A lung abscess is a localized necrotic lesion of the lung parenchyma containing purulent material that collapses and forms a cavity. It is generally caused by aspiration of anaerobic bacteria. By defini-tion, the chest x-ray will demonstrate a cavity of at least 2 cm. Pa-tients who have impaired cough reflexes and cannot close the glottis, or those with swallowing difficulties, are at risk for aspi-rating foreign material and developing a lung abscess. Other at-risk patients include those with central nervous system disorders (seizure, stroke), drug addiction, alcoholism, esophageal disease, or compromised immune function, those without teeth, as well as patients receiving nasogastric tube feedings and those with an altered state of consciousness from anesthesia.
Most lung abscesses are a complication of bacterial pneumonia or are caused by aspiration of oral anaerobes into the lung. Abscesses also may occur secondary to mechanical or functional obstruc-tion of the bronchi by a tumor, foreign body, or bronchial steno-sis, or from necrotizing pneumonias, TB, pulmonary embolism, or chest trauma.
Most abscesses are found in areas of the lung that may be af-fected by aspiration. The site of the lung abscess is related to grav-ity and is determined by the patient’s position. For patients who are confined to bed, the posterior segment of an upper lobe and the superior segment of the lower lobe are the most common areas in which lung abscess occurs. However, atypical presenta-tions may occur, depending on the position of the patient when the aspiration occurred.
Initially, the cavity in the lung may or may not extend directly into a bronchus. Eventually the abscess becomes surrounded, or encapsulated, by a wall of fibrous tissue. The necrotic process may extend until it reaches the lumen of a bronchus or the pleural space and establishes communication with the respiratory tract, the pleural cavity, or both. If the bronchus is involved, the purulent contents are expectorated continuously in the form of sputum. If the pleura is involved, an empyema results. A communication or connection between the bronchus and pleura is known as a bron-chopleural fistula.
The organisms frequently associated with lung abscesses are S.aureus, Klebsiella, and other gram-negative species. Anaerobicorganisms, however, may also be present. The organism varies depending on the underlying predisposing factors.
The clinical manifestations of a lung abscess may vary from a mild productive cough to acute illness. Most patients have a fever and a productive cough with moderate to copious amounts of foul-smelling, often bloody, sputum. Leukocytosis may be present. Pleurisy or dull chest pain, dyspnea, weakness, anorexia, and weight loss are common. Fever and cough may develop insidiously and may have been present for several weeks before diagnosis.
Physical examination of the chest may reveal dullness on percus-sion and decreased or absent breath sounds with an intermittent pleural friction rub (grating or rubbing sound) on auscultation.Crackles may be present. Confirmation of the diagnosis is made by chest x-ray, sputum culture, and in some cases fiberoptic bron-choscopy. The chest x-ray reveals an infiltrate with an air–fluid level. A computed tomography (CT) scan of the chest may be re-quired to provide more detailed pictures of different cross-sectional areas of the lung.
The following measures will reduce the risk of lung abscess:
· Appropriate antibiotic therapy before any dental procedures in patients who must have teeth extracted while their gums and teeth are infected
· Adequate dental and oral hygiene, because anaerobic bacte-ria play a role in the pathogenesis of lung abscess
· Appropriate antimicrobial therapy for patients with pneu-monia
The findings of the history, physical examination, chest x-ray, and sputum culture indicate the type of organism and the treatment required. Adequate drainage of the lung abscess may be achieved through postural drainage and chest physiotherapy. The patient should be assessed for an adequate cough. A few patients need a percutaneous chest catheter placed for long-term drainage of the abscess. Therapeutic use of bronchoscopy to drain an abscess is un-common. A diet high in protein and calories is necessary because chronic infection is associated with a catabolic state, necessitating increased intake of calories and protein to facilitate healing. Surgi-cal intervention is rare, but pulmonary resection (lobectomy) is performed when there is massive hemoptysis (coughing up of blood) or little or no response to medical management.
Intravenous antimicrobial therapy depends on the results of the sputum culture and sensitivity and is administered for an ex-tended period. Penicillin G or clindamycin (Cleocin) is the med-ication of choice, followed by penicillin with metronidazole. Large intravenous doses are generally required because the anti-biotic must penetrate the necrotic tissue and the fluid in the ab-scess. The intravenous dose is continued until there is evidence of symptom improvement.
Long-term therapy with oral antibiotics replaces intravenous therapy after the patient shows signs of improvement (usually 3 to 5 days). Improvement is demonstrated by normal tempera-ture, decreased white blood cell count, and improvement on the chest x-ray (resolution of surrounding infiltrate, reduction in cav-ity size, absence of fluid). Oral administration of antibiotic ther-apy is continued for an additional 4 to 8 weeks. If treatment stops too soon, a relapse may occur.
The nurse administers antibiotics and intravenous therapies as prescribed and monitors for adverse effects. Chest physiotherapy is initiated as prescribed to facilitate drainage of the abscess. The nurse teaches the patient to perform deep-breathing and cough-ing exercises to help expand the lungs. To ensure proper nutri-tional intake, the nurse encourages a diet high in protein and calories. The nurse also offers emotional support because the ab-scess may take a long time to resolve.
The patient who has had surgerymay return home before the wound closes entirely or with a drain or tube in place. Thus, the patient or a caregiver needs instruc-tion on how to change the dressings to prevent skin excoriation and odor, how to monitor for signs and symptoms of infection, and how to care for and maintain the drain or tube. The nurse instructs the patient to perform deep-breathing and coughing ex-ercises every 2 hours during the day and shows a caregiver how to perform chest percussion and postural drainage to facilitate ex-pectoration of lung secretions.
Referral for home care may be required bysome patients whose condition requires therapy at home. During visits to the patient at home, the nurse assesses the patient’s phys-ical condition, nutritional status, and home environment as well as the patient’s and family’s ability to carry out the therapeutic regimen. Patient teaching is reinforced during home visits, and nutrition counseling is provided with the goal of attaining and maintaining an optimal state of nutrition. To prevent a relapse, the nurse emphasizes the importance of completing the antibiotic regimen and of following the suggestions for rest and appropri-ate activity. If intravenous antibiotic therapy is to continue at home, the services of a home care nurse may be arranged to ini-tiate intravenous therapy and to evaluate its administration by the patient or family. Although most outpatient intravenous therapy is administered in the home setting, a patient may visit a nearby clinic or physician’s office for this treatment. In some cases the patient with lung abscess may have ignored his or her health. Therefore, it is important to use this opportunity to address health promotion strategies and health screening with the patient.
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