NEONATAL RESPIRATORY DISORDERS DR. MAHMOUD MOHAMED OSMAN MBBCh, MSc (Pedia), MRCPCH (UK), FRCP (Edinburgh) Consultant Pediatrician & Neonatologist Consultant Pediatrician & Neonatologist Al Yammamah Hospital, MOH Al Yammamah Hospital, MOH 1. Respiratory distress (General) 2. Respiratory distress syndrome 3. Transient tachypnea of the newborn 4. Meconium aspiration syndrome 5. Diaphragmatic Hernia OBJECTIVES: 1. RESPIRATORY DISTRESS (GENERAL) 3 1) Respiratory Distress: Respiratory distress is a general term used to describe. respiratory symptoms and is not synonymous with.. ..respiratory distress syndrome (RDS). Signs of respiratory distress include: Tachypnea a respiratory rate greater than 60/min. Expiratory grunt breathing against a closed glottis. Chest retraction or recession. Flaring of the nostrils. Cyanosis or low arterial oxygen saturation in room air. General Considerations 2) Common causes of respiratory distress: A - Primary Respiratory Causes: Transient tachypnea of the newborn RDS due to surfactant deficiency [Preterms] Aspiration syndromes {meconium, milk, blood} Pulmonary air leaks {Pneumothorax; pneumomediastinum} Pneumonia Pulmonary hypoplasia {with oligohydramnios} Pulmonary haemorrhage Chronic neonatal lung disease {BPD} 6 B- Secondary to extrapulmonary pathology: Congenital heart diseases. Birth asphyxia. Infections (Sepsis). Surgical conditions: Choanal atresia. Pierre robin sequence. Diaphragmatic hernia. Lobar emphysema. Tracheo-oesophageal fistula. Persistence of fetal circulation (PPHN). Anaemia, Polycythaemia. Metabolic diseases. 7 3. Diagnosis of Respiratory Distress: A. A full Perinatal history includes Gestational age Polyhydramnios, or oligohydramnios Anomalies on ultrasound Risk factors for sepsis The passage of meconium Poor condition at birth Duration of amniotic membrane rupture. B.Physical examination includes Observation of vital signs and auscultation of the lungs for symmetry of air entry, and heart sounds. C.Appropriate investigations Investigations for respiratory distress: Chest radiograph. Bacteriological cultures on blood, urine and cerebrospinal fluid (CSF). Viral cultures and rapid-yield immunodiagnostic tests. Haematocrit and full blood count. Chest transillumination if pneumothorax is suspected. Passage of nasogastric catheters if choanal or oesophageal atresias are suspected. Hyperoxia test to differentiate between cardiac and respiratory disease. Echocardiography. 4. Treatment of Respiratory Distress 1. Supportive care The supportive care of the infant with respiratory distress is similar regardless of the etiology. Frequent or continuous observations of respiratory and heart rates, temperature, blood pressure and signs of respiratory distress. Accurate fluid balance charts are essential. Adequate temperature control Adequate nutrition is essential part of respiratory care 11 2. Oxygen Oxygen is a useful and life-saving therapeutic agent, but is also potentially dangerous, particularly in the preterm baby, as it may damage the eyes ( retinopathy of prematurity ), or the lungs ( bronchopulmonary dysplasia ). Oxygen should be warmed to 3437C and humidified. 3. Fluids In mild respiratory distress nasogastric feeding may be adequate. In moderate to severe respiratory distress; babies should not be enterally fed. Intravenous fluids will be required. Usually a 10% dextrose and electrolytes or total parenteral nutrition.. 4. Blood gases and acidbase status Assessment of the arterial acidbase status, with samples from an intra-arterial catheter or capillary blood gases. Continuous transcutaneous monitoring of PO 2 and PCO 2 decreases blood sampling and enables rapid detection of fluctuations in clinical status. If respiratory acidosis is severe (pH 60 mmHg) assisted ventilation may be necessary. For a severe metabolic acidosis (base deficit > 8), an infusion of sodium bicarbonate may be indicated. But one should always try to treat the underlying cause first !!!!. 5. Artificial respiratory support: In more severe cases artificial respiratory support may be necessary. This may be in the form of noninvasive respiratory support such as: Continuous positive airway pressure (CPAP) Bilevel positive airway pressure (BiPAP) or Non-invasive positive-pressure ventilation (NIPPV) In a proportion of cases, such treatment may fail and switch to invasive mechanical ventilation becomes a must. Indications for mechanical ventilation: Failure to initiate or establish spontaneous breathing. Worsening apneas and bradycardias. Major respiratory or cardiac collapse. Surfactant administration. Need to maintain airway patency. Impaired pulmonary gas exchange. 14 6. Treatment of the Etiological Cause: Medical or surgical treatment of the etiological cause is the corner stone in management of the neonatal respiratory diseases. 