Meconium

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Information about Meconium
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Published on January 4, 2008

Author: VolteMort

Source: authorstream.com

Meconium:  Meconium Dr .Ashraf Fouda Ob/Gyn. Consultant Damietta General Hospital E. mail : ashraffoda@hotmail.com INTRODUCTION:  INTRODUCTION The detection of meconium stained amniotic fluid during labour often causes anxiety in the delivery room because of its association with increased perinatal mortality and morbidity. INTRODUCTION:  Meconium is composed of : Small dried amniotic fluid debris, Bile pigment and The residue from intestinal secretions. It is a sterile compound made up primarily of water (75 %), with mucous glycoproteins, lipids and proteases. INTRODUCTION INTRODUCTION:  Although meconium is sterile, its passage into amniotic fluid is important because of the risk of meconium aspiration syndrome (MAS) and its sequelae. INTRODUCTION INTRODUCTION:  Infants delivered through meconium-stained amniotic fluid are more likely to be depressed at birth and to require resuscitation and neonatal intensive care. INTRODUCTION INCIDENCE:  INCIDENCE Meconium-stained liquor is rare in premature infants (<5 % of preterm pregnancies); if it does occur, there is an association with infection and chorioamnionitis. INCIDENCE:  Passage of meconium is increasingly common in infants >37 weeks' gestation and occurs in up to 50 % of post-mature infants ( >42 weeks). The incidence of MAS varies between 1 and 5 % of all deliveries where there has been meconium-stained liquor. INCIDENCE INCIDENCE:  There are a number of factors associated with an increased risk of developing MAS; these include a: Lack of antenatal care, Black race, Male fetus, Abnormal fetal heart rate monitoring, Thick meconium, Oligohydramnios, Operative delivery, Poor Apgar scores, No oropharyngeal suctioning and The presence of meconium in the trachea. INCIDENCE AETIOIOGY:  Many theories have been proposed to explain the passage of meconium in utero; however, the precise mechanisms remain unclear. The fetal bowel has little peristaltic action and the anal sphincter is contracted. It is thought that hypoxia and academia cause the anal sphincter to relax, whilst at the same time increasing the production of motilin, which promotes peristalsis. AETIOIOGY PATHOPHYSIOLOGY:  PATHOPHYSIOLOGY Meconium aspiration syndrome is a disease of term and post-term infants and its severity is linked to co-existing fetal asphyxia. Aspiration of meconium into the distal airways can occur either antenatally or postnatally, but in the majority of affected infants the exact timing is not clear. PATHOPHYSIOLOGY:  Aspiration is known to occur prior to delivery, as meconium has been found in the lungs of stillbirths and in infants delivered pre-labour by caesarean section without evidence of fetal distress. PATHOPHYSIOLOGY PATHOPHYSIOLOGY:  Postnatal inhalation can occur late in the second stage or immediately after delivery if the infant gasps or makes breathing movements while the oropharynx, nasopharynx or trachea contains meconium-stained liquor. PATHOPHYSIOLOGY PATHOPHYSIOLOGY:  Meconium has a number of adverse effects on the neonatal lung, which may ultimately lead to the respiratory failure (and hypoxaemia) which characterizes MAS. PATHOPHYSIOLOGY PATHOPHYSIOLOGY:  Meconium: Causes mechanical blockage of the airway, Acts as a chemical irritant causing pneumonitis, alveolar collapse and cell necrosis Although initially sterile, predisposes to secondary bacterial infection PATHOPHYSIOLOGY PREVENTION OF MECONIUM ASPIRATION SYNDROME:  PREVENTION OF MECONIUM ASPIRATION SYNDROME Because of potential morbidity and mortality from MAS, prevention would clearly be beneficial. This has led to a number of antenatal, intrapartum and postnatal preventative therapies, with a varying degree of success. Antenatal therapies:  Amnioinfusion Delivery by caesarean section Maternal sedation Antenatal therapies Amnioinfusion:  The idea behind amnioinfusion is that by increasing the liquor volume, meconium will be diluted. In addition, in cases of oligohydramnios, the increased volume will prevent : cord compression, subsequent hypoxia, fetal gasping and passage of meconium. Amnioinfusion Amnioinfusion:  Amnioinfusion A meta-analysis of amnioinfusion trials showed that this therapy has a role in the prevention of MAS. However, the use of amnioinfusion requires further evaluation, as the therapy is associated with a number of complications, including a higher incidence of instrumental delivery and endometritis. Delivery by caesarean section:  Delivery by caesarean section Although most studies suggest that infants with MAS are more likely to be delivered by caesarean section than by vaginal delivery, this is largely due to the suspicion or confirmation of fetal distress. Delivery by caesarean section:  There is currently no evidence to suggest that MAS would be prevented by elective delivery by caesarean section of infants with meconium-stained liquor; Perhaps this is not surprising, as neither The conditions for nor The timing of aspiration can be predicted. Delivery by caesarean section Maternal sedation:  Maternal sedation It has been suggested that the administration of narcotics to laboring women will prevent fetal gasping in utero by suppressing fetal breathing. Although there has been success in the prevention of MAS in animal models, there are no data to support this therapy in humans. Moreover, the likely maternal and neonatal complications would preclude its use . Intrapartum/postpartum management:  Intrapartum/postpartum management Oropharyngeal suctioning Physical manoeuvres Oropharyngeal suctioning:  Oropharyngeal suctioning Suction of the oropharynx and nasopharynx before delivery of the shoulders and trunk is a well-established