Bronchopulmonary Dysplasia• Summary• Introduction• Risk Factors• Clinical Features• Management of BPD in Level 3 Units• Respiratory Criteria for Transfer to a Level 2 Hospital• Management in the Level 2 SCN• Oxygen• Home oxygen• Follow up
SUMMARY• the most severely affected babies are the most premature, particularly 23-26 week gestation babies diuretics and corticosteroids are effective in achieving short-term improvement in the status of ventilator dependant babies. Safety issues of steroid use are unresolved. There is no place for long term therapy with diuretics in level 2 SCNs there is no consensus on how to wean oxygen in babies with BPD• the transition from a tertiary hospital nursery to a level 2 SCN is a difficult time for parents as they adjust to different staff and practices
INTRODUCTION-1• In line with the recommendations from a recent workshop in North America the term bronchopulmonary dysplasia (BPD) will be used in this chapter rather than Chronic Lung Disease.• Over the past decade the clinical definition of BPD has evolved from oxygen dependency at 28 days of age to oxygen dependency at 36 weeks corrected gestational age.•
INTRODUCTION-2• The National Institute for Health in the USA has further divided this definition into mild (in supplemental oxygen at 28 days of age, but in air by 36 weeks corrected age), moderate (requiring <30% supplemental oxygen at 36 weeks corrected age and severe (in >30% supplemental oxygen and/or requiring positive pressure support, CPAP or ventilation, at 36 weeks corrected age).• BPD is the single most important factor determining length of stay in babies born at less than 29 weeks. The most severely affected babies are the most premature, particularly 23 - 26 week gestation babies.
RISK FACTORS• prematurity • peripartum inflammation/infection associated with preterm labour and/or clinical or subclinical chorioamnionitis• postnatal lung Injury due to volutrauma, barotrauma,oxygen toxicity, hypocarbia or infection
CLINICAL FEATURES• babies dependant on endotracheal mechanical ventilation (MV)• babies dependant of Nasal CPAP• babies who are oxygen dependant, usually by nasal prongs
MANAGEMENT• endotracheal ventilation is increasingly being replaced by NCPAP, for even the tiniest babies many are being managed with NCPAP from birth. Results from a recent randomised controlled trial have shown that 50% of babies 25-28 weeks gestation are able to manage without ever requiring intubation and ventilation, and that infants of this age who commence NCPAP from birth have no increased risk of death or BPD, and in fact are less likely to be in oxygen at 28 days of age.• for those who do require intubation and ventilation there is an intense focus on minimizing ventilator associated lung injury from the moment a baby is placed on a ventilator. Synchronised modes of MV with close monitoring of tidal volumes are key features of current practice. In addition there is a more liberal approach to carbon dioxide control, allowing CO2 to rise into the 50s and 60s providing the pH remains better than 7.25
MANAGEMENT 2• oxygen damages delicate lung tissue as well as the immature retina. Pulse oximetry targets are typically set between 85 to 94% in the first weeks after birth• ongoing randomised trials (BOOST2 trial in Australia) are attempting to determine whether we should be aiming for the bottom or top end of this target range. Babies in this trial may be transferred to level 2 nurseries with their trial saturation monitors in place as we continue to try to answer this question. • babies who require endotracheal ventilation are aggressively weaned and extubated to NCPAP often within 1-2 days of birth
DRUG THERAPY- Corticosteroids•• dexamethasone is effective in achieving short-term improvement in the status of ventilator dependant babies as well as longer term reductions in BPD, however, there is now level evidence showing that dexamethasone in the first week of life is associated with an increased risk of cerebral palsy in survivors• safety of corticosteroids used later in the course of evolving BPD between 14 - 28 days is unresolved and the Cochrane review of current evidence suggests reserving the use of late corticosteroids to infants who cannot be weaned from mechanical ventilation, and minimising the dose and duration of treatment.• in light of this evidence frequency of the use of steroids for BPD in NICUs has dramatically declined in the past 5 years and a "low" dose regimen (eg 0.15 - 0.25mg/ kg/day) weaned and ceased over a 7 - 10 day period is recommended• typical clinical scenarios where steroids would be considered are a baby > 2 weeks of age who is unable to be weaned from endotracheal MV• there is no place for the use of steroids in the treatment of BPD outside a tertiary neonatal unit• early use of inhaled steroids is ineffective in preventing BPD, although there is some evidence they can be used to assist extubation in ventilator dependant infants. More work is needed in this area before this approach is taken.
