Treatment of meconium aspiration syndrome and its prevention

Intranatal amnioninfusion in the presence of meconium in waters

This procedure is most indicated in the presence of densely colored meconium of amniotic fluid. The results of four randomized trials of recent years have been processed by meta-analysis of Hofmeyr. As a result, there was a decrease in the cesarean section according to the indications from the fetus (distress of the fetus), there was a significant decrease in the number of newborns in which meconium was located in the airways at least the vocal cords and meconium aspiration syndrome was significantly less in frequency. There was no perinatal death of children either in the group with amnioninfusion or in the control group.

Among the complications of amnioninfusion, mention should be made of the appearance of hypertension of the uterus and, possibly, of neonatal respiratory failure.

As is known, respiratory distress can develop immediately after birth. However, more often its symptoms appear after 12-24 hours in the form of cyanosis, tachypnea, hoarse breathing, widening or retraction of the intercostal spaces or overstretch of the chest. At auscultation, rough rales, tender crepitus, prolonged exhalation are heard. Radiographically visible areas of large, irregular form of darkening, alternating with areas of increased transparency. Often the lungs look emphysematic, the diaphragm is flattened, the bases of the lungs are distinguished by increased transparency, the anteroposterior size of the thorax is increased. In 1/2 cases, fluid and air are determined in the pleura and interlobar spaces. Pneumothorax usually develops within the first 24 hours, often spontaneously in newborns who have not been ventilated. For profuse aspiration, the X-ray symptom of a "snow storm" and cardiomegaly are characteristic. It must be said that there are no radiologic symptoms pathognomonic for meconium aspiration, and sometimes it is difficult to distinguish it from pneumonia and hemorrhage into the lungs. The radiological picture usually normalizes after 2 weeks, however, increased pneumonia of the lungs and the formation of pneumatology can be observed for several months.

Metabolic acidosis in the first hours after birth indicates that the newborn has already had asphyxia. Initially, minute ventilation is normal or even slightly increased, but in more severe cases, the development of hypercapnia necessitates artificial ventilation. The severity of hypoxemia depends largely on the degree of lung damage, as well as persistent pulmonary hypertension. While in mild cases it can be limited to oxygen therapy for several hours or days, in severe cases, respiratory distress may develop or there may be a need for prolonged (days, weeks) artificial ventilation. Such respiratory complications as air leakage, secondary infection and bronchopulmonary dysplasia, delay the healing process. Combined complications, including hypoxic-ischemic encephalopathy, renal failure, coagulopathy and necrotizing enterocolitis, are due to perinatal asphyxia, rather than aspiration of meconium.

Treatment of meconium aspiration syndrome in the delivery room

• suction of the contents of the oropharynx immediately after the birth of the head to the first inhalation of the child;
• additional heating of the child;
• removal of meconium from the mouth, pharynx, nasal passages and stomach after the birth of the child;
• intubation of the trachea followed by sanation of the tracheobronchial tree;
• Manual ventilation with an Ambu bag through a mask or an intubation tube.

Further, the method of oxygen therapy is determined: through a mask, an oxygen tent with a mild aspiration; IVL with massive aspiration after removal of the meconium from the trachea by means of infusion into the trachea 1-2 ml of sterile isotonic sodium chloride solution. Sanitation in the first 2 hours of life is repeated every 30 minutes, using postural drainage, back massage.

Prevention of meconium aspiration

With the aim of improving the possibilities of prevention of aspiration syndrome of newborns, a new method of intra-amniotic perfusion of amniotic fluid in labor with their microfiltration was developed and studied.

