Perinatal acute respiratory disease Notes

NOTES NOTES PERINATAL ACUTE RESPIRATORY DISEASE GENERALLY, WHAT IS IT? PATHOLOGY & CAUSES ▪ Respiratory problems in newborns/infants; dyspnea to sudden death SIGNS & SYMPTOMS ▪ Respiratory distress ▫ Cyanosis, bradypnea, tachypnea, etc. OTHER DIAGNOSTICS ▪ Pulse oximetry, arterial blood gases ECG ▪ Congenital heart defects TREATMENT OTHER INTERVENTIONS ▪ Supplemental oxygen therapy, assisted ventilation DIAGNOSIS DIAGNOSTIC IMAGING Chest X-ray MECONIUM ASPIRATION SYNDROME (MAS) osms.it/meconium-aspiration-syndrome PATHOLOGY & CAUSES ▪ Respiratory condition caused by aspiration of amniotic fluid contaminated by meconium (fetal stool) before/during birth ▪ Bile pigments ▫ Meconium with black-green color ▪ MAS in approx. 10% of neonates exposed to meconium ▪ Meconium in airways ▫ Airway obstruction: atelectasis ▫ Surfactant deactivation, synthesis inhibition ▫ Chemical pneumonitis: irritates air pathways ▫ Persistent pulmonary hypertension of newborn (PPHN): hypertrophy of pulmonary vessels due to chronic distress ▫ Medium for bacterial growth + reduces antibacterial activity → increases risk of infection OSMOSIS.ORG 899

CAUSES ▪ Initiated by fetal distress due to perinatal complications (e.g. maternal hypertension, preeclampsia, placental insufficiency, oligohydramnios, infection, acidosis, maternal drug abuse) ▫ Hypoxia → increased vagal stimulation → gastrointestinal (GI) tract peristalsis + sphincter relaxation → meconium release ▫ Hypoxia → fetus gasping, aspiration of meconium-stained amniotic fluid RISK FACTORS ▪ Term/post-term gestation (> 40 weeks); perinatal complications → fetal hypoxia, stress COMPLICATIONS ▪ Pneumothorax, pulmonary hypertension, neonatal infection, infant respiratory distress syndrome, acidosis SIGNS & SYMPTOMS ▪ Meconium spotting during labor ▫ Green-yellow colour of amniotic fluid, infant’s skin, umbilical cord ▪ Low APGAR score ▫ Appearance, Pulse, Grimace, Activity, Respiration ▪ Respiratory distress ▫ Labored breathing, tachypnea, bradycardia, intercostal/subcostal/ substernal retractions, cyanosis, nasal flaring ▪ Blood gas ▫ Hypoxemia, hypercarbia, acidosis Figure 127.1 A plain chest radiograph of a neonate demonstrating bilateral, diffuse, coarse opacities secondary to meconium aspiration. DIAGNOSIS DIAGNOSTIC IMAGING Chest X-ray ▪ Patchy atelectasis, consolidation areas ▪ Hyperexpansion due to airway obstruction ▪ Pneumomediastinum due to air leak Ultrasound ▪ ECG to assess pulmonary hypertension OTHER DIAGNOSTICS Meconium ▪ In amniotic fluid, on infant, in trachea (if intubation required) Respiratory distress Pulse oximetry ▪ Low oxygen saturation Auscultation ▪ Crackles, rhonchi sounds 900 OSMOSIS.ORG

Chapter 127 Perinatal Acute Respiratory Disease TREATMENT MEDICATIONS ▪ Antibiotics ▪ Maintain circulatory volume; correct existing metabolic imbalances ▫ IV fluids; electrolytes, glucose; correct acidosis OTHER INTERVENTIONS ▪ Transfer to neonatal intensive care unit (NICU) Amnioinfusion ▪ Intrauterine saline infusion ▪ If meconium-stained amniotic fluid, preventative measures Maintain oxygenation, ventilation ▪ Neutral thermal environment ▪ Decreased oxygen consumption ▪ Supplemental oxygen ▪ Mechanical ventilation ▪ If PPHN ▫ Inhalation of nitric oxide (iNO), phosphodiesterase inhibitors ▪ If severe ▫ ECMO Figure 127.2 Flowchart depicting the pathophysiology of MAS. OSMOSIS.ORG 901

Figure 127.3 A histology photomicrograph of the fetal membranes containing meconium laden macrophages. NEONATAL RESPIRATORY DISTRESS SYNDROME osms.it/neonatal-resp-distress PATHOLOGY & CAUSES Respiratory disease in neonates: loss of lung compliance (distensibility) due to lack of surfactant. ▪ AKA neonatal respiratory distress syndrome/surfactant deficiency disorder (SDD) ▪ Surfactant deficiency → ↑ surface tension → ↓ lung compliance → alveoli collapse upon expiration (microatelectasis) → V/Q mismatch → intrapulmonary shunting + extrapulmonary shunting (e.g. through patent ductus arteriosus) → hypoxemia 902 OSMOSIS.ORG CAUSES ▪ Surfactant production inhibition by insulin due to maternal diabetes ▪ Genetic mutations affect production of surfactant proteins ▪ Surfactant inactivation by meconium ▪ Pulmonary inflammation, edema may complicate respiratory distress RISK FACTORS ▪ Premature delivery, cesarean delivery, maternal diabetes, intrauterine asphyxia, meconium aspiration syndrome

