Pneumocystis carinii pneumonia
Pneumocystis carinii pneumonia: Excerpt from Professional Guide to Diseases (Eighth Edition)
Because of its association with human immunodeficiency virus (HIV) infection, Pneumocystis carinii pneumonia (PCP), an opportunistic infection, has increased in incidence since the 1980s. Before the advent of PCP prophylaxis, this disease was the first clue in about 60% of patients that HIV infection was present.
PCP was the leading cause of death in these patients. Prophylactic therapy with co-trimoxazole in HIV patients with low immune function has prevented PCP from higher mortality rates. Disseminated infection doesn't occur.
PCP is also associated with other immunocompromising conditions, including organ transplantation, leukemia, lymphoma, and steroid use.
Causes and incidence
P. carinii, the cause of PCP, usually is classified as a protozoan, although some investigators consider it more closely related to fungi. The organism exists as a saprophyte in the lungs of humans and various animals as part of the normal flora in most healthy people. It becomes an aggressive pathogen in the immunocompromised patient. Impaired cell-mediated (T-cell) immunity is thought to be more important than impaired humoral (B-cell) immunity in predisposing the patient to PCP, but the immune defects involved are poorly understood. P. carinii becomes activated in immunocompromised patients when the CD4+ T-cell count falls below 200/µl.
P. carinii invades the lungs bilaterally and multiplies extracellularly. As the infestation grows, alveoli fill with organisms and exudate, impairing gas exchange. The alveoli hypertrophy and thicken progressively, eventually leading to extensive consolidation.
The primary transmission route seems to be air, although the organism is already present in most people. The incubation period probably lasts for 4 to 8 weeks.
Signs and symptoms
The patient typically has a history of an immunocompromising condition (such as HIV infection, leukemia, or lymphoma) or procedure (such as organ transplantation).
PCP begins insidiously with increasing shortness of breath and a nonproductive cough. Anorexia, generalized fatigue, and weight loss may follow. Although the patient may have hypoxemia and hypercapnia, he may not exhibit significant symptoms. He may, however, have a low-grade, intermittent fever.
Other signs and symptoms include tachypnea, dyspnea, accessory muscle use for breathing, crackles (in about one-third of patients), marked pallor, and decreased breath sounds (in advanced pneumonia). Cyanosis may appear with acute illness; pulmonary consolidation develops later.
Diagnosis
CONFIRMING DIAGNOSIS Histologic studies confirm P. carinii in all patients. Fiber-optic bronchoscopy remains the most commonly used study to confirm PCP. Invasive procedures, such as transbronchial biopsy and open-lung biopsy, are performed less commonly.
In patients with HIV infection, initial examination of a first-morning sputum specimen (induced by inhaling an ultrasonically dispersed saline mist) may be sufficient; however, this technique usually is ineffective in patients without HIV infection.
Chest X-rays may show slowly progressing, fluffy infiltrates and, occasionally, nodular lesions or a spontaneous pneumothorax, but these findings must be differentiated from findings in other types of pneumonia or acute respiratory distress syndrome.
Gallium scan may show increased uptake over the lungs even when the chest X-ray appears relatively normal. Arterial blood gas (ABG) studies detect hypoxia and an increased A-a gradient.
Treatment
PCP may respond to drug therapy with co-trimoxazole. Other agents used to treat PCP include pentamidine, trimethoprim-dapsone, clindamycin, primaquine, and atovaquone. Corticosteroids are frequently used as well. However, because of immune system impairment, many patients with PCP, who also have HIV, experience severe adverse reactions to drug therapy.
Supportive measures, such as oxygen therapy, mechanical ventilation, adequate nutrition, and fluid balance, are important adjunctive therapies. Oral morphine sulfate solution may reduce the respiratory rate and anxiety, thereby enhancing oxygenation.
Special considerations
❑Implement standard precautions to prevent contagion.
❑Frequently assess the patient's respiratory status, and monitor ABG levels every 4 hours.
❑Administer oxygen therapy as ordered. Encourage the patient to ambulate as well as to perform deep-breathing exercises and incentive spirometry to facilitate effective gas exchange.
❑Administer antipyretics as ordered, to relieve fever.
❑Monitor the patient's intake and output and daily weight to evaluate fluid balance. Replace fluids as ordered.
❑Provide diversionary activities and coordinate health care team activities to allow adequate rest periods between procedures.
❑Teach the patient energy conservation techniques.
❑Supply nutritional supplements as needed. Encourage the patient to eat a high-calorie, protein-rich diet. Offer small, frequent meals if the patient cannot tolerate large amounts of food.
❑Reduce anxiety by providing a relaxing environment, eliminating excessive environmental stimuli, and allowing ample time for meals.
❑Give emotional support and help the patient identify and use meaningful support systems.
❑Instruct the patient about the medication regimen, especially about the adverse effects.
❑Emphasize the importance of continuing chemoprophylaxis for those patients at high risk of developing PCP.
❑If the patient will require oxygen therapy at home, explain that an oxygen concentrator may be most effective.
❑Because this infection is usually associated with acquired immunodeficiency syndrome (AIDS), provide the patient with resources and support organizations for both AIDS and HIV.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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- "Professional Guide to Diseases (Eighth Edition)" (2005)
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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