Meconium is the newborn’s first evacuation that can be recognized for his color dark green or black and the lack of odor . It consists of gastrointestinal secretions, bile acids, mucus, pancreatic juice, cellular waste, amniotic fluid, caseous vernix, lanugo and swallowed blood . Furthermore, it is believed that its formation begins around the 12th week of gestation, when the fetus begins to swallow the amniotic fluid .
The concentration of meconium in the amniotic fluid depends on the amount of amniotic fluid present in the amniotic cavity and how much meconium has been eliminated . In cases of hypoxia or presence of perinatal infection, a probable cause may be due to the elimination of intrauterine meconium, being dispersed in the amniotic fluid in greater concentration and quantity, favoring aspiration by the fetus .
This aspiration of meconium amniotic fluid is facilitated if the fetus presents forced respiratory movements, causing airway obstruction, interference with gas exchange and severe breathing difficulties, which may develop meconium aspiration syndrome. In the same sense, if there is elimination or thickening of meconium during labor, the chances of the newborn developing complications are doubled  .
The Meconial Aspiration Syndrome (MAS) is a complication caused by the presence of meconium amniotic fluid with consequent aspiration, being responsible for important rates of perinatal morbidity and mortality . The diagnosis is made by a history of meconium amniotic fluid, presence of meconium in the newborn’s trachea and compatible radiological alteration, with areas of coarse granular atelectasis alternating with areas of hyperinflation in the pulmonary fields, and areas of lobar or multilobar consolidation may also appear, interstitial emphysema, pneumothorax and/or pneumomediastinum .
There are some maternal antecedents that are frequently observed in association with Meconial Aspiration Syndrome, such as: arterial hypertension, chronic cardiovascular or pulmonary disease, acute hypotension, placenta previa, premature displacement of the placenta, presence of prolapses, circular and cord nodes .
The Meconial Aspiration Syndrome causes mechanical, chemical and inflammatory responses that interfere with the passage from the intrauterine to the extrauterine environment, leading the newborn to develop complications . If there are no complications of meconium aspiration, such as barotrauma and/or pulmonary hypertension, meconium is absorbed gradually with an improvement in the condition of 5 to 7 days .
In the development of pregnancy, 10% to 20% of cases can be observed the presence of meconium amniotic fluid and 1% to 2% of these newborns will present MAS . In industrialized countries, the occurrence of birth with the presence of meconium amniotic fluid corresponds to 8% to 25% of births after the 34th week of pregnancy and MAS occurs in about 1% to 3% of newborns .
The conditions of pregnancy, childbirth and especially the quality of care that is provided in the delivery room, strongly imply situations of greater or lesser severity in cases of MAS. The newborns with MAS needs intensive care, with a specialized team and advanced equipment, being referred to a Neonatal Intensive Care Unit (NICU) . Technological advances and knowledge about therapeutic modalities have reduced the rate of morbidity and mortality, however, further studies on the topic are still needed .
Thus, the aim of the present study was to analyze the bibliographic production on assistance provided to the newborn with meconium elimination in the delivery room through an integrative literature review.
To carry out the study, it was decided to conduct an integrative literature review. Integrative analysis is a specific review method that enables the analysis and synthesis of knowledge about a particular phenomenon or health problem. The method allows the inclusion of several methodologies and has a strong influence on evidence-based nursing practices .
For this, the present study was carried out in 6 methodological stages. The first stage consisted of identifying the problem, the search engine presented and the descriptors or keywords described. In the second stage, the inclusion and exclusion criteria of the articles were established for a sample composition. The third stage consisted of an exploratory reading of the titles and abstracts of the articles for pre-selection. The fourth stage consisted of the analytical reading of the articles to compile, analyze and categorize the information. In the fifth stage, the results were interpreted. And, in the last stage, the results were synthesized and presented, which permeate the guiding question (Figure 1) .
Then, the selected articles were characterized based on the identification of the study (title, authors, journal), year of publication, database, type of study, objectives and main results (Chart 1).
Figure 1. Flowchart of selection of publications.
Chart 1. Distribution of studies regarding assistance to newborns with meconium elimination in the delivery room according to study identification, year of publication, type of study, objectives and main results.
The selected articles were characterized based on the identification of the study (title, authors, journal), year of publication, database, type of study, objectives and main results (Chart 1).
An exploratory reading and selection of the material was carried out, followed by an analytical reading, through the reading of the selected works, which made it possible to organize the ideas in order of importance and later fixation. After the analytical reading, the interpretative reading started, which dealt with the comment made by linking the data obtained, emphasizing the main ideas. Next, the data presented were submitted to content analysis and a synthesis of knowledge was carried out for the construction of the article.
