at birth.
2, respiratory distress mainly manifested as shortness of breath (> 60 times / min), nasal fan, respiratory three concave signs and cyanosis, due to the severity of meconium contamination of amniotic fluid, the degree of respiratory distress can also be different, general cases It usually occurs within 4 hours after birth. Mild people only show temporary dyspnea and often self-healing. Heavier patients have difficulty breathing and cyanosis, but need to inhale 40% oxygen to maintain normal PaO2 and PaCO2. Severe dyspnea and bruising can occur within a few minutes after birth or within hours after birth. General oxygen therapy is ineffective and requires comprehensive treatment such as mechanical ventilation. Some children may only show mild respiratory distress at the beginning, but after a few hours The condition may worsen due to chemical pneumonia.
3, barrel-thorax thick meconium-contaminated amniotic fluid inhalation, children may cause airway obstruction or semi-blocking, acute airway obstruction clinical manifestations of wheezing breathing, cyanosis, must be immediately taken in the tracheal, gas In children with semi-occlusion, the anteroposterior diameter of the thoracic cage is enlarged by the barrel, the breathing is shallow, the breathing sound is reduced or the wet snoring and wheezing. When the pneumothorax occurs, the cyanosis and dyspnea may suddenly appear.
4, some children can be complicated by persistent pulmonary hypertension (see persistent pulmonary hypertension).
Examine
Amniocentesis and meconium aspiration syndrome
1, arterial blood gas hypoxemia is a characteristic manifestation, mild children may be due to excessive courage as respiratory alkalosis, severe children due to airway obstruction often manifested as increased PaCO2, respiratory acidosis, such as child asphyxia Blood gas can be expressed as mixed acidosis.
2. The meconium inhaled by chest X-ray generally reaches the alveoli after 4 hours after birth, and the chest X-ray can show special performance. The X-ray signs of about 85% of children with MAS are most obvious at 48 hours after birth, but about 70% of children with MAS Chest X-ray findings may be inconsistent with clinical performance, and MAS is classified according to chest X-ray findings:
Mild - thickened lung texture, mild emphysema, mild decrease in diaphragm, normal heart shadow.
Moderate - The lung field has coarse particles or flaky masses with increased density, cloud-like shadows or segmental atelectasis, with diffuse cystic emphysema and small heart shadow.
Severe - In addition to the above-mentioned moderate performance, accompanied by interstitial emphysema, mediastinal gas or pneumothorax and other air leakage phenomenon.
Diagnosis
Diagnosis and differential diagnosis of amniotic fluid and meconium aspiration syndrome
Need to be identified with the following diseases:
(1) Cardiac pulmonary edema: acute cardiogenic pulmonary edema in newborn children is caused by acute myocarditis caused by intrauterine infection. Symptoms are similar to MAS. It is characterized by shortness of breath, foam of oral discharge, sometimes with bloodshot eyes, and bruising. The lungs have a thick wet voice, the chest X-ray shows the heart enlargement, and the amniotic fluid has no history of meconium contamination, which can be identified.
(2) neonatal respiratory distress syndrome (NRDS): NRDS occurs mostly in premature infants, is a primary PS deficiency, no history of meconium contamination of amniotic fluid.