15 2. Respiratory Distress Syndrome 16 1. PATHOPHYSIOLOGY: The primary cause of respiratory distress syndrome, also known as (hyaline membrane disease (HMD)), is inadequate production of surfactant due to prematurity. The manifestations of the disease are caused by the diffuse alveolar atelectasis, edema, and cell injury. Subsequently, serum proteins that inhibit surfactant function leak into the alveoli. 17 18 Interdependent relationship of factors involved in pathology of respiratory distress syndrome. Normal Expiration With Surfactant Surfactant Function Abnormal Respiration Without Surfactant The lung in respiratory distress syndrome of the neonate. The alveoli are atelectatic, and dilated alveolar ducts are lined by a fibrin-rich hyaline membrane. 20 Advances made in the management of RDS include : Prenatal diagnosis to identify infants at risk. Antenatal administration of glucocorticoids. Improvements in perinatal and neonatal care. Surfactant replacement therapy. As a result: The mortality from RDS has decreased. Survival of increasing numbers of extremely immature infants has provided new challenges. RDS remains an important contributing cause of neonatal mortality and morbidity. 21 2. DIAGNOSIS: A. Perinatal risk factors: 1. Factors that affect lung development at birth: Prematurity, maternal diabetes, and genetic factors (white race, history of RDS in siblings, male sex). Thoracic malformations that cause lung hypoplasia, (such as diaphragmatic hernia). Genetic disorders of surfactant production and... metabolism (such as surfactant protein B or C deficiency cause a severe RDS like picture, often in term infants). 2. Factors acutely impair surfactant function: Perinatal asphyxia in premature infants. Cesarean section before labor starts. B. Postnatal diagnosis: A premature infant with RDS has clinical signs shortly after birth. These include tachypnea, retractions, nasal flaring, grunting, and cyanosis. The classic radiographic appearance is of low- volume lungs with a characteristic diffuse reticulogranular pattern ground glass appearance, and air bronchograms. 3. MANAGEMENT: I.General lines of manegment 1. Prevent hypoxemia and acidosis. 2. Optimize fluid management. 3. Reduce metabolic demands. 4. Prevent atelectasis and pulmonary edema. 5.Minimize lung injury caused by oxygen, or mechanical ventilation. II.Specific lines of manegment A.Surfactant replacement therapy B.Continuous positive airway pressure C.Mechanical ventilation D.Supportive therapy Dosing may be divided into 2 alliquots and adminitered via a 5-Fr catheter passed in the ET Mode of administration of Surfactant III. Antenatal corticosteroid therapy (Prophylaxes): Should be given to pregnant women 24 to 34 weeks gestation with intact membranes or with (PROM) without chorioamnionitis, who are at high risk for delivery within the next 7 days. It induces sufactant production and accelerates maturation of the lungs and other fetal tissues. It results in marked reduction of : RDS, Intraventricular hemorrhage (IVH), Necrotizing enterocolitis, and Perinatal mortality. Drugs used are: betamethasone or dexamethasone. 4. COMPLICATIONS: Pneumothorax, and other air leaks Patent ductus arteriosus (PDA). Subglottic stenosis (causing stridor). Chronic lung disease (CLD). Necrotising enterocolitis (NEC). Intraventricular-periventricular haemorrhage. Periventricular leukomalacia (PVL). Retinopathy of prematurity (ROP). 3. TRANSIENT TACHYPNEA OF THE NEWBORN I. DEFINITION. Transient tachypnea of the newborn (TTN), known as wet lung, is a relatively mild, self- limited disorder most commonly affecting infants who are born at or near term. Transient tachypnea of the newborn occurs in 12% of all newborn infants and is due to respiratory mal-adaptation at birth causing retention of fluids in the lungs. Tachypnea is generally the outstanding feature. TTN is usually benign and self-limiting, with symptoms rarely persisting beyond 48 hs. II. PATHOPHYSIOLOGY. Disruption or delay in clearance of fetal lung fluid from a number of conditions results in the transient pulmonary edema that characterizes TTN. Retained fluid accumulates in the peribronchiolar lymphatics and bronchovascular spaces, causing compression and bronchiolar collapse with areas of air trapping and hyperinflation. These changes result in a net decrease in lung compliance accounting for the clinical manifestations of the condition. 30 31 Characteristic features of retained pulmonary fluid with airspace filling and fluid in the horizontal fissure. Fluid in the fissure III. RISK FACTORS. Premature birth, precipitous birth, and operative birth without labor, associated with an increased risk of TTN. Delayed cord clamping or cord milking, promoting placental-fetal transfusion, leads to an elevation in the central venous pressure. Congenital disrupting clearance of fluid by the thoracic duct or pulmonary lymphatics. Additional risk factors include: Birth to an asthmatic mother. Administration of large amounts of IVF to the mother. Male gender, macrosomia and multiple gestations. 