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A 4-month-old, former 28-week premie with bronchopulmonary dysplasia (BPD) presents for eye surgery.
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PREOPERATIVE CONSIDERATIONS
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Bronchopulmonary dysplasia, the most common cause of chronic lung disease in infants, is a disease of small airways and lung parenchyma, characterized by abnormal growth of alveoli and vasculature, and dilation of distal sites of gas exchange (alveolar ducts). It is the consequence of both oxygen toxicity and ventilator-induced lung injury to immature lungs.
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Bronchopulmonary dysplasia is a clinical diagnosis based on oxygen requirement and the need for ventilator support. It results when neonates with respiratory distress syndrome develop persistent respiratory distress characterized by airway obstruction, increased airway reactivity and resistance, and lung hyperinflation. This results in a ventilation-to-perfusion mismatch, reduced pulmonary compliance, increased work of breathing, and compromised gas exchange, leading to hypoxia, hypercarbia, tachypnea, and, in severe cases, right heart failure, resulting in pulmonary hypertension and ultimately cor pulmonale. The clinical manifestations are rapid respiration, wheezing, cough, and frequent episodes of fever, desaturation, and bradycardia. Oxygen consumption is increased by as much as 25%. Failure to thrive is a sign of chronic hypoxia. Auscultation of the lungs may not reveal wheezing because the site of airway hyperactivity is primarily in the small airways at the periphery of the lungs as a result of increased thickness of the airway wall.
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Infants with mild forms of BPD improve with age and may become asymptomatic, but airway hyperreactivity may persist. Most infants with moderate to severe BPD remain oxygen dependent, with or without ventilator dependence, beyond 4 weeks of age. Maintenance of adequate oxygenation, with partial pressure of oxygen (PaO2) >55 mm Hg and oxygen saturation (SpO2) >94%, is necessary to prevent or treat cor pulmonale and to promote growth of lung tissue and remodeling of the pulmonary vascular bed. Reactive airway bronchoconstriction is treated with bronchodilating agents and steroids. Cor pulmonale and severe chest retractions that draw fluid into the interstitial space cause fluid retention, necessitating fluid restriction and diuretic administration in order to decrease pulmonary edema and improve gas exchange. Consequently, abnormal serum electrolyte levels (eg, hypokalemia, hypochloremia, or metabolic alkalosis) are common preoperatively.
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ANESTHETIC MANAGEMENT
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Obtain a baseline oxygen saturation measurement with a pulse oximeter prior to administering an anesthetic. A normal oxygen saturation level does not guarantee the absence of lung dysfunction.
Arterial saturation should be maximized to reduce pulmonary hypertension.
Desaturation may be rapid when apnea occurs.
Infants with BPD with near-normal SpO2 on room air may develop marked desaturation after induction with sevoflurane because of a loss of hypoxic pulmonary vasoconstriction under general anesthesia.
Avoid nitrous oxide to avoid exacerbation of pulmonary gas trapping and pulmonary vascular resistance.
In children with a history of mechanical ventilation, an endotracheal tube (ETT) one size smaller than the appropriate-sized ETT for the patient’s age should be ...