Chapter 127 Perinatal Acute Respiratory Disease COMPLICATIONS Acute ▪ Acidosis, hypoglycemia, hypotension, infection, diffuse atelectasis, respiratory failure, death Chronic ▪ Intracranial hemorrhage, retinopathy of prematurity, bronchopulmonary dysplasia, pulmonary hemorrhage, neurologic impairment SIGNS & SYMPTOMS ▪ Respiratory distress ▫ Tachypnea, tachycardia, intercostal/ subcostal/substernal retractions, cyanosis, nasal flaring, expiratory grunting ▪ Ventilatory failure (↑ blood CO2), apnea DIAGNOSIS DIAGNOSTIC IMAGING Chest X-ray ▪ Low lung volume ▪ Bilateral, diffuse granular/”ground glass” appearance ▪ Air bronchograms ▫ Pulmonary edema secondary to inflammation, atelectasis TREATMENT OTHER INTERVENTIONS ▪ Reduce oxygen consumption ▪ Radiant warmer, intravenous (IV) fluids with glucose Assisted ventilation ▪ If symptoms do not subside ▪ Endotracheal intubation with synthetic/ animal exogenous surfactant therapy Prevention ▪ Fetal lung maturity test (if preterm delivery anticipated) ▫ Assess surfactant levels by amniocentesis; administer corticosteroids, promote lung maturity Continuous positive airway pressure (CPAP) If severe ▪ Extracorporeal membrane oxygenation (ECMO) INSURE ▪ INtubation-SURfactant-Extubation LAB RESULTS ▪ Oxygen saturation monitor ▫ ↓ SaO2, consider influence of preductal/ postductal gradients ▪ Metabolic acidosis, hypoxia OTHER DIAGNOSTICS Physical examination ▪ Lung auscultation (decreased breath sounds); respiratory distress Post-mortem histopathology ▪ Lungs interspersed with hyper-distended alveolar ducts, collapsed alveoli ▪ Hyaline membranes lining/filling alveoli Figure 127.4 A plain chest radiograph of a neonate with infant respiratory distress syndrome. Both lung fields are granular in appearance. OSMOSIS.ORG 903

SUDDEN INFANT DEATH SYNDROME (SIDS) osms.it/sids PATHOLOGY & CAUSES ▪ Sudden unexplainable death of infants < one year old despite thorough death scene investigation, analysis of perinatal history, autopsy ▪ Leading cause of death in infants < one year old; peak incidence, 8–16 weeks CAUSES Triple risk model ▪ Triggering event ▫ Sleeping prone, infection ▪ Underlying vulnerability ▫ Genetic polymorphisms involving autonomic nervous system function, cardiac conduction channels, altered cerebral serotonin (5-HT) signaling ▪ Developmental vulnerability ▫ Immature neuroregulation of cardiorespiratory control, delayed immune functionality RISK FACTORS ▪ Previous loss of infant from SIDS ▪ Periconceptional/postnatal smoking, substance abuse ▪ Teenage (< 20 years) pregnancy ▪ Inadequate prenatal care ▪ Premature birth ▪ Low birth weight ▪ Intrauterine growth restriction ▪ Infant of genetically male sex ▪ Sleep environment ▫ Prone position (strongest modifiable risk factor); soft sleeping surface; loose blankets, pillows, stuffed toys; overheating; bed sharing 904 OSMOSIS.ORG SIGNS & SYMPTOMS ▪ Infant fed, put to bed without sign of distress; found unresponsive DIAGNOSIS OTHER DIAGNOSTICS ▪ Diagnosis of exclusion ▪ Forensic autopsy, clinical history, death scene investigation TREATMENT OTHER INTERVENTIONS ▪ Emergency responders ▫ Attempt cardiopulmonary resuscitation; document scene ▪ Transport to healthcare facility ▫ Resuscitation attempt continued ▪ Physical examination, lab tests documented ▪ Interview of family members ▫ When was infant last seen alive; who found infant, when; history of illnesses; sleeping environment ▪ Protective factors ▫ Prone sleeping position, elimination of environmental risk factors; breastfeeding, room-sharing, not bedsharing, immunizations

Chapter 127 Perinatal Acute Respiratory Disease TRANSIENT TACHYPNEA OF THE NEWBORN osms.it/newborn-transient-tachypnea PATHOLOGY & CAUSES ▪ Respiratory condition; presents in first hours of life, periods of non-acute rapid breathing ▪ AKA “quiet tachypnea” CAUSES ▪ Delayed reabsorption of alveolar fluid through epithelial aquaporin channels → increased alveolar fluid → decreased pulmonary compliance, partial collapse of small airways, air trapping → hypoxemia, hypercapnia RISK FACTORS ▪ Cesarean delivery without labor; maternal diabetes, asthma, smoking during pregnancy; pulmonary immaturity; surfactant deficiency SIGNS & SYMPTOMS ▪ Symptoms present immediately after birth in response to excessive fluid in lungs ▪ Tachypnea (> 60 breaths/minute), nasal flaring, expiratory grunting, intercostal/ subcostal/substernal retractions ▪ Hypoxemia → hypoxia, cyanosis DIAGNOSIS DIAGNOSTIC IMAGING Lung sonography Chest X-ray ▪ Radiopaque levels of fluid in horizontal fissure of lungs; hyperinflated lungs; diaphragm flattening OTHER DIAGNOSTICS ▪ Pulse oximetry ▪ Arterial blood gas assessment ▫ Evaluate gas exchange, monitor acidbase balance TREATMENT OTHER INTERVENTIONS ▪ Commonly resolves during first three days of life ▪ Supplemental oxygen therapy; nasal CPAP if additional support required ▪ Neutral thermal environment: decrease oxygen consumption ▪ Orogastric feedings/IV fluids with glucose if PO feedings avoided due to increased respirations ▪ Antibiotics, if infection suspected OSMOSIS.ORG 905