32 DIFFERENTIAL DIAGNOSIS AND EVALUATION. lV. DIFFERENTIAL DIAGNOSIS AND EVALUATION. Diagnosis of TTN requires the exclusion of other potential etiologies for respiratory distress presenting in the first 6 hous of age. The differential diagnosis includes: Pneumonia - sepsis, Cyanotic congenital heart disease, Hyaline membrane disease (HMD), Pulmonary hypertension, Meconium aspiration, Hypoxic-ischemic encephalopathy (HIE), Polycythemia. 33 34 V. INVESTIGATIONS & MANAGEMENT. A full sepsis evaluation, including complete blood count and appropriate cultures (pneumonia or sepsis) should be done. If risk factors or laboratory data suggest sepsis, or if respiratory distress does not improve within 4 hours, initiate broad-spectrum antibiotics. TTN does not usually require respiratory support, other than extra inspired oxygen. Regular blood-gas measurements. In more severe cases CPAP may aid resolution Diuretic therapy has no significant effect.. 4. MECONIUM ASPIRATION SYNDROME 35 I. BACKGROUND A. Cause. Acute or chronic hypoxia and/or infection can result in the passage of meconium. In this setting, gasping by the fetus or newly born infant can cause aspiration of amniotic fluid contaminated by meconium. Meconium aspiration before or during birth can obstruct airways, interfere with gas exchange, and cause severe respiratory distress. B. Incidence. Meconium-stained amniotic fluid (MSAF) complicates delivery in approximately 8% to 15% of live births. Most meconium-stained infants are post-mature and small for gestetianal age (SGA). The incidence of MSAF in preterm infants is very low. Approximately 5% of neonates born through MSAF develop meconium aspiration syndrome (MAS). Approximately 50% of meconium aspiration syndrome infants require mechanical ventilation. 37 II. Pathogenesis: Meconium causes a number of anatomical and physiological problems that make lung function worse: Plugging of the airways, with consequent atelectasis. Meconium causes a ball-valve obstruction with hyperinflation of the lungs and a high risk of pulmonary air leaks. Meconium irritations the airways, causing a chemical pneumonitis. Meconium impairs surfactant production and function. Possible secondary bacterial infection. 38 In a proportion of babies with severe MAS, there is development of marked persistent pulmonary hypertension (PPHN), with right-to-left shunt at PFO& PDA. 39 40 Meconium Aspiration Syndrome (MAS) Severe MAS & Rt sided pneumothorax before and after drainage. 41 III. PREVENTION OF MAS III. PREVENTION OF MAS A. Prevention of passage of meconium in utero. 1. Mothers at risk for placental insufficiency include: Those with preeclampsia or increased blood pressure. Chronic respiratory or cardiovascular disease. Poor uterine growth. Post-term pregnancy. Heavy smokers. 2. These women should be carefully monitored during pregnancy. 3. In pregnancies past the due date, induction as early as 41 weeks may help prevent MAS by avoiding passage of meconium. IV. LABOUR ROOM MANAGEMENT: During labor the fetal heart rate should be monitored, with fetal scalp blood samples obtained for pH determination. If the infant appears vigorous, routine care should be provided, regardless of the meconium. If respiratory distress develops or the infant becomes depressed, the trachea should be intubated, and intratracheal suctioning performed. In questionable cases, it is safer to intubate and do suction, as MAS can occur in infants delivered through thinly stained amniotic fluid. V. NICU MANAGEMENT OF MAS: V. NICU MANAGEMENT OF MAS: A. Observation. Infants who are depressed at birth should be closely observed. A chest radiograph may help determine those infants who are most likely to develop respiratory distress. A number of asymptomatic infants will have an abnormal-appearing chest. The classic findings are diffuse, asymmetric patchy infiltrates, areas of consolidation, and hyperinflation. B. Routine care. 1. The infant should be maintained in a neutral thermal environment. 2. Monitor blood glucose, calcium, and electrolytes. 3. Severely depressed infants may have metabolic acidosis that to be corrected. 4. Fluids should be restricted to prevent cerebral and pulmonary edema. 5. Circulatory support with normal saline, dopamine,. or packed red blood cells. (hemoglobin >15 g ; hematocrit > 40%). 6. Renal function should be continuously monitored. 45 C. Oxygen therapy. Monitoring blood gases and pH aids assessment of the severity and avoids hypoxemia. Hypoxic insults may result in pulmonary vasoconstriction and contribute to the development of PPHN. Management of hypoxemia by increasing the inspired oxygen. D. Assisted ventilation. Mechanical ventilation is indicated for excessive CO 2 retention (PaCO 2 >60 mm Hg) or for persistent hypoxemia (PaO 2