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INTRODUCTION

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Bronchopulmonary dysplasia (BPD) is a form of chronic lung disease associated with prolonged mechanical ventilation and oxygen toxicity in the preterm neonate. Antenatal glucocorticosteroid, early surfactant therapy, and gentler modalities of ventilation currently utilized have minimized the severity of lung injury than was previously seen.

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It is observed in neonates with a history of respiratory distress syndrome, birth weight less than 1500 g and oxygen requirements to maintain the arterial partial pressure of oxygen (PaO2) greater than 50 mmHg at 28 days of life. Subsequently, these patients are subjected to endotracheal intubation, prolonged mechanical ventilation, and oxygen toxicity which may cause further dependence on steroids, oxygen therapy, and ventilator dependence.

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ETIOLOGY

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The specific etiology is unknown but may have multifactorial influences including barotrauma secondary to intubation and mechanical ventilation, oxygen toxicity, and infection.

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The risk of developing BPD has increased as the survival of very premature infants (24–26 weeks gestation, birth weight < 1000 g) has increased. The incidences for neonates weighing 501–750 grams, under 1000 grams and between 1251 and 1500 grams are 52%, approximately 30% and up to 7%, respectively. It is uncommon for neonates born after 30 gestational weeks weighing more than 1500 grams to be diagnosed with BPD. Additional risk factors include elevated inspired oxygen concentration (FiO2), positive-pressure ventilation, patent ductus arteriosus, and hypervolemia in first 5–6 days of life.

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CLINICAL MANIFESTATIONS

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BPD is characterized by decreased lung compliance, hyperactive airways, and increased oxygen consumption which contributes to ventilation perfusion mismatching.

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Clinical signs and symptoms include:

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  • Dyspnea

  • Tachypnea

  • Airway hyperactivity

  • Oxygen dependence

  • Hypoxemia

  • Hypercarbia

  • Abnormal functional airway growth

  • Tracheobronchomalacia

  • Subglottic stenosis

  • Increased pulmonary vascular resistance leading to pulmonary hypertension, cor pulmonale, and congestive heart failure

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Pulmonary function abnormalities include:

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  • Decreased functional residual capacity

  • Decreased diffusion capacity

  • Airway obstruction and decreased exercise tolerance

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Many of these children also suffer neurodevelopmental problems and seizures due to intraventricular hemorrhage or hypoxic insults. Some may have a cardiomyopathy due to corticosteroid therapy in the neonatal period or the combination of corticosteroid therapy and viral infections; others may have systemic hypertension. These children are often discharged home on oxygen therapy, diuretics (pulmonary interstitial edema increases the possibility of respiratory failure), and beta-2 adrenergic receptor agonists. Hyperinflation and areas of increased density are often seen on chest radiographs.

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A severity index for BPD based on the need for supplemental oxygen and/or positive-pressure ventilation or nasal continuous positive airway pressure (CPAP) has been developed. The index classifies BPD as requiring therapy with oxygen >21% for at least 28 days plus:

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  • Mild BPD—Breathing room air

  • Moderate BPD—Need for <30% oxygen

  • Severe BPD—Need for ≥30% oxygen and/or positive-pressure ventilation or nasal continuous airway pressure

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These criteria have shown to identify a spectrum of risk for adverse pulmonary and neurodevelopmental outcomes in prematurely born infants. Although this severity index has not been studied in the context of anesthetic risk, experience suggests that such infants requiring supplemental oxygen, positive pressure, or medications for reactive airways are at greater risk for perioperative pulmonary complications. Anesthetic goals include minimizing inspired oxygen concentration and peak ...

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