Idiopathic Respiratory Disease Syndrome

Idiopathic Respiratory Disease Syndrome

Idiopathic Respiratory Disease Syndrome  respiratory distress usually occurring within 4 hours of

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birth and persistently worsening for 48 to 72 hours. If not fatal, it resolves by 72 hours. Surfactant replacement therapy has shortened the duration of the disease and reduced mortality by 40%. Surfactant deficiency results in high alveolar surface tension; with each breath the baby must reinflate the collapsed alveoli. Thus every breath is like the first - a large effort for relatively poor expansion. This condition is now being treated with administration of synthetic or animal surfactant. RDS affects about 1% of newborn infants and is the leading cause of death in preterm infants. The incidence decreases with advancing gestational age, from about 50% in babies born at 26-28 weeks, to about 25% at 3031 weeks. The syndrome is more frequent in infants of diabetic

Pathophysiology

Normal ductus arteriosus closure  In the developing fetus, the ductus arteriosus (DA) is the vascular connection

between the pulmonary artery and the aortic arch that allows most of the blood from the right ventricle to bypass the fetus' fluid-filled compressed lungs. During fetal development, this shunt protects the right ventricle from pumping against the high resistance in the lungs, which can lead to right ventricular failure if the DA closes in-utero.  When the newborn takes its first breath, the lungs open and pulmonary vascular resistance decreases. After birth, the lungs release bradykinin to constrict the smooth muscle wall of the DA and reduce bloodflow through the DA as it narrows and completely closes, usually within the first few weeks of life. In most newborn infants with a patent ductus arteriosus the blood flow is reversed from that of in utero flow, ie. the blood flow is from the higher pressure aorta to the now lower pressure pulmonary arteries.  In normal newborns, the DA is substantially closed within 12-24 hours after birth, and is completely sealed after three weeks. The fall in circulating maternal prostaglandins contributes to this. The residual scar tissue from the fibrotic remnants of DA, called the ligamentum arteriosum, remains in the normal adult heart.

Surfactant

Surfactant is a mixture of phopholipids and proteins which is produced by type II pneumocytes from 24 weeks of gestation onwards. Surfactant has the following functions:  reduction of surface tension, preventing collapse of alveoli  facilitation of gas transport between air and fluid phases Neonatal respiratory distress syndrome (RDS) is a disease of premature babies which results primarily from a deficiency of surfactant. Surfactant used in treating neonatal RDS may be:  synthetic: contains phospholipid but no surfactant proteins

 animal-derived: contains phospholipid and surfactant proteins

Predisposing factors      

* prematurity * small for dates * male sex * maternal diabetes mellitus * hypothermia * perinatal asphyxia

Clinical features  Respiratory distress syndrome begins shortly after birth and is manifest by

tachypnea, tachycardia, chest wall retractions (recession), expiratory grunting, flaring of the nostrils and cyanosis during breathing efforts.  As the disease progresses, the baby may develop ventilatory failure (rising carbon dioxide concentrations in the blood), and prolonged cessations of breathing ("apnea"). Whether treated or not, the clinical course for the acute disease lasts about 2 to 3 days. During the first, the patient worsens and requires more support. During the second the baby may be remarkably stable on adequate support and resolution is noted during the third day, heralded by a prompt diuresis. Despite huge advances in care, RDS remains the most common single cause of death in the first month of life. Complications include metabolic disorders (acidosis, low blood sugar), patent ductus arteriosus, low blood pressure, chronic lung changes, and intracranial hemorrhage. The disease is frequently complicated by prematurity and its additional defects in other organ function.

Complications

1. Hypoxia As a result of hypoxia, pulmonary blood vessels constrict and their resistance increases, which reduces pulmonary blood flow. The increase in pulmonary blood vessel resistance may cause a return to fetal circulation as the ductus opens and blood flow is shunted around the lungs. This shunting increases the hypoxia and further decreases pulmonary perfusion. Hypoxia also causes impairment or absence of metabolic response to cold; reversion to anaerobic metabolism, resulting in lactate accumulation (acidosis); and impaired cardiac output, which decreases perfusion to vital organs. 2. Respiratory acidosis. Persistently rising Pco2 and decreases in pH are poor prognostic signs of pulmonary function and adequacy because increased Pco2 and decreased pH are results of alveolar hypoventilation.

3. Metabolic acidosis. Because the cells lack oxygen, the newborn begins an anaerobic pathway of metabolism, with an increase in lactate levels and a resulting base deficit (loss of bicarbonate). As the lactate levels increase, the pH decreases in an attempt to maintain acid-balance homeostasis.

Treatment Prevention: * avoiding preterm delivery where possible * careful control of diabetes in pregnancy * administration of dexamethasone to mothers before preterm deliveries * avoidance of hypothermia after delivery Management: * ventilation * surfactant

Prevention  Most cases of hyaline membrane disease can be ameliorated or

prevented if mothers who are about to deliver prematurely can be given one of a group of hormones glucocorticoids. This speeds the production of surfactant. For very premature deliveries, a glucocorticoid is given without testing the fetal lung maturity. In pregnancies of greater than 30 weeks, the fetal lung maturity may be tested by sampling the amount of surfactant in the amniotic fluid, obtained by inserting a needle through the mother's abdomen and uterus. Several tests are available that correlate with the production of surfactant. These include the lecithin-sphingomyelin ratio (" L/S ratio"), the presence of phosphatidol glycerol (PG), and more recently, the surfactant/albumin (S/A) ratio. For the L/S ratio, if the result is less than 2:1, the fetal lungs may be surfactant deficient. The presence of PG usually indicates fetal lung maturity. For the S/A ratio, the result is given as mg of surfactant per gm of protein. An S/A ratio <35 indicates immature lungs, between 35-55 is indeterminate, and >55 indicates mature surfactant production(correlates with an L/S ratio of 2.2 or greater).

