lecture 46- bronchiolitis: causes and management.ppt
- 2. Introduction • Acute bronchiolitis is predominantly a viral disease • Respiratory syncytial virus (RSV) is responsible for >50% of cases • Other agents include parainfluenza • adenovirus • Mycoplasma
- 3. There is no evidence of a bacterial cause for bronchiolitis, although bacterial pneumonia is sometimes confused clinically with bronchiolitis bronchiolitis is rarely followed by bacterial superinfection.
- 4. •Approximately 50,000–80,000 of hospitalizations annually among children <1 yr old are attributable to RSV infection • 200–500 deaths per yr in the United States DUE TO RSV
- 5. •Increasing rates of hospitalization may reflect increased attendance of infants in daycare centers, changes in criteria for hospital admission, and/or improved survival of premature infants and others at risk for severe RSV-associated disease.
- 6. •Bronchiolitis is more common in males • in those who have not been breast-fed • in those who live in crowded conditions • Older family members are a common source of infection • they may only experience minor respiratory symptoms.
- 7. •The clinical manifestations of lower respiratory tract illness (LRTI) seen in young infants may be minimal in older patients, in whom bronchiolar edema is better tolerated. •Not all infected infants develop LRTI
- 8. •Host anatomic and immunologic factors seem to play a significant role in the severity of the clinical syndrome • Infants with pre-existent smaller airways and diminished lung function have a more severe course • In addition, RSV infection incites a complex immune response..
- 9. •Acute bronchiolitis is characterized by bronchiolar obstruction with edema, mucus, and cellular debris • Even minor bronchiolar wall thickening significantly affects airflow because resistance is inversely proportional to the 4th power of the radius of the bronchiolar passage
- 10. •Resistance in the small air passages is increased during both inspiration and exhalation •because the radius of an airway is smaller during expiration • the resultant respiratory obstruction leads to early air trapping and overinflation
- 11. •If obstruction becomes complete, there will be resorption of trapped distal air, and the child will develop atelectasis •Hypoxemia is a consequence of ventilation-perfusion mismatch early in the course • With severe obstructive disease and tiring of respiratory effort, hypercapnia may develop
- 12. Clinical features •is usually preceded by exposure to an older contact with a minor respiratory syndrome within the previous wk • The infant 1st develops a mild upper respiratory tract infection with sneezing and clear rhinorrhea
- 13. •This may be accompanied by diminished appetite and fever of 38.5–39°C (101–102°F), although the temperature may range from subnormal to markedly elevated • Gradually, respiratory distress ensues, with paroxysmal wheezy cough, dyspnea, and irritability
- 14. •The infant is often tachypneic, which may interfere with feeding •The child does not usually have other systemic complaints, such as diarrhea or vomiting • Apnea may be more prominent than wheezing early in the course of the disease, particularly with very young infants (<2 mo old) or former premature infants.
- 15. •The physical examination is characterized most prominently by wheezing •The degree of tachypnea does not always correlate with the degree of hypoxemia or hypercarbia, so the use of pulse oximetry and noninvasive carbon dioxide determination is essential • Work of breathing may be markedly increased, with nasal flaring and retractions
- 16. •Auscultation may reveal fine crackles or overt wheezes, with prolongation of the expiratory phase of breathing • Barely audible breath sounds suggest very severe disease with nearly complete bronchiolar obstruction • Hyperinflation of the lungs may permit palpation of the liver and spleen.
- 17. DIAGNOSTIC EVALUATION •The diagnosis is clinical, particularly in a previously healthy infant presenting with a first-time wheezing episode during a community outbreak • Because concurrent bacterial infection (sepsis, pneumonia, meningitis) is highly unlikely, confirmation of viral bronchiolitis remove the need for a sepsis evaluation in a febrile infant •Allow to assist with respiratory precautions and isolation if the patient requires hospitalization
- 18. •chest radiography • reveals hyperinflated lungs with patchy atelectasis •full blood count • The white blood cell and differential counts are usually normal • Viral testing (usually rapid immunofluorescence, polymerase chain reaction, or viral culture) • is helpful if the diagnosis is uncertain or for epidemiologic purposes
- 19. TREATMENT Infants with acute bronchiolitis who are experiencing respiratory distress should be hospitalized the mainstay of treatment is supportive If hypoxemic, the child should receive cool humidified oxygen
- 20. •Sedatives are to be avoided because they may depress respiratory drive •The infant is sometimes more comfortable if sitting with head and chest elevated at a 30-degree angle with neck extended
- 21. •The risk of aspiration of oral feedings may be high in infants with bronchiolitis • owing to tachypnea and the increased work of breathing •The infant may be fed through a nasogastric tube •If there is any risk for further respiratory decompensation potentially necessitating tracheal intubation • however, the infant should not be fed orally but be maintained with parenteral fluids •Frequent suctioning of nasal and oral secretions often provides relief of distress or cyanosis •Oxygen is indicated in all infants with hypoxia.
- 22. adjunctive therapies Bronchodilators produce modest short-term improvement in clinical features, but the statistical improvement in clinical scoring systems seen with them is not always clinically significant Nebulized epinephrine may be more effective than - β agonists A trial dose of inhaled bronchodilator may be reasonable, with further therapy predicated on response in the individual patient .
- 23. •Corticosteroids, whether parenteral, oral, or inhaled, have been used for bronchiolitis despite conflicting and often negative studies • Differences of diagnostic criteria, measures of effect, timing and route of administration, and severity of illness complicate these studies •Corticosteroids are not recommended in previously healthy infants with RSV
- 24. •Ribavirin, an antiviral agent administered by aerosol, has been used for infants with congenital heart disease or chronic lung disease •There is no convincing evidence of a positive impact on clinically important outcomes such as mortality and duration of hospitalization • Antibiotics have no value unless there is secondary bacterial pneumonia • Likewise, there is no support for RSV immunoglobulin administration during acute episodes of RSV bronchiolitis
- 25. PROGNOSIS •Infants with acute bronchiolitis are at highest risk for further respiratory compromise in the 1st 48–72 hr after onset of cough and dyspnea • the child may be desperately ill with air hunger, apnea, and respiratory acidosis •The case fatality rate is <1% • death attributable to • apnea • uncompensated respiratory acidosis •severe dehydration
- 26. •After this critical period, symptoms may persist •The median duration of symptoms in ambulatory patients is ≈12 days •Infants with conditions such as •congenital heart disease • bronchopulmonary dysplasia • immunodeficiency often have more severe disease, with higher morbidity and mortality
- 27. •there is a higher incidence of wheezing and asthma in children with a history of bronchiolitis unexplained by family history or other atopic syndrome •It is unclear whether • bronchiolitis incites an immune response that manifests as asthma later • whether those infants have an inherent predilection for asthma that is merely unmasked by their episode of RSV •Approximately 60% of infants who wheeze will stop wheezing.
- 28. PREVENTION •Reduction in the severity and incidence of acute bronchiolitis due to RSV is possible through the administration of pooled hyperimmune RSV •intravenous immunoglobulin (RSV-IVIG, RespiGam) and palivizumab (Synagis), an intramuscular monoclonal antibody to the RSV F protein, before and during RSV season
- 29. •Palivizumab is recommended for infants <2 yr of age with chronic lung disease (bronchopulmonary dysplasia) or prematurity •. Meticulous handwashing is the best measure to prevent nosocomial transmission