Pneumocystis Carinii Pneumonia - Causes, Symptoms and Treatments
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 occurs in up to 90% of HIVinfected patients in the United States at some point during their lifetime. It is the leading cause of death in these patients. Disseminated infection doesn't occur. PCP also is associated with other immunocompromised conditions, including organ transplantation, leukemia, and lymphoma.
Causes of Pneumocystis carinii pneumonia:
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.
Part of the normal flora in most healthy people, P. carinii 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.
The organism 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 of Pneumocystis carinii pneumonia:
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), and decreased breath sounds (in advanced pneumonia). Cyanosis may appear with acute illness; pulmonary consolidation develops later.
Diagnosis of Pneumocystis carinii pneumonia:
Histologic studies confirm P. carinii. 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.
Fiberoptic bronchoscopy remains the most commonly used study to confirm PCP. Invasive procedures, such as transbronchial biopsy and open lung biopsy, are performed less commonly.
Chest X-ray may show slowly progressing, fluffy infiltrates and occasionally nodular lesions or a spontaneous pneumothorax. 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 alvcolararterial gradient.
These findings must be differentiated from findings in other types of pncumonia, adult respiratory distress syndrome, asthma, heart failure, and lung cancer.
Treatment of Pneumocystis carinii pneumonia:
PCP may respond to drug therapy with cotrimoxazole or pentamidine isethionate. Because of immune system impairment, many patients who also have HIV experience severe adverse reactions to drug therapy. These reactions include bone marrow suppression, thrush, fever, hepatotoxicity, and anaphylaxis. Nausea, vomiting, and rashes are common. Diphenhydramine may be prescribed to treat the latter effects and leucovorin may reduce bone marrow suppression (and may be used prophylactically in patients with HIV infection).
Pentamidine may be administered I.V. or in aerosol form. I.V. pentamidine is associated with a high incidence of severe toxic effects. The inhaled form usually is well tolerated. However, inhaled pentamidine may not effectively reach the lung apices. Adverse reactions associated with inhalation include metallic taste, pharyngitis, cough, bronchospasm, shortness of breath, rhinitis, and laryngitis.
Supportive measures, such as oxygen therapy, mechanical ventilation, adequate nutrition, and fluid balance, are important adjunctive therapies.
Oral or I.V. morphine sulfate solution may reduce the respiratory rate and the patient's anxiety, thereby enhancing oxygenation.
Special considerations of Pneumocystis carinii pneumonia:
1. Implement universal precautions to prevent contagion.
2. Frequently assess the patient's respiratory status, and monitor ABG levels every 4 hours.
3. Administer oxygen therapy as necessary. Encourage the patient to ambulate and to perform deep-breathing exercises and incentive spirometry to facilitate effective gas exchange.
4. Administer antipyretics, as required, to relieve fever.
5. Monitor intake and output and daily weight to evaluate fluid balance. Replace fluids as necessary.
6. Give antimicrobial drugs as required. Never give pentamidine I.M. because it can cause pain and sterile abscesses. Administer the I.V. drug form slowly over 60 minutes to reduce the risk of hypotension.
7. Monitor the patient for adverse reactions to antimicrobial drugs. If he's receiving cotrimoxazole, watch for nausea, vomiting, rash, bone marrow suppression, thrush, fever, hepatotoxicity, and anaphylaxis. If he's receiving pentamidine, watch for cardiac arrhythmias, hypotension, dizziness, azotemia, hypocalcemia, and hepatic disturbances.
8. Provide diversional activities and coordinate health care team activities to allow adequate rest periods between procedures. a Teach the patient energy conservation techniques as well.
9. Supply nutritional supplements as needed. Encourage the patient to eat a highcalorie, protein-rich diet. Offer small, frequent meals if the patient cannot tolerate large amounts of food.
10. Reduce anxiety by providing a relaxing environment, eliminating excessive environmental stimuli, and allowing ample time for meals.
11.Give emotional support and help the patient identify and use meaningful support systems.
12. Instruct the patient about the medication regimen, especially about possible adverse effects.
13. If the patient will require oxygen therapy at home, explain that an oxygen concentrator may be most effective.
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