3. Results and Discussion
Characterization of the studies
The sample consisted of 10 articles, two of them were in Portuguese, one was in Spanish and 7 in English. The works were published from 2005 to 2015, one in a periodical in England, one in a periodical in Germany, one in a periodical in Argentina, three in Brazilian periodicals and four in American periodicals (Chart 1).
Regarding the research design, six studies were retrospective studies, a cohort study work, a systematic review work, a controlled clinical trial work and one work was an observational and cross-sectional study. The clinical trial was conducted with women and newborns and the cohort study was composed of newborns.
Risk factors, maternal variables and neonatal variables for the prevention of meconium aspiration syndrome
The maternal variables for the presence of meconium in the amniotic fluid include: arterial hypertension, pre-eclampsia/eclampsia, diabetes mellitus, smoking, cardiovascular diseases, chronic respiratory diseases, post-term pregnancy and oligodramnios, fewer prenatal consultations. Among neonatal variables, intrauterine growth restriction (IUGR), cardiac congenital anomalies, male, the lowest Apgar score   stand out. Neonatal asphyxia, acute tocolysis, fetal distress and complicated delivery are still among the main risk factors for the development of MAS .
Thus, the incidence of MAS varies from population to population and from one country to another  . And the apparent reduction in the incidence of this pathology in some countries is due to a greater knowledge of risk factors and advances in obstetric practices .
Assistance provided to the newborn with meconium elimination in the delivery room
Neonatal management has changed based on new studies carried out in recent years . Aspiration at birth, before leaving the shoulders, followed by tracheal intubation (TI) and tracheal aspiration of newborns with MAS, has been a routine procedure for the past 25 years. However, multicenter studies indicate the discontinuation of the practice of secretion aspiration in the intrapartum period, as this procedure does not decrease the frequency of MAS  . In addition, a prospective, randomized and controlled study, conducted by Halliday and Sweet , concluded that TI and aspiration of the NB with vigorous MAS did not show a reduction in the incidence of MAS compared to the usual assistance recommended for transport procedures in depressed newborns. A Cochrane review in 2007 came to the same conclusion, using the recommendations of the American Academy of Pediatrics and the American Heart Association (AHA) .
According to the AHA if there is MAS fluid or thick, the professional should not perform aspiration of the airways, since this procedure does not reduce the incidence of MAS, the need for mechanical ventilation in newborns who develop aspiration pneumonia, nor the oxygenation time or even hospitalization. Therefore, the assistance of the professional through the presence of red MAS will depend on vitality at the time of birth. If the newborn presents, at birth, regular and rhythmic respiratory movements, good muscle tone and heart rate (HR) greater than 100 beats per minute (bpm), he/she should be referred to the resuscitation table, placed under a radiant heat source, and must have the head positioned with a slight extension of the neck, and be aspirated, if there is an excess of secretions in the mouth and nose with a tracheal tube number 10, then dried, with subsequent disregard of the wet fields. After these procedures, check the head position again, assessing breathing and HR. If the evaluation shows a normal result, the NB will receive routine care in the delivery room .
In the other hand, if the NB with fluid or thick MAS, at birth, does not have a regular respiratory rhythm and/or has a flaccid muscle tone and/or HR below 100 bpm, the professional should remove the residual meconium from the hypopharynx and the trachea with direct visualization, under a radiant heat source. Tracheal aspiration will be performed by means of a tracheal cannula connected to a device for meconium aspiration and vacuum aspiration, with a maximum pressure of 100 millimeters of Mercury (mmHg), aspirating excess meconium only once; if the newborn remains with HR below 100 bpm, irregular breathing or apnea, start positive pressure ventilation (PPV). It is also recommended that PPV should only be performed after the removal of meconium from the airways and gastric aspiration, with this sequence the aim is to reduce the risk of vomiting and consequently aspiration  .
Various types of mechanical ventilation have been discussed at MAS. Continuous positive airway pressure (CPAP) has been described as beneficial, possibly because it controls atelectasis, stabilizing the collapsing terminal airways, however, it should be used with caution in pulmonary hypertension, and must monitor complications frequently .
According to Walsh and Faranoff  the advancement of technology and knowledge in assisting MAS contributes to the reduction of mortality rates, citing the use of surfactant and extra-corporeal circulation (ECMO) as new techniques.
