Fungi a Danger to Cancer Patients (And others)

Watch Out—Fungi a Danger to Cancer Patients (And others)
Monday, October 5, 2009 8:50 AM
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Watch Out—Fungi a Danger to Cancer Patients
Debra Wood, RN
Oncology Nursing News - New York,n,USA

http://www.oncology nursingnews. com/Watch- OutFungi- a-Danger- to-Cancer- Patients/ article/150938/

LAKE BUENA VISTA, FLA—Fungus lives among us, typically causing minimal trouble in healthy individuals. But for patients with compromised immune systems, a fungal infection can often prove fatal.

"We're seeing a higher prevalence of fungal infections in our patient population," noted Susan McCollom, RN, ND, CPON, a clinical manager at Children's Medical Center Dallas. Dr McCollom spoke at the Association of Pediatric Hematology/Oncology Nurses Annual Conference.

Statistically, fungal sepsis has increased 207% in the last 20 years. Fungal infections develop in 19% of people with acute lymphocytic leukemia patients, 47% of those with acute myelogenous leukemia with remission induction therapy, 5% of autograft transplant patients, and 18% to 45% of persons undergoing an unrelated allogeneic transplant. According to Dr McCollom, 30% to 95% of these individuals will die.

Fungal spores float in the air. Once they land, they begin to grow in an environment containing moisture, nutrients, and the right temperature. Controlling moisture is the key to controlling fungal growth, advised Dr McCollom.

People can inhale or ingest the spores. A healthy person's respiratory tract cilia, normal flora, and immune system will prevent the fungus from becoming harmful. But immunocompromised individuals often cannot fight off fungal infections.

Many patients arrive for treatment colonized with fungi, and once their immune system is suppressed by chemotherapy treatment, the fungi flourish. Broadspectrum antibiotics, graft-versus- host disease, intravenous catheters, and environmental contaminants also increase the risk of fungal infections.

Three Main Types of Fungi
Dr McCollom described 3 fungus types— Fusarium, Candida, and Aspergillus—that commonly cause infection in patients.

Fusarium is found on plants and in the soil. Hence, Ms McCollom's hospital does not allow patients to have potted plants. "It's the most emergent opportunistic infection in humans," she reported.

Fusarium is often drug-resistant and can cause superficial and systemic disease, with resultant thrombosis.

"Patients with a malignancy or stem-cell transplant often have a poor outcome [with this fungal infection] because the immune system is so suppressed," Ms McCollom explained. "We use combination therapy, but when [the disease is] invasive, it's typically fatal."

Candida is the most common mycosis worldwide and the fourth most common bloodborne infection. This fungus is found on human skin, in the mucous membranes, and throughout the body, and grows rapidly.

Another common fungus, Aspergillus, is found in soil, building materials, spices, and the hospital environment. Although most people breathe it in daily and it is then dispatched by the immune system, Aspergillus can be very invasive and start to take over in an immunocompromised patient.

Symptoms of fungal infection include wheezing, cough, fever, bloody mucus, and hemorrhage. Infections are diagnosed by x-ray; by computed tomography (CT) scan, which might show a halo shadow around the fungal wall; by bronchial alveolar lavage; and by biopsy.

Treatment
Providers typically begin antifungal treatment on patients with neutropenia who have had a fever for 5 or more days, when a blood culture grows yeast, or when a CT scan indicates something suspicious.

"You want a drug that's fungistatic and fungicidal," counseled Virginia Koepsell, RN, MSN, MBA, CPON, a nursing educator at Children's Medical Center Dallas. (Fungistatic drugs are used to stop fungi growth; fungicides kill fungi.) "The optimal [drug] has wide-spectrum activity, because you often don't know what [the infection] is in the beginning, [and] is effective but has low toxicity and low cost."

The 3 drug classes used to treat fungal infections are azoles, polyenes, and echinocandins, also known as fungins. They are often given in combination, with the different agents using different mechanisms of action to combat the infection. "You can bring down the drug dose to get less toxicity [with combinations] , and it decreases the emergence of drug resistance," said Ms Koepsell.

Azoles inhibit fungal growth by preventing formation of ergosterol, which is vital for cell membrane integrity. An older azole, fluconazole, is fungistatic but will not kill fungi. It is often used to treat Candida albicans.

Voriconazole is a newer drug that inhibits growth and kills the fungus. It's commonly prescribed to treat Fusarium and Aspergillus infections. Voriconazole is nephrotoxic when given intravenously. It is hepatotoxic in the IV and oral formulations; therefore prescribers may need to decrease the dose of cyclosporine or tacrolimus if those drugs are also ordered. A high-fat meal will decrease absorption by 25%. About 30% of patients report visual disturbances within 30 minutes of starting the dose, but these resolve within another 30 minutes.

Polyenes or amphotericin derivatives interact with the cell membrane to kill the fungus. Amphotericin B has been used for more than 50 years, and although very little resistance has developed, the drug has many toxicities. Nurses noticed that when it was given with lipids, patients experienced fewer side effects, and now it is available in 3 lipid formulations: Abelcet, Amphotec, and AmBisome. AmBisome can be given in higher doses than amphotericin B, with fewer toxicities, but it is more expensive. It causes potassium depletion and is not compatible with normal saline. Because of sterility issues, nurses must administer AmBisome within 6 hours of preparation. The patient should receive a bolus of normal saline prior to starting the AmBisome intravenous infusion to salt-load the kidneys and protect the renal tubules.

Echinocandins block synthesis of the fungal cell wall and are used in treating Aspergillus and Candida. One such agent, caspofungin, is not compatible with dextrose.

Providers also may add GM-CSF (granulocyte- macrophage colony-stimulating factor) and interferon in an attempt to enhance the body's immune response, especially when treating overwhelming fungal infections.

"We want to reverse the immunosuppression, " clarified Ms Koepsell. "In order for the patient to get over the infection, we have to boost the white-cell count."

Prevention
Hospitals have taken many measures to decrease the risk of fungal infections, such as installing HEPA filters, controlling clutter, prohibiting flowers and plants, and having nurses educate patients and their families about methods of modifying the home environment.

Patients should avoid dusty areas and construction zones. If they must pass through such an area, they should wear an N95 respirator. They should keep at the home humidity level at 40% to 50%. "Fungal spores are greater in the natural environment than in the hospital, where we have more control," Ms McCollom said. "Controlling the relative humidity will help."

Patients should use air conditioners and dehumidifiers, but not fans. The home should have adequate ventilation and bathrooms and basements should be tiled or concrete, with no carpeting. Patients should not vacuum, dust, or reuse towels.
From the October 2009 Issue of ONN