Treatment of aspiration syndrome in newborns

It is believed that meconium aspiration can almost always be prevented by conducting appropriate monitoring in the antenatal period, promoting the acceleration of labor, and immediately clearing the trachea of the newborn. Doctors studied the clinical and pathological features of meconium aspiration syndrome based on the analysis of 14 births with the presence of meconium in the waters, where meconium aspiration syndrome was the cause of neonatal mortality. In the studied group, all mothers were primiparous. Intranatally, 6 (42.8%) fetuses died; in all these cases, labor was completed by applying abdominal obstetric forceps and a vacuum extractor. The remaining newborns had an Apgar score of 5 points or less at birth. Immediately after birth, all children had their upper respiratory tracts suctioned, artificial ventilation was used, solutions of soda, glucose, and ethylisole were injected into the umbilical vein, and a session of hyperbaric oxygenation was prescribed.

Despite the resuscitation measures taken, 7 (50%) children died on the first day after birth from massive meconium aspiration, the rest - on the 2nd-4th day from severe aspiration pneumonia. The diagnosis of meconium aspiration was confirmed at autopsy. The characteristic pathological picture was filling the lumen of the bronchi with a large amount of mucus, elements of amniotic fluid, meconium. The alveoli were dilated in all cases, a large amount of amniotic fluid and meconium particles were detected in their lumen. In three cases, there was a rupture of the alveolar wall, extensive hemorrhages were found under the pleura.

When the meconium is thick and lumpy, an attempt should be made to clear it from the nose and oropharynx before the chest emerges from the birth canal. Immediately after birth, if the meconium is thick or the Apgar score is below 6, endotracheal intubation should be performed to aspirate the tracheal contents before artificial respiration is initiated. If these measures are not taken immediately after birth, the incidence of aspiration syndrome and mortality increase. This procedure is indicated even in cases where meconium is absent from the oropharynx (as shown, 17% of neonates with meconium in the trachea had no meconium in the oropharynx). Suctioning of the trachea during repeated intubation or through a catheter should be repeated until the trachea is completely clear. An additional procedure in the delivery room - removal of swallowed meconium from the stomach - prevents repeated aspiration.

The neonate should be placed in an intensive care unit. Continuous monitoring of pulse and respiratory rate is important. Radiographic examination is performed to confirm the diagnosis and exclude pneumothorax; it is repeated if the clinical picture worsens. Any neonate requiring 30% air-oxygen mixture to maintain pink skin color should have an arterial catheter inserted to continuously monitor the blood gases. Broad-spectrum antibiotics are recommended because bacterial sepsis may be the cause of fetal hypoxia and the passage of meconium into the fluid. In some cases, pneumonia cannot be distinguished from meconium aspiration syndrome, and even if the meconium is sterile, its presence promotes bacterial growth. There is no evidence of a beneficial effect of steroids in this syndrome. Physical therapy and postural drainage can be used to remove residual meconium from the lungs.

Approximately 50% of neonates with meconium aspiration develop respiratory failure. Mechanical ventilation is indicated when Ra is below 80 mmHg on 100% oxygen, Ra is above 60 mmHg, or apnea occurs. Recommended mechanical ventilation parameters are: respiratory rate 30-60/min; inspiratory pressure 25-30 cm H2O; positive end-expiratory pressure (PEEP) 0-2 cm H2O; inspiratory-to-expiratory ratio 1:2 to 1:4.

In cases of high risk of hypoxic pulmonary vasoconstriction and low probability of retinopathy in the mature neonate, Pa should be maintained at the upper limit, i.e. 80-100 mmHg. To reduce Pa, increasing the respiratory rate is preferable to increasing the tidal volume by creating a high peak pressure.

High PEEP increases the risk of decreased venous return to the heart and hence cardiac output, decreased lung compliance (which may lead to hypercapnia) and air trapping (leading to alveolar rupture). However, if Pa remains below 60 mmHg despite artificial ventilation with pure oxygen, an attempt can be made to improve blood oxygenation by increasing PEEP to 6 cm H2O. This maneuver should be performed under close monitoring because of possible complications. PEEP should be reduced if systemic hypotension, hypercapnia or pulmonary air leak occur. Oxygenation is improved by combining artificial ventilation with muscle relaxation. This method is especially recommended if interstitial pulmonary emphysema is detected on chest x-ray, the child is not synchronized with the machine and an increase in PEEP is required. Deterioration during such treatment is possible due to the development of pneumothorax or blockage of the endotracheal tube with meconium. The most likely cause of persistent or increasing hypoxemia is persistent pulmonary hypertension.

In conclusion, it should be noted that, according to literary and our data, the mortality rate for meconium aspiration syndrome is 24-28%; in cases where artificial ventilation was required, the mortality rate reached 36-53%.

If, however, immediately after birth, before the first breath, the nasopharynx was cleared or the contents of the trachea were suctioned, not a single fatal outcome was recorded.

The final prognosis depends not so much on the developed lung disease as on perinatal asphyxia. No specific chronic lung dysfunctions have been described.