Diagnostic Procedure

Other Tests & Procedures • Heart cath/Pulmonary artery pressure increased • Amniocentesis/Abnormality • PFT/Abnormal pulmonary function tests • PFT/Carbon monoxide diffusion (DLCO)/Abnormal • PFT/Diffusion defect • PFT/Vital capacity decreased Pathology • BX/Lung biopsy/Interstitial cell infiltrate Electrodiagnosis • Pulse oximetry/low O2 saturation X-RAY • Xray/Chest abnormal • Xray/Atelectasis, whole lung/Chest • Xray/Atelectasis/Chest • Xray/Chest/Lung fields/Abnormal • Xray/Interstitial infiltrate/fibrosis/Chest • Xray/Miliary nodule pattern/Chest • Xray/Pulmonary Lesions/Lung • Xray/Whiteout/lung fields/Chest Ultrasound • Echo/Pulmonary artery hypertension

NURSING DIAGNOSIS

 Impaired Gas Exchange r/t alveolar membrane change

(inadequate surfactant levels) as evidenced by tachypnea, expiratory grunting, pallor or cyanosis, abnormal ABG findings & tachycardia.

 Impaired Spontaneous Ventilation r/t respiratory muscle

fatigue & metabolic factors as evidenced by dyspnea, restlessness, inc. metabolic rate, use of accessory muscle & abnormal ABG findings.

 Risk for Infection r/t inadequate primary defense (dec. ciliary

action, stasis of body fluids, traumatized tissue) or secondary defense (dec. neutrophils & immunoglobulins)

 Risk for ineffective GI tissue perfusion r/t persistent fetal

circulation

 Risk for impaired parent=infant attachment r/t ineffective

initiation of parental contact.

Nursing Interventions

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Evaluate degree of compromise by: Note respiratory rate, depth, use of accessory muscle, pursedlip breathing, pallor/cyanosis and capillary refill. Compare peripheral (nail beds) vs. central (circumoral). Auscultate breath sounds, note areas of adventitious breath sounds and fremitus. Note characteristic of cough mecahnism. Correct/improve the existing deficiency: Elevate head of bed to maintain airway Encourage frequent position changes & deep-breathing exercise to promote optimal chest expansion & drainage of secretions. Provide supplemental oxygen @ lowest concentration as indicated by lab. results – 2L/min Maintain I/O foe mobilization of secretions but avoid fluid overload. Encourage adequate rest & limit activities w/in tolerance. Helps oxygen needs/consumption.

TEACHING HIGHLIGHTS You can help parents understand their baby’s respiratory distress by having them think of the air sacs (alveoli) of the lungs as tiny balloons filled with water and no air. When the tiny balloon (alveolus) is emptied (as in expiration), water droplets can remain inside the balloon. The sides of the balloon stick together, increasing the surface tension, making the next inspiration breath very difficult.

NURSING PRACTICE In babies with RDS who are on ventilators, increased urination (determined by weighing diapers) may be an early clue that the baby’s condition is improving. As fluid moves out of the lungs and into the bloodstream, alveoli open and kidney perfusion increases, which results in increased voiding. At this point, monitor chest expansion closely. If chest expansion is increasing, ventilator settings may have to be decreased. Too high a ventilator setting may “blow the lung,” resulting in pneumothorax.

Evidence-Based Nursing (EBN)

Clinical Question Can continuous positive airway pressure (CPAP) reduce the use of intermittent positive pressure ventilation (IPPV) in preterm infants, without an increase in adverse effects? Evidence The standard treatment for many newborns with RDS is intermittent positive pressure ventilation. IPPV has been demonstrated effective, but it is invasive and may result in airway and lung injury. In order to determine if CPAP was a viable alternative for spontaneously breathing infants with RDS, four neonatal specialists conducted a systematic review for the Cochrane Library. CPAP by mask, nasal prong, nasopharyngeal tube, or endotracheal tube was included. In these trials, CPAP was associated with benefits in terms of reduced respiratory failure and mortality. The studies had varying levels of pressure and delivery mode, so no final conclusions can be drawn about optimal administration methods. Babies on CPAP were reported to have a high rate of pneumothorax.

Implications CPAP can be effective in reducing respiratory failure in spontaneously breathing preterm infants. It is less invasive, results in fewer complications, and costs less than IPPV. The infants in these trials tended to have a greater birth weight, but very small preterm infants may still require IPPV, even if spontaneously breathing. You can assure parents that CPAP is an effective treatment for RDS in preterm infants who are breathing spontaneously, particularly if they are of greater birth weight. It is a less invasive procedure resulting in fewer injuries, and it is as effective as IPPV when used correctly and judiciously. More research is needed to identify specific characteristics of those preterm Diagnostic Procedure infants who can safely forgo IPPV for CPAP. Critical Thinking What assessments will you plan for the preterm infant on CPAP to help you identify early signs of pneumothorax? Reference Ho, J. J., Subramaniam, P., Henderon-Smart, D. J., & Davis, P. G. (2003). Continuous distending pressure for respiratory distress syndrome in preterm infants (Cochrane Review). In: The Cochrane Library, Issue 4. Chichester, UK: John Wiley & Son

End of Presentation  Thanks for listening ;-p  BSN034 Group-134  Professor Jill Angeles