Risk factors for meconium aspiration syndrome in infants born through thick meconium.

OBJECTIVE: To determine risk factors for meconium aspiration syndrome (MAS). METHOD: A cohort study was conducted of 70 consecutive singleton pregnancies complicated with thick meconium-stained amniotic fluid delivered at > or = 37 weeks' gestation. Cases were randomized either for elective abdominal delivery or spontaneous vaginal delivery after 20 min of external fetal heart rate (FHR) monitoring. Risk estimation analysis for MAS was performed calculating relative risks (RR) and odds ratios (OR). RESULTS: The presence of meconium below the vocal cords (RR=7.3, 95% CI=2.6-20.3), non-reassuring FHR tracings (RR=3.0, 95% CI=1.2-7.5), Apgar score < or = 6 at 5 min (RR=3.8, 95% CI=1.7-8.4) and an umbilical cord plasma erythropoietin (UCPer) level > 50 mlU/ml (RR=5.0, 95% CI=2.1-12.0) were found to be significant risk factors for MAS. The presence of meconium below the vocal cords (OR=33.4, 95% CI=3.6-303.7) and non-reassuring FHR tracings (OR=12.2, 95% CI=1.3-111.7) remained as significant risk factors at the end of the multivariate analysis. CONCLUSION: Non-reassuring FHR tracings and the presence of meconium below vocal cords are associated with an increased risk for MAS in infants born through thick meconium.     

Severe meconium aspiration syndrome is not caused by aspiration of meconium

Meconium aspiration syndrome can present clinically with different degrees of severity, ranging from a mild form of respiratory compromise to severe forms that may result in perinatal death despite mechanical ventilation or extracorporeal membrane oxygenation. However, advances in our knowledge concerning meconium aspiration syndrome have revealed that most cases of severe meconium aspiration syndrome are not in fact causally related to the aspiration of meconium but rather are caused by other pathologic processes occurring in utero, primarily chronic asphyxia and infection. Proper understanding of the causative processes underlying fetal or neonatal compromise in these cases is essential to direct future research into preventive or therapeutic treatments and for counseling of the parents of an affected child.     

Controversies in the treatment of meconium aspiration syndrome

MAS remains an infrequent but challenging condition confronting neonatologists. Avoidance of postterm pregnancies, improved intrapartum monitoring,and amnioinfusion have been beneficial. Studies have not demonstrated conclusively that any form of ventilation is superior to others, but strategies that recruit alveoli are desirable. Surfactant lavage or replacement may be beneficial. When hypoxic respiratory failure progresses, iNO may improve oxygenation and avoid ECMO.     

Nucleated red blood cells in meconium aspiration syndrome

OBJECTIVE: To evaluate whether the absolute nucleated red blood cell (RBC) count is higher in infants who had meconium aspiration with respiratory symptoms compared with infants with asymptomatic meconium aspiration and controls. METHODS: We compared the absolute nucleated RBC counts during the first 12 hours of life in three groups of term, vaginally delivered infants, including those who had meconium aspiration with respiratory symptoms (n = 11), asymptomatic meconium aspiration (n = 45), and control healthy infants (n = 32). We excluded infants of women with diabetes in pregnancy; hypertension; alcohol, tobacco, or drug abuse; and those with hemolysis, blood loss, or chromosomal anomalies. RESULTS: There were no significant differences among groups in gestational age; gravidity; parity; maternal analgesia; lymphocyte, platelet, and granulocyte counts; and hematocrit. The median nucleated RBC count was significantly higher in the meconium aspiration group with respiratory symptoms (0.007 x 10(9)/L) than the asymptomatic meconium aspiration group (0.004 x 10(9)/L) or controls (0.003 x 10(9)/L). CONCLUSION: At birth, infants with meconium aspiration syndrome had higher absolute nucleated RBC counts compared with infants with asymptomatic meconium aspiration and normal infants.     

Surfactant lavage and replacement in meconium aspiration syndrome with pulmonary hemorrhage

We reported two case studies of meconium aspiration syndrome (MAS) with pulmonary hemorrhage in which we applied surfactant lavage and replacement. Surfactant lavage and replacement of MAS with pulmonary hemorrhage appears to be effective and safe adjunctive therapy. The relatively small replacement doses of surfactant required may be attributed to surfactant lavage followed by surfactant replacement. We suggest that surfactant lavage and replacement of MAS with pulmonary hemorrhage should be further investigated by a randomized controlled trial.     

