Chapter 17 Cystic Fibrosis
PATHOPHYSIOLOGY
Cystic fibrosis (CF), inherited as an autosomal-recessive trait, is caused by a mutation of the CF gene on chromosome 7. This results in absence or decreased function of a protein called cystic fibrosis transmembrane regulator (CFTR), which leads to abnormal sodium and chloride transport across the epithelium. The disorder affects the exocrine glands and causes the production of viscous mucus, which leads to obstruction of the small passageways of the bronchi, the small intestine, and the pancreatic and bile ducts. The effects of this biochemical defect on the involved organs are as follows:
3. Small intestine—absence of pancreatic enzymes (trypsin, amylase, lipase) causes impaired absorption of fats and proteins, which results in steatorrhea and azotorrhea.
INCIDENCE
1. CF affects 1 in every 3700 infants born in the United States, with the birth prevalence varying based on race and ethnicity:
2. CF rarely affects infants of Asian descent (1 in 31,000).
3. Odds are 1 in 4 (25%) that each subsequent pregnancy after the birth of a child with CF will result in a child with CF.
4. CF affects males and females equally.
5. Newborn screening for CF is available and, when positive, could lead to an earlier age at diagnosis compared with when diagnosis is symptom-based. This would lead to earlier nutritional management and result in improved growth and development. At present, newborn screening for CF has improved outcomes for the child with CF but has not been universally adopted.
6. Symptoms vary greatly, resulting in variable life span—95% survival to age 16 years, with a median predicted age of survival of 35.1 years. About 42% of patients with cystic fibrosis are 18 years of age or older. Infants born in the 1990s or later have a predicted median survival age of 40 years.
7. Length and quality of life have greatly increased in recent years, but the disease is ultimately terminal.
CLINICAL MANIFESTATIONS
1. Meconium ileus (at birth in 15% to 20% of infants with CF)
2. Cough—initially dry and nonproductive, changing to loose and productive
3. Viscous sputum, increasing in amount, normally yellow-gray and greenish during infection
4. Wheezy respirations, moist crackles
5. Cyanosis, clubbed fingers and toes, increased anteroposterior diameter of chest (later signs)
7. Bulky, loose, foul-smelling stools
10. Failure to thrive (below norms for height and weight despite large food intake)
COMPLICATIONS
1. Pulmonary: emphysema, pneumothorax, pneumonia, bronchiectasis, hemoptysis, cor pulmonale, respiratory failure
2. Gastrointestinal: cirrhosis, portal hypertension, esophageal varices, fecal impactions, enlarged spleen, intussusception, cholelithiasis, pancreatitis, rectal prolapse
3. Endocrine: CF-related diabetes mellitus, poor bone mineralization leading to osteopenia and osteoporosis, poor growth, heat prostration
LABORATORY AND DIAGNOSTIC TESTS
1. Genetic blood testing for CF marker
2. Sweat test—to measure concentration of sodium and chloride in sweat; most definitive diagnostic test; not reliable for newborns younger than 1 month old (two positive results on sweat tests are diagnostic; value higher than 60 mEq/L represents positive result for CF)
3. Pulmonary function testing—used to assess respiratory status and severity of condition, and to determine therapy
4. Chest radiographic study—for evaluation of pulmonary complications
MEDICAL MANAGEMENT
The child with symptoms of CF is hospitalized for the diagnostic work-up, initiation of treatment, clearing of any symptoms of respiratory tract infection, and education of the child and family. The goal of this hospitalization is to stabilize the child’s condition so that care can be managed for long periods at home.
Antibiotics are given based on the suspected organisms, sensitivity to antibiotics, the severity of infection, and the child’s response to therapy. The course of therapy is usually at least 14 days. After the initial admission, when respiratory tract infections are not responsive to intensive home treatment measures or oral antibiotic therapy, the child may either be readmitted for intravenous (IV) antibiotic therapy or have home IV antibiotic therapy.
Pulmonary toilet includes adequate hydration to loosen secretions and chest percussion and postural drainage to clear mucus from the small airways. Breathing exercises and devices designed to loosen and mobilize pulmonary secretions are also used. Aerosol generators may be used to administer normal saline, bronchodilators (such as albuterol or other β-agonist drugs), antibiotics (such as tobramycin), and mucolytics. Dornase alfa is used to reduce the viscosity of sputum and improve lung function in children with CF. Some bronchodilators are administered through a metered-dose inhaler, with or without a spacer. Intermittent positive pressure breathing does not improve drug delivery and may aggravate the pulmonary status.
