| Chapter 11: | The Infant |   |
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Respiratory Distress Syndrome (RDS)
This syndrome, also known as hayline membrane disease, is one of the most predominant lung problems experienced by neonates. It mainly strikes infants under 35 weeks old, affecting the younger newborns more than older infants. Diagnostic improvements and treatment advances including CPAP, PEEP have significantly cut the RDS mortality rates, but it remains a serious problem.
The etiology of RDS is well understood: a significant deficiency in pulmonary surfactant production. This deficiency decreases lung compliance, increases the infant's work of breathing (WOB), tiring an already weakened system and causing atlectasis, decreased alveolar ventilation, hypoperfusion, and even asphyxia. Problems during pregnancy, including maternal diabetes and bleeding prior to labor can be factors contributing to the incidence of RDS.
Although many factors contribute to the deficiency of surfactant, the main contributor is prematurity of the neonatal pulmonary system. Although surfactant is produced near gestational week 22, it can easily be disrupted by hypoxemia, hypothermia, and acidosis, all of which plague the premature neonate. It is not until the mature surfactant is produced near week 35 that these stressors do not disrupt the production, and the fetal lungs are considered mature.
The symptoms of RDS usually worsen gradually for the first 48-72 hours, followed by a stabilization, and a slow recovery period. Stabilization of the disease is often associated with diuresis. The highest incidence of mortality from RDS occurs within the first 72 hours. If death occurs following 72 hours, RDS is usually secondary to complications such as barotraumatic air leaks, intracranial hemorrhages, or infections rather than being due to the lung disease.
The ideal treatment for RDS would obviously be to prevent it from occurring. The administration of glucocorticoids to the mother at least two days prior to delivery has been shown to promote fetal lung and surfactant development. The difficulty in treating RDS is in maintaining adequate alveolar ventilation without inflicting damage on the lungs. Therefore the goal of treatment is to support the patient's respiratory system adequately while minimizing complications--something that is easy to envision, but difficult to accomplish.
Treatment of RDS involves a variety of issues, including:
- maintenance of a patent airway and respiratory acid base balance
- remaining alert to other systems being affected by decreased ventilation
- providing support until the infant matures is crucial
Treatment of RDS also requires adequate hydration, including electrolyte balance. Diuretics, such as furosemide, are used widely in the management of fluid balance in the neonate. Maintenance of thermoregulation is also of vital importance in treating RDS. The use of a pulse oximeter and transcutaneous monitor, along with supportive blood gases, allows for the titration of ventilatory support to meet the neonate's needs, and should be considered mandatory equipment for treating RDS.
Successful management of neonatal RDS patients requires anticipation of potential complications. That anticipation can prevent some complications and allow for rapid treatment of others. Potential complications include:
- Intracranial hemorrhage occurs in 40% of infants weighing less than 1500 g, and the risk increases as positive pressure is initiated.
- Barotraumatic injury leading to pulmonary air leaks, particularly as higher ventilator pressures are needed to maintain adequate ventilation and oxygenation.
- Disseminated intravascular coagulation (DIC) which leads to profuse bleeding throughout the body is caused by a disruption of coagulation factors; neonates with RDS have an increased incidence of DIC.
- Infection is common because of the presence of an endotracheal tube; sterile techniques when intubating and suctioning can reduce chances of pulmonary infection.
- Patent ductus arteriosus (PDA) is another common complication of RDS.