Management of HIV/AIDS
With the advances in antiretroviral therapy and increased life expectancy of
patients with HIV infection, the emergency physician must also consider noninfectious pathologies in the differential diagnosis.
Pneumocystis Jiroveci Pneumonia. Although HAART has markedly decreased its incidence, Pneumocystis jiroveci pneumonia (PJP), formerly Pneumocystis carinii pneumonia, remains the most common opportunistic infection amongst US patients with AIDS. The classic presentation of PJP is subacute. Fatigue, fever, and malaise associated with dry cough are common symptoms. Dyspnea, especially with exertion, is common. The classic chest X-ray finding in PJP is a diffuse, bilateral interstitial infiltrate. However, findings vary widely and can include lobar or nodular infiltrates, hilar lymphadenopathy, spontaneous pneumothorax, cavitation, and, rarely, pleural effusions. Furthermore, the chest X-ray findings may also be normal. Due to this varied presentation it is often difficult to reliably distinguish PJP from bacterial pneumonia or tuberculosis.
The special stains that are used to confirm the presence of Pneumocystis jiroveci in induced sputum or bronchoalveolar lavage usually are not available in the ED. Diagnosis and empirical treatment may hinge on the patient’s medical history and the presence of a CD4 count less than 200 cells/µL. An increase in the alveolar-arterial (A-a) oxygen gradient and an elevated lactate dehydrogenase level are both associated with a diagnosis of PJP pneumonia.
The drug of choice for PJP is intravenous (IV) trimethoprim/sulfamethoxazole (TMP-SMX) administered every 6 hours. The usual regimen is 15 to 20 mg/kg/d (based on the trimethoprim). For patients who cannot tolerate TMP-SMX, IV pentamidine (4 mg/kg once daily) is regarded as the second-line choice. Alternative treatment regimens include trimethoprim plus dapsone, and atovaquone. Steroids reduce the incidence of respiratory failure and mortality in those with a pulmonary partial pressure of oxygen, arterial less than 70 mm Hg or an A-a gradient greater than 35 mm Hg. Prednisone 40 mg orally twice a day should be used as adjunctive therapy for patients in this subgroup.
Mycobacterium Avium Complex. Mycobacterium avium complex (MAC) is a group of nontuberculous mycobacteria that cause one of the most common serious opportunistic infections in people with AIDS, and historically has affected almost exclusively individuals with CD4 counts <50 cells/µL. These mycobacteria are ubiquitous in the environment, including water and soil. Patients with disseminated MAC infections frequently have nonspecific symptoms, signs, and laboratory abnormalities. In many instances, worsening of chronic constitutional symptoms alone may reflect disseminated MAC infection and thus may be attributed incorrectly to the progression of other HIV-related illnesses. In a study at San Francisco General Hospital, a history of fever for >30 days, a hematocrit <30%, or a serum albumin level <3.0 g/dL were sensitive predictors of MAC bacteremia.17 However, severe fatigue, diarrhea, weight loss, neutropenia, and thrombocytopenia were not associated with MAC bacteremia.
Diagnosis is normally made by culturing the peripheral blood for mycobacteria. Performing two cultures yields a sensitivity of 98% for disseminated MAC. Acid-fast staining of tissue biopsies may also be useful, but is rarely a part of ED management.
The treatment regimen for disseminated MAC should include at least two drugs. The most efficacious therapies are the newer macrolide antibiotics clarithromycin and azithromycin. The preferred treatment regimen should include one of these agents along with ethambutol and/or rifabutin.
Cytomegalovirus Retinitis. Cytomegalovirus (CMV) retinitis accounts for up to 90% of HIV-related infectious retinopathies and is the most common cause of blindness in AIDS patients. Fortunately, HAART has reduced the incidence of this disease by 75% in AIDS patients; however, patients with a CD4 count <50 cells/µL are still at risk. Symptoms include blurred vision, floaters, photophobia, scotomata, or pain. Fundoscopic examination will reveal fluffy white retinal lesions. Although the appearance of CMV retinitis is usually sufficient to make the diagnosis, the differential is broad and includes HIV retinopathy, toxoplasmosis, syphilis, tuberculosis, pneumocystis, and cryptococcosis. The cornerstone of CMV retinitis therapy is reconstitution of the immune system with HAART, but parenteral and/or intravitreal antivirals such as ganciclovir should also be considered in consultation with an ophthalmologist.
Toxoplasmosis. Toxoplasma gondii is a leading cause of death attributed to foodborne illness in the United States. More than 60 million men, women, and children in the United States carry the toxoplasma parasite, but most are asymptomatic. This intracellular parasite is the leading cause of central nervous system (CNS) disease in patients with AIDS, with the greatest risk seen with CD4 counts <50 cells/µL, but occurring in those with CD4 counts <200 cells/µL as well. Symptoms may include headache, seizure, altered mental status, fever, or focal neurological deficits. Serologic testing for toxoplasma is not helpful due to the widespread presence of antibodies in the population. A contrast-enhanced CT scan typically reveals multiple ring-enhancing lesions. Parasites can also be isolated from tissues and CSF. A brain biopsy is sometimes necessary to distinguish between toxoplasmosis and other causes of CNS disease such as CNS lymphoma. In general, therapy should not be delayed pending tissue diagnosis if imaging studies are consistent with toxoplasmosis. Standard therapy consists of pyrimethamine, sulfadiazene and folinic acid in combination. Trimethoprim-sulfamethoxazole (TMP-SMZ) can be used as an alternative regimen. Steroids may be merited and prophylactic antiepileptics may also be beneficial in those with significant mass effect from toxoplasma lesions.