Pancreatic enzyme supplements are given with meals and snacks; dosages are individualized for the child and generally increase as the child gets older. Supplements of fat-soluble vitamins (A, D, E, and K) are needed in greater than the normal dosage because they are not well absorbed. Diet is modified to increase the number of calories provided (up to 150% more than normal needs based on age, weight, and activity). High levels of protein and normal amounts of fat (about 40%) should be included in the child’s diet.
Lung or heart-lung transplantation may be an option for end-stage CF lung disease. The waiting period for donor organs is between 6 months and 2 years; it is increasing at all transplant centers. Transplant criteria include progressive respiratory function impairment with severe hypoxemia and hypercarbia, increasing functional impairment, major life-threatening pulmonary complications, and antibiotic resistance of bacteria infecting the lungs. Individual transplant centers may have additional criteria or restrictions. On behalf of the federal government, in the spring of 2005, United Network for Organ Sharing (UNOS) put priority guidelines into place for deciding who should get available donor lungs, which eliminated the first-come-first-served system for persons older than age 12. A twice-yearly evaluation serves to determine the person’s health status before transplant and what his or her projected health will be after the transplant; then a mathematical formula is used to arrive at a “lung allocation score” that allows donor lungs to be given to the person who needs them the most at the time. The current 5-year survival rate for lung transplant in individuals with CF is 50%. The child with CF who undergoes transplantation is at risk for the same complications as other child transplant recipients (effects of immunosuppression, infection, acute rejection, and bronchiolitis obliterans). In addition, because of CF, such a child may have malabsorption of the immunosuppressive agents.
NURSING INTERVENTIONS
1. Monitor respiratory status and report any significant changes (in respiratory rate, presence of intercostal retractions, presence of cyanosis, and color and amount of sputum).
2. Monitor effects of aerosolized treatment (performed before postural drainage).
3. Administer and evaluate effects of postural drainage and percussion.
4. Administer and monitor side effects and actions of medications.
5. Teach and supervise breathing exercises (exhalation, inhalation, coughing), although these are not a substitute for percussion and postural drainage.
6. Encourage physical activity and a regular exercise program as condition permits.
7. Obtain baseline information about dietary habits (food preferences and dislikes, eating attitudes, developmental abilities).
8. Monitor and record characteristics of stool (color, consistency, size, frequency).
9. Promote nutritional status.
10. Observe for and report signs of complications (see the Complications section in this chapter).
11. Provide emotional support to child and parents during hospitalization and in the ambulatory setting.
12. Provide guidance related to independence, self-care, sexuality, and educational planning as adolescent undergoes transition to adulthood.
Discharge Planning and Home Care
1. Instruct parents and child about techniques of home management.
2. Monitor family’s compliance with home management.
3. Assist family in contacting support systems for financial, psychologic, and medical assistance (e.g., Cystic Fibrosis Foundation).
4. Provide genetic counseling.
5. Immunize the child and all household members annually against influenza.
Centers for Disease Control and Prevention. Newborn screening for cystic fibrosis: Evaluation of benefits and risks and recommendations for state newborn screening programs. MMWR. 2004;53(RR-13):1.
Cystic Fibrosis Foundation. Patient registry annual data report 2004. www.cff.org/living_with_cf. (website): Accessed April 1
Orenstein DM, Higgins LW. Update on the role of exercise in cystic fibrosis. Curr Opin Pulm Med. 2005;11(6):519.
Powers SW, et al. Randomized clinical trial of behavioral and nutrition treatment to improve energy intake and growth in toddlers and preschoolers with cystic fibrosis. Pediatrics. 2005;116(6):1442.
Stark LJ, Powers SW. Behavioral aspects of nutrition in children with cystic fibrosis. Curr Opin Pulm Med. 2005;11(6):539.
Starner TD, McCray PB. Pathogenesis of early lung disease in cystic fibrosis: A window of opportunity to eradicate bacteria. Ann Intern Med. 2005;143(11):816.
Zindani GN, et al. Adherence to treatment in children and adolescent patients with cystic fibrosis. J Adolesc Health. 2006;38(2006):13.