NUTRITION• provision of adequate calories in a nutritionally appropriate form is critical, infants with BPD utilise 20-40% more kcal than infants without BPD• caloric requirements of babies with moderate to severe lung disease can be as high as 130 - 150 calories/kg/day• babies with BPD tolerate fluid overload poorly and are modestly fluid restricted (150 - 160mL/kg/day) and fed fortified breast milk or low birthweight formula• growth is closely monitored and caloric intake titrated against growth• Vitamin A supplementation reduces death and oxygen requirements at 36 weeks corrected gestational age. Vitamiin A is currently given as Pentavite to all infants from day 5 until discharge.• babies sufficiently stable to transfer to a level 2 unit should not require a caloric density of > 24 cal/30mls
OXYGEN• oxygen is the one constant in the treatment of BPD but it has been poorly studied• once weaned from NCPAP, oxygen is delivered by nasal prongs using low flow (<0.5L/min)• there is no consensus on how to wean oxygen in babies with BPD• weaning is dictated to some extent by the equipment available. Some tertiary centres have only recently moved from having flow meters with a lower limit of 0.25L/min/O2. Other units use flow meters that allow weaning down to as low as 0.005mL/min/O2. Most believe that weaning should be slow, but what this means varies from institution to institution• babies with BPD have a degree of pulmonary hypertension, and are therefore likely to benefit from a more generous oxygen administration regimen rather than from a restrictive policy, however the corrected gestational age and the state of vascularistion of the retina needs to be taken into consideration before saturation targets are liberalised . Whilst there is some logic to this approach, there is indirect evidence from randomized controlled trials conducted for other reasons suggesting that a more liberal oxygen policy in these babies can actually increase the pulmonary morbidity. RCTs are in progress to address this question
Criteria for Home Oxygen - General• Appropriate social/home environment including reasonable accessibility to medical care• Baby is on 4 hourly or demand oral feeding regimen• Baby is normothermic in an open cot• Satisfactory growth• All babies discharged from tertiary units on home oxygen have specific Paediatric Thoracic specialist follow up. It is strongly recommended that Paediatricians manage babies on home oxygen in collaboration with a Paediatric Thoracic physician
Criteria for Home Oxygen - Respiratory• Baby must pass an "air test". The oxygen is turned off, the nasal prongs removed and the baby monitored over 30 minutes• If saturations are maintained >86% for 30 minutes the test should be repeated in 48 hours. If a second test is satisfactory the baby is eligible for discharge on home oxygen on respiratory grounds. In other words the baby has demonstrated a reasonable level of respiratory reserve
FOLLOW UP• These babies require term follow up throughout childhood• There is an increased pulmonary morbidity in the first 2 years of life. Parents should be counselled about this morbidity and ways to minimise it.• Influenza vaccine is recommended for infants with ongoing cardiac, respiratory or neurological illnesses at 6 months of age. Recommendations are 2 doses, 4 weeks apart• Influenza vaccine is not officially recommended for these babies• RSV prophylaxis is not routinely recommended, the American Academy of Pediatrics recommends use of RSV prophlaxis for infants <2yrs, with BPD requiring treatment within the last 6 months, who are discharged home prior to the RSV season. The Department of Health in the UK recommends its use in children <2yrs with BPD on home oxygen or who have had prolonged use of oxygen
DRUG THERAPY0-Diuretics• insufficient studies of suitable size reporting on important outcomes exist to strongly support the use of diuretics for the treatment of BPD• diuretics are an effective short term therapy for ventilated babies• There is no evidence for efficacy in non ventilated babies therefore diuretic therapy should be weaned and ceased once babies are stable off mechanical ventilation• typical combinations include hydrochlorothiazide and spironolactone• NaCl and KCl supplementation are commonly required• chronic frusemide administration is generally avoided, as it has been associated with the development of nephrocalcinosis and hyperchloremic metabolic alkalosis• there is no place for long term therapy with diuretics in level 2 SCNs