A 21-year-old female with cystic fibrosis presents for Broviac placement for total parenteral nutrition. She was hospitalized for a pulmonary infection last month, which has resolved. She also has pancreatic insufficiency. She is adamant that she should be completely asleep for the procedure.
Physical examination: 35 kg. Thin female with intermittent cough; O2 saturation 98% on room air.
Laboratory findings: Hematocrit 35; international normalized ratio 1.2; prothrombin time 21; partial thromboplastin time 38; blood glucose 180.
Chest x-ray: Flattening of costal margins, prominent bronchovascular markings, peribronchial cuffing, bibasilar atelectasis.
Cystic fibrosis (CF) is an autosomal recessive disorder that results from a gene mutation of the cystic fibrosis transmembrane regulator (CFTR) protein on chromosome 7. It is the most common fatal genetic disorder among Caucasians, but it can also be found in other ethnic groups. The identification of the CFTR gene in 1989 and substantial medical advancements have changed the once fatal childhood disease into a more chronic, progressive disease of adults, with the median survival age now being 38 years. Approximately 1000 new cases are diagnosed each year. It is estimated that there are about 30,000 patients with CF living in the United States, and about 45% of these are adults.
The CFTR protein is a chloride channel that regulates electrolyte and water movement across epithelial membranes. The mutation results in defective chloride ion transport with disturbances of sodium and water transport in epithelial cells that express this gene, notably those found in the lungs, pancreas, liver, gastrointestinal tract, and reproductive organs. Dehydrated, viscous secretions cause luminal obstruction and lead to destruction and scarring of exocrine glands. This results in pancreatic insufficiency, meconium ileus at birth, diabetes mellitus, obstructive hepatobiliary tract disease, and azoospermia. Mortality usually results from chronic pulmonary infection.
The gold standard for the diagnosis of CF is the sweat test. The presence of a chloride concentration higher than 60 mEq/L in sweat is a positive test in children. Clinical manifestations include cough, chronic purulent sputum production, and exertional dyspnea. Chronic parasinusitis is almost always present, and evidence of normal sinuses on x-ray is strong enough to rule out CF. Stasis of viscous mucus in the respiratory tract predisposes patients to Pseudomonas aeruginosa and Staphylococcus aureus infection. Recurrent infection and chronic inflammation eventually lead to bronchiectasis, chronic airway obstruction from mucus plugging, impaired gas exchange, pulmonary hypertension, and hemoptysis. Early effective management employing chest physiotherapy with postural drainage and mucolytics has improved these patients’ quality of life and longevity. Those with poor lung function may require bilateral lung transplantation with a 5-year survival rate of 50%.
Blockage of pancreatic ducts will lead to the retention of digestive enzymes, which can result in autodigestion, destruction, and reactive fibrosis of the pancreas. Patients will eventually develop pancreatic insufficiency and malabsorption from impairment of exocrine and endocrine glands ...