RESPIRATORY DISTRESS SYNDROME By Dr. Gacheri Mutua

DEFINITION Also known as Hyaline Membrane Disease Is a respiratory disorder that affects newborns More common in premature infants especially born 6wks or more before their due date Their lungs have insufficient surfactant, necessary to maintain lung compliance

Disease is exacerbated by: Cold stress Hypoxia Acidosis Sepsis Natural history- clinical signs develop within 6hrs of life with progressive worsening over the first 48 to 72hrs of life

Predisposing factors Prematurity Male gender and are more likely to die from the disease Caucasian > black Caesarean section Low APGAR score Maternal diabetes Congenital hypothyroidisim Familial predisposition Twins Postnatal hypothermia Maternal malnutrition Intrauterine growth retardation Hemolytic disease of the newborn

DIAGNOSIS Clinical:- Radiological features:- Haematological:- tachypnoea grunting respirations intercostals recession, sternal indrawing nasal flaring cyanosis increased oxygen requirements deranged cardiovascular parameters: HR, BP Radiological features:- Air bonchograms with characteristic ground glass appearance Haematological:- anaemia Thrombocytopenia Blood gas measurements Mixed metabolic and respiratory acidemia

PREVENTION Prevent premature delivery Antenatal steroid therapy Drugs to mature surfactant synthetic pathways: aminophylline Prevent asphyxia Avoid drugs that cause respiratory depression The course of the disease is altered by exogenous surfactant therapy and assisted ventilation

MANAGEMENT Non-respiratory Temperature control Avoid enteral feeding IV therapy 5% or 10% dextrose Closely monitor blood glucose Antibiotics: penicillin, gentamicin Assess the baby's circulatory status by monitoring heart rate, peripheral perfusion, and blood pressureAdminister blood or volume expanders, and use appropriate vasopressors to support circulation where necessary.

Respiratory Airway- place infant in lateral or prone posture rather than supine Repeated suctioning of pharynx is not required and may cause apnoea and hypoxia

Oxygen Administer humidified oxygen at flow rates of 6-8l/min Monitor arterial blood gases, aim to keep pO2 between 50 and 80mmHg Desired range of monitored pulse oxymeter for infants <34weeks gestation is 88 to 95% but for more mature infants 88 to 100%

INTUBATION AND IPPV IPPV- Intermittent Positive Pressure Ventilation Indications: Cyanosis that persists in spite of maximal oxygen therapy Severe recurrent apnoea Respiratory failure (pCO2 >70 and pH <7.2)

CPAP Continuous Positive Airway Pressure is used to treat preterm infants whose lungs have not yet fully developed such as in RDS or bronchopulmonary dysplasia It’s functionally similar to PEEP, except that PEEP is an applied pressure against exhalation and CPAP is a pressure applied by a constant flow CPAP:- improves survival decreases the need for steroid treatment for their lungs decreases the need for IPPV

Surfactant ventilator settings Ventilator rate 60 breaths per minute Inspiratory time 0.3sec; expiratory time 0.7sec PEEP 5cm Oxygen set to maintain saturations of 88 to 95% Peak inspiratory pressure (PIP) 20-30cm water

SURFACTANT ADMINISTRATION Premature neonates with surfactant deficiency and respiratory distress syndrome have an alveolar pool of about 5mg/kg. Full-term animal models have pools of 50-100mg/kg. Recommended dosages of clinically available surfactant preparations are 50- 200mg/kg, approximately the surfactant pool of term newborn lungs

Rapid bolus administration of surfactant after adequate lung recruitment with 3-4cm of positive end-expiratory pressure (PEEP) and adequate positive pressure may improve its homogeneous distribution. Most neonates require 2 doses; however, as many as 4 doses, given at 6-hour to 12-hour intervals, were used in several clinical trials. NB: Dosages could be given as a rapid bolus or intermittent administration. Prophylactic doses can be given soon after delivery

If the patient rapidly improves after 1 dose, respiratory distress syndrome is unlikely. Conversely, in infants who have a poor or no response, patent ductus arteriosus (PDA), pneumonia, and complications of ventilation (air leak) should be excluded, especially before subsequent surfactant doses are given.

SUDDEN DETERIORATION In spontaneously ventilating: pneumothorax failure of oxygen supply increase in severity of the underlying disease In a ventilated infant: endotracheal tube blockage or displacement mechanical failure with the ventilator increase in the severity of the underlying lung disease massive intraventricular haemorrhage necrotizing enterocolitis, especially if perforation has occurred patent ductus arteriosus

FAMILY PSYCHOTHERAPY Staff members (preferably a physician and a nurse) should keep the patient’s parents well informed by frequently talking to them, especially during the acute stage of respiratory distress syndrome

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