胎粪吸入综合征的防治

我院自1988年1月到1990年12月活产婴4447例,于宫口开大3cm时行人工破膜,分娩时常规清除新生儿第一口吸气前气道内粪染粘液,微泵吸尽咽喉部、食道和胃内粘液。对Ⅱ、°Ⅲ°胎粪污染儿,采用中药煎汤蒸气吸雾疗法,同时用氨芐或先锋1号静推。结果:胎粪污染率16.2％,MAS 发生率1.8％,MAS病死率(5例)0.69％,与对照组比较,均有显著性差异。本文方法对减少MAS发生率和MAS儿的病死率起到明显作用。     

Delivery room risk factors for meconium aspiration syndrome

The objective of this study is to identify risk factors for meconium aspiration syndrome (MAS) in newborns born through meconium-stained amniotic fluid (MSAF). From May 27, 1994 to June 9, 1997 maternal and neonatal data were prospectively collected on all infants born through MSAF. Development of MAS was the primary outcome. Using bivariate and logistic regression analysis we identified risk factors for MAS. There were 8,967 births during this period: 7.9% (708 of 8,967) were delivered through MSAF. Respiratory symptoms developed in 6.8% (48 of 708) of births. Of these, 50% (24 of 48) were excluded due to the diagnosis of transient tachypnea of the newborn (17), respiratory distress syndrome (4), group B streptococcus pneumonia (1), congenital cytomegalic inclusion disease (1), and supraventricular tachycardia (1). Of the 24 infants with respiratory symptoms consistent with MAS, 45.8% (11 of 24) required ventilatory support, one required extracorporeal-membrane oxygenation. Bivariate analysis identified six risk factors ( p <0.05): Apgar <7 at 1 minute, Apgar <7 at 5 minutes, thick meconium, fetal distress, suction of infant's stomach by delivery room team at <5 minutes of age, and need for resuscitation. Tracheal meconium was very prevalent in our population at 74% of all intubated infants, and was not significantly associated with MAS. Logistic regression analysis identified four independent risk factors. Looking at multiple prediction models, an infant with fetal distress, Apgar <7 at 1 and 5 minutes and thick meconium has a 79.8% probability of developing respiratory symptoms. If these risk factors are not present, there is a 0.8% risk. In our cohort, this group had 16.7% positive predictive value (4 of 24) and 99.6% negative predictive value (657 of 660). In meconium deliveries, infants with thick meconium, fetal distress, and Apgar scores <7 at 1 and 5 minutes are at high risk for development of respiratory symptoms. Infants delivered in the absence of all of these risk factors are at low risk for development of MAS.     

Treatment of severe meconium aspiration syndrome with dilute surfactant lavage.

BACKGROUND AND PURPOSE: Despite the development of new adjuvant therapies, meconium aspiration syndrome (MAS) remains a serious respiratory disorder in neonates. Surfactant inactivation by meconium can be overcome by use of exogenous surfactant. This study sought to assess the efficacy and safety of dilute surfactant lavage at 2 different concentrations to treat severe MAS. METHODS: We retrospectively reviewed the charts of all term infants with a diagnosis of MAS who had an oxygenation index (OI) > 20 during a 2-year period. Tracheobronchial lavage was performed with a dilute surfactant suspension (5 mg/mL or 10 mg/mL) to reach a total dose of 60 to 70 mg/kg of phospholipid, administered in aliquots of 2 mL. RESULTS: The records of 22 patients were reviewed, of whom 12 had undergone lavage. These patients were subdivided into low-concentration (surfactant concentration, 5 mg/mL; n = 6) and high-concentration (surfactant concentration, 10 mg/mL; n = 6) subgroups. There were no significant differences in demographic characteristics between these 2 subgroups. The lavaged infants had a significantly higher arterial partial pressure of oxygen (PaO(2)) 24 hours after lavage than the infants without lavage (178.3 mm Hg vs 80.6 mm Hg, p < 0.05). The incidence of pneumothorax (1/12 vs 7/10, p < 0.05) and requirement for inhaled nitric oxide (5/12 vs 9/10, p < 0.05) were significantly lower in the lavaged group. All infants tolerated the procedure well except for 2 with transient complications. There were no significant differences in duration of lavage, response and complications between subgroups lavaged at low and high surfactant concentration. CONCLUSIONS: Early lavage with dilute surfactant solution at a phospholipid concentration of either 5 mg/mL or 10 mg/mL is effective for the treatment of severe MAS. Further large-scale, prospective, randomized, controlled trials are necessary to establish the optimal dose, concentration, surfactant product, and instillation method of this treatment before it can be recommended for routine use.     