The obstruction of the airways by meconium can increase the resistance and the deficiency of surfactant, as well as changes in the lung parenchyma may require the use of ventilatory support, supplemental oxygen, so to break this cycle there is an indication of the use of exogenous surfactant. In this sense, two approaches have been discussed: the first is the replacement of surfactant and the second is the washing with surfactant. In the first approach, exogenous surfactant is administered via an endotracheal tube, usually at the same dose as indicated for Hyaline Membrane Syndrome (HMS), using standard surfactant preparations .
The surfactant has proven benefits, such as improved oxygenation, consequently reducing the need for mechanical ventilation and hospital stay, in addition to reducing respiratory complications and mortality in newborns. Several diseases that affect the term newborn are associated with the reduction or inhibition of the surfactant, especially MAS. The use of surfactant has a possible detergent effect on meconium .
Halliday et al.  was one of the first scholars to discuss the use of surfactants at MAS. In its retrospective review study it included 54 newborns with MAS who received surfactant therapy on average 14 hours after birth, with varying doses used. The results showed that one third of the NBs needed a repeat dose, 18% showed a significant improvement in gas exchange, 44% showed little or no response, plus only two NBs needed extracorporeal membrane oxygenation therapy. ECMO has been indicated when failures in ventilatory assistance occur with different ventilation strategies, however, it is an expensive treatment that requires an adequate infrastructure, limiting its use in certain health centers .
The second approach, still according to studies by Steven, Donn and Dalton  is the use of bronchoalveolar lavage with surfactant, which aims to remove the harmful substances that are present in the airways, among them the meconium itself, neutrophils, protein exudate and mediators inflammatory. Colvero and Garcia  argue that due to the conflicting results between the use of surfactant and that of bronchoalveolar lavage with surfactant in MAS, it would be important to carry out further studies to assess whether there are benefits in its use, as well as to define the ideal dose and the way to be administered. They still argue that the use of antibiotic therapy is controversial, however these drugs are usually recommended due to the severity of the condition, as well as the difficulty of excluding infectious processes, since meconium has great potential for colonization by germs, mainly by gram-negative.
Amnioinfusion or transcervical infusion of saline into the amniotic cavity is a procedure that has been proposed to reduce the risk of MAS. The mechanisms include the dilution of meconium, thus reducing the inflammatory effects, its mechanics and cushioning the umbilical cord, in order to correct the umbilical cord compressions that lead to fetal acidemia (a predisposing condition for the elimination of meconium in the uterus). However, there is still a need for more studies on the subject to prove the benefits of the technique, since in the end the study does not recommend the performance of amnion fusion for the prevention of MAS . The studies show the importance of a trained and coordinated team for a quick response in this situation, with the aim of reducing neonatal morbidity and mortality, since frailty perinatal care can contribute to increase these rates. In addition, greater investments in health are needed, as they vary according to the distribution of wealth in each region, with greater investment in the main centers industrial activity and in the capitals .
After initial care in the delivery room, the newborn may need strict monitoring, which will include monitoring of capillary blood glucose and cardiorespiratory, nutrition, use of other drugs to prevent sepsis as well as ventilatory assistance . Furthermore Nona et al.  identified a longer time of mechanical ventilation in newborns who were admitted outside and were transferred when compared with newborns who were born in the maternity ward (median time of ten days versus 4.5 days in newborns in maternity), but not statistically significant, and longer oxygen supplementation time also for those admitted from outside (median time of 15 versus 45 days), with a value of p = 0.0063, considered statistically significant. Such information emphasizes the importance of monitoring the progress of labor and delivery, fetal and neonatal conditions at birth, so that the team can carry out the required care according to the newborn’s needs .
Like any type of study, the integrative literature review has advantages and limitations of the method itself, and care should be taken regarding the conclusions related to the findings. However, it’s necessary to highlight the potential of the integrative literature review, since it is valid among experts in the review area. In addition, the study presented as a limitation especially when the number of the studies is reduce, however this limitation can be minimized through discussion and consensus among reviewers.
The main concern in relation to meconium amniotic fluid is related to the elimination and consequent aspiration by the fetus, which may result in MAS, with high morbidity and mortality rates for newborns. Studies show a problem experienced by health professionals in the prevention of MAS, since in the routine there are divergences in the standardization in the different services in relation to the assistance provided to the newborn with the elimination of meconium amniotic fluid.
Therefore, it is concluded that more studies are needed that address the theme, so that early and qualified intervention in conjunction with systematized actions by different health professionals can reduce neonatal morbidity and mortality rates.
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