practice that has been used since the 1970s. Oropharyngeal suctioning:  It seems reasonable that suctioning in this way would minimize the amount of meconium in the upper airway and thus reduce the amount aspirated during the onset of respiration. Oropharyngeal suctioning Oropharyngeal suctioning:  The evidence relating to routine suctioning of the oropharynx as a preventative measure is conflicting. What is clear, is that meticulous cleaning of the upper airway after delivery is beneficial in reducing MAS Oropharyngeal suctioning EVIDENCE l a Physical manoeuvres:  Physical manoeuvres It has been suggested that MAS may be prevented if the infant is prevented from breathing after delivery. Physical manoeuvres:  Methods advocated include: Thoracic compression, in which the thoracic cage of the infant is compressed by a healthcare professional in order to prevent respiration and subsequent aspiration of the contents of the upper airway, and Cricoid pressure, in which external pressure is applied to the cricoid, thus preventing aspiration. Physical manoeuvres Physical manoeuvres:  It is suggested that if used, these interventions be continued until a second resuscitator undertakes oral and/or endotracheal suctioning. There is no evidence supporting the use of either of these methods in preventing MAS. Physical manoeuvres Physical manoeuvres:  In fact, both Thoracic compression and Cricoid pressure are potentially dangerous and cannot be recommended EVIDENCE IV Physical manoeuvres Postnatal intervention:  Postnatal intervention Intratracheal suctioning Intratracheal suctioning:  Intratracheal suctioning Until relatively recently, all infants with meconium-stained amniotic fluid underwent endotracheal intubation and suction, as this was known to reduce the incidence of MAS. Intratracheal suctioning:  More recently, evidence has suggested a change in practice depending on whether or not an infant is deemed vigorous. Intratracheal suctioning Intratracheal suctioning:  A recent meta-analysis suggests that routine intubation of vigorous term infants in order to aspirate the lungs should be abandoned EVIDENCE l a Intratracheal suctioning Intratracheal suctioning:  Suctioning of the oropharynx may be beneficial, but endotracheal suctioning should be reserved for: Depressed or Non-vigorous infants or Those who deteriorate following initial assessment. Intratracheal suctioning Slide35:  Aspiration of gastric contents to remove swallowed meconium is still done in many centers. The passage of an orogastric tube is likely to cause apnoea and/or bradycardia and is potentially harmful. This practice should be abandoned EVIDENCE IV Aspiration of gastric contents Saline lavage:  Saline lavage is used in order to loosen meconium. Saline lavage is potentially harmful, as saline will displace endogenous surfactant, which could in turn worsen the respiratory illness. In cases where saline lavage has been used, infants developed respiratory distress secondary to 'wet lung'. Saline lavage Slide37:  It is important that a person experienced in neonatal resuscitation attends the delivery of all infants in whom thick meconium-stained liquor is noted, particularly if accompanied by suspected fetal compromise. DELIVERY ROOM MANAGEMENT OF INFANTS BORN WITH MECONIUM-STAINED LIQUOR Slide38:  The Neonatal Resuscitation Program of the American Academy of Pediatrics incorporates guidelines for the management of these infants If an infant is vigorous after delivery: No tracheal suctioning should be undertaken, Secretions should be cleared from the mouth and nose using a wide-bore suction catheter, Routine care should be given. DELIVERY ROOM MANAGEMENT OF INFANTS BORN WITH MECONIUM-STAINED LIQUOR DELIVERY ROOM MANAGEMENT OF INFANTS BORN WITH MECONIUM-STAINED LIQUOR:  DELIVERY ROOM MANAGEMENT OF INFANTS BORN WITH MECONIUM-STAINED LIQUOR However, if an infant is not vigorous afterbirth (defined as : depressed respirations, decreased muscle tone and/or heart rate < 100 beats per minute): Direct endotracheal suctioning should be undertaken as soon as possible, Suction should be applied for no more than 5 seconds and the tube withdrawn. DELIVERY ROOM MANAGEMENT OF INFANTS BORN WITH MECONIUM-STAINED LIQUOR:  If meconium is aspirated from below the cords, the infant should be reintubated and the process repeated, Unless the infant has a profound bradycardia, in which case: Resuscitation should proceed with intermittent positive pressure ventilation (IPPV) without suctioning, Further suctioning can be attempted at a later stage. DELIVERY ROOM MANAGEMENT OF INFANTS BORN WITH MECONIUM-STAINED LIQUOR DELIVERY ROOM MANAGEMENT OF INFANTS BORN WITH MECONIUM-STAINED LIQUOR:  If after the first suctioning no meconium is aspirated : No further suctioning should be attempted and The infant should be resuscitated using IPPV via an endotracheal tube. DELIVERY ROOM MANAGEMENT OF INFANTS BORN WITH MECONIUM-STAINED LIQUOR Slide42:  IS MENONIUM PRESENT YES NO SUCTION MOUTH,NOSE AND POSTERIOR PHARYNX AFTER DELIVERY OF HEAD BUT BEFORE DELIVERY OF SHOULDERS IS THE BABY VIGOROUS? SUCTION MOUTH AND TRACHEA CONTINUE WITH RESUSCITATION CLEAR MOUTH AND NOSE FROM SECRETIONS DRY,STIMULATE AND REPOSITION GIVE OXYGEN AS NECESSARY NO YES KEY POINTS:  KEY POINTS Meconium-stained liquor is associated with increased morbidity and mortality in babies. MAS is linked to perinatal asphyxia. Good neonatal resuscitation skills reduce the incidence of MAS KEY POINTS:  In the prevention of MAS , there is no evidence supporting the use of: Saline lavage, Gastric aspiration or Thoracic compression KEY POINTS KEY POINTS:  The evidence relating to routine suctioning of the oropharynx as a preventative measure is conflicting. Intratracheal suctioning should be reserved for the non-vigorous baby. KEY POINTS

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