It should be emphasized that in modern literature much attention is paid to the determination of the concentration of meconium in the amniotic fluid, which is divided into the recently passed meconium ("fresh"), the increase in the concentration of which requires rapid delivery, and "old". So, scientists have developed a method of spectrophotometric determination of meconium concentration in waters, using the principle of determining bilirubin in hemolytic disease of the fetus and the newborn. Meconium is determined in the 410 nm spectrum (405-415 nm) and the amount can fluctuate in confidence intervals from 370 to 525 nm. Weitzner et al. Also developed an objective method for determining the content of meconium in waters, since the amount of meconium is usually determined subjectively, visually and is divided into two types: a minor admixture and a significant admixture of meconium in the waters. The authors developed a simple, fast and inexpensive method for determining meconium in waters ("Meconium crit") and its concentration in waters. The procedure was as follows: 15 g of fresh neonatal meconium (no more than 3 hours ago) were taken, placed in light amniotic fluid and observed for 15 min. Then, 15 g of meconium was diluted in 100 ml of amniotic fluid and then diluted in a concentration of 10 g, 7.5 g, 5 g, 3 g and 1.5 g per 100 ml of amniotic fluid. Then 1 ml of each sample was diluted with additionally pure water with 0.5 ml, 1 ml, 2 ml, 4 ml and 9 ml. 10 ml of a mixture of meconium and water were placed in a standard hematocrit tube, centrifuged, and then the amount of meconium was determined as determined by the hematocrit. These methods are important, since the development of aspiration syndrome (about 2%) can lead to neonatal mortality in more than 40% of newborns. In the presence of so-called "thick" meconium, the incidence of complications in newborns is increased. Therefore, in the presence of "thick" meconium, a number of authors perform amnioninfusion. In contrast to Molcho et al., Where very strong meconium dilution is required below clinically significant (1 g / 100 ml was the maximum concentration), the Weitzner et al. Usually uses those concentrations of meconium that are observed in clinical practice and require the presence of only a centrifuge in the delivery room. Nuclear magnetic resonance is also used to determine meconium in the amniotic fluid. In two independent studies, doctors determined by echography the presence of "thick" meconium in the amniotic fluid. Ohi, Kobayashi, Sugimura, Tegao have developed a new method for determining meconium in the amniotic fluid with monoclonal antibodies to determine the meconium-type meconium-glycoprotein component. Horiuchi et al. Also isolated and identified as the main fluorescent component of meconium.

Davey, Becker, Davis described new data on meconium aspiration syndrome: physiological and inflammatory changes in the model of newborn piglets. It is shown that the meconium aspiration syndrome causes an acute decrease in gas exchange and dynamic lung plasticity, which return to the baseline level after 48 hours. The endogenous surfactant function is also significantly inhibited by meconium. All signs of pulmonary trauma were significantly more pronounced in a group of animals with meconium in the waters. According to Kariniemi, Harrela, the latter is more associated with placental insufficiency compared with umbilical insufficiency of blood flow. Proceeding from these data, amnioninfusion should be performed as early as possible in labor, because it contributes simultaneously to the improvement of the fetus and the prevention of fetal distress.

It should be emphasized that, according to Parsons, meconium aspiration syndrome remains constant in the range of 6.8-7%. Other authors estimate a frequency of about 2%, despite the active suction of meconium from the upper respiratory tract. At the same time, in Carson et al., Where there was no suction of mucus, the incidence of aspiration syndrome remained low. Therefore, Goodlin believes that a more effective method of treating meconium aspiration syndrome is to induce apnea in the fetus with drugs, especially in fetuses with increased motor activity in the presence of meconium in the waters. A confirmation of the expediency of this is the early work of Goodlin, which found that aspiration syndrome is not manifested in newborns whose mothers received sedatives and narcotic drugs. However, this issue needs further study, since the frequency of meconium aspiration syndrome remains high up to the present day - up to 7 %.

Doctors developed the following procedure for intra-amniotic perfusion of waters with microfiltration. The amnion cavity is catheterized with a double-lumen catheter, after which perfusion with self-amniotic fluid is started through an external system containing microfilters with a hole diameter of 4 μm, at a rate of 10-50 ml / min until the child is born. To the present part of the fetus, a sealing cuff is introduced, allowing prolonged perfusion without significant loss of amniotic fluid.

In 29 observations, when a pronounced meconium impurity appeared in the amniotic fluid in the first stage of labor, their complete purification occurred 60-80 min after the start of perfusion in the absence of repeated entry of meconium. Fourteen parturient women (49%) showed a second occurrence of meconium. In these observations, a complete purification of the perfusion system also took place within 60-80 min. In parallel with the microfiltration of water, given that the presence of meconium may serve as a sign of a possible fetal asphyxia, periodic monitoring of the fetus with a Zaling assay was performed. Indeed, 24 women giving birth were found to have signs of fetal hypoxia according to the pH, pO ₂ and pCO ₂ of fetal blood. In these cases, one of the methods used to treat fetal hypoxia with antihypoxants, antioxidants and other agents was used. Continuation of perfusion was carried out in cases of sufficient effectiveness of antihypoxic therapy. In 22 parturient women (76%) with a satisfactory fetal condition in labor, the method of intra-amniotic perfusion was applied from the moment of meconium detection to the birth of the child, while the average duration of perfusion was 167 min.

The state of newborns on the Apgar scale in 18 cases (82%) corresponded to 8-10 points, in 4 cases (18 %) - 6-7 points. There were no cases of perinatal mortality. Syndrome of respiratory disorders, as well as violations of the external respiration of children during their comprehensive examination in the next 10 days were not detected.

Given the high incidence of respiratory disorders in newborns in the presence of meconium in amniotic fluid, the method of intra-amniotic perfusion of amniotic fluid with their microfiltration can be an effective preventive method in detecting meconium admixture in waters in the first stage of labor and with sufficient therapy for fetal hypoxic conditions often encountered in these cases.