Prolonged resuscitation in a newborn recovering from meconium aspiration syndrome

A complication during the course of meconium aspiration syndrome associated with persistent pulmonary hypertension in a newborn results in hypotension, bradycardia, and desaturation. The dilemmas and critical actions during the resuscitation are presented.     

Fatal meconium aspiration syndrome occurring despite airway management considered appropriate

A combined obstetric-pediatric approach to tracheal toilet is said to prevent serious cases of the potentially fatal meconium aspiration syndrome. After delivery of the head a DeLee trap is used to suction the oropharynx and nasopharynx. Immediately following delivery, endotracheal suction is performed in an effort to remove any remaining meconium-stained amniotic fluid. Although routinely using this approach, we continue to have occasional cases of fatal meconium aspiration syndrome. Therefore, we reviewed the outcome of infants born through meconium-stained fluid. During a 5-year period, 1420 (15%) of 9299 live-born infants had meconium-stained fluid. Thirty (2.1%) of these 1420 developed meconium aspiration syndrome and 12 (40%) died; eight received a postmortem examination. Four had unequivocal evidence of meconium aspiration, two had large numbers of intra-alveolar squamous cells, and two had no evidence of aspiration. We conclude that aggressive airway management during and immediately after delivery does not always prevent fatal meconium aspiration syndrome.     

应用胎粪吸引管气管内吸引防治胎粪吸入综合征的临床效果分析

目的 评价气管内吸引防治胎粪吸入综合征(meconium aspiration syndrome,MAS)的有效性,探讨新生儿活力与胎粪吸入的关系. 方法 2004年1月至2006年12月我院分娩胎粪Ⅲ度污染新生儿(简称粪染儿)495例,随机分为观察组249例,生后常规气管插管、应用胎粪吸引管抽吸胎粪;对照组246例,生后插管、气管内冲洗.观察两组MAS发生率、并发症及预后. 结果 观察组与对照组MAS发生率分别为7.6%和11.4%(x2=2.45,P＞0.05);观察组重型MAS发生率明显低于对照组[0.8%(2/249)和4.5%(11/246),x2=6.51,P＜0.05];观察组机械通气率为0.4%,对照组为2.8%(x2=3.12,P＞0.05);观察组病死率为0,对照组病死率1.2%(3/246).观察组1 min Apgar评分9～10分有活力新生儿气管抽出胎粪中位数为0.86 ml,明显少于≤8分无活力新生儿的1.65 ml(z=1.44,P＜0.05);观察组有活力粪染儿中17.8%(38/214)气管内可抽到胎粪,其中26.3%(10/38)可抽出大量胎粪.结论 (1)粪染儿生后早期进行气管内吸引不能减少MAS发生率,但可减轻临床症状,防止并发症,降低病死率.(2)有活力新生儿亦可发生胎粪吸入,应积极处理.     

Prevention of meconium aspiration

The aim of the study was to determine the risk of meconium aspiration by perinatal and obstetric characteristics and to give directions for prophylactic management. 67 infants with meconium-stained amniotic fluid received intrapartum pharyngeal suctioning and postpartum direct laryngoscopy and suctioning of the trachea. The risk for the presence of meconium in airways is increased if meconium is visible at the vocal cords (p less than 0.01), amniotic fluid showing thick meconium staining (p less than 0.001) Fischer-score being below 7 points (p less than 0.05) or Apgar-score being below 8 points(p less than 0.05).Immediately after delivery inspection of the vocal cords is necessary by direct laryngoscopy. Suctioning of the trachea under direct vision after delivery should be done if meconium is visualized at the vocal cords. Meticulous care of the fetus exposed to a meconium containing amniotic fluid environment and the avoidance of acute fetal stress may decrease the incidence of